ENORASIS Deliverables 1.2 v1.3 · Artur Lopatka 3. MODELLING ECONOMIC OPTIMIZATION OF IRRIGATION...

Project:

ENORASIS (Grant Agreement 282949)

“ENVIRONMENTAL OPTIMIZATION OF IRRIGATION MANAGEMENT WITH THE COMBINED USE AND

INTEGRATION OF HIGH PRECISION SATELLITE DATA, ADVANCED MODELING, PROCESS CONTROL AND

BUSINESS INNOVATION” Funding Scheme: Collaborative Project Theme: FP7-ENV

D1.2: Agricultural Process Analysis Report

Issued by: INSTYTUT UPRAWY NAWOZENIA I GLEBOZNAWSTWA, PANSTWOWY INSTYTUT BADAWCZY

Issue date: 31/05/2012

Due date: 15/06/2012

Work Package Leader: UNIVERZITET U NOVOM SADU FAKULTET TEHNICKIH NAUKA

Start date of project: 01 January, 2012 Duration: 36 months

Document History

(Revisions – Amendments)

Version and date Changes

0.1 25.01.2012 Creation of the table of contents’ draft. R. Wawer

0.2 14.02.2012 Changes after kick-off meeting. Re-design of methodological approach. R. Wawer

1.0 15.02.2012 Changes in the document structure. R. Wawer, Jerzy Kozyra

1.1 10.03.2012 Adding chapter on fundamentals of irrigation management . R. Wawer

1.2 30.05.2012 1st draft of the report, two chapters need to be added, formatting harmonized

1.3 31.05.2012 1st version

Dissemination Level PU Public PU

PP Restricted to other programme participants (including the EC Services)

RE Restricted to a group specified by the consortium (including the EC Services)

CO Confidential, only for members of the consortium (including the EC)

Report authors

Autor Chapter

Adriana Bruggeman 2.1.2 Atmosphere. Weather as driving force for calculating irrigation needs 2.1.3 Plant. Growth factors and water needs.

Artur Lopatka 3. MODELLING ECONOMIC OPTIMIZATION OF IRRIGATION The FAO56 and CROPWAT model documentation

Ioannis Kioutsioukis The Weather Research and Forecasting (WRF) Model documentation

Jürg Hammer 2.2 Water for irrigation.

Rafal Wawer 1.INTRODUCTION 2.1.1 Soil. Land classification for irrigation 2.3 Irrigation systems MODEL REPOSITORY MODEL DOCUMENTATION TEMPLATE

LEGAL NOTICE Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use, which might be made, of the following information. The views expressed in this report are those of the authors and do not necessarily reflect those of the European Commission

© ENORASIS Consortium, 2012

Reproduction is authorised provided the source is acknowledged

Statement of originality: This deliverable contains original unpublished work except where clearly indicated otherwise. Acknowledgement of previously published material and of the work of others has been made through appropriate citation, quotation or both.

FP7-ENV “ENORASIS”

D1.2 Agricultural Process Analysis Report

Version – issue date: 1.3 – 31/05/2012 Page i

Table of Contents

1. INTRODUCTION ............................................................................. 1

KEY CONCEPTS & TERMS....................................................................................................... 5

SOIL-PLANT HYDROLOGICAL PROPERTIES ............................................................................... 7

Critical Soil Water Content ..................................................................................................... 7

IRRIGATION EFFICIENCY AND SUSTAINABILITY ........................................................................ 9

2. FUNDAMENTALS OF IRRIGATION PLANNING ............................... 12

2.1 Factors affecting irrigation planning ................................................. 12

2.1.1 Soil. Land classification for irrigation ......................................................................... 12

2.1.2 Atmosphere. Weather as driving force for calculating irrigation needs ............................. 14

2.1.3 Plant. Growth factors and water needs. ..................................................................... 15

2.2 Water for irrigation. ......................................................................... 17

2.2.1 Sources and use of water in Irrigation ....................................................................... 17

2.2.2 Water quality ........................................................................................................ 18

2.2.3 Water Conservation and harvesting ........................................................................... 19

2.2.4 Water productivity in irrigation management .............................................................. 22

2.3 Irrigation systems. .......................................................................... 22

Surface Irrigation ............................................................................................................... 22

Localized Irrigation ............................................................................................................. 23

Sprinkler Irrigation ............................................................................................................. 24

Sub-irrigation .................................................................................................................... 26

Manual using buckets or watering cans .................................................................................. 26

Automatic, non-electric using buckets and ropes ..................................................................... 26

Using water condensed from humid air .................................................................................. 26

3. MODELLING ECONOMIC OPTIMIZATION OF IRRIGATION ............. 27

4. BIBLIOGRAPHY ................................................................................ 31

ANNEXES ............................................................................................ 33

MODEL REPOSITORY ................................................................................ 33

MODEL DOCUMENTATIONS ......................................................................... 40

The FAO56 and CROPWAT model documentation ..................................... 40

The Weather Research and Forecasting (WRF) Model .............................. 45

MODEL DOCUMENTATION TEMPLATE ............................................................ 48

Abbreviations and terminology ............................................................... 48

Technical Guidelines ............................................................................... 49

Software description ........................................................................................................... 49

Main Features .................................................................................................................... 50

Installation ....................................................................................................................... 51

Software limitation/known issues/errors (if any) ...................................................................... 51

Manual / FAQ / Acronyms .................................................................................................... 51

Community / users links ...................................................................................................... 51

General Remarks & Conclusions ............................................................................................ 51

Appendix A – Example for a documentation table .................................................................... 51



Version – issue date: 1.3 – 31/05/2012 Page ii

List of figures Figure 1. Distribution of Earth's water ( Shiklomanov, 1993) ........................................................... 1

Figure 2. Various components of the hydrologic cycle (Oram, 2010).................................................. 2

Figure 3. Withdrawal of water for agriculture as percent of all human water usee4. FAO Aquastat. ......... 2

Figure 4. Global extent of area equipped for irrigation in the period 1900–2003 (data sources: SHIKLOMANOV 2000; FAOSTAT). ................................................................................................ 4

Figure 5. Area equipped for irrigation. FAO Aquastat. ..................................................................... 4

Figure 6. Area equipped fir irrigation as percentage of cultivated area FAO Aquastat. ........................... 4

Figure 7. Increased drought in Europe by 2070 (IPCC, 2007) ........................................................... 5

Figure 8. Transpiration and evapotranspiration. ............................................................................. 6

Figure 9. Infiltration and ground water flow . (USGS, 2010 ) ............................................................ 6

Figure 10. The Effect of Application Depth and Uniformity on Application Efficiency ............................ 11

Figure 11. Crop development stages and crop coefficients (Bos et al., 2009). ................................... 16

Figure 12. Diagram for classifying irrigation water in Oklahoma (Division of Agricultural Sciences and Natural Resources, Oklahoma State University). SAR = sodium adsorption ratio................................ 19

Figure 13. Drip Irrigation Layout and its parts ............................................................................. 23

List of tables Table 1. Key soil attributes for plant growth ............................................................................... 12

Table 2. Structure of the suitability classification.......................................................................... 13

Table 3. Expected water losses on spray irrigation systems(Edkins E., 2006) .................................... 27

Table 4. ENORASIS Model Repository. Model names and scope ...................................................... 33

Table 5. ENORASIS Model Inventory. Models' references. .............................................................. 35

Table 6. ENORASIS Model Repository. Models' webpages. ............................................................. 38

Table 7. ENORASIS Model Repository. Model features. .................................................................. 39

List of photographs Photograph 1. Large sprinkler system ........................................................................................ 21

Photograph 2. Brass Impact type sprinkler head1 ......................................................................... 23

Photograph 3. Drip Irrigation - A dripper in action1 ...................................................................... 23

Photograph 4. Grapes in Petrolina, just possible in this semi arid area due to drip irrigation1. .............. 23

Photograph 5. Sprinkler irrigation of blueberries in Plainville, New York, United States.1 ..................... 24

Photograph 6. A traveling sprinkler at Millets Farm Centre, Oxfordshire, United Kingdom .................... 24

Photograph 7. A small center pivot system from beginning to end1 ................................................. 25

Photograph 8. The hub of a center-pivot irrigation system1 ............................................................ 25

Photograph 9. Rotator style pivot applicator sprinkler1 .................................................................. 25

Photograph 10. Center pivot with drop sprinklers. Photo by Gene Alexander, USDA Natural Resources Conservation Service .............................................................................................................. 25

Photograph 11. Wheel line irrigation system in Idaho. 2001. Photo by Joel McNee, USDA Natural Resources Conservation Service1 .............................................................................................. 26



Version – issue date: 1.3 – 31/05/2012 Page 1

1. INTRODUCTION GENERAL INFORMATION OF WATER USE BY AGRICULTURE

The amount of freshwater available for the use by humans remains only the 2,5% of the global water on Earth (

Figure 1). From this amount almost barely 1,3% is available as free surface freshwater of which almost ¾ is enclosed in ice caps and glaciers. Remaining 26,9% is potentially directly available for human use. Additionally a large amount of groundwater – 30% of Earth’s freshwater stock, lies beneath the surface of the continents on various depths.

Figure 1. Distribution of Earth's water ( Shiklomanov, 19931)

All the Earth’s free water circulates within a general cycle, shaped by the energy of the Sun,

reaching Earth’s atmosphere and surface (Figure 2). The dynamics of freshwater part of the cycle influences the availability of water for human civilisation, especially agriculture, which presently is by far the largest water-use sector, accounting for about 70 percent of all water withdrawn worldwide from rivers and aquifers for agricultural, domestic and industrial purposes (Shiklomanov, 2000) (Figure 3). Most of the fresh water used in agriculture is consumed by crops, both in natural (rainfed crops) and induced (irrigated crops) way. Irrigated crops play a vital role in securing global food production. Approximately 40% of food globally is produced from irrigated crops, sustaining the livelihood of billions of people (Abdullah, 2006).

1 USGS Water Science for Schools, source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York).




Figure 2. Various components of the hydrologic cycle (Oram, 20101)

Figure 3. Withdrawal of water for agriculture as percent of all human water usee4. FAO Aquastat.

Irrigation is the artificial application of water to the land or soil. It is used to assist in the growing

of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in grain fields and helping in preventing soil consolidation In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dryland farming. Irrigation systems are also used for dust suppression, disposal of sewage, and in mining. Irrigation is often studied together with drainage, which is the natural or artificial removal of surface and sub-surface water from a given area.2

Archaeological investigations have identified evidence of irrigation where the natural rainfall was

insufficient to support crops.

1 Oram, B. (2010). Drinking water testing, water quality and pathogenic disease laboratories. Retrieved June 10, 2010 from Wilkes University Center for Environmental Quality Environmental Engineering and Earth Sciences Web site: http://www.water-research.net/images/grounwaterfigure1.jpg 2 WIKIPEDIA. http://en.wikipedia.org/wiki/Irrigation




Perennial irrigation was practised in the Mesopotamian plain whereby crops were regularly watered throughout the growing season by coaxing water through a matrix of small channels formed in the field.

Ancient Egyptians practiced Basin irrigation using the flooding of the Nile to inundate land plots which had been surrounded by dykes. The flood water was held until the fertile sediment had settled before the surplus was returned to the watercourse. There is evidence of the ancient Egyptian pharaoh Amenemhet III in the twelfth dynasty (about 1800 BCE) using the natural lake of the Faiyum Oasis as a reservoir to store surpluses of water for use during the dry seasons, the lake swelled annually from flooding of the Nile.

The Ancient Nubians developed a form of irrigation by using a waterwheel-like device called a sakia. Irrigation began in Nubia some time between the third and second millennium BCE. It largely depended upon the flood waters that would flow through the Nile River and other rivers in what is now the Sudan.

In "sub-Saharan Africa" irrigation reached the Niger River region cultures and civilizations by the first or second millennium BCE and was based on wet season flooding and water harvesting.

Terrace irrigation is evidenced in pre-Columbian America, early Syria India and China. In the Zana Valley of the Andes Mountains in Peru, archaeologists found remains of three irrigation canals radiocarbon dated from the 4th millennium BCE, the 3rd millennium BCE and the 9th century CE. These canals are the earliest record of irrigation in the New World. Traces of a canal possibly dating from the 5th millennium BCE were found under the 4th millennium canal. Sophisticated irrigation and storage systems were developed by the Indus Valley Civilization in present-day Pakistan and North India, including the reservoirs at Girnar in 3000 BCE and an early canal irrigation system from circa 2600 BCE. Large scale agriculture was practiced and an extensive network of canals was used for the purpose of irrigation.

Ancient Persia (modern day Iran) as far back as the 6th millennium BCE, where barley was grown in areas where the natural rainfall was insufficient to support such a crop. The Qanats, developed in ancient Persia in about 800 BCE, are among the oldest known irrigation methods still in use today. They are now found in Asia, the Middle East and North Africa. The system comprises a network of vertical wells and gently sloping tunnels driven into the sides of cliffs and steep hills to tap groundwater. The noria, a water wheel with clay pots around the rim powered by the flow of the stream (or by animals where the water source was still), was first brought into use at about this time, by Roman settlers in North Africa. By 150 BCE the pots were fitted with valves to allow smoother filling as they were forced into the water.

The irrigation works of ancient Sri Lanka, the earliest dating from about 300 BCE, in the reign of King Pandukabhaya and under continuous development for the next thousand years, were one of the most complex irrigation systems of the ancient world. In addition to underground canals, the Sinhalese were the first to build completely artificial reservoirs to store water. Due to their engineering superiority in this sector, they were often called 'masters of irrigation'. Most of these irrigation systems still exist undamaged up to now, in Anuradhapura and Polonnaruwa, because of the advanced and precise engineering.

The oldest known hydraulic engineering works in China date to 6th century BCE. In the Szechwan region the Dujiangyan Irrigation System was built in 256 BCE to irrigate an enormous area of farmland that today still supplies water.

In the Americas, extensive irrigation systems were created by numerous groups in prehistoric times. One example is seen in the recent archaeological excavations near the Santa Cruz River in Tucson, Arizona. They have located a village site dating from 4,000 years ago. The floodplain of the Santa Cruz River was extensively farmed during the Early Agricultural period, circa 1200 BC to AD 150. These people constructed irrigation canals and grew corn, beans, and other crops while gathering wild plants and hunting animals.1

Today at the global scale, 2,788,000 km² of agricultural land was equipped with irrigation

infrastructure around the year 2000 and the share of land under irrigated agriculture is constantly growing since the beginning of XX’th century (Figure 4). About 68% of the area equipped for irrigation is located in Asia, 17% in America, 9% in Europe, 5% in Africa and 1% in Oceania (Figure 5 and Figure 6). The largest contiguous areas of high irrigation density are found in North India and Pakistan along the rivers Ganges and Indus, in the Hai He, Huang He and Yangtze basins in China, along the Nile river in Egypt and Sudan, in the Mississippi-Missouri river basin and in parts of California.

The area actually irrigated (AAI) was estimated to be in the range of 213–242 Mio ha for the same period, while irrigated area harvested (IAH) was about 315 Mio ha (PORTMANN, University of Frankfurt, unpublished).

