Water Productivity in Agriculture: Potential for Improvements

Madar Samad, B. R. Sharma, K. Palanisami and M. Dinesh Kumar

with

OP Singh, Malkit Singh and Chaitali Purohit

Objectives of the Research

The Overall Objective: To analyze the potential for improving the water productivity at different river basins. The specific objectives are:

Opportunities and constraints for improving dry land/rain-fed agriculture

Potential of spreading water saving technologies

Potential and pitfall of rainwater harvesting and decentralized recharge and

Institutional and policy mechanisms and the implications of the growth scenarios on water demand drivers.

Objective I: Opportunities and Constraints for improving rain-fed/dry-land agricultureHypothesis:

For purely rain-fed crops in sufficiently high rainfall areas, proper nutrient management can help enhance yield and water productivity

For dry-land crops, supplementary irrigation and nutrient can help enhance not only yield but also water productivity

Better reliability and adequacy of irrigation can improve yield and water productivity of irrigated crops through better agronomic practices and better water management

Methodology for Analyzing Productivity of Crops with Supplementary IrrigationThe combined water productivity for rain-fed crops with supplementary irrigation would be estimated as:

Average Net Economic Return of crop “k”/ {[ETk - ∆k max] + ∆k average}

Here, ∆k max will be the maximum irrigation applied for a crop. For paddy, the crop water requirement instead of consumptive use (ET) is considered.

Marginal Productivity: Multiple regressions to estimate the differential impact of irrigation and other inputs on combined water productivity. From this, the impact of irrigation and fertilizer inputs on water productivity could be analyzed.

Methodology for Analyzing Water Productivity of Irrigated CropsFarm level water productivity of crop i and farmer j = Yield or Net Return (C ii)/ (∆ ij)

System level water productivity of crop i and farmer j=Yield or Net return ((C ii)/ (ETi)

This is when ∆ ij > ETi; and groundwater table is shallow. When the groundwater is deep or saline, then total applied water would be considered in the denominator for water productivity.

But if ∆ ij < ETi then system level water productivity would be based on the applied water.

If system level water productivity is higher than the farm level water productivity, it means that on farm water management can improve agricultural water management.

Locations Studied

Sabarmati River Basin in Gujarat--21,676 sq. km

Bhawani river basin in Tamil Nadu

Narmada River Basin in Madhya Pradesh--1,00,000 sq. km

Bist Doab Area in Punjab in Indus Basin--10,000 sq. km

Progress

Field studies completed in Sabarmati river basin--6 locations (agro-climatic sub-zones)

Field studies completed in Narmada river basin-9 locations and seven agro-climatic sub—zones

Analysis of average water productivity (spatial, and also crop-wise completed; marginal productivity to be done

Field studies completed and initial analysis and draft paper ready for Palar basin--Climate?

Field studies almost completed in Bist Doab area in Punjab--Two agro climatic zones

Issues being investigated

Analyzing impact of water control on WP: Comparative average water productivity in conjunctive use and well irrigation and also marginal productivity in both (Punjab; Sabarmati)

Analyzing impact of water allocation on water productivity through: 1] comparing green water productivity and combined water productivity in dry land crops; 2] analyzing marginal water productivity of applied water in irrigated crops with irrigation and fertilizer inputs (all basins)

Impact of climatic variations on WP: spatial analysis of water productivity (Sabarmati;

Narmada; Indus; Bhawani) District-wise estimates of average WP of major crops

Some results from Bhawani basin work

Water control has impact on water productivity: well irrigated crop has higher physical productivity and economic efficiency in paddy as compared to those irrigated by system and non-system tanks & canals

Functional analysis of paddy yield shows highest impact of water input on yield, followed by fertilizer and labour

Water productivity in fish and floriculture was also estimated and economic efficiency much higher in these crops.

Marginal productivity analysis is to be done

Studies to be done for different climates

Scope of Water Saving Technologies in Water Productivity Improvements Basic Premise: There are several constraints in the

adoption of water-saving irrigation technologies, while there are opportunities for real or “wet” water saving through technology adoption.

