Basin Impacts of Irrigation Water Conservation

1. Basin Impacts of Irrigation Water Conservation University of California Department of Environmental Sciences Riverside Frank A. Ward (NM State University) February 25, 2011

2. Background • Climate Change: more floods/droughts • Continued Population Growth (esp poor countries) • Growing values reduced supplies of ecological assets • Growing values of treated urban water • Search for ways to conserve water in irrigated agriculture • Special search for ag water conservation, esp if it protects the farm economy (food security) • technology (drip, sprinkler, water saving crops) • policy (subsidies, regulations, pricing) • Projects (infrastructure, leveling, … )

3. Road Map • Pose questions • What is water conservation in agriculture? • What policies could promote it? • Can river basin policy models help discover? • Findings about effects of water conservation incentives in the Rio Grande Basin? • Lessons learned? • About water conservation • Generally • Possibly for California

5. Rio Grande Basin

6. Journey down the Rio Grande

7. High Valued Uses of Water in RGB, Albuquerque, El Paso

8. High Valued Use: Rio Grande Silvery Minnow

9. High Uses of Water in RGB, Irrigation

10. Approach

11. Policy Debates Basin Models Can Inform • Water Pricing and Cost Recovery • Timing, sizing, sequencing of new storage • Population growth, increased food demands, ‘more crop per drop.’ • Water rights adjudication • Meeting growing demands for environment • How to develop/allocate water for food security • Cheapest way to reduce water use (conservation)

12. Basin Models: The Dark Side • Too academic, too theoretical, too little use to inform real policy debates • Nobody understands them • Models are hungry for data that aren’t there. • Expensive and slow to build • Who wants to work with a bunch of academics with uncertain use of results?

13. Basin Model (Optimization) • Maximize • Objective • Economic • Environmental • Social Justice • Hydrologic • Subject to • Constraints • Hydrologic • Agronomic • Institutional • Economic

14. GAMS Basin Model Structure SETS H: time, reservoirs, diversion locations, headwater flow locations, aquifers, U: cities, income levels …; A: irrigated areas, crops…; E: assets, services DATA prices, costs, population, compact delivery requirements, elasticities, acres available, headwater flows… (DEPENDENT) VARIABLES diversions, use, return flows, acres in production, pumping, prices, reservoir levels, NPV… EQUATIONS objective functions and constraints SOLVER

15. Policy Assessment Framework Data Policy Outcomes Process Headwater supplies Min Flows Sharing rules Outflows Crop prices Crop costs Water price Treat cost Elasticities Land supply Maximize NPV for the basin Crop prodn Crop ET Urban water diversions, use, Return flows, Flows by gauge Urban, farm, environmental benefits NPV Baseline: no new policy Alt 1: Constrain aquifers to return to start Alt 2: Renew aquifers to historical levels

16. Connections • Connections: River basin models • Hydrologic: stocks, flows, over time, space • Economic: optimizes total benefits from use • Agronomic: acreage, water use, crops • Demographic: urban income, population, demand • Institutional: rules that limit use or require delivery • Use connections to gain insights for policies that best adapt to climate: resilient conservation institutions • For basin as a whole • For targeted users (farm, city, environment)

17. Aquifer mass balance

18. Reservoir mass balance

19. Water Balance

21. NM Pecans: Water Balance Flood Drip 6’ 3.2’ 3.2’ 2.6’ 0 3.4’ 0

22. Under the Hood

23. Objective

24. Constraints • Irrigable land, Headwater supplies • Sustain key ecological assets • Hydrologic balance • Reservoir starting levels (sw, gw) • Reservoir sustainability constraints (sw, gw) • Institutional • Endangered Species Act • Rio Grande Compact (CO-NM; NM-TX) • US Mexico Treaty of 1906 • Rio Grande Project water sharing history (NM/TX)

25. Gauged Flows: Hydro Balance • E.g.: Lobatos gauge (CO-NM border): X(Lobatos_v,1) = X(RG_h,1) - X(SLV_d,1) + X(SLV_r,1)

26. Ag water use

27. Reservoir Stocks

28. Institutions: e.g. Rio Grande Compact

29. Potential Institutional Constraints • U.S. Mexico Groundwater Sharing Treaty • U.S. Mexico Water Quality Treaty • Limiting domestic well development • Adjudicate MRG water rights

30. Results • Ag Water Use and Savings • Status Quo • Sustain Natural Capital • Renew Natural Capital

32. Lessons Learned: Water Conservation • Farmers seek income, not conservation. Conservation must be profitable for irrigators to do it. • Subsidizing water conserving irrigation technology will reduce water applied per unit land for a given crop • But if a water right is for total water applied to a farm • Acreage may increase to maintain total water applied • Crop mix may change to maintain total water applied • Reduced water applied doesn’t mean reduced water depleted by the crop. • Requiring sustainable reservoirs and aquifers in NM reduces the use of drip irrigation.

33. Lessons Learned: Research Challenges • Water conservation is hard to define, measure, forecast, evaluate, alter. • Counterfactual: How much less water would have been (will be) used if X irrigation technology would have been (is) subsidized. • River basin models are fun to build and write about, if you start small and grow them • Check that your model re-produces what you publish. • Mathematically document model, data, assumptions. • Calculate sensitivities:

34. Lessons learned for California: “California Water Myths” • California is running out of water. • ________ is responsible for California’s water problems. • We can build our way out of California’s water problems. • We can conserve our way out of California’s water problems. • Effectiveness of conservation is often overstated. • Principle: Look for cheapest ways to reduce use. • Practice: Requires defining use, comparing B, C of saving. • Water markets can solve California’s water problems • Healthy aquatic ecosystems conflict with a healthy economy. • More water will lead to healthy fish populations. • California’s water laws impede sustainable management.

35. Top 10 Lies told by Watershed Policy Modelers 1. The model is well-documented with all limits • The model is user-friendly • The model fits the data • Results make sense • The model does that • We did a sensitivity analysis • Anyone can run this model • This model links to other models • The model will be in the public domain • The new version fixes all previous problems