1 WIKIPEDIA. http://en.wikipedia.org/wiki/Irrigation




The main irrigated crops at the global scale are rice (IAH of 103 Mio ha), wheat (IAH of 67 Mio ha), maize (IAH of 29 Mio ha) and cotton (IAH of 16 Mio ha).1

Figure 4. Global extent of area equipped for irrigation in the period 1900–2003 (data sources: SHIKLOMANOV 2000; FAOSTAT).

Figure 5. Area equipped for irrigation. FAO Aquastat.

Figure 6. Area equipped fir irrigation as percentage of cultivated area FAO Aquastat.

In many developing countries more than 90 percent of the water withdrawals are for irrigation (FAO AQUASTAT-database, http://www.fao.org/ag/agl/aglw/aquastat/main/index.stm, 2005). In arid regions, irrigation is the prerequisite for crop production. In semi-arid and humid areas, irrigation serves to increase yields, to attenuate the effects of droughts or, in the case of rice production, to minimize weed growth. Average yields are generally higher under irrigated conditions as compared to rainfed agriculture (Bruinsma, 2003). In the United States, for example, average crop yields of irrigated farms

1 Siebert, S. & P. Döll (2007): Irrigation water use – A global perspective. In: LOZÁN, J.L., H. GRAßL, P. HUPFER, L. MENZEL & C-D. SCHÖNWIESE (eds.): Global Change: Enough Water for all? Universität Hamburg / GEO, 104-107.




exceeded, in 2003, the corresponding yields of dryland farms by 15% for soybeans, 30% for maize, 99% for barley, and by 118% for wheat (Veneman et al., 2004). Although globally only 18% of the cultivated area is irrigated (FAO, 2005a), 40% of the global food production comes from irrigated agriculture (UNCSD, 1997).1

Irrigation is expected to be much more crucial for the food production in the near future, as most probable climate change scenarios predict large water deficits in certain areas (Figure 7), especially Poland and Ukraine as well as some of Mediterranean states, especially Spain.

Figure 7. Increased drought in Europe by 2070 (IPCC, 2007)

IRRIGATION IN AGRICULTURE

KEY CONCEPTS & TERMS

An understanding of the following definitions is essential to understand the irrigation information (NRI, 2000).2

• Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid.3 • Evapotranspiration (ET) is a term used to describe the sum of evaporation and plant

transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves. Evapotranspiration is an important part of the water cycle. 3

1 S. Siebert, P. Doell, J. Hoogeveen, J.-M. Faures, K. Frenken, and S. Feick. 2005. Hydrology and Earth System Sciences, 9, 535–547. 2 2000 NRI (August 21, 2000) — 5–77 3 WIKIPEDIA




• Infiltration (Figure 9) is the process by which water on the ground surface enters the soil.

Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimetres per hour. The rate decreases as the soil becomes saturated. If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier. It is related to the saturated hydraulic conductivity of the near-surface soil.1

Figure 9. Infiltration and ground water flow . (USGS, 2010 2)

• Irrigated land. Land that shows evidence of being irrigated during the year’s vegetation period

or having been irrigated during two or more of the last four years. Water is supplied to crops by ditches, pipes, or other conduits.

• Irrigation delivery system. The method of delivery of irrigation water to a field from the water source, including (1) canal or ditch, or (2) pipeline. [NRI-97]

• Irrigation systems, type. Systems operated by gravity, pressure, or a combination designed to deliver water to a farm or field. Systems recognized are: [NRI-2000]

• Gravity • Pressure • Gravity and pressure

• Canal. An artificial waterway used for irrigation. [NRI-97] • Ditch. A long, narrow trench or furrow dug in the ground, as for irrigation. [NRI-97] • Gravity and pressure irrigated. Farm delivery and field distribution of irrigation water are a

combination of gravity and pressure facilities. For example, a valve is used to reduce pressurized water delivered to a farm or field for subsequent distribution by a gravity surface irrigation system. [NRI-92]

1 WIKIPEDIA: http://en.wikipedia.org/wiki/Infiltration_%28hydrology%29 2 USGS Water Science for Schools. http://ga.water.usgs.gov/edu/watercyclesummary.html#infiltration

Figure 8. Transpiration and evapotranspiration1.




• Gravity irrigated. Water is delivered to the farm and/or field by canals or pipelines open to the atmosphere; and, water is distributed by the force of gravity down the field by: [NRI-92]

• A surface irrigation system (border, basin, furrow, corrugation, wild flooding), or • Subsurface irrigation pipelines or ditches.

• Lake. An inland body of water, fresh or salt, extending over 40 acres or more and occupying a basin or hollow on the earth’s surface, which may or may not have a current or single direction of flow. [NRI-97]

• Plant transpiration (Błąd! Nie można odnaleźć źródła odwołania.) is a process similar to evaporation. It is a part of the water cycle, and it is the loss of water vapor from parts of plants (similar to sweating), especially in leaves but also in stems, flowers and roots. It is a part of the water cycle, and it is the loss of water vapor from parts of plants (similar to sweating), especially in leaves but also in stems, flowers and roots.

• Pipeline. A conduit of pipe used for the conveyance of water. [NRI-97] • Pressure irrigated. Water is delivered to the farm and/or field in pump or elevation induced

pressure pipelines; and water is distributed across the field by: [NRI-92] • Sprinkle irrigation (center pivot, linear move, traveling gun, side roll, hand move, big un, or fixed set sprinklers) • Micro irrigation (drip emitters, continuous tube bubblers, microspray or microsprinklers).

• Pond. A water impoundment made by constructing a dam or an embankment or by excavating a pit or dugout. [NHCP]

• Reservoir. A pond, lake, basin, or other space created in whole or in part by the building of engineering structures, that is used for storage, regulation, and control of water. [NRI-97]

• Source of irrigation water (irrigation system). The initial source of irrigation water delivered to a field, including (1) well; (2) pond, lake, or reservoir; (3) stream, ditch, or canal; (4) lagoon or wastewater; or (5) combination of sources. [NRI-97]

• Stream. A flow of water in a channel or bed, as a brook, rivulet, or small river. [NRI-97] • Water spreading. Diverting or collecting runoff from natural channels, gullies, or streams with a

system of dams, dikes, ditches, or other means, and spreading it over a relatively flat area. [NHCP]

• Well. A hole drilled or bored into the earth providing access to water. [NRI-97]1

SOIL-PLANT HYDROLOGICAL PROPERTIES

Critical Soil Water Content

The assumption is made that the goal of irrigation is to avoid loss of income due to crop stress induced by low soil water content. To achieve this goal it is necessary to irrigate, at the latest, when the soil water content has dropped to the point where the crop comes under sufficient stress to cause loss of income. We will refer to this as the critical soil water content. In general, it varies with crop type and soil type.

To determine the critical soil water content it is necessary to know the leaf water pressure (or potential) at which leaf stomata begin to close. If leaf water pressure falls below this threshold the stomata begin to close to reduce evaporative water loss and hence maintain plant tugor. Closure of the stomata also means a reduction in the assimilative capacity of the plant and hence its productivity. It is assumed, for the purpose of irrigation design and operation, that the soil water pressure at which the stomata close is the same as the critical leaf water pressure.

To determine the critical soil water content it is also necessary to know the soil moisture characteristic for the soil to be irrigated because the minimum allowable soil water pressure occurs at different soil water contents for different soil types. The soil moisture characteristic is the relationship between soil water pressure and soil water content.

In summary, the critical soil water content depends on the critical leaf water pressure of the crop to be grown, and the soil moisture characteristic of the soil in which the crop is to be grown. Different combinations of crops and soil(s) will lead to a range of critical soil water contents on each farm.

1 2000 NRI (August 21, 2000) — 5–77




Field Capacity

Field capacity is an estimate of the maximum volume of water that may be temporarily stored in the soil profile for plant use (Skaggs et al., 1980).

Field capacity is defined to be the water content in a field soil after the rate of drainage beyond a specified soil depth has become small. The soil profile should initially be at saturation, and there should be no evaporative losses during the drainage period. The time for drainage to decrease to a small amount varies from a few hours, for coarse-textured soils, to several days for fine-textured soils. The soil water content at field capacity depends on the soil moisture characteristic and the unsaturated hydraulic conductivity for each of the layers that make up the soil profile of interest, the depth to the water table, gravity, and the definition of what is a small drainage rate.

Field capacity has value, as a concept, because it simplifies estimation of the depth of water that might usefully be stored in the soil profile, and the depth of water that may drain from the profile after application of a given depth of water.

Infiltrability and Infiltration Rate

Infiltrability (or infiltration capacity) is the rate that water will infiltrate soil when the rate is limited by soil factors only. Infiltrability decreases as the pressure difference, or hydraulic gradient, across the infiltration surface reduces.1

The infiltration rate is the smaller of the rate at which water is applied and the infiltrability. As long as the infiltrability is greater than the application rate the water will infiltrate as quickly as it is supplied. If the infiltrability decreases with time, which it often does, to be less than the application rate then the soil surface will become ponded. The infiltration rate will then be controlled by the soil profile.

Average Application Depth

Application depth is generally calculated from measurements of flow-rate, irrigation time, and the area irrigated (intended or actual). Because irrigation is non-uniform, this depth is strictly the average application depth. Average application depth can be determined for sprinkler irrigation systems by using a grid of catch-cans to measure the application depth at specific points throughout the wetted area and calculating the areally weighted-average of the measured application depths.

Uniformity of Application Depth

The critical water content and water retention characteristics of the soil, along with crop water use, vary spatially within a field. Ideally, irrigation would apply water in a manner that accounts for this spatial variability. However, this level of precision is currently uneconomic and the assumption is made that the soil water deficit at the time of irrigation is the same over the whole field. This leads to the requirement that irrigation systems apply water in a manner that results in an infiltrated depth that is uniform throughout the field. This is rarely achieved in practice and the non-uniformity of application depth markedly affects design and management decisions.

In practice, some areas may receive more water than is necessary to return soil water content to field capacity. The excess water drains beyond the effective root zone and becomes of no value to the crop. Other areas are under-irrigated in the sense that the soil water content is not returned to the target soil water content. Consequently these areas will reach the critical soil water content much sooner than areas that were returned to the target level (i.e. were fully irrigated). If irrigation proceeds on the basis that all areas are fully irrigated, crop yield or quality reduction will occur on those areas that were under-irrigated.

The degree of variability of application depth about the average application depth is the most commonly used measure of application uniformity. The uniformity coefficient calculated by the

1 New Zealand’s Ministry for Primary Industries, 2000. Designing Irrigation Systems. Technical Report.




following formula is referred to, in the irrigation industry, as Christiansen’s uniformity coefficient. It is the most widely used measure of application depth uniformity.

where xi = application depth for subarea i

X = mean application depth over all subareas i.1

IRRIGATION EFFICIENCY AND SUSTAINABILITY

The sustainability of irrigated agriculture depends upon consistently achieving high irrigation application efficiency. High efficiency depends upon excellent design, as well as effective management.

Irrigation performance measures are outputs, the results of design and operating decisions. To be useful they need to predictably quantify the effects of design and operating decisions on the extent to which the purpose of irrigation is achieved, and how efficiently the purpose was achieved. They must do this in a way that assists designers and operators to make appropriate decisions.

Unfortunately it is not uncommon for irrigation design courses to focus on one performance measure – irrigation efficiency – and to use it as an input to the design process, rather than using it as one measure of system performance that is to be optimised, along with others, during the design process. It is not surprising, therefore, that performance in the field rarely exceeds, and typically does not match, the assumed performance.

Performance measures, if they are to serve their purpose, must take full account of the following important physical factors. These are:

• Optimum crop growth and yield depends on the maintenance of a specific level of water pressure within the plant. This implies maintaining soil water pressure above a certain threshold.

• At the time of irrigation, the soil’s capacity to store additional water is limited. • There is a limit to the rate at which water can infiltrate soil, and this limit varies over

time. • Irrigation almost always results in the infiltrated depth of water varying throughout the

field. Irrigation is not uniform.2

True measures of irrigation efficiency take account of the spatial uniformity of application depth, the average application depth, and the soil’s capacity to store more water at the time of irrigation. Irrigation efficiency varies with each water application throughout the season, and with site, soil type, and application system.

There are many definitions of irrigation efficiency. The irrigation efficiency principles put forward by Painter and Carran (1978) are conceptually very sound, but are too detailed for general use. For practical purposes it is useful to simplify matters by combining two of their efficiency measures – application efficiency and distribution pattern efficiency. Combining these provides a measure of how much of the water that is applied is actually retained within the effective plant root zone in an irrigation event. By "applied" we mean water leaving the nozzle of a pressurized system, or passing over the sill for border-strip systems.

The overall on-farm irrigation efficiency is determined by combining the effect of the application efficiency and the on-farm distribution system efficiency.

1 New Zealand’s Ministry for Primary Industries, 2000. Designing Irrigation Systems. Technical Report. 2New Zealand’s Ministry for Primary Industries, 2000. Designing Irrigation Systems. Technical Report.




Farm Distribution System Efficiency

Farm distribution system efficiency is a measure of how much of the water supplied to a farm is actually applied. It is a function of losses incurred in conveying water from its point of entry onto the farm, to the application device. Quantifying this efficiency requires measuring flow rates through the turnout or pump and over the sill or out of sprinkler nozzles. This efficiency is typically high.

While there are likely to be differences in the distribution system efficiency between piped and open channel systems, the differences are not expected to be as great as for application efficiency. The distribution system efficiency of a piped distribution system, or an open-channel distribution system on a NZ border-strip irrigated farm, is not likely to be significantly affected by application system design decisions, other than the decision to use a sprinkler or surface application method.

Application Efficiency

Application efficiency is a measure of how much of the water that is applied is actually retained in the root zone, in the target area, after an irrigation event. It is principally a function of the soil water status before irrigation, the depth of water that infiltrates the soil, and the soil’s water retention characteristic. All of these factors have a considerable degree of spatial variability and this significantly affects the efficiency. It is also a function of evaporative losses, spray drift off the target area, and run-off.

Application efficiency is defined as follows:

1

This definition takes into account losses due to spray drift, evaporation, run-off and drainage beyond the effective root zone.

Sometimes a so-called efficiency is calculated using the average application depth to represent the volume of water applied, and the soil water deficit at the time of irrigation to represent the change in the volume of stored water. As will be seen below, this approach over-estimates the real application efficiency because it does not take account of the non-uniformity of application depth.

Measurement of the spatial variation in application depth resulting from sprinkler irrigation, under a wide range of conditions, has shown the distribution of application depth to be normally distributed. Therefore the change in the volume of water stored in a given depth of soil can be calculated from the mean application depth, Christiansen’s uniformity coefficient, and the soil water content at the time irrigation commences (Bright, 1986). The volume of water applied is calculated from the average application depth and the area irrigated.

The relationship between application efficiency and mean application depth is shown in Figure 2-1 for a range of uniformity coefficients. For the purpose of this figure it has been assumed that evaporative, drift, and run-off losses are negligible. The soil water deficit at the time of irrigation is 50 mm.

1 New Zealand’s Ministry for Primary Industries, 2000. Designing Irrigation Systems. Technical Report.




Figure 10. The Effect of Application Depth and Uniformity on Application Efficiency1

For irrigation systems that apply water perfectly uniformly (Uc = 100 percent), and for the assumptions stated, it is clear that the application efficiency is 100 percent until the application depth exceeds the soil water deficit – the depth needed to bring the soil to field capacity. Increasing the mean application depth beyond that point results in a linear decrease in application efficiency.

