WHERE AND WHEN DO WE NEED WATER? Dr. Francisco J. Meza Project Mentor Dr. Guillermo Podestá...
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Transcript of WHERE AND WHEN DO WE NEED WATER? Dr. Francisco J. Meza Project Mentor Dr. Guillermo Podestá...
WHERE AND WHEN DO WE WHERE AND WHEN DO WE NEED WATER? NEED WATER?
Dr. Francisco J. MezaDr. Francisco J. MezaProject MentorProject Mentor
Dr. Guillermo PodestáDr. Guillermo Podestá
Facultad de Agronomía e Ingeniería ForestalFacultad de Agronomía e Ingeniería ForestalPontificia Universidad Católica de Chile Pontificia Universidad Católica de Chile
ObjectivesObjectives
Main objective: Main objective: Characterize the main components of the agricultural Characterize the main components of the agricultural hydrological cycle as well as the possible crop yield hydrological cycle as well as the possible crop yield outcomes of irrigated sectors under ENSO scenarios. outcomes of irrigated sectors under ENSO scenarios.
Specific objectives were:Specific objectives were:– ENSO impacts on the water cycle and crop growth. ENSO impacts on the water cycle and crop growth. – Probability distribution functions of potential and actual Probability distribution functions of potential and actual
evapotranspirationevapotranspiration– Identify regions and seasons that are particularly sensitive to water Identify regions and seasons that are particularly sensitive to water
scarcityscarcity– Perform preliminary estimates of the benefits of using climate Perform preliminary estimates of the benefits of using climate
forecasts in agricultural water resources planning.forecasts in agricultural water resources planning.
Region Under StudyRegion Under StudyMaipo River Basin Maipo River Basin
Climatic Variability in Chile and El NiClimatic Variability in Chile and El Niño ño PhenomenonPhenomenon
Mean Annual Precipitation (1950-1999) at six Chilean Localities
Locality Locality Lat (S)Lat (S) El NiEl Niññoo NormalNormal La NiLa Niññaa
PudahuelPudahuel 33.2333.23 412.9412.9 217.8217.8 231.0231.0
Curicó Curicó 34.5834.58 1003.81003.8 589.9589.9 612.3612.3
Concepción Concepción 36.4636.46 1513.81513.8 1091.51091.5 1095.71095.7
Temuco Temuco 38.4638.46 1258.01258.0 1087.91087.9 1116.91116.9
Valdivia Valdivia 39.3839.38 2237.92237.9 1946.31946.3 1983.01983.0
Puerto Montt Puerto Montt 41.2641.26 1765.41765.4 1719.51719.5 1806.41806.4
Climatic Variability in Chile and El NiClimatic Variability in Chile and El Niño ño PhenomenonPhenomenon
In central Chile, ENSO does have an influence on other In central Chile, ENSO does have an influence on other meteorological variables that play a fundamental role on meteorological variables that play a fundamental role on
reference evapotranspiration (Meza, 2005)reference evapotranspiration (Meza, 2005)
0
0.2
0.4
0.6
0.8
1
1.2
130 150 170 190 210
ETo (mm)
P(X
<x) EN
LN
N
Water DemandsWater Demands
Surface of crops was determined in each Surface of crops was determined in each section of the basin based on the Chilean section of the basin based on the Chilean Agricultural CensusAgricultural Census
Crop Potential ET was calculated using Crop Potential ET was calculated using FAO crop coefficientsFAO crop coefficients– ETp = Kc * EToETp = Kc * ETo
Irrigation was triggered ony when soil Irrigation was triggered ony when soil water budget fell below a threshold level water budget fell below a threshold level
Soil Water Balance AlgorithmSoil Water Balance Algorithm
max1max1
max1
11
1
12
)(
0
1.0
RPpRPp
RPpD
PpR
ETp
ETpETa
DRETaPp
cc
c
ENSO Effect on Water Demands in ENSO Effect on Water Demands in Central ChileCentral Chile
Water Demands in the Maipo River Basin
0
50000
100000
150000
200000
250000
300000
350000
400000
450000
La Niña Normal El Niño
m3 *1
000 La Niña
Normal
El Niño
ENSO Forecats for Water Resurces ENSO Forecats for Water Resurces ManagementManagement
In Chile, basins are regulated by the “Water In Chile, basins are regulated by the “Water Code Bill”Code Bill”
There are water rights that guarantee There are water rights that guarantee specific amouts to the holders. This limits specific amouts to the holders. This limits the possibility of allocating water according the possibility of allocating water according to the demand (i.e. conditioned on ENSO)to the demand (i.e. conditioned on ENSO)
Only in a situation of severe water scarcity it Only in a situation of severe water scarcity it will be possible to use climatic-oceanic will be possible to use climatic-oceanic indicesindices
Getting the right frameworkGetting the right framework
Up to this moment the objectives were achieved Up to this moment the objectives were achieved – ENSO does play a role determining different ENSO does play a role determining different
evapotranspiration ratesevapotranspiration rates– Greater demands are observed in the second section Greater demands are observed in the second section
(“where”) and during La Niña years (“when”)(“where”) and during La Niña years (“when”)– Due to regulatory issues the real decision maker for Due to regulatory issues the real decision maker for
water allocation is the farmer not the local authoritywater allocation is the farmer not the local authority
Can farmers take advantage of ENSO information Can farmers take advantage of ENSO information for irrigation management? for irrigation management?
