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

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

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

Overview 1) Groundwater’s 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...

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

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

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

Some Questions

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

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?

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

Why Economics? “When the well’s dry, we know the worth of water.” Benjamin Franklin (1746), Poor Richard’s Almanac.

Economic Values for Water ë Willingness to pay ë Agricultural ë Urban ë Environmental

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

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

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

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

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

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

Urban Outputs ë Monthly values of water ë 20 Urban regions

Urban Cost of Shortage Curves

CALVIN An Economic-Engineering Optimization Model for California’s Water Supplies

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

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

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

Optimization Components

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

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

CALVIN and Other Models

CALVIN’s 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

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

Schematic Transparencies Here

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

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

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

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

CALVIN and Groundwater ë Some very preliminary results ë Semi-calibrated model run ë Some ideas ë Don’t trust these numbers.

Mojave Groundwater

Mojave Flows

What does this show? ë Groundwater can serve both seasonal and drought demands. ë “Optimized” groundwater doesn’t necessarily drain basins. ë External inflows and outflows have economic value statewide.

MWD Area Groundwater

Long-Term Storage

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

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

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

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