For irrigation systems that apply water with a uniformity coefficient of 70 percent, for example, the decrease in application efficiency begins to occur at mean application depths significantly less than the soil water deficit. When the mean application depth equals the deficit the application efficiency is about 85 percent. Work by John et al. (1985) suggests that sprinkler irrigation systems in NZ are likely to be achieving application uniformity coefficients of around 70 percent. Therefore assessments of the application efficiency of spray irrigation that ignore spatial variability are likely to over-estimate efficiency by about 15 percent.

There are currently no field measurements of the depth distribution for NZ border-strip systems that would enable field-based measurement of application efficiency.

The potential uniformity of irrigation applications is largely determined by design decisions. Operating conditions such as wind (sprinkler) and surface roughness (border-strip) subsequently modify it. Application system design decisions significantly affect the application efficiency.2

1 New Zealand’s Ministry for Primary Industries, 2000. Designing Irrigation Systems. Technical Report. 2 New Zealand’s Ministry for Primary Industries, 2000. Designing Irrigation Systems. Technical Report.




2. FUNDAMENTALS OF IRRIGATION PLANNING

2.1 Factors affecting irrigation planning

Irrigation has always been a crucial element in increasing crop productivity. Starting from historical record till present day farming, human civilizations largely depended from food supply, which us such was and still remains highly variable responding to high climate variability, vulnerable to droughts and natural catastrophes. Irrigation allowed agriculture to raise the crop yield and even grow a second crop during the drier season, while the yields are potentially higher.

The upper limit of crop yield is shaped by the genetic potential of the crop, nutrient and water availability as well as the climate and soil. Providing the nutrients are assured in the agricultural practise the most important elements for irrigation are soil, water and plant.

2.1.1 Soil. Land classification for irrigation

The suitability of soil cover for agriculture depends on numerous soil features, i.a.: - Moisture holding capacity; - Infiltration rate to replenish the soil-water loss through evapotranspiration and minimize runoff

and soil erosion supported by it - Internal drainage throughout the root zone to provide proper aeration and replenishment of soil-

water reserves - Depth of the soil profile to allow necessary root growth and provide storage for water and

nutrients - Suitable texture, structure and consistency to allow necessary on-time agro technique - Absence of toxic elements and excess of salts.

The soil serves the needs of the plant by providing:

• Water • Air • Nutrients • Stability

The ability of a soil to provide these services may be evaluated by key soil attributes (see table following).1 Table 1. Key soil attributes for plant growth

A fuller use of land and water resources by the development of irrigation facilities could lead to substantial increases in food production in many parts of the world. The process whereby the suitability of land for specific uses such as irrigated agriculture is assessed is called land evaluation.

1 USDA




Land evaluation provides information and recommendations for deciding 'Which crops to grow where' and related questions. Land evaluation is the selection of suitable land, and suitable cropping, irrigation and management alternatives that are physically and financially practicable and economically viable. The main product of land evaluation investigations is a land classification that indicates the suitability of various kinds of land for specific land uses, usually depicted on maps with accompanying reports.

The evaluation and suitability classification system described in this bulletin is based on 'A Framework for Land Evaluation' (FAO 1976a). The structure of the FAO Framework classification is given in Table 2.

Table 2. Structure of the suitability classification

Order Categories class Subclass

S Suitable

S1

S2

S2t

S2d

S2td

etc.

S3

N Not suitable

N1 N1y

N1z

etc

N2

Legend: S1 Highly Suitable S2 Moderately Suitable S3 Marginally Suitable N1 Marginally Not Suitable N2 Permanently Not Suitable

Lower case letters in a Subclass indicate the nature of a requirement of limitation (e.g. t and d for topography and drainage). See list of Subclass symbols in Table 2. Land suitability units (subdivisions of Subclasses) may also be used to indicate minor differences in management.1

Land zoning

Land evaluation provides crucial information of soil suitability of certain plot in given topographical and climatic conditions of particular area. Land zoning instead provides a way of differentiating the water needs irrigated crops require to grow in optimal way within uniform landscape conditions (soil and topography).

Land zoning is bound to land classification which means classification of land categories (soil and topography) that have the same features for irrigation use. Generally speaking, land class indicates the general capability of land to accept irrigation. Land zone within a land class is alike or nearly alike in its potential to sustain crops in response to a similar level of management.

In the context of irrigation management, the goal of land classification and zoning is to map an area to classify the land according to its suitability to irrigation, especially the hydrological properties of soil. The usual classification provides the following: 1. An inventory of land characteristics 2. The extent and degree of suitability of land for irrigation 3. Indicates relative capability for sustained production under irrigation 4. Identities potential problems that may occur with irrigation 5. Facilitates making recommendations for appropriate management under irrigation 6. Facilitates optimal land resource utilization 7. Indirectly provides an economic assessment, that is, justify the expenditure on irrigating land2

1 FAO 1976 2 Ali M. H., 2010. Fundamentals of Irrigation and On-Farm Water Management, Tom 1. Springer Verlag.




Land classification provides the means of making logical choices between alternative forms of development. In some countries and/or provinces, land classification is a mandatory requirement for irrigation activities.

2.1.2 Atmosphere. Weather as driving force for calculating irrigation needs

The two main factors that control the processes that convert liquid water molecules to vapor are the supply of energy to provide the latent heat of vaporization and the ability to transport the vapour away from the water surface. Direct solar radiation and, to a lesser extent, the ambient temperature of the air are the main source of heat energy. The transport of water vapour depends on the wind velocity and the humidity gradient in the air. Thus, solar radiation, air temperature, air humidity and wind speed are the climatological parameters that affect the evaporation process (Chow et al., 1988; Allen et al., 1998, Shuttleworth, 2007).

When vapor transport is not limited, evaporation can be computed from the energy balance (Chow et al., 1988; Allen et al., 1998):

λEr = Rn - H - G

where λEr is the latent heat flux, Rn is the net radiation flux, H is the sensible heat flux to the air and G is the heat flux to the ground, which can all be expressed in MJ/m2 per day.

The latent heat of vaporisation of water (λ) is a function of the temperature:

λ = 2.501 – 0.002361 T

The units for λ are MJ/kg. Thus the energy input into a 1-m2 surface evaporates 1 mm water, assuming a water density of 1000 kg/m3 (or 1 kg / (m2 × mm).

When energy supply is not limited, evaporation can be described by the aerodynamic method. Evaporation can be computed by coupling the equations for vapor (mass) and momentum flux in the air (Chow et al., 1988):

E� �0.622kρau2

pρw�ln��z2/z0��e� � e��

where Ea is the evaporation rate, related to aerodynamics (mm/d), k is the von Karman constant, ρa and ρw are the density of air and water, respectively (kg/m3), u2 is the wind velocity at height 2 (above the surface) (m/s), es and ea are the actual vapor pressure and the saturated vapor pressure, respectively (kPA), p is the air pressure, z0 is the roughness height and z2 is elevation 2 (m).

These two equations were combined by Penman in the well-known Penman equation for open water evaporation (Craig, 2006):

γ+∆

−+γ+

γ+∆

−∆=λ

)ee)(u536.01(43.6)GR(E as2n

where ∆ is the slope of the saturated air vapor pressure temperature curve (kPa/⁰C) and γ is the psychrometric constant (kPa/⁰C).

Evapotranspiration is a combination of evaporation from a bare soil surface and transpiration from plants. Evaporation and transpiration can often not be unlinked, as water evaporates both directly from the soil and indirectly through uptake by plant roots and subsequent transpiration. As plants develop, the surface area becomes more and more shaded and evapotranspiration moves from an evaporation-dominant process towards a transpiration-dominant process.

Transpiration refers to water loss from a bounded surface, e.g., plants or humans. The presence of a bounded surface implies that a resistance must be overcome for water loss to occur. In plants the resistance to transpiration is controlled by stomatal aperture. Transpiration is controlled by the climatological parameters mentioned above, as well as the crop characteristics, environmental aspects and management practices.

An evaluation of methods for estimating evapotranspiration was included in the ASCE manual published by Jensen et al. (1990). Similar to the conclusions of Jensen et al. (1990), a 1990 expert consultation recommended the use of the Penman-Monteith method for estimating reference evapotranspiration. The guidelines for the use of the Penman-Monteith method for computing crop evapotranspiration were subsequently published as FAO Irrigation and Drainage Paper 56, commonly referred to as FAO-56, by Allen et al (1998). These authors selected a hypothetical crop with a height of 0.12 m, a surface resistance of 70 s/m and an albedo of 0.23 as reference surface, for the basis of the computations. The hypothetical crop resembles an extensive surface of healthy green grass of uniform height, actively growing, completely shading the ground and not short of water. Thus, reference




evapotranspiration is fully determined by atmospheric conditions. The resulting, so-called FAO-56 Penman-Monteith equation (Allen et al. 1998) is given as:

)u34.01(

)ee(u273T

900)GR(408.0

ET2

as2n

o+γ+∆

−+

γ+−∆=

where ETo is reference evapotranspiration (mm day-1), ∆ is the slope vapour pressure curve (kPa ⁰C-1), Rn is the net radiation at the crop surface (MJ m-2 day-1), G is the soil heat flux density (MJ m-2 day-1), T is the daily mean air temperature (⁰C), u2 is the wind speed at 2-m height (m s-1), es is the saturation vapour pressure (kPa), ea is the actual vapour pressure (kPa) and γ is the psychometric constant (kPa ⁰C-

1).

A disadvantage of the PM-FAO56 method is that it requires temperature, relative humidity, wind speed and radiation data, some of which are difficult or expensive to obtain and requiring regular maintenance. Allen et al. (1998) provide procedures for using PM-FAO56 with missing climatic data. A number of studies have also found good performance of the Hargreaves method in semi-arid environments (e.g., Droogers and Allen, 2002; Martinez-Cob and Tejero-Juste, 2004; Lopez-Urrea et al., 2006; Benli et al., 2010), although under- or overestimations have been found under non average wind speed and humidity conditions.

The Hargreaves equation requires minimum and maximum temperature only (Hargreaves and Samani, 1985) and is expressed as follows:

a

5.0

minmaxmeano R)TT)(8.17T(0023.0ET −+=

where Tmean is the daily mean air temperature (⁰C), Tmax is the daily maximum air temperature (⁰C), Tmin is the daily minimum air temperature (⁰C) and Ra is the extraterrestrial radiation (mm/d).

An important issue for the computation of evapotranspiration from meteorological observations is the accurate measurement of these variables. Methods for assessing the integrity of measured weather data have been presented by Allen (1996) and Allen et al. (1998).

2.1.3 Plant. Growth factors and water needs.

The upper limit of crop production is determined by climatic conditions and the genetic potential of the crop (Doorenbos and Kassam, 1979). To reach this upper limit sufficient water need to be available for the crop. Crop evapotranspiration under standard conditions is defined as the evapotranspiration from healthy, well-fertilized crops, grown in large fields and achieving full production (Allen et al., 1998). The amount of water that needs to be supplied to compensate the evapotranspiration loss of the field is the crop water requirement. Thus, crop evapotranspiration is a loss and crop water requirement a supply. The irrigation water requirement is the difference between the crop water requirements and effective precipitation, and includes additional water needs for leaching and irrigation in-efficiencies. Effective precipitation is that part of the precipitation that does not runoff from the soil surface or leaches below the root zone.

Whereas reference evapotranspiration indicates the effect of climate on the water requirements of the reference crop, the water requirements of different crops (or cultivars) depend not only on climate, but also on crop characteristics; notably the type of crop and its growth stage.

The relationship between the reference evapotranspiration and crop evapotranspiration is expressed by crop coefficients. These coefficients represent the crop characteristics and the growth stage. The computation of crop evapotranspiration is expressed as follows (Allen et al., 1998):

ETc = Kc ETo

where ETc is the crop evapotranspiration (mm) and Kc is a crop coefficient.

This equation represents crop evapotranspiration under standard conditions, meaning well managed, irrigated fields with healthy crops. In case of adverse growth conditions (salinity, low fertility, water logging, dense soil layers, pests or diseases) or low soil moisture levels, the Kc is adjusted with stress coefficients.

Thus, the crop coefficient presents the characteristics of the crop, as it differs from the hypothetical reference crop. These characteristics are:

The albedo (reflectance) of the crop-soil surface, which influences the net radiation of the surface (Rn), which is the primary source of the energy exchange for the evaporation process.




The crop height, which influences the aerodynamic resistance (ra), in the Penman-Monteith equation and the turbulent transfer of vapor from the crop into the atmosphere.

The canopy resistance, which depends on the leaf area (number of stomata), leaf age and condition, and degree of stomatal control, and contributes to the surface resistance (rs).

Canopy cover, which affects the evaporation from the soil.

The surface resistance (rs) in the Penman-Monteith equation is a combination of the canopy resistance and the soil resistance. The soil resistance depends on the canopy cover and wetness of the soil.

The changing characteristics of the crop during the growing season, as opposed to the constant appearance and complete groundcover of the grass reference, is captured by four development stages and three crop coefficients, as illustrated in Figure 1. These crop stages can be described as follows (Doorenbos and Pruitt, 1984; Allen et al., 1998):

The initial stage runs from planting to approximately 10% ground cover. The leaf area is small and soil evaporation is the dominant process.

The crop development stage runs from the end of the initial stage to effective full ground cover (ground cover 70-80%). For many crops the initiation of flowering can be considered the start of full cover.

The mid-season stage runs from the attainment of effective full ground cover to the start of maturity (as indicated by discolouring or falling off of leaves). This stage is generally the longest, except for crops that are harvested fresh for their green vegetation. During full cover (mid-season), soil evaporation is small, and the crop coefficient mainly reflects differences in the transpiration.

The late-season stage runs from the end of mid-season until full senescence, harvest or leaf drop.

During the development and the late season period the crop coefficients are determined by linear interpolation.

Figure 11. Crop development stages and crop coefficients (Bos et al., 2009).

Typical values of the crop coefficients of common agricultural crops have been listed by Allen et al. (1998; p.110-114). The value of Kc ini should be selected as a function of the soil wetting interval and reference evaporation. For climates that differ from standard, sub-humid conditions, i.e., average minimum relative humidity (RHmin) of 45% and calm to moderate wind speeds (2 m/s), Kc mid should be adjusted as follows:

Kc = Kc + [(0.04 (u2 – 2) – 0.004 (RHmin - 45)] (h/3)0.3

where RHmin is the daily minimum relative humidity, h is the mean plant height (m), and all other parameters are as defined previously.




Allen et al. (1998) also provide a table (p.104-108) with general lengths of growing stages for common agricultural crops, planting seasons, and climates or locations. These published growth-stage lengths should be used as guidance. However, agricultural research or extensions staff or farmers may be able to come up with average stage lengths for the crops in their region based on their experience. Crop development is, of course, affected by the actual climatic conditions. Thus, for on-farm irrigation decision making, growth-stage lengths should be adjusted based on field observations during the season.

Many crop models (e.g., Steduto et al., 2009) compute crop development as a function of growing degree days (thermal time). However, this will also require adjustments of coefficients based on local observations.