Use of ENSO driven climatic Use of ENSO driven climatic information for optimum water information for optimum water
allocation allocation International Workshop on Climate Prediction and
Agriculture: Advances and Challenges. May 9-13, 2005.
Dr. Francisco J. MezaDr. Francisco J. Meza
Facultad de Agronomía e Ingeniería ForestalFacultad de Agronomía e Ingeniería ForestalPontificia Universidad Católica de Chile Pontificia Universidad Católica de Chile
Droughts in ChileDroughts in Chile
Occurrence of Severe DroughtsOccurrence of Severe Droughts
Source: Urrutia de Hazbun et al, 1993.Source: Urrutia de Hazbun et al, 1993.
Year Affected Regions ENSO phase (Trenberth)1960-1962 IV Normal
1965 IV, V La Niña1967 IV , V , RM Normal
1968-1969 III, IV, V, RM , VI El Niño1970-1971 III, IV La Niña
1979 VIII, IX, X Normal1985 IV La Niña
1990-1991 III, IV, V Normal1998 V, RM, VI, VII, VIII La Niña
Mean Economic Impact of Droughts in Mean Economic Impact of Droughts in Chile Chile (Source: MOP-UC, 1997)(Source: MOP-UC, 1997)
05000
1000015000200002500030000
7 13 18 22 26 30 34 38 42 46
Unidad de Análisis
M$/
Añ
o
Basin Number
Can we take advantage of ENSO Can we take advantage of ENSO information for water resources information for water resources
management problems?management problems?
Requisites of valuable information Requisites of valuable information (ENSO forecast)(ENSO forecast)
Climatic Predictability + Systems Vulnerability
+ Decission Capacity
Hansen, J.W., 2002
Climatic PredictabilityClimatic Predictability(ENSO Forecast)(ENSO Forecast)
Irrigation ManagementIrrigation Management
When water is not a limiting factor, irrigation is reduced to When water is not a limiting factor, irrigation is reduced to the management of the soil water budget to minimize plant the management of the soil water budget to minimize plant stress. stress.
When water is scarce the operation of irrigation increases When water is scarce the operation of irrigation increases in complexity, becoming a traditional resource allocation in complexity, becoming a traditional resource allocation problem.problem.
Optimum allocation of resources is achieved when the Optimum allocation of resources is achieved when the consequences associated to all possible combinations of consequences associated to all possible combinations of alternatives and states of the variable are known.alternatives and states of the variable are known.
Traditional ApproachTraditional Approach
Assumes that Water Demands are constant (i.e. Assumes that Water Demands are constant (i.e. fixed at climatological values)fixed at climatological values)
Uses Doorenbos and Kassam empirical equations Uses Doorenbos and Kassam empirical equations or Jensen´s formula to estimate yield changes as a or Jensen´s formula to estimate yield changes as a function of actual evapotranspiration function of actual evapotranspiration
4
1
n
i
i
j
jm ETc
ETa
Y
Jensen´s formula (Jensen, 1968)
Traditional ApproachTraditional Approach
Mathematical programming formulationMathematical programming formulation
lmlmlmXl
QETcEXc ,;max ,,,
M
mmm YP
1
*)(
lm
ml QX ,
ml
X ml
,
0,
Objective Function
Constraints
ENSO based ApproachENSO based Approach
Since ENSO does influence reference Since ENSO does influence reference evapotranspiration, it is reasonable to incorporate evapotranspiration, it is reasonable to incorporate that information and perform an optimization that information and perform an optimization conditioned on ENSO phaseconditioned on ENSO phase
The problem is rewritten asThe problem is rewritten as
lmlmlmXl
QoETcEXo ,|;max ,,,
Where o represents El Niño, Normal or La Niña phase
Expected Value of InformationExpected Value of Information
The information (ENSO forecast) will be The information (ENSO forecast) will be valuable if valuable if at least one of the optimal actions at least one of the optimal actions (i.e. irrigation strategies) associated with the (i.e. irrigation strategies) associated with the forecast information differs from the one forecast information differs from the one selected without forecast.selected without forecast.
