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Groundwater as a Statewide Resource Professor Richard E. Howitt Agricultural & Resource Economics, UC Davis Professor Jay R. Lund Civil & Environmental Engineering, UC Davis

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Real work done by Dr. Marion W. JenkinsAndrew J. Draper Matthew D. Davis Kenneth W. Kirby Kristen B. Ward Brian J. Van Lienden Brad D. Newlin Pia M. Grimes Jennifer L. CorduaSiwa M. Msangi

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A Study Funded by State of California Resources Agency National Science Foundation US Environmental Protection Agency

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Overview 1) Groundwaters statewide importance 2) Some questions 3) Why Economics? 4) Economic values for water use 5) CALVIN statewide model 6) Some early groundwater results 7) Conclusions and ongoing work...

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Is Groundwater Important? 30-40% of Californias off-stream supplies in average years More groundwater use in dry years Total storage capacity = 850 MAF

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Major Groundwater Areas Sacramento Valley San Joaquin Valley Tulare Basin Salinas Valley South Coast

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Major State Groundwater Issues 1. Managing Conjunctive Use 2. Groundwater Mining 3. Recharge and Surface Activities

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Some Questions

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Conjunctive Use? 1. Promising locations? 2. Local Control and Coordination? 3. Operating Coordination? 4. Statewide Coordination?

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Groundwater Mining? 1. Balancing short and long-term benefits and costs? 2. Economic use of mined water? 3. Effects of actions statewide on local groundwater mining?

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Recharge and Surface Activities? 1. Agricultural return flows? 2. Urban return flows? 3. Stream-aquifer interaction?

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Why Economics? When the wells dry, we know the worth of water. Benjamin Franklin (1746), Poor Richards Almanac.

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Economic Values for Water Willingness to pay Agricultural Urban Environmental

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Agricultural Water Use Values Economic value of water to farmers SWAP model 24 Regions Values by month

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Agricultural Production Model - SWAP Based on CVPM model Expanded to include entire state Monthly water decisions More detailed production decisions

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Agricultural Inputs Available acreage, water, technology Production function for each crop Prices and costs Observed farm data

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Agricultural Water Use Values 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 050100150200250300350400 Deliveries (taf) Benefits ($ 000 ) March August June July May April September October 0 1,000 2,000 3,000 51015 October February January

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Urban Demand Model Residential demand curves to estimate value of water use Lost production survey to estimate value of industrial water use

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Urban Inputs 2020 demands Industrial and residential Observed residential demand curve Industrial production lost 1995 retail water prices

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Urban Outputs Monthly values of water 20 Urban regions

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Urban Cost of Shortage Curves

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CALVIN An Economic-Engineering Optimization Model for Californias Water Supplies

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What is CALVIN? Entire inter-tied California water system Surface and groundwater systems Prescribes monthly system operation Based on economic benefits Maximizes economic objectives

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Data Flow Results Input Databases CALVIN Optimization SWAP Model Urban Demand Model Ag InputsUrban Inputs

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Optimization vs Simulation Optimization - Whats best? What water operations and allocations give the best performance? Simulation - What if? What is performance given a set of water operation and allocation rules?

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Optimization Components

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Optimization vs Simulation? Should be used together Optimization needs more simplification Provides economic information not available from simulation Promising solutions for detailed study

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CALVIN vs Other Models Other models like DWRSIM, PROSIM, and CVGSM are simulation models CALVIN is an optimization model

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CALVIN and Other Models

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CALVINs Innovations 1) Groundwater and Surface Water 2) Statewide model 3) Optimization model 4) Economic perspective and values 5) Data - model management 6) New management options

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Model Schematic Over 1,200 spatial elements 56 Surface reservoirs 38 Ground water reservoirs 47 Agricultural regions 20 Urban demand regions 600+ Conveyance Links

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Schematic Transparencies Here

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Model Inputs Agricultural water values Urban water values Hydrology: Surface & ground water Facility capacities Operating costs Environmental Flow Constraints Policy Constraints

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Hydrology Inputs 1921 - 1993 historical period Monthly inflows Surface inflows from DWR and USBR data Groundwater from CVGSM and local studies

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CALVIN Represents Groundwater 1921 - 1993 historical period 38 Groundwater reservoirs Pumping and recharge decisions Fixed interbasin flows, inflows, and losses Calibrated to CVGSM and local studies

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CALVINs Engine Army Corps of Engineers Hydrologic Engineering Center Prescriptive Reservoir Model (HEC-PRM) A data-driven network flow programming model

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CALVIN and Groundwater Some very preliminary results Semi-calibrated model run Some ideas Dont trust these numbers.

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Mojave Groundwater

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Mojave Flows

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What does this show? Groundwater can serve both seasonal and drought demands. Optimized groundwater doesnt necessarily drain basins. External inflows and outflows have economic value statewide.

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MWD Area Groundwater

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Long-Term Storage

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So what? Values of storage capacity and reach. Aquifer suited for drought storage. Groundwater mining has some economic value. Groundwater coordinated with other supplies and demands.

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Conclusions Groundwater is a statewide resource. Coordination is important. Economics and Markets can help us better employ groundwater. Optimization models can suggest promising solutions.

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Ongoing Efforts Running model to working model Policy and capacity alternatives Database & tool development Much left to do...

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More Information... Web site: cee.engr.ucdavis.edu/faculty/lund/CALVIN Workshop: Friday, Sept. 24, 10am-3pm UC Davis Campus, 1120 Bainer Hall