2.2 Water for irrigation.

2.2.1 Sources and use of water in Irrigation

In agriculture, water is managed for the production of crops for food, fiber, fuel, and oils and for fisheries and livestock husbandry. In generating outputs, agricultural producers aim to meet their specific livelihood objectives. Water is only one input to production, and its relative importance and the way it is managed vary by agricultural system. The impacts of water uses for agriculture are far-reaching because water management draws heavily on natural and human resource bases.

Agriculture is a major user of water resources, requiring one hundred times more than is used for personal needs. Up to 70 % of the water we take from rivers and groundwater goes into irrigation, about 10% is used in domestic applications and 20% in industry. Globally, about 3800 km3 of freshwater are withdrawn for human use. Of these, roughly half is really consumed as a result of evaporation, incorporation into crops and transpiration from crops. The other half recharges groundwater or surface flows or is lost in unproductive evaporation. (FAO 2012).

Agricultural water management systems rely on several sources, including rainfall, groundwater, water withdrawals from surface water, and water that is used and then recycled. Agriculture uses water through evapotranspiration (transpiration by plants and evaporation from soils). A distinction can be made between the withdrawal of water from rivers, reservoirs, lakes, and aquifers and the direct use of rainwater stored in the soil. Water from rivers, reservoirs, lakes, and aquifers are sometimes called blue water, and the direct use of rainwater stored in the soil green water. (Molden 2007).

There is a range of options for using blue and green water for crop production. Pure rainfed agriculture uses only green water. Practices to upgrade rainfed agriculture supplement rainwater with blue water. Irrigation uses blue water in addition to green water to maintain adequate soil moisture levels, allowing crops to fulfill their yield potential. Blue water is the measured and managed freshwater resource that is also used to meet domestic, industrial, and hydropower demands and that sustains aquatic ecosystems in rivers and lakes (UN 2006).

Globally, about 80% of agricultural evapotranspiration is directly from green water, with the rest from blue water sources. The implications of green and blue water use are quite different. Increased evapotranspiration from blue water sources reduces stream flow and groundwater levels. Increased evapotranspiration from green water sources is usually due to expansion of agricultural land area, a terrestrial impact, but has less impact on blue water flows. Still, any change in land use can affect river flows.

The net evapotranspiration from irrigation is 1,600 cubic kilometers, while the remainder of the 7,000 cubic kilometers used is directly from rain. About 1,000 cubic kilometers (25%–30%) of the 3,800 cubic kilometers withdrawn originate from groundwater, mostly for drinking water and irrigation. (FAO 2012).

Irrigation is the artificial application of water to the soil for growth of plants. Sources of irrigation water can be surface water withdrawn from rivers, lakes or reservoirs, groundwater extracted from springs or by using wells, or non-conventional sources like treated wastewater, desalinated water or drainage water. Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and sub-surface seepage. Sometimes water from natural ponds are used. However, many natural ponds have slow recharge capacity even though storage capacity allows pumping rate higher than recharge.

Diversion from streams and rivers is by gravity flow or pumping. Streams particularly have often low flows when irrigation water is needed most. Diversion from lakes, ponds, reservoirs gravity flow or pumping, and a source of water need for replenishing according to the rate and duration of diversion. Sub-surface water, or groundwater, is fresh water located in the pore space of soil and rocks. It is also water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction between sub-surface water that is closely associated with surface water and deep sub-surface water in an aquifer (sometimes called "fossil water").




Treated wastewater is water that has been used for domestic or industrial purposes and was subsequently treated in order to return it to a water course or for further use. There are numerous processes that can be used to clean up waste waters depending on the type and extent of contamination. Most wastewater is treated in industrial-scale wastewater treatment plants which may include physical, chemical and biological treatment processes.

Desalination is an artificial process by which saline water (generally sea water) is converted to fresh water. The most common desalination processes are distillation and reverse osmosis. Desalination is currently expensive compared to most alternative sources of water, and only a very small fraction of total human use is satisfied by desalination. It is only economically practical for high-valued uses in arid areas.

The availability of the water sources are gradually changing. Climate change could affect water supply and agriculture through changes in the seasonal timing of rainfall and snow pack melt, as well as higher incidence and severity of floods and droughts. The Intergovernmental Panel on Climate Change projects shifts and variability in hydrological regimes resulting from climate change. For agriculture this implies changes in the seasonal timing of rainfall and snow pack melt and the higher incidence and severity of floods and droughts.

2.2.2 Water quality

This section deals with the quality of water used for irrigation and not with the effects of agriculture activities to surface and ground waters.

From the environmental and economical point of view, the quality of irrigation water plays a major role since it influences the: • Choice of the ideal crop • Amount of fertilizers needed • Irrigation techniques • Soil properties

The choice of the ideal chemical composition of irrigation water has therefore to be integrated in a decisional process which considers all the mentioned aspects. In particular the pedological properties (chemical composition, pH, granulometry, porosity, ecc.) play a major role.

Chemical quality

Waters naturally contain nutrients that are essential for plant growth: • Macronutrients: nitrogen, phosphorus, potassium, calcium, magnesium and sulphur • Micronutrients: Fe, Mn, B, Cu, Mo, Zn and Si. These elements are needed at low concentrations,

otherwise they become toxic for plants and environment However, usually concentrations of macronutrients are not high enough to satisfy the crop needs and it becomes therefore necessary to add fertilizers. Furthermore, their concentration and availability may naturally change during the year, as it is the case e.g. for nitrate.

At the same time other natural or artificial substances are unwanted in irrigation water, mainly if present at high concentrations. These substances are e.g. sodium, boron, hydrocarbons and heavy metals. The most common and damaging effects of poor-quality irrigation water are excessive accumulation of highly soluble salts in soil (in particular sodium). These salts make soil moisture more difficult for plants to extract ,and crops become water stressed even when the soil is moist.

The degree to which sodium is damaging to soil is strongly influenced by the amounts of calcium and magnesium present. To classify irrigation waters according to this principle the sodium adsorption ratio (SAR) may be used.

According to the classification proposed by the Oklahoma State University 6 quality classes may be defined: excellent, good, fair, poor, very poor and unsuitable. In this classification irrigation waters are categorized on the basis of their sodium percentage and electrical conductivity (Figure 12).




Figure 12. Diagram for classifying irrigation water in Oklahoma (Division of Agricultural Sciences and Natural Resources, Oklahoma State University). SAR = sodium adsorption ratio.

To improve the water quality, the only solution which seems to be effective from the technical

and economical point of view is to remove sodium from the exchange complex by adding correctives. If the water’s sodium percentage is high, gypsum (CaSO4) can be used periodically as a corrective to remedy the problem. The exchange reaction removes sodium from the colloids and from the carbonates forming sodium salts.

Microbiological quality

In many countries poor-quality irrigation water still stems from (partially) treated sewage sludge, containing therefore pathogens such as E. coli or Enterococcus, as well as organic pollutants, and heavy metals. These pathogens are problematic from both the hygienic (infection risk) and technical (biofouling of sprinkler) point of view. In other countries, e.g. in Switzerland in 2008, the use of domestic sewage sludge in agriculture has been forbidden. Often sludge stemming from farmhouses is excluded from this ban.

Water treatment for irrigation purposes

The unsatisfactory quality of irrigation water may be imputed to the presence of toxic chemicals or pathogens. Their elimination may be performed using ad hoc treatments, either artificial (flocculation, acidification, mineralization, ecc.) or natural (infiltration, phytodepuration), maybe coupled with contemporary addition of fertilizers or plant protection products. Another solution would be the dilution of this water with higher-quality water in order to meet the quality targets (chemical and bacteriological) established for irrigation.

Protecting water quality

As for drinking water, sources of irrigation water have to be protected from the qualitative and quantitative point of view. This means that human activity has to be limited or even excluded, when approaching the sources (springs, wells, reservoirs, lakes or rivers). Water conservation

Water quality may be altered during its conservation e.g. storage in artificial reservoirs. In regions with high agriculture pressure or sewage discharge, reservoirs may be affected by eutrophication, showing unwanted effects such as algal blooms, anoxic hypolimnion, presence of toxic reduced substances (NH3/NH4+, NO2-, H2S, CH4).

2.2.3 Water Conservation and harvesting

Water harvesting




Water harvesting is the collection and storage of surface water during the off-season, when rainfall and stream flows are high. Water harvesting for irrigation becomes necessary when rainfall does not meet crop needs.

Rainfall is unevenly distributed over the crop-growing season and often comes with high intensity. As a result, rainfall in this environment cannot support economical dryland farming. In the Mediterranean areas, rain usually comes in sporadic, unpredictable storms and is mostly lost in evaporation and runoff, leaving frequent dry periods during the crop growing season. Part of the rain returns to the atmosphere, directly from the soil surface by evaporation after it falls, and part flows as surface runoff, usually joins streams and flows to swamps or to “salt sinks”, where it loses quality and evaporates; a small portion joins groundwater. The overall result is that most of the rainwater in the drier environments is lost with no benefits and/or productivity (Oweis et al., 1999).

Water harvesting in agriculture is based on the principle of depriving part of the land of its share of rainwater and adding it to the share of another part. This brings the amount of water available to the target area closer to the crop water requirements so that economical agricultural production can be achieved and thus improving the water productivity. Thus water harvesting may be defined as "the process of concentrating precipitation through runoff and storing it for beneficial use" (Oweis and Hachum 2004).

A water harvesting system has the following three components: - A catchment area that is part of the land that contributes some or all its share of rainwater to another area outside its boundaries. - A storage facility which is a place where runoff water is held from the time it is collected until it is used. Storage can be in surface reservoirs, subsurface reservoirs such as cisterns, in the soil profile as soil moisture, and in groundwater aquifers. - A target area which is where the harvested water is used. In agricultural production, the target is the plant or the animal, while in domestic use.

One way to expand irrigation capability is to build reservoirs that are not on primary drainage basins but are located off-stream, either on smaller drainage basins or on other land with terrain suitable for building water storage facilities.

An example of this is a case where a large creek or stream flows by a farm, and a drainage basin leading into that creek has a site that would hold enough water to irrigate the farm if a dam were built across it. This drainage basin need not be able to fill the reservoir on its own. Water can be pumped from the large creek or stream into the reservoir during the winter and spring, filling it and saving the water for summer use.

If no suitable off-stream drainage basin that can be dammed in the traditional way to provide storage for an adequate quantity of water, a non-traditional type of reservoir would be used, such as a hillside reservoir where an earth embankment is constructed on two or three sides, or in a curved shape, to hold the desired amount of water. Water can be pumped from the nearby stream in winter and spring to fill the reservoir. Some recharge from natural drainage can be expected, depending on site topography, but this is likely to be slight. Sometimes water is also stored in circular or four-sided reservoir built on essentially flat land. This is the most expensive reservoir to build and would depend entirely on pumping from the nearby stream, as there would be practically no natural recharge. Water conservation

Water conservation refers reduction of water losses, waste or use. Water conservation in irrigation can be achieved by efficient transport and efficient application of irrigation water or irrigation scheduling.

Transport of irrigation water from the source of supply to the irrigated field via open canals and laterals can be a source of water loss if the canals and laterals are not lined. Water is also transported through the lower ends of canals and laterals because of the flow-through requirements to maintain water levels in them. In many soils, unlined canals and laterals lose water via seepage in bottom and side walls. Seepage water either moves into the ground water through infiltration or forms wet areas near the canal or lateral. This water will carry with it any soluble pollutants in the soil, thereby creating the potential for pollution of ground or surface water.

Irrigation scheduling is the use of water management strategies to prevent over-application of water while minimizing yield loss due to water shortage or drought stress. Irrigation scheduling will ensure that water is applied to the crop when needed and in the amount needed. Effective scheduling requires knowledge of the following factors (Evans et al., 1991a): - Soil properties; - Soil-water relationships and status; - Type of crop and its sensitivity to drought stress; - The stage of crop development;




- The status of crop stress; - The potential yield reduction if the crop remains in a stressed condition; - Availability of a water supply; and - Climatic factors such as rainfall and temperature. There are three ways to determine when irrigation is needed (Evans et al., 1991b): - Measuring soil water; - Estimating soil water using an accounting approach; and - Measuring crop stress.

Most important is the determination of the amount of water to apply. Irrigation needs are a function of the soil water depletion volume in the effective root zone, the rate at which the crop uses water, and climatic factors. Accurate measurements of the amount of water applied are essential to maximizing irrigation efficiency. The quantity of water applied can be measured by such devices as a totalizing flow meter that is installed in the delivery pipe. If water is supplied by ditch or canal, weirs or flumes in the ditch can be used to measure the rate of flow.

Photograph 1. Large sprinkler system

Deep percolation can be greatly reduced by limiting the amount of applied water to the amount that can be stored in the plant root zone.

Reducing overall water use in irrigation will allow more water for stream flow control and will increase flow for diversion to marshes, wetlands, or other environmental uses. If the source is ground water, reducing overall use will maintain higher ground-water levels, which could be important for maintaining base flow in nearby streams.

Surface irrigation systems are usually designed to have a percentage (up to 30 percent) of the applied water lost as tailwater. This tailwater should be managed with a tailwater recovery system. Tailwater recovery systems usually include a system of ditches or berms to direct water from the end of the field to a small storage structure. Tailwater is stored until it can be either pumped back to the head end of the field and reused or delivered to additional irrigated land. In some locations, there may be downstream water rights that are dependent upon tailwater, or tailwater may be used to maintain flow in streams.

Well-designed and managed irrigation systems remove runoff and leachate efficiently; control deep percolation; and minimize erosion from applied water, thereby reducing adverse impacts on surface water and ground water. If a tailwater recovery system is used, it should be designed to allow storm runoff to flow through the system without damage. Additional surface drainage structures such as filter strips, field drainage ditches, subsurface drains, and water table control may also be used to control runoff and leachate if site conditions warrant their use. Sprinkler systems will usually require design and installation of a system to remove and manage storm runoff.




A properly designed and operated sprinkler irrigation system should have a uniform distribution pattern. The volume of water applied can be changed by changing the total time the sprinkler runs; by changing the pressure at which the sprinkler operates; or, in the case of a center pivot, by adjusting the speed of travel of the system. There should be no irrigation runoff or tailwater from most well-designed and well-operated sprinkler systems.

The type of irrigation system used will dictate which practices can be employed to improve water use efficiency and to obtain the most benefit from scheduling. Flood systems will generally infiltrate more water at the upper end of the field than at the lower end because water is applied to the upper end of the field first and remains on that portion of the field longer. This will cause the upper end of the field to have greater deep percolation losses than the lower end.

2.2.4 Water productivity in irrigation management

Water productivity is defined as the ratio of the net benefits from crop, forestry, fishery, livestock, and mixed agricultural systems to the amount of water required to produce those benefits. In its broadest sense it reflects the objectives of producing more food, income, livelihoods, and ecological benefits at less social and environmental cost per unit of water used, where water use means either water delivered to a use or depleted by a use. Put simply, it means growing more food or gaining more benefits with less water. Physical water productivity is defined as the ratio of the mass of agricultural output to the amount of water used, and economic productivity is defined as the value derived per unit of water used. Water productivity is also sometimes measured specifically for crops (crop water productivity) and livestock (livestock water productivity).

