Long-Term River Basin Planning: GA-LP Approach Daene McKinney Center for Research in Water Resources University of Texas at Austin Ximing Cai International Food Policy Research Institute Leon Lasdon Department of Management Science University of Texas at Austin

Outline Sustainability in River Basin Planning Modeling Framework Solution Approach (GA-LP) Application Conclusions & Next steps

Sustainability in River Basin Planning Concepts of sustainable development –Demand management, supply reliability and flexibility, environmental impact control, technology adaptation, economic efficiency, etc Broad guidelines –Provide guidance to planners, but –Not translated into operational concepts that can be applied to specific systems

Modeling Framework Incorporate quantified sustainability criteria into long-term water resource systems models –Relations between water uses and their long-term consequences –Tradeoffs in benefits received over many generations

Application Water resources management in river basins with (semi) arid climate –Large diversions to irrigated agriculture –Potential for environmental degradation from water and soil salinity Sustainability (one might define it as) –Ensuring long-term, stable and flexible water supply capacity –Meeting irrigation and growing M&I demands, –Mitigating negative environmental consequences

Modeling Framework Basic Premise –Short-term decisions should be controlled by long- term sustainability criteria Long-term (Multi-year) Control –Inter-Year Control Program (IYCP) –Long-term model controlling short-term decisions to approach sustainability Short-term (Annual) Control –Sequencing of Yearly Models (YMs) –Short-term models optimizing benefits for a year

Modeling Framework Inter-Year Control Program (IYCP) Inter-Year Control Variables (IYCV) wsEnd of year water storage AAvailable area of a crop  1Water distribution efficiency  2Water application efficiency  3Water drainage efficiency taxSalt discharge tax rate Yearly models YM 1 YM 2 YM Y Sustainability Criteria REL i Reliability criterion, i = a or e REVi Reversibility criterion, i = a or e VUL i Vulnerability criterion, i = a or e ENV Environment criterion SEQ Spatial equity criterion TEQ Temporal equity criterion EA Economic acceptability criterion Each is NLP or LP Solve by GA

Demand site (d)Area (a)Field (f) Groundwater Crop (c) ER RF P Yearly Model Objective Irrigation benefit Hydropower benefit Environmental benefit Constraints Flow balances Salinity balances Policy constraints

Solving the Yearly Model IYCP IYCV(y) IYCV(y+1) solution for year y solution for year y+1 Stored water Water salinity, Soil salinity, Salt discharge Flows YM(y) YM(y+1) FM(y)FM(y+1) SM(y) SM(y+1) Water salinity, Soil salinity, Salt discharge Soil salinity, Salt discharge Stored water YM  FM + SM Decompose Linearize LPs for each year

IYCP Objective Function Weighted sum of sustainability criteria: –Risk criteria (expressed in terms of agricultural and ecological water use) Reliability (frequency of system failure) Reversibility (time to return from system failure) Vulnerability (severity of system failure) –Environmental criteria Max allowable water and soil salinities –Equity criteria Temporal (equitable access to benefits over time) Spatial (equitable geographic access to water) –Economic acceptability criteria (impact of investment benefits)

Year y=1,…,Y Performance for year y Performance of individual i: F(IYCV g,i )=F(Risk, Env, Equity, Econ) Performance of generation g: F i = F(IYCV g,i ), i=1,…,I Individual i=1,…,I Generation g=1,…,G YM(y) Inter-Year Control Variables (IYCV) wsWater storage AArea for crop  1Distribution efficiency  2Application efficiency  3Drainage efficiency taxSalt discharge tax rate Solving the IYCP

Application – Syr Darya Basin Syr Darya Amu Darya

Aral Sea Basin XX Cent.

Aral Sea Basin (1989 – 2000) Question: Can irrigated agriculture be sustained while minimizing environmental impacts? Amount being used for Irrigation

ASB River System

Irrigation Profit Scenarios Baseline: No change Master: Area & efficiencies are DV’s Low Irrigation: reduced area

Crop Areas (Master Scenario)

Efficiencies (Master Scenario) Application Efficiency Distribution Efficiency

Soil Salinity Salt Discharge

Sustainability Criteria Scenario RELREVVULENVTEQSEQEA Baseline NA Master Low Irrigation High Irrigation Sustainability criteria

Conclusions Modeling framework developed –short-term decisions combined with long-term decisions to find sustainable patterns in irrigation- dominated river basins Results –Both soil and water salinity sensitive to changes in irrigated area over the long-term –Small increases in irrigated area without accompanying infrastructure improvements places the environment at risk

Conclusions Next Steps –Linking water and salt to energy –WB GEF project has incorporated sustainability criteria into their project and are beginning to use the models –Agricultural policy in the region –Both basins together (linked by energy) –Water allocation agreements

CAR Energy System X – Small H – Thermal G – Hydro A – User O – Pool Amu Darya Syr Darya CAEP Tajikistan Turkmenistan Uzbekistan Kazakhstan Kyrgyzstan X1 H1 G1 G2 H2 X2 X3 H3 G3 X4 H4 G4 X5 H5 G5 A1 A2 A3 A4 A5 O1 O2 O3 O4 O5

Water Results Display

Energy Results Display