The constraints are due to:

Source-wise irrigated area in different agro-ecological regions; the existing irrigated cropping patterns and systems; power supply restrictions

There are opportunities for water-saving through yield enhancing as well as ET reducing crop technologies

Methodology

The study is based on analysis of secondary data on cropping pattern in some typical river basins; and the data available from both field-based and laboratory research on the impact of WSTs on “applied water” and consumptive use (ET) in conventional irrigation and micro irrigation systems.

The study involves extensive literature review to find out the physical impact of water-saving irrigation and crop technologies on yield, crop consumptive use and “depleted water” in irrigation.

Analytical Procedures

The total water saved through water saving technologies = Ai* [WDi trad –WDi micro].

Where “i” varies from 1 to n; “n” is the number of crops for which MI systems can be used.

In the case of traditional irrigation method, water depleted per unit area (WDi trad) is estimated as =

Total Volume of water applied per unit cropped area + Soil Moisture Depletion in Root Zone – Recharge to Groundwater per unit area.

In the case of micro irrigation, the Total Water Depleted per unit area (WDi micro) is estimated as =

Total Volume of water applied per unit cropped area + Soil Moisture Depletion in Root zone. Realistic estimates of “recharge to groundwater” would be arrived at using data from past research for various irrigated crops on soil and groundwater balance.

Progress so far

Extensive review of literature on water saving irrigation devices and their potential impacts on water use, yield

Review of literature on the return flows from conventionally irrigated fields

Analysis of primary data from research station for water-saving and yield impacts of irrigation devices--different types of drips & sprinklers and plastic mulching for different crops (groundnut, potato, alfalfa, castor etc.) completed

Analysis of data on irrigated cropping pattern (source-wise) in different agro-ecological regions of India completed

Water Harvesting: Potentials and Pitfalls

Hypothesis

In regions where rainfall and runoff are excessively high, and system losses are low (low ET and E), potential for water harvesting is high; but demand for water is low due to poor access to arable land and low PET/Rainfall ratios.

In regions where rainfall and runoff are low; and system losses such as ET and E, the potential for additional water supplies would be low, while the demand for water would be quite high due to large arable land, high PET/rainfall ratios.

Hypothesis: Continued

Many basins in water scarce regions are “closed”. Hence, increasing water harvesting increases only helps reallocation of water rather than adding to the overall hydrological balance.

In many basins, the upper catchments are water-rich than lower catchments. But water demands are higher in lower catchments.

But, allocation of water harvested through small water harvesting might contribute to improved water use efficiency in irrigated crops

Approach

The approach is eclectic involving analysis of secondary data on macro hydrology of selected river basins covering water-rich and water-scarce ones; hydrological monitoring and simulations for selected sub-basins/watersheds; and primary data collection using social science research methods.

Analysis of macro hydrology of India

Micro level hydrological monitoring

Farmer surveys in intensive water harvesting areas covering beneficiaries and non-beneficiaries

Objectives of Field Research

Analyze the trade off between local and basin level impacts of small water harvesting interventions vis-à-vis hydrological benefits

Examining the impact on local groundwater regime

Impact of water harvesting on surplus value product from a unit of water diverted for irrigation (supplementary or otherwise) Through improvement in WUE (physical) Through reduction in irrigation costs

Comparing the net surplus value product in crops irrigated through harvested water and crops irrigated with the surplus water in the downstream area

Locations for Field Study

Arawari basin in Alwar, Rajasthan Full of Johads and anicuts, water for cattle main

Paupogni catchment of Krishna basin Full of small and large tanks, water used for

irrigation, cattle

Kundi basin of Narmada in MP in Narmada valley Full of small water harvesting structures, no direct

use of water for any purpose (recharge and soil moisture conservation

Galo basin in Saurashtra in Gujarat Full of check dams (recharge and surface storage)

Progress made so far

Kundi basin study completed--draft ready

Hydrological data gathering and groundwater monitoring completed in the rest three basins

Hydrological analysis completed for Galo—runoff estimation, simulations using US Curve number method

Mapping of water harvesting structures completed in the four basins completed using GPS

Remote sensing imageries of the basins obtained and mapping being done

Analysis of macro hydrology completed

Outputs expected by March

Synthesis report on water harvesting based on four location studies

Papers on water productivity in irrigated agriculture (two at least)

Paper on water saving technologies