Crop water productivity (CWP) in essence represents the output of a given activity to the water input. In the agricultural field, people are concerned how to produce more grains with less water input, to meet the growing food demand and ensure food security. Thus, the ratio of crop marketable yield to the practical evapotranspiration during the phenophase can be defined as the crop water productivity, as (Sander et al., 2004):

Where CWP is the crop water productivity (kg/m3), CY is the yield of this crop(kg/ha); Eta is the practical evapotranspiration during the phenophase;10 is a conversion coefficient.

2.3 Irrigation systems.

Various types of irrigation techniques differ in how the water obtained from the source is distributed within the field. In general, the goal is to supply the entire field uniformly with water, so that each plant has the amount of water it needs, neither too much nor too little. The modern methods are efficient enough to achieve this goal. Surface Irrigation

In surface irrigation systems, water moves over and across the land by simple gravity flow in order to wet it and to infiltrate into the soil. Surface irrigation can be subdivided into furrow, borderstrip or basin irrigation. It is often called flood irrigation when the irrigation results in flooding or near flooding of the cultivated land. Historically, this has been the most common method of irrigating agricultural land. Where water levels from the irrigation source permit, the levels are controlled by dikes, usually plugged by soil. This is often seen in terraced rice fields (rice paddies), where the method is used to flood or control the level of water in each distinct field. In some cases, the water is pumped, or lifted by human or animal power to the level of the land.




Localized Irrigation

Photograph 2. Brass Impact type sprinkler head1

Localized irrigation is a system where water is distributed under low pressure through a piped

network, in a pre-determined pattern, and applied as a small discharge to each plant or adjacent to it. Drip irrigation, spray or micro-sprinkler irrigation and bubbler irrigation belong to this category of irrigation methods. Drip Irrigation

Photograph 3. Drip Irrigation - A dripper in action1

Photograph 4. Grapes in Petrolina, just possible in this semi arid area due to drip irrigation1.

Drip irrigation, also known as trickle irrigation, functions as its name suggests.In this system

water falls drop by drop just at the position of roots. Water is delivered at or near the root zone of plants, drop by drop. This method can be the most water-efficient method of irrigation, if managed properly, since evaporation and runoff are minimized. In modern agriculture, drip irrigation is often combined with plastic mulch, further reducing evaporation, and is also the means of delivery of fertilizer. The process is known as fertigation.

Figure 13. Drip Irrigation Layout and its parts1

1 WIKIPEDIA




Deep percolation, where water moves below the root zone, can occur if a drip system is operated for too long or if the delivery rate is too high. Drip irrigation methods range from very high-tech and computerized to low-tech and labor-intensive. Lower water pressures are usually needed than for most other types of systems, with the exception of low energy center pivot systems and surface irrigation systems, and the system can be designed for uniformity throughout a field or for precise water delivery to individual plants in a landscape containing a mix of plant species. Although it is difficult to regulate pressure on steep slopes, pressure compensating emitters are available, so the field does not have to be level. High-tech solutions involve precisely calibrated emitters located along lines of tubing that extend from a computerized set of valves. Sprinkler Irrigation

Photograph 5. Sprinkler irrigation of blueberries in Plainville, New York, United States.1

In sprinkler or overhead irrigation, water is piped to one or more central locations within the field

and distributed by overhead high-pressure sprinklers or guns. A system utilizing sprinklers, sprays, or guns mounted overhead on permanently installed risers is often referred to as a solid-set irrigation system. Higher pressure sprinklers that rotate are called rotors and are driven by a ball drive, gear drive, or impact mechanism. Rotors can be designed to rotate in a full or partial circle. Guns are similar to rotors, except that they generally operate at very high pressures of 40 to 130 lbf/in² (275 to 900 kPa) and flows of 50 to 1200 US gal/min (3 to 76 L/s), usually with nozzle diameters in the range of 0.5 to 1.9 inches (10 to 50 mm). Guns are used not only for irrigation, but also for industrial applications such as dust suppression and logging.

Photograph 6. A traveling sprinkler at Millets Farm Centre, Oxfordshire, United Kingdom1

Sprinklers can also be mounted on moving platforms connected to the water source by a hose.

Automatically moving wheeled systems known as traveling sprinklers may irrigate areas such as small farms, sports fields, parks, pastures, and cemeteries unattended. Most of these utilize a length of polyethylene tubing wound on a steel drum. As the tubing is wound on the drum powered by the irrigation water or a small gas engine, the sprinkler is pulled across the field. When the sprinkler arrives back at the reel the system shuts off. This type of system is known to most people as a "waterreel" traveling irrigation sprinkler and they are used extensively for dust suppression, irrigation, and land application of waste water. Other travelers use a flat rubber hose that is dragged along behind while the sprinkler platform is pulled by a cable. These cable-type travelers are definitely old technology and their use is limited in today's modern irrigation projects. Center pivot Main article: Center pivot irrigation

1 WIKIPEDIA: http://en.wikipedia.org/wiki/Irrigation




Photograph 7. A small center pivot system from beginning to end1

Photograph 8. The hub of a center-pivot irrigation system1

Photograph 9. Rotator style pivot applicator sprinkler1

Center pivot irrigation is a form of sprinkler irrigation consisting of several segments of pipe

(usually galvanized steel or aluminum) joined together and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length. The system moves in a circular pattern and is fed with water from the pivot point at the center of the arc. These systems are found and used in all parts of the world and allow irrigation of all types of terrain. Newer systems have drop sprinkler heads as shown in the image that follows.

Photograph 10. Center pivot with drop sprinklers. Photo by Gene Alexander, USDA Natural Resources Conservation Service1

Most center pivot systems now have drops hanging from a u-shaped pipe attached at the top of

the pipe with sprinkler heads that are positioned a few feet (at most) above the crop, thus limiting evaporative losses. Drops can also be used with drag hoses or bubblers that deposit the water directly on the ground between crops. Crops are often planted in a circle to conform to the center pivot. This type of system is known as LEPA (Low Energy Precision Application). Originally, most center pivots were water powered. These were replaced by hydraulic systems (T-L Irrigation) and electric motor driven systems (Reinke, Valley, Zimmatic). Many modern pivots feature GPS devices.





Photograph 11. Wheel line irrigation system in Idaho. 2001. Photo by Joel McNee, USDA Natural Resources Conservation Service1

Lateral move (side roll, wheel line)

A series of pipes, each with a wheel of about 1.5 m diameter permanently affixed to its midpoint and sprinklers along its length, are coupled together at one edge of a field. Water is supplied at one end using a large hose. After sufficient water has been applied, the hose is removed and the remaining assembly rotated either by hand or with a purpose-built mechanism, so that the sprinklers move 10 m across the field. The hose is reconnected. The process is repeated until the opposite edge of the field is reached. This system is less expensive to install than a center pivot, but much more labor intensive to operate, and it is limited in the amount of water it can carry. Most systems utilize 4 or 5-inch (130 mm) diameter aluminum pipe. One feature of a lateral move system is that it consists of sections that can be easily disconnected. They are most often used for small or oddly shaped fields, such as those found in hilly or mountainous regions, or in regions where labor is inexpensive. Sub-irrigation

Subirrigation has been used for many years in field crops in areas with high water tables. It is a method of artificially raising the water table to allow the soil to be moistened from below the plants' root zone. Often those systems are located on permanent grasslands in lowlands or river valleys and

combined with drainage infrastructure. A system of pumping stations, canals, weirs and gates allows it to increase or decrease the water level in a network of ditches and thereby control the water table.

Sub-irrigation is also used in commercial greenhouse production, usually for potted plants. Water is delivered from below, absorbed upwards, and the excess collected for recycling. Typically, a solution of water and nutrients floods a container or flows through a trough for a short period of time, 10–20 minutes, and is then pumped back into a holding tank for reuse. Sub-irrigation in greenhouses requires fairly sophisticated, expensive equipment and management. Advantages are water and nutrient conservation, and labor-saving through lowered system maintenance and automation. It is similar in principle and action to subsurface drip irrigation. Manual using buckets or watering cans

These systems have low requirements for infrastructure and technical equipment but need high labor inputs. Irrigation using watering cans is to be found for example in peri-urban agriculture around large cities in some African countries. Automatic, non-electric using buckets and ropes

Besides the common manual watering by bucket, an automated, natural version of this also exist. Using plain polyester ropes combined with a prepared ground mixture can be used to water plants from a vessel filled with water.

The ground mixture would need to be made depending on the plant itself, yet would mostly consist of black potting soil, vermiculite and perlite. This system would (with certain crops) allow to save expenses as it does not consume any electricity and only little water (unlike sprinklers, water timers, ...). However, it may only be used with certain crops (probably mostly larger crops that do not need a humid environment; perhaps e.g. paprikas). Using water condensed from humid air

In countries where at night, humid air sweeps the countryside, water can be obtained from the humid air by condensation onto cold surfaces. This is for example practiced in the vineyards at Lanzarote using stones to condense water or with various fog collectors based on canvas or foil sheets.1





Each of the mentioned irrigation systems has its own characteristics of the efficiency of water delivery to plant, generating various water losses (tab. 3)

Table 3. Expected water losses on spray irrigation systems(Edkins E., 2006)

Source of loss Range Typical

Open races 0-30% 10%

Leaking pipes 0-10% <1%

Evapotranspiration in the air 0-10% <3%

Blown away by wind 0-20% <5%

Watering non-target areas 0-5% <2%

Interception by plants 0-3% <2%

Surface runoff 0-10% <2%

Uneven application 5-30% 15%

Excessive application depth 0-50% 10%

3. MODELLING ECONOMIC OPTIMIZATION OF

IRRIGATION

Irrigation as a high cost consuming process must be optimized. Optimization may have different goals – targeting yield or income maximalization. In free market conditions the goal of a farmer is to maximize income. Farmer’s income for a crop yield per hectare could be written as:

( ) cwPPwyI wy −−=

Where: I – income [€/ha], y(w) – crop yield function [t/ha] dependent on depth of water (w) applied for irrigation, Py – crop yield price [€/t], w – applied water [m3/ha], Pw – price of water [€/m3], c – other costs [€/ha] not dependent upon applied water (constant cost of irrigation and other cultivation costs).

The request of finding the amount of applied irrigation water for which income is maximal could be solved mathematically by finding the amount of water (wopt) for which first derivative of income function (I) is equal to zero and second derivative is negative. Of course it is simple only for some easy cases. Good example could be a simplified situation when the reaction of yield on the amount of water applied for irrigation is expressed in an averaged way for the whole cultivation season. In such way the yield function is similar to parabola and could be written as a quadratic function:

( ) 0;0;0;2 >><++= γβαγβα wwwy

and solution of extremum condition:

0=∂

∂

w

I

gives optimal amount of irrigation water (English 1990; English, Raja 1996):




y

w

y

w

optP

Pw

P

Pw

ααα

β

2

1

2

1

2max +=+−=

Result is presented in graphical way on below figure where it can be seen that optimal amount of water for irrigation is smaller than amount of water for which yield is maximal.

The reason for this kind of distribution comes from the fact that income is a difference between

value of production (yield multiplied by crop price) and costs.

In ENORASIS project function of yield will be dependent on water stress calculated with use of FAO56 model (Allen et al 1998). The literature many forms of such yield functions are considered, but most of them are a variant of the multiplier model (Jensen 1968):

( )( )

k

kNk

i

ci

Nk

i

ai

ET

wET

ywy

λ

∏∑

∑=

=

=

=4

1

1

1max

Where k is crop growth stage (the same which is used in FAO56 model), ETa is actual crop

ewapotranspiration dependent on amount water used for irrigation, ETc crop ewapotranspiration without water stress and λk is coefficient of crop yield sensitivity to water deficits dependent on crop growth stage. Examples of crop yield sensitivity coefficient designated for crops cultivated in Greece Chalkidiki region (Georgiou, Papamichail, Vougioukas 2006) are collected in table 1:

crop Coefficient of crop yield sensitivity λ Length of k period Nk (days) k=1 k=2 k=3 k=4 k=1 k=2 k=3 k=4

corn 0,35 1,82 0,44 0,17 40 25 45 15 cotton 0,17 0,44 0,35 0,21 30 60 30 20 tomato 0,35 1,13 0,75 0,35 20 25 25 20 watermelon 0,39 0,75 0,75 0,26 25 20 30 20 olive 0,17 0,26 0,44 0,35 30 30 60 30 apricot 0,08 0,30 0,44 0,08 30 30 60 30

[€]

wmax wopt

value of production: (αw2+βw+γ)P

cost: wP +c

w (applied




Multiplicative Jensen model unlike the additional models has the advantage that it reflects a strong destructive effect of short period water deficits which in additive models are averaged to whole cultivation period.

Because crop growth stages have different length, summation of ewapotranspiration in different stages is done for different numbers of days or other short periods Nk. In ENORASIS project the suggested length of such period is 5 days because this is also meteorological forecast horizon. On that basis problem of income maximalization is solved for each 5 days time period inside growth stages as it is showed on example below:

Calculations of each model parameters (values of actual and potential ewapotranspiration) before such period will be based on past data registered by sensors and meteorological stations, and within the target 5 days forecast period calculations will be performed with use of metereological forecast information. For the calculation of the future values an assumption can be made, that irrigation fully reduces water deficits so future ratio of sums ETa and ETc will be equal to one. In such case the income can be written as:

cwPP

ET

ETwETET

ET

ET

yIwyNq

i

ci

Nq

ji

ciaj

j

i

aiq

kNq

i

ci

Nq

i

ai

qq

−−

++

=

+

∑

∑∑∏

∑

∑+

=

+

=

−

=

=

=

=

1

1

1

11

1

1

1

1max

)(

λλ

where c is sum of all fixed costs and variable cost before and after actual j period.

In agreement with FAO56 model actual ewapotranspiration ETa equals:

−−

−+−

+==

))(1(

1,0

;0max;1min)()(

exp0exp

0WPCFp

WPr

wKcETPVSM

ETwKsKcETwET ca

where VSM is last measured volumetric soil moisture, FC is field capacity and WP wilting point of soil moisture – all expressed in % of soil volume. Variable r is a crop rooting depth expressed in mm and coefficient p is a depletion factor defining average fraction of total soil available water in root zone which can be depleted by crop without evapotranspiration and yield reduction. For calculation of the expected values of precipitation Pexp and evapotranspiration ET0exp meteorological forecast will be used. Such calculation basing on a forecast with 5 days horizon for precipitation (and analogously for other meteorological data) could be based on formula:

( )∑=

−−− +++=5

1

302020101000exp ...25155l

lPP ρρρ

time

k=1 k=2 k=3 k=4 Kc

5

N1 days N3 days N2 days N4 days




where: P0 is probability of rain event in selected day and ρ values are conditional probability of precipitation in selected range or alternatively described by parameters commonly used precipitation probability distribution (Weibull, gamma, etc).

Important feature considered formula for evapotranspiration is that amount irrigation water higher than:

( )( )expexp0max ))(1(10 PKcETVSMWPFCpWPrw −+−−−+=

is lost on the deep percolation way and have no effect on evapotranspiration and yield. This means that we could reduce problem of seeking optimal solution to consider only increasing part of water stress function and limit from the top founded solution for amount of needed irrigation water w. For this case income function could be rewritten in simplified but equivalent way which hides structure of factors independent on amount of irrigation water w used in j period:

( ) cwPPgwfeyI wy −−+=γ

max

where: e, f, g are factors independent on w value. Solution such equation is easier and could be written as:

+−=

−γγ 1

1

max1

w

y

optP

Pegyf

gw

This formula with further discussed top limitation (and lower limit if cost of activating irrigation

system is high) is practical economical optimization algorithm which could be used for irrigation scheduling. Alternatives described in literature are more complicated because are using dynamic programming optimization software for solve full no simplified problem (Kipkorir et al 2001).