According to Bayes´ theorem one can According to Bayes´ theorem one can calculate the expected value of information calculate the expected value of information as:as: coPoEVI
o
)(*
Case StudyCase StudyMaipo River BasinMaipo River Basin
Parameters usedParameters used
CropTomato Potato Watermelon
Price USD/ton 250 220 320Ym (ton) 65 50 401 0.33 0.37 0.622 1.15 0.74 0.743 0.74 0.62 0.744 0.33 0.15 0.24
ResultsResults
Expected Value of Information for the different Expected Value of Information for the different phases of ENSO phases of ENSO
Available water at each irrigation time was equivalent to 55 mm Available water at each irrigation time was equivalent to 55 mm
0
50
100
150
200
250
300
350
La Niña Normal El Niño
EV
I (U
SD
/ha)
____
ResultsResults
Expected Value of Information as a function of Expected Value of Information as a function of different levels of water supplydifferent levels of water supply
-50
0
50
100
150
200
250
0 20 40 60 80 100 120 140 160 180 200
Available Water for Irrigation (mm)
EV
I (U
SD
/ha)
___
ResultsResults
So far results show that ENSO information can be used to So far results show that ENSO information can be used to select an irrigation strategy, representing a case of perfect select an irrigation strategy, representing a case of perfect information (i.e. the forecasted evapotranspiration is equal information (i.e. the forecasted evapotranspiration is equal to the observed one in susequent periods)to the observed one in susequent periods)
A more realistic approach should be a case where A more realistic approach should be a case where irrigation strategy is revised based on irrigation strategy is revised based on – a) Previous water demandsa) Previous water demands– b) Forecasted evapotranspirationb) Forecasted evapotranspiration
In that situation the decision maker can correct “wrong” In that situation the decision maker can correct “wrong” allocations due to climate variability allocations due to climate variability
ResultsResults Evolution of the objective function Evolution of the objective function of the decision maker that of the decision maker that
allocates water using El Niño forecasts and the one that allocates water using El Niño forecasts and the one that bases his decision on historical ETc valuesbases his decision on historical ETc values
14300
14350
14400
14450
14500
14550
14600
14650
14700
14750
14800
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Irrigation Moment
Obje
ctiv
e Funct
ion (U
SD
)___
__
Revised Strategy ENSO Forecast
Value of Forecast
Conclussions and Future StepsConclussions and Future Steps
In locations where ENSO signal has an effect on In locations where ENSO signal has an effect on water demands there is an economic potential for water demands there is an economic potential for climate forecasts in water resources allocation at climate forecasts in water resources allocation at the farm level.the farm level.
The expected value of information is not a The expected value of information is not a monotonic function because when water is very monotonic function because when water is very scarce the allocation decissions are limitted.scarce the allocation decissions are limitted.
The next step is to refine the translation of yields The next step is to refine the translation of yields because they also are affected by climatic because they also are affected by climatic variability (use process based crop simulation variability (use process based crop simulation models) models)
Where and When do we Need Where and When do we Need Water?Water?
Summary of Scientific ActivitiesSummary of Scientific Activities √√ Regional Water Demand Model Conditioned on ENSO Regional Water Demand Model Conditioned on ENSO
phasesphases √√ Assessment of potential use of ENSO information for Assessment of potential use of ENSO information for
Irrigation ManagementIrrigation Management √√ Communication and DisseminationCommunication and Dissemination
– 84th AMS Annual Meeting, Seattle Washington84th AMS Annual Meeting, Seattle Washington– Local Seminar Local Seminar “Climatic Variability and Change: Issues in Water “Climatic Variability and Change: Issues in Water
Resources, Agriculture and Forest Ecosystems”Resources, Agriculture and Forest Ecosystems” Dr Carlos Nobre, CPTECDr Carlos Nobre, CPTEC Dr Bonifacio Fernandez. School of EngineeringDr Bonifacio Fernandez. School of Engineering Dr Francisco Meza. ATI participantDr Francisco Meza. ATI participant
Summary of Scientific ActivitiesSummary of Scientific Activities
– 85th AMS Annual Meeting, San Diego, California85th AMS Annual Meeting, San Diego, California– Papers:Papers:
Meza, F.J. 2005. Use of ENSO driven climatic information for Meza, F.J. 2005. Use of ENSO driven climatic information for optimum irrigation under drought conditions: Preliminary optimum irrigation under drought conditions: Preliminary assessment based on model results. Climate Research: assessment based on model results. Climate Research: submitted.submitted.
Meza, F.J. 2005. Obtaining daily precipitation parameters from Meza, F.J. 2005. Obtaining daily precipitation parameters from meteorological yearbooks. Agricultural and Forest Meteorology: meteorological yearbooks. Agricultural and Forest Meteorology: submitted.submitted.
Meza, F.J. 2005. Variability of reference evapotranspiration and Meza, F.J. 2005. Variability of reference evapotranspiration and water demands. association to ENSO at the Maipo river basin, water demands. association to ENSO at the Maipo river basin, Chile. Global and Planetary Change: In press Chile. Global and Planetary Change: In press
"You don't get points for predicting rain. "You don't get points for predicting rain. You get points for building arks."You get points for building arks."
– – Lou Gerstner, IBM CEO (Quoted by Lou Gerstner, IBM CEO (Quoted by Richard Katz, UCAR)Richard Katz, UCAR)
QUESTIONS????QUESTIONS????