Illustration of situation analogical to simple model described on the beginning this chapter is showed below:

From graphical analysis we can see that only when value coefficient of crop yield sensitivity is

smaller than one - optimal water irrigation amount wopt is smaller than maximal value wmax. It is consistent in common knowledge because coefficients of yield sensitivity as it can be seen in table 1 are close or higher than one only in mid crop development phases and in this period optimal solution is always irrigation with maximal value wmax.

value of [€]

w (applied water)

γ<1

γ>1

γ=1

costs

wopt wmax




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• English, M., Raja, S.N., 1996. Perspectives on deficit irrigation. Agr. Water Manage. 32, 1–14.




• Georgiou P.E., Papamichail D. M., Vougioukas S. G., 2006: Optimal irrigation reservoir operation and simultaneous multi-crop cultivation area selection using simulated annealing, Irrig. and Drain. 55: 129–144.

• Jensen M.E., 1968: Water consumption by agricultural plants. In Water Deficits and Plants Growth, vol. II, Kozlowski TT (ed.). Academic Press: New York; 1–22.

• Kipkorir E.C., D. Raes D., Labadie J., 2001: Optimal allocation of short-term irrigation supply Irrigation and Drainage Systems 15: 247–267.

ANNEXES

Model Repository

Table 4. ENORASIS Model Repository. Model names and scope

Model's name Scope

FAO56/CROPWAT Procedure for calculating crop water requirements based on Penman-Monteith

method as a standard for reference potential evapotranspiration and empirical crop

coefficients for including influence of crop individual characteristics in each

development stage on actual evapotranspiration. Irrigation is recommended before or

at the moment when calculated from water balance equation readily available water

in root zone is depleted. Irrigation amount is equal to readily available water capacity

of root zone. According to computational simplicity, large number of studies and wide documentation crop coefficients for different plants in various climatic

conditions around the world FAO56 model is a commonly accepted standard for

irrigation purposes. All algorithms of FAO56 were implemented in developed by

FAO model CROPWAT. Additionally CROPWAT provide various user-defined

options for water supply and irrigation management conditions.

APSIM Agricultural Production Systems Simulator (APSIM). Decision Support System for

farm management. Paddock (field) based. It contains two modules related to

irrigation: Water Supply, Irrigation Management. IM contains following setup

variables (example values in quotations): waterBalanceModule

".MasterPM.paddock1.Soil Water" paddockArea "20.0" dam_module

".masterpm.dam" irrigate_module ".masterpm.paddock1.Irrigation1"

irrigate_threshold "30" [% of ASW] irrigate_efficiency "0.8" Requires detailed soil

information.

SWAP PSWAP (Soil, Water, Atmosphere and Plant) simulates transport of water, solutes

and heat in unsaturated/saturated soils. The model is designed to simulate flow and transport processes at field scale level, during growing seasons and for long term

time series. It offers a wide range of possibilities to address both research and

practical questions in the field of agriculture, water management and environmental

protection. Published, typical examples are given by Van Dam et al. (2008) for: field

scale water and salinity management. Irrigation scheduling, Transient drainage

conditions, Plant growth affected by water and salinity, Pesticide leaching to ground

water and surface water, Regional drainage from top soils towards different surface

water systems, Optimization of surface water management, effects of soil

heterogeneity SWAP also serves to generate soil water fluxes for pesticide and

nutrient models. The model can be used to explore new flow and transport concepts

for agro- and ecohydrology and on the analysis of laboratory and field experiments.

Dripper Uniformity Calculator This calculator page is used to generate maps of dripper application rates over an

irrigation block. This should help irrigators with their understanding of variations in crop water use. To calculate maps of variations in crop water use over a block, three

sets of information are needed. They are: Block Information - information about

the block such as row spacing, emitter spacing and vine spacing Block Corners - a

list of geo coordinates (from a GPS) marking the corners of the block Flow-rate

Points - measurements, in ml/min for as many points in the block as possible




Model's name Scope

CropSyst CropSyst is a is a user-friendly, conceptually simple but sound multi-year multi-crop

daily time step simulation model. The model has been developed to serve as an

analytic tool to study the effect of cropping systems management on productivity and

the environment. The model simulates the soil water budget, soil-plant nitrogen

budget, crop canopy and root growth, dry matter production, yield, residue

production and decomposition, and erosion. Management options include: cultivar

selection, crop rotation (including fallow years), irrigation, nitrogen fertilization,

tillage operations (over 80 options), and residue management.

SUCROS SUCROS1&2 is a mechanistic crop growth model as influenced by environmental

conditions. SUCROS2 simulates both potential and water limited growth of a crop,

i.e. its dry matter accumulation under resp. ample and rainfed supply of water and nutrients in a pest-, disease- and weed-free environment under the prevailing weather

conditions.

GECROS GECROS (Genotype-by-Environment interaction on CROp growth Simulator) model

uses robust, yet simple algorithms to summarize the current knowledge of individual

physiological processes and their interactions and feedback mechanisms. Main

attention has been paid to interactive aspects in crop growth such as photosynthesis-

transpiration coupling via stomatal conductance, carbon-nitrogen interaction on leaf

area index, functional balance between shoot and root activities, and interplay

between source supply and sink demand on reserve formation and remobilization.

LINTUL 1-6 LINTUL1 simulates potential growth of a crop, i.e. its dry matter accumulation under

ample supply of water and nutrients in a pest-, disease- and weed-free environment,

under the prevailing weather conditions. The rate of dry matter accumulation is a

function of irradiation and crop characteristics. Further versions (2-6) include simple

simulation algorithms of water and nutrient influence on the crop growth.

WOFOST WOFOST is a model that can simulate the growth of any annual crop at any location.

To facilitate this, the crop, soil and weather parameters and data are stored in separate

data files. Production analyses and yield forecasting at the regional, national and

continental scales can easily be done by doing simulation runs for combinations of

soil, crop and weather types representative for the studied area. The crop growth

simulation approach is similar to that in the SUCROS model.

CGMS 9.2 GMS is implemented in C and designed to run crop models over a spatial domain,

therefore CGMS integrates other functionality such as the ability to interpolate

weather data over the spatial domain. All I/O in CGMS is implemented through a

database which makes batch runs (many locations and years) easy. Moreover this

database facilitates efficient data management.

GEPIC GIS-based EPIC model (GEPIC) is a agroecosystem model using EPIC model

(Environmental Policy Integrated Climate) code in spatial form based on ArcGIS

software.

SEBAL The Surface Energy Balance Algorithm for Land (SEBAL) is a actual

evapotranspiration model based on meteorological data (wind speed, air temperature,

solar radiation, humidity), NDVI index and land surface temperature derived from

satellite imaginery. Spatial distribution of actual evapotranspiration indicate crop

water stress conditions and could be incorporated to irrigation sheduling process.

WRF The Weather Research and Forecasting (WRF) Model is a next-generation mesoscale

numerical weather prediction system designed to serve both operational forecasting

and atmospheric research needs. It features multiple dynamical cores, a 3-

dimensional variational (3DVAR) data assimilation system, and a software

architecture allowing for computational parallelism and system extensibility. WRF is

suitable for a broad spectrum of applications across scales ranging from meters to

thousands of kilometers.

SIRMOD The irrigation model SIRMOD simulates the hydraulics of surface irrigation (border,

furrow and basin) at the field scale. The principle role of SIRMOD is the evaluation

of alternative field layouts (field length and slope) and management practices (water

application rates and cut-off times).




Model's name Scope

CropWat Calculation of crop water requirements and irrigation requirements based on soil,

climate and crop data. In addition, the program allows the development of irrigation

schedules for different management conditions and the calculation of scheme water

supply for varying crop patterns. CROPWAT 8.0 can also be used to evaluate

farmers’ irrigation practices and to estimate crop performance under both rainfed and

irrigated conditions.

AquaCrop AquaCrop is a crop water productivity model developed by the Land and Water

Division of FAO. It simulates yield response to water of herbaceous crops, and is

particularly suited to address conditions where water is a key limiting factor in crop

production.

h.interception estimation of canopy interception

Table 5. ENORASIS Model Inventory. Models' references.

Model's name References

FAO56/CROPWAT General references: for FAO56: 1) Allen, R.G., Pereira, L.S., Raes, D., Smith, M.,

1998. Crop Evapotranspiration-Guidelines for Computing Crop Water Requirements,

Irrigation and Drain, Paper No. 56. FAO, Rome, Italy, 300 pp. 2) Allen, R.G., 2000.

Using the FAO-56 dual crop coefficient method over an irrigated region as part of an

evapotranspiration intercomparison study. J. Hydrol. 229, 27–41. 3) Allen, R.G., Pereira, L.S., Smith, M., Raes, D., Wright, J.L., 2005a. FAO-56 dual crop coefficient

method for estimating evaporation from soil and application extensions. J. Irrig.

Drain Eng. ASCE 131 (1), 2–13. 4) Doorenbos, J., and Pruitt, W. O. (1977). “Crop

water requirements.” Irrigation and Drainage Paper No. 24, (rev.) FAO, Rome. 5)

Lorite IJ, Mateos L, Fereres E (2004a) Evaluating irrigation performance in a

Mediterranean environment. I. Model and general assessment of an irrigation

scheme. Irrig Sci 23:77–84. 6) Lorite IJ, Mateos L, Fereres E (2004b) Evaluating

irrigation performance in a Mediterranean environment. II. Variability among crops

and farmers. Irrig Sci 23:85–92. 7) Fortes, P.S., Platonov, A.E., Pereira, L.S., 2005.

GISAREG – a GIS based irrigation scheduling simulation model to support improved

water use. Agricultural Water Management 77, 159–179. for CROPWAT: 8) FAO

1993. CLIMWAT for CROPWAT, a climatic database for irrigation planning and management by M. Smith. FAO Irrigation and Drainage Paper No. 49. Rome. 9)

FAO. 1992. CROPWAT, a computer program for irrigation planning and

management by M. Smith. FAO Irrigation and Drainage Paper No. 46. Rome. 10)

Clarke D, Smith M, El-Askari K, 1998. CropWat for Windows: User Guide.

Southampton: University of Southampton, 1–43. Examples of regional references:

11) Marrakech, MOROCCO: Er-Raki, S., Chehbouni, G., Guemouria, N., Duchemin,

B., Ezzahar, J., Hadria, R., 2007. Combining FAO-56 model and ground-based

remote sensing to estimate water consumptions of wheat crops in a semi-arid region.

Agric. Water Manage. 87, 41–54. 12) Marrakech, MOROCCO: Er-Raki, S.,

Chehbouni, A., Duchemin, B., 2010. Combining satellite remote sensing data with

the FAO-56 dual approach for water use mapping in irrigated wheat fields of a semi

arid region. Remote Sens. 2 (1), 375–387. 13) POLAND: Łopatka A., Stuczyński T.:

Zastosowanie modelu FAO56 do oszacowania spadku plonów wywołanego suszą na

terenie Polski. Roczniki Gleboznawcze, 2008, Tom LIX Nr 2: 154-161. 14)

Andalusia, SPAIN: Santos C., Lorite I.J., Tasumi M., Allen R.G., Fereres E., 2007.

Integrating satellite-based evapotranspiration with simulation models for irrigation

management at the scheme level. Irrig Sci (2008) 26:277–288. 15) Beijing-Tianjin-

Hebei Region, CHINA: Feng Z., Liu D., Zhang Y., Water Requirements and

Irrigation Scheduling of Spring Maize Using GIS and CropWat Model in Beijing-

Tianjin-Hebei Region. Chinese Geographical Science 2007 17(1) 056–063. 16)

Texas, USA; Henan, CHINA: Simulation of winter wheat evapotranspiration in

Texas and Henan using three models of differing complexity. Agricultural Water

Management 96 (2009) 167–178. 17) PERU: Ertsen M.W., van der Spek J., Modeling an irrigation ditch opens up the world. Hydrology and hydraulics of an

ancient irrigation system in Peru. Physics and Chemistry of the Earth 34 (2009) 176–

191. 18) Harran Plain, TURKEY: Ozdogan M., Woodcock C.E., Salvucci G.D.,

Demir H., Changes in Summer Irrigated Crop Area and Water Use in Southeastern

Turkey from 1993 to 2002: Implications for Current and Future Water Resources.




Water Resources Management (2006) 20: 467–488. 19) Craiova and Alexandria,

ROMANIA: Stancalie G., Marica A., Toulios L., Using earth observation data and CROPWAT model to estimate the actual crop evapotranspiration. Physics and

Chemistry of the Earth 35 (2010) 25–30. 20) TAIWAN: Kuo S-F., Ho S-S., Liu Ch-

W., Estimation irrigation water requirements with derived crop coefficients for

upland and paddy crops in ChiaNan Irrigation Association, Taiwan. Agricultural

Water Management 82 (2006) 433–451. 21) Lake Alemaia, ETHIOPIA: S.G. Setegn,

V. M. Chowdary, B. C. Mal, F. Yohannes, Y. Kono, Water Balance Study and

Irrigation Strategies for Sustainable Management of a Tropical Ethiopian Lake: A

Case Study of Lake Alemaya. Water Resour Manage (2011) 25:2081–2107. 22) The

Quinto Basin, ITALY: P. Mollema, M. Antonellini, G. Gabbianelli, M. Laghi, V.

Marconi, A. Minchio, Climate and water budget change of a Mediterranean coastal

watershed, Ravenna, Italy. Environ Earth Sci (2012) 65:257–276. 23) Upper East Region, GHANA: M.V. Mdemu, C. Rodgers, P.L.G. Vlek, J.J. Borgadi, Water

productivity (WP) in reservoir irrigated schemes in the upper east region (UER) of

Ghana. Physics and Chemistry of the Earth 34 (2009) 324–328. 24) Agro-ecological

region 12.0, INDIA: G. Kar, H.N. Verma, Climatic water balance, probable rainfall,

rice crop water requirements and cold periods in AER 12.0 in India. Agricultural

Water Management 72 (2005) 15–32. 25) Central-western POLAND: L. Martyniak,

K. Dabrowska-Zielinska, R. Szymczyk, M. Gruszczynska, Validation of satellite-

derived soil-vegetation indices for prognosis of spring cereals yield reduction under

drought conditions – Case study from central-western Poland. Advances in Space

Research 39 (2007) 67–72. 26) Makanaya catchment, TANZANIA: J. Mutiro, H.

Makurira, A. Senzanje, M.L. Mul, Water productivity analysis for smallholder

rainfed systems: A case study of Makanya catchment, Tanzania. Physics and

Chemistry of the Earth 31 (2006) 901–909. 27) Southern IRAN: A. M. Hassanli, S.

Ahmadirad, S. Beecham, Evaluation of the influence of irrigation methods and water

quality on sugar beet yield and water use efficiency. Agricultural Water Management

97 (2010) 357–362.

APSIM 373 publications: http://www.apsim.info/Wiki/Publications.ashx, including 17

addressing irrigation.

SWAP Van Dam, J.C., P. Groenendijk, R.F.A. Hendriks and J.G. Kroes, 2008. Advances of

modeling water flow in variably saturated soils with SWAP. Vadose Zone J., Vol.7,

No.2, May 2008. Van Dam, J.C., 2000. Field-scale water flow and solute transport.

SWAP model concepts, parameter estimation, and case studies. PhD-thesis,

Wageningen University, Wageningen, The Netherlands, 167 p., English and Dutch

summaries Singh, R., J.G. Kroes, J.C. van Dam, and R.A. Feddes. 2006. Distributed

ecohydrological modelling to evaluate the irrigation system performance in Sirsa district. I. Current water management and its productivity. J. Hydrol. 329: 692-713.

Singh, R., R.K. Jhorar, J.C. van Dam, and R.A. Feddes. 2006. Distributed

ecohydrological modelling to evaluate the irrigation system performance in Sirsa

district. II. Impact of alternative water management scenarios. J. Hydrol. 329: 714-

723. Dam, J.C. van, R. Singh, J.J.E. Bessembinder, P.A. Leffelaar, W.G.M.

Bastiaanssen, R.K. Jhorar, J.G. Kroes, and P. Droogers, 2006. Assessing options to

increase water productivity in irrigated river basins using remote sensing and

modeling tools. Water Res. Development 22: 115-133. Bastiaanssen, W.G.M., R.G.

Allen, P. Droogers, G.D’Urso and P. Steduto, 2007. Twenty-five years modeling

irrigated and drained soils: state of the art. Agric. Water Manage. 92: 111-125.

Vazifedoust, M., J.C. van Dam, R.A. Feddes and M. Feizi, 2008. Increasing water

productivity of irrigated crops under limited water supply at field scale. Agric. Water Manage., 95, 89-102

Dripper Uniformity Calculator

CropSyst CropSyst has been applied to several crops (corn, wheat, barley, soybean, sorghum,

and lupins) and regions (Western US, Southern France, Northern and Southern Italy,

Northern Syria, Northern Spain, and Western Australia), generally with good results

and also a few problems (e.g. Donatelli et al., 1996), particularly for applications to

conditions not simulated by the model (for example, water balance of cracking

vertisols).

SUCROS http://www.csa.wur.nl/NR/rdonlyres/2F7C121F-6748-437A-9651-

D1750B91876A/8546/sucrostext.pdf Rabbinge R., S.A. Ward & H.H. van Laar




(editors), 1989. Simulation and systems management incrop protection. Pudoc.

Simulation Monographs; 32, 420 pp. Keulen, H. van & G.W.J. van de Ven, 1988. Applicaton of interactive multiple goal linearprogramming techniques for analysis

and planning of regional agricultural development: a case studyfor the mariut region

(Egypt). In: Agriculture. Socio-economic factors in land evaluation.Proceedings of a

conference held in Brussels 7 to 9 October 1987. 36-57 Rossing, W.A.H., 1993. On

damage, uncertainty and risk in supervised control: aphids and brown rustin winter

wheat as an example. PhD thesis, Wageningen Agricultural University. 201 pp. Laar,

H.H. van, J. Goudriaan & H. van Keulen (editors), 1992. Simulation of crop growth

for potentialand water-limited production situations, as applied to spring wheat.

Simulation Reports 27, 72 pp.

GECROS

LINTUL 1-6

WOFOST http://www.wofost.wur.nl/UK/documentation/ Included in the Crop Growth

Monitoring System (CGMS) as Crop monitoring by simulation component.

CGMS 9.2 http://www.marsop.info/marsopdoc/cgms92/references_en.htm

GEPIC 1) World: Liu, J., Williams, J.R., Zehnder, A.J.B., Yang, H., 2007b. GEPIC –

modelling wheat yield and crop water productivity with high resolution on a global

scale. Agricultural Systems 94 (2), 478–493. 2) China: Liu, J., Wiberg, D., Zehnder,

A.J.B., Yang, H., 2007a. Modelling the role of irrigation in winter wheat yield, crop

water productivity, and production in China. Irrigation Science 26 (1), 21–33. 3) Sub-

Saharan Africa: Liu J., Fritz S., van Wesenbeeck C.F.A., Fuchs M., Obersteiner M.,

Yang H., 2008. A spatial explicit assessment of current and future hotspots of hunger

in Sub-Saharan Africa in the context of global change. Global and Planetary

Change.64 (3-4) 222-235.

SEBAL General: 1) Bastiaanssen, W.G.M., M. Menenti, R.A. Feddes, A.A.M. Holtslag. A

remote sensing surface energy balance algorithm for land (SEBAL): 1) Formulation.

Journal of Hydrology 1998, 212 (213):213-229. 2)Bastiaanssen, W.G.M., M.

Menenti, R.A. Feddes, and A.A.M. Holtslag; 1998b; The Surface Energy Balance

Algorithm for Land (SEBAL): Part 2 validation, J. Hydrology , 212-213: 213-229. 3) Bastiaanssen, W.G.M., E.J.M. Noordman, H. Pelgrum, G. Davids, B.P. Thoreson and

R.G. Allen. SEBALmodel with remotely sensed data to improve water resources

management under actual field conditions. Journal of irrigation and drainage

engineering 2005, 131 (1):85-93. Regional: 4) Turkey: Bastiaanssen, W.G.M.

SEBAL-based sensible and latent heat fluxes in the irrigated Gediz Basin, Turkey.

Journal of Hydrology 2000, 229:87-100. 5) Sri Lanka: Bastiaanssen, W.G.M.,

Bandara, K.M.P.S., 2001. Evaporative depletion assessments for irrigated watersheds

in Sri Lanka. Irrig. Sci. 21 (1), 1–15. 6) Brazil: Bastiaansssen, W.G.M., Brito,

R.A.L., Bos, M.G., Souza, R.A., Cavalcanti, E.B., Bakker, M.M., 2001. Low cost

satellite data for monthly irrigation performance monitoring: benchmarks from Nilo

Coelho, Brazil. Irrig. Drain. Syst. 15, 53–79. 7) India: Bastiaanssen, W.G.M., Ahmed, M.-ud-D., Chemin, Y., 2002. Sattellite surveillance of evaporative depletion

across the Indus Basin. Water Resour. Res. 38, 1273–1282.

WRF http://www.wrf-model.org/wrfadmin/publications.php

SIRMOD National irrigation plan, Burundi, http://nip.burundi.gov

CropWat All calculation procedures used in CROPWAT 8.0 are based on the two FAO publications of the Irrigation and Drainage Series, namely, No. 56 "Crop

Evapotranspiration - Guidelines for computing crop water requirements” and No. 33

titled "Yield response to water".

AquaCrop AquaCrop results from the revision of the FAO Irrigation and Drainage Paper No. 33

“Yield Response to Water” (Doorenbos and Kassam, 1979), a key reference for

estimating the yield response to water. AquaCrop evolves from the fundamental

equation of Paper No. 33, where relative yield (Y) loss is proportional to relative

evapotranspiration (ET) decline, with Ky as the yield response proportional factor.

h.interception Cannata M., Brovelli M. A. and Salvetti A.,2005, Hydrological Modelling Using

Free and Open Source Software, International Journal of GeoInformatics, Special

Issue of the FOSS/GRASS & GIS-IDEAS 2004, Vol.1, N. 1, ISSN 1686-6576, pp.

21-32.




Table 6. ENORASIS Model Repository. Models' webpages.

Model's name Link to the model's webpages

FAO56/CROPW

AT

FAO56 documentation: http://www.fao.org/docrep/X0490E/X0490E00.htm FAO56 source code:

http://www.fao.org/docrep/X0490E/x0490e0p.htm#annex 8. calculation example for applying the

dual kc procedure in irrigation sc CROPWAT official web page:

http://www.fao.org/nr/water/infores_databases_cropwat.html

APSIM http://www.apsim.info/Wiki/

SWAP http://www.swap.alterra.nl/

Dripper Uniformity

Calculator

http://www.irrigateway.net/tools/du/Calculator.aspx

CropSyst http://www.bsyse.wsu.edu/CS_Suite/CropSyst/index.html

SUCROS FORTRAN code

GECROS http://www.csa.wur.nl/UK/Downloads/Gecros/?wbc_purpose=Basic&WBCMODE=PresentationUnpublished

LINTUL 1-6 http://www.csa.wur.nl/UK/Downloads/LINTUL/?wbc_purpose=Basic&WBCMODE=Presentatio

nUnpublished

WOFOST http://www.wofost.wur.nl/UK/ http://www.wofost.wur.nl/UK/documentation/

CGMS 9.2 http://www.marsop.info/marsopdoc/cgms92/index_en.htm download:

ftp://mars.jrc.ec.europa.eu/CGMS/

GEPIC http://www.eawag.ch/forschung/siam/software/gepic/index_EN

SEBAL no model webpage

WRF http://www.wrf-model.org/index.php

http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/contents.html

SIRMOD http://irrigation.usu.edu/htm/software/sirmod/

CropWat http://www.fao.org/nr/water/infores_databases_cropwat.html

AquaCrop http://www.fao.org/nr/water/infores_databases_aquacrop.html

h.interception http://svn.osgeo.org/grass/grass-addons/grass6/HydroFOSS/r.interception/description.html




Table 7. ENORASIS Model Repository. Model features.

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X APSIM X X X X X X

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X CropSyst X X X X X

X SUCROS X X X X X X X

X GECROS X X X X X

X LINTUL 1-6 X X X X X

X WOFOST X X X X

X CGMS 9.2 X X X X X

X GEPIC X X X X X X X X X X

X SEBAL X X X X

X WRF X X X

X X SIRMOD X X X X

X CropWat X X X X

X AquaCrop X X X

X h.interception X X X




Model documentations

The FAO56 and CROPWAT model documentation

Software Name FAO56/CROPWAT

Software Description

Short Description Procedure for calculating crop water requirements based on Penman-Monteith method as a standard for reference potential evapotranspiration and empirical crop coefficients for including influence of crop individual characteristics in each development stage on actual evapotranspiration. Irrigation is recommended before or at the moment when calculated from water balance equation readily available water in root zone is depleted. Irrigation amount is equal to readily available water capacity of root zone.

According to computational simplicity, large number of studies and wide documentation crop coefficients for different plants in various climatic conditions around the world FAO56 model is a commonly accepted standard for irrigation purposes.

All algorithms of FAO56 were implemented in developed by FAO model CROPWAT. Additionally CROPWAT provide various user-defined options for water supply and irrigation management conditions.

Category Irrigation optimization model

General Use / Goal / Aim Computing crop water requirements in different climatic conditions, applicable for all crops around the world

Owner for CROPWAT: Food and Agriculture Organization (FAO)

Operating System for CROPWAT: Windows platforms: 95/98/ME/2000/NT/XP and Vista

Programming Language / Compiler

for FAO56: Microsoft Excel spreadsheet formulas

for CROPWAT: Visual Delphi 4.0

Auxiliary Programmes CLIMWAT 2.0 for CROPWAT – climatic database to be used with combination with CROPWAT model, offers observed agroclimatic data of over 5000 stations worldwide distributed and long term monthly means of seven main climatic parameters. http://www.fao.org/nr/water/infores_databases_climwat.html

Supported open standards can be easily adopted to all popular open source spreadsheet software like OpenOffice Calc

Current Version for FAO56: not applicable

for CROPWAT: 8.0

Update Frequency for FAO56: not applicable




for CROPWAT: version 8.0 (2007); version 7.0 (1999)

Type of License for FAO56: not applicable

for CROPWAT: freeware, no free code

References for FAO56: 1) Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop Evapotranspiration-

Guidelines for Computing Crop Water Requirements, Irrigation and Drain, Paper No.

56. FAO, Rome, Italy, 300 pp.

2) Allen, R.G., 2000. Using the FAO-56 dual crop coefficient method over an irrigated

region as part of an evapotranspiration intercomparison study. J. Hydrol. 229, 27–41.

3) Allen, R.G., Pereira, L.S., Smith, M., Raes, D., Wright, J.L., 2005a. FAO-56 dual crop

coefficient method for estimating evaporation from soil and application extensions. J.

Irrig. Drain Eng. ASCE 131 (1), 2–13.

4) Doorenbos, J., and Pruitt, W. O. (1977). “Crop water requirements.” Irrigation and

Drainage Paper No. 24, (rev.) FAO, Rome.

5) Er-Raki, S., Chehbouni, G., Guemouria, N., Duchemin, B., Ezzahar, J., Hadria, R.,

2007. Combining FAO-56 model and ground-based remote sensing to estimate water

consumptions of wheat crops in a semi-arid region. Agric. Water Manage. 87, 41–54.

6) Er-Raki, S., Chehbouni, A., Duchemin, B., 2010. Combining satellite remote sensing

data with the FAO-56 dual approach for water use mapping in irrigated wheat fields of

a semi arid region. Remote Sens. 2 (1), 375–387.

7) Lorite IJ, Mateos L, Fereres E (2004a) Evaluating irrigation performance in a

Mediterranean environment. I. Model and general assessment of an irrigation scheme.

Irrig Sci 23:77–84.

8) Lorite IJ, Mateos L, Fereres E (2004b) Evaluating irrigation performance in a

Mediterranean environment. II. Variability among crops and farmers. Irrig Sci 23:85–92.

9) Fortes, P.S., Platonov, A.E., Pereira, L.S., 2005. GISAREG – a GIS based irrigation

scheduling simulation model to support improved water use. Agricultural Water

Management 77, 159–179.

10) Łopatka A., Stuczyński T.: Zastosowanie modelu FAO56 do oszacowania spadku

plonów wywołanego suszą na terenie Polski. Roczniki Gleboznawcze, 2008, Tom LIX

Nr 2: 154-161.

for CROPWAT:

11) FAO 1993. CLIMWAT for CROPWAT, a climatic database for irrigation planning and

management by M. Smith. FAO Irrigation and Drainage Paper No. 49. Rome.

12) FAO. 1992. CROPWAT, a computer program for irrigation planning and management

by M. Smith. FAO Irrigation and Drainage Paper No. 46. Rome.

13) Clarke D, Smith M, El-Askari K, 1998. CropWat for Windows: User Guide.

Southampton: University of Southampton, 1–43.

Link(s) FAO56 documentation: http://www.fao.org/docrep/X0490E/X0490E00.htm FAO56 source code: http://www.fao.org/docrep/X0490E/x0490e0p.htm#annex 8. calculation example for applying the dual kc procedure in irrigation sc CROPWAT official web page: http://www.fao.org/nr/water/infores_databases_cropwat.html

Contact Person for FAO56: Richard G. Allen - Utah State University; Logan, Utah, USA Luis S. Pereira -Instituto Superior de Agronomia; Lisbon, Portugal Dirk Raes - Katholieke Universiteit Leuven; Leuven, Belgium Martin Smith - Water Resources, Development and Management Service FAO

for CROPWAT:

CROPWAT 8.0 has been developed by Joss Swennenhuis for the Water Resources Development and Management Service of FAO.

[email protected]

Main Features




Meteorological forecast not applicable

Remote sensing tool not applicable

Evapotranspiration calculation Actual evapotranspiration ETa calculated as a product of: potential evapotranspiration ET0 (recommended calculation by Penman-Monteith method or in case of meteorological data scarcity by Hargreaves method), crop coefficient Kc dependent on plant type and development stage, Ks factor defining reduction of evapotranspiration in soil water stress conditions.

Land zoning no restricted - user can define soil by enter soil parameters: total soil available water and initial soil water depletion (also maximum rooting depth and rain infiltration rate for CROPWAT)

Complete crop irrigation needs'

estimation

based on calculation of readily available water amount in crop root zone and assumption that irrigation amount should be equal to readily available water capacity of root zone if readily available water is depleted

Plant water needs water consumed by crop equal actual evapotranspiration

Plant growth modelling done by assumption of typical development pattern of selected crop or empirical local observation of crop development stage

Plant condition estimation no direct measurement of water deficit - estimation based on water balance calculation but measurement of soil moisture can be easily introduced as a correction to calculation procedure

A fully operational integrated

DSS irrigation system

no

Other for CROPWAT: no import data options, import data possible only by replacing data in ASCI files used by program

Input data characteristics

Number of input variables Recommended: 14

Minimal: 10 – precipitation, minimum and maximum air temperature, latitude, altitude, crop coefficient, depletion fraction, max root depth, wilting point, field capacity

Input data precipitation (+irrigation) [mm] (0;100) real number

Spatial and temporal extents no restrictions

Spatial and temporal resolution day

Crop or irrigation method specific no

Input data minimum air temperature [0C] (-50;50) real number







Input data maximum air temperature [0C] (-50;50) real number




Input data average vapour pressure [kPa] (0;10) real number

(could be replaced by minimum and maximum relative humidity, mean relative humidity or by dewpoint temperature)




Input data latitude [decimal degrees] (-90;90) real number


Spatial and temporal resolution no restrictions


Input data solar radiation [MJ m-2 day-1] (0;40) real number

(could be estimated from duration of bright sunshine or from minimum and maximum air temperature)




Input data wind speed [m s-1] (0;50) real number




Input data altitude above sea level [m] (-300;6000) integer number


Spatial and temporal resolution no restrictions


Input data crop coefficient Kc [no unit] (0;1.4) real number





Spatial and temporal resolution day, decade, month

Crop or irrigation method specific crop specific

Input data maximum root depth [m] (0;10) real number


Spatial and temporal resolution no applicable

Crop or irrigation method specific crop and soil specific

Input data soil water depletion fraction for no stress [no unit] (0;1) real number



Crop or irrigation method specific crop specific

Input data soil water content at wilting point [%] (0;30) real number

(could be assessed from USDA texture class or amount of clay or sand fraction)



Crop or irrigation method specific soil specific

Input data soil water content at field capacity [%] (10;100) real

number

(could be assessed from USDA texture class or amount of clay or sand fraction)



Crop or irrigation method specific soil specific

Input data initial soil moisture [%] (0;100) real number

(assumed equal to field capacity after heavy rain or irrigation)



Crop or irrigation method specific yes

Output data characteristics

Number of output variables 2 main




Output data soil moisture [%] (0;100) real number

(could be also presented as a value of depletion in root zone)




Input data actual evapotranspiration [mm] (0;100) real number




Tutorial and or Sample Data FAO56 documentation: http://www.fao.org/docrep/X0490E/X0490E00.htm Excel calculator with database: http://biomet.ucdavis.edu/irrigation_scheduling/bis/BIS.htm

Crop Coefficients (Kc) values for Mediterranean climate:

http://www.meliaproject.eu/workgroups-area/workgroup.wp2/working-documents/CropCoeff.pdf/view

Crop data for different climatic zones:

http://www.unesco-ihe.org/Project-Activities/Project-Portfolio/Virtual-Water-Trade-Research-Programme/Chapagain-A.K.-and-Hoekstra-A.Y.-2004-.-Water-footprints-of-nations-Volume-2-Appendices-Value-of-Water-Research-Series-No.-16-UNESCO-IHE

CROPWAT example of use:

http://www.fao.org/nr/water/docs/CROPWAT8.0Example.pdf

Community/users links for FAO56: not applicable

for CROPWAT: no forums and community links

The Weather Research and Forecasting (WRF) Model

Software Name Weather Research and Forecasting (WRF) Model


Short Description The Weather Research and Forecasting (WRF) Model is a next-generation mesoscale numerical weather prediction system designed to serve both operational forecasting and atmospheric research needs. It is used at RIUUK to calculate the meteorological fields for air quality forecast

Category Meteorological forecasting model




General Use / Goal / Aim Computing relevant meteorological fields for numerical weather forecast or subsequent applications.

Owner Public domain

Operating System UNIX, LINUX


FORTRAN

Auxiliary Programmes WPS (WRF Pre-processing System), WRFDA (WRF Data Assimilation Tool)

Supported open standards LINUX

Current Version 3.3.1

Update Frequency Version update every 6 month

Type of License Public licence

References Skamarock, W. C., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, W. Wang and J. G. Powers, 2005: A Description of the Advanced Research WRF Version 2, NCAR Technical Note.

Klemp, J. B., W. C. Skamarock, and J. Dudhia, 2007: Conservative split-explicit time integration methods for the compressible nonhydrostatic equations. Mon. Wea. Rev., 2897-2913.

Link(s) http://www.wrf-model.org/index.php

Contact Person Bill Skamarock (lead), NCAR, Stan Benjamin, FSL, Jim Purser, NCEP

Main Features

Meteorological forecast Fully Non hydrostatic model for meteorological forecast

Remote sensing tool not applicable

Evapotranspiration calculation not applicable

Land zoning not applicable

Complete crop irrigation needs' estimation

not applicable

Plant water needs not applicable

Plant growth modelling not applicable

Plant condition estimation not applicable

A fully operational integrated DSS irrigation system

not applicable

Other





Number of input variables Terrestrial input data: 9

NCEP/GFS global analysis and forecast data for initialization: 6 2d vaiables, 5 3d variables

Input data Terrestrial:

soil category [no unit] (1;17) binary

land use category [no unit] (1;25) binary

terrain height [m] (0;10000) binary

annual mean deep-soil temperature [K] (0;10000) binary

monthly vegetation fraction [%] (0;100) binary

monthly albedo [%] (0;100) binary

maximum snow albedo [%] (0;100) binary

slope category [no unit] (0;100) binary

Meteorological:

2D:

Surface Pressure [hPa] (0;1200) binary

Mean Sea Level Pressure [hPa] (0;1200) binary

Skin Temperature [K] (0;500) binary

2-meter Temperature [K] (0;500) binary

2-meter Relative or Specific Humidity [%] (0;500) binary

10-meter U and V components of wind [m/s] (0;500) binary

3D:

Temperature [K] (0;500) binary

U and V components of wind [m/s] (0;500) binary

Geopotential Height [m²/s²] (0;100000) binary

Relative Humidity [%] (0;100) binary

Spatial and temporal extents Urban scale to continental scale 10 - 10000 km , 1 – 5 days

Spatial and temporal resolution 1 - 250 km; 1 h



Number of output variables

Output data 2D:

Surface Pressure [hPa] (0;1200) netcdf

Mean Sea Level Pressure [hPa] (0;1200) netcdf

Ground Temperature [K] (0;500) netcdf

2-meter Temperature [K] (0;500) netcdf




2-meter Relative or Humidity [%] (0;500) netcdf

10-meter U components of wind [m/s] (0;500) netcdf

10-meter V components of wind [m/s] (0;500) netcdf

Precipitation [mm] (0:1000) netcdf

3D:

Temperature [K] (0;500) netcdf

U components of wind [m/s] (0;500) netcdf

V components of wind [m/s] (0;500) netcdf

W components of wind [m/s] (0;500) netcdf

Geopotential Height [m²/s²] (0;100000) netcdf

Basic State Pressure [hPa] (0;10000) netcdf

Pressure Perturbation[hPa] (0;10000) netcdf

Relative Humidity [%] (0;100) netcdf

Spatial and temporal extents Urban scale to continental scale 10 - 10000 km , 1 – 5 days in forecast mode, 1 year in climatological mode

Spatial and temporal resolution 1 - 250 km; 1 h

Crop or irrigation method specific Yes/no, maize only

Tutorial and or Sample Data

Community/users links http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/contents.html

Model Documentation Template

Preface

The existence of documentation guidelines for documenting existing open source irrigation modelling tools does not imply that there are no other ways to explore, classify and certify this software. The suggested guideline provides minimum requirements for the structure and information content for the documentation.

The guidelines outlined in this document are intended to cover as much as possible a balanced interest for the currently available agricultural irrigation modelling tools in the market. For this reason, it is not up to the author to claim that a partly or fully adoption of these guidelines would guarantee a full review of a certain software, it is the task of the person who will carry out the documentation to ensure a well-documented report.

Abbreviations and terminology

When appropriate, the first time an abbreviation is used the expanded version will also be included. A glossary of terms is provided in Appendix B – Glossary.




Technical Guidelines

Software description

Category

The models are divided into four categories: • Meteorological forecasting models • Irrigation optimization models • Spatial Analysis and Modelling Tools • Integrated ready-to use Irrigation DSS

Short description

A description consists of an enumeration of the quantitative and qualitative parameters, which seek to provide a definition of the software or algorithm.

A short summary description for the software should be the start point to document any software. This short abstract will include the general characteristics associated with it.

General use/goal/aim

The more effort required specializing a product, the greater is its generality. A more narrowly focused product will reduce the effort required to deploy it, but may lack flexibility.

This section includes a concise synopsis of the general use, the goal and aim behind the development of this software.

Few elements must be clear within the general use of the software, the objective behind its use, purpose of using it, the type of domain where the particular software is used and the expected results by using it.

Input data

Data required to perform a successful model run, including: variable, units, format, constraints.

Output data

Information returned as model’s output, including: variable, units, format, constraints.

Model’s spatial and temporal resolution

Range of spatial resolution accepted by the model. Accepted frequency of input and output data.

Owner

In the world of open source modelling tools, change of owner or developer or even shared ownership is a common practice. It is important to clarify the software history in order to ensure its credibility.

Operating system

Stating the operating system(s) under which the programme is able to run successfully.

Programming language / Compiler

Exact details of programming language(s) under which the software is developed and/or availability of compiler and its version.

Interoperability

Supported open standards.

Auxiliary programme

List of all auxiliary programmes and/or programme libraries that can be coupled with the software.

Current version

An active open source software project is noticed through the continuous revise of its content, this is traced via its last version update.




The software documentation available on its web site should correspond to the latest released version of the software. The user should be able to trace a clear history of bug fixes, feature changes, etc…

In case applicable, all different variants (derivatives) of the software will be reported.

In order to ensure having the most recent information, the OSS latest version is noted.

Update frequency

In current rapidly changing markets, software needs to respond quickly to changes in customer demand and adapt quickly to changes in technology. This results in a continuous update.

Software update is an essential element in order to show how fast the developers respond to the software shortcomings/bugs or the user needs. An up-to-date OSS is distinguished by a rapid and frequent update.

As community opinion changes as to recommend approach, the documentation should be updated to reflect this change in thinking.

The software update frequency through the software history is traced and summarized.

Type of license

The term license is used to describe the legal way a copyright and patent owner grants permission to others to use his intellectual property. An open source license is the way a copyright and patent owner grants permission to others to use his intellectual property in such a way that software freedom is protected for all.

Any developer/licensor can draft an agreement that conforms to the OSD, though most licensors use existing agreements like GNU, LGPL, Mozilla public license, etc…

The type of license for every documented software will be clearly identified and documented.

References

The documentation will include list of available references this may include universities, consulting companies, governmental agencies, study offices, or any other project or community associated with the documented software.

This clause is optional and not compulsory, depending on reference availability.

Link(s)

The link address to the main developing website must be documented, if not available then a link to the main source of information to be consulted for further enquiry. In addition to links to any related information sources.

Contact person

Name and e-mail of the software project’s main contact person.

Main Features

The software documentation (primarily the User's and the Developer's Guides) should contain a comprehensive overview of the software features. As new features are added to source control, these guides should be updated at the same time and stored in source control.

The different domain(s) where the software belongs will be here further classified, i.e. the software can be associated with one or more than domains.

The suggested domains bound to the management of irrigation in agriculture may be distinguished to following list:

Meteorological prediction models, plant water demand calculators, actual evapotranspiration estimators as well as complete integrated DSS tools.

A summary of the main features associated with every software will be documented. This can be also included in the general checklist (see 7).




Installation

The ease of installation will be checked and summarized under this clause. In case that several steps are needed to fulfil the installation, then it will be described.

In general, two installation levels can be distinguished for every software; basic or advanced.

Software limitation/known issues/errors (if any)

Most of developers are proud of the strong capabilities of their software, yet the software limitation (if exists) is important to be reported. This can save valuable time for the user and can influence his/her final decision of using the software. Documentation shall address all known problems in using the software in sufficient detail such that the user can either recover from the problem or find a workaround awaiting for a final solution.

Getting information about bugs and/or known errors should not be a difficult issue, many software developers devote a special section to receive/view these type of things, this can be also recuperated from the archive of their mailing lists.

A reference to a more detailed error description/solution maybe added here, in addition to the way the end-user may follow in order to find a solution, reporting a problem or suggesting improvements.

Manual / FAQ / Acronyms

Checking the availability of manual associated with the software either online or documented together with its FAQ will be addressed in this clause.

A great deal of the OSS developers will assume that all users can understand the various acronyms spread throughout the documentation! Yet most of the users need a concise acronym with sufficient explanation.

Availability of the acronyms with definitions would be encouraged and would be taken into consideration when documenting OSS.

Community / users links Direct links to websites of users and user communities.

General Remarks & Conclusions

Open source software is arguably more stable and reliable than its closed source equivalent. We need to build on that technical success by fixing open source software issues with documentation. Writing reasonable and useful documentation is not difficult. It entails getting the trust of the users, introducing them to the basics of the software, addressing their concerns and doing a little self-promotion.

Documentation is vitally important if software and systems are to be understood by those not intimately involved in its creation.

Taking into account the huge amount of open source software that are available at the moment of preparing this document and that needs to be documented, this guideline is prepared in such a way to make a balance between the amount of info that needs to be gathered and the ease of use in order to make it easy to compare the documented info for the different software at a later stage.

Appendix A – Example for a documentation table

Software Name




Classification Type


Short Description

Category

General Use / Goal / Aim

Owner

Operating System


Auxiliary Programmes

Supported open standards

Current Version

Update Frequency

Type of License

References

Link(s)

Contact Person

Main Features

Meteorological forecast

Remote sensing tool

Evapotranspiration calculation

Land zoning

Complete crop irrigation needs' estimation

Plant water needs

Plant growth modelling

A fully operational integrated DSS irrigation system

Other


Number of input variables




Input data VARIABLE [unit] (min;max) format

Spatial and temporal extents MIN- MAX m, MIN-MAX h

Spatial and temporal resolution MIN- MAX m; MIN-MAX h



Number of output variables

Output data VARIABLE [unit] (min;max) format

Spatial and temporal extents MIN- MAX m, MIN-MAX h

Spatial and temporal resolution MIN- MAX m; MIN-MAX h


Tutorial and or Sample Data

Community/users links

ENORASIS Deliverables 1.2 v1.3 · Artur Lopatka 3. MODELLING ECONOMIC OPTIMIZATION OF IRRIGATION...

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