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Projects Worked On

Project Name Description
California Water Myths

In collaboration with the Public Policy Institute of California and other researchers, the Center prepared California Water Myths—a report highlighting eight common water myths, focusing on water supply, ecosystems and legal and governance issues. In providing information to combat these myths, the study establishes a more informed approach to water policy and management in California.

Myths of California Water: Virtual Tour was created as a interactive companion to the California Water Myths report. Experience aerial views of California in locations that relate to the myths and get in-depth information about the realities that combat these myths. The tour also provides links to visual images and further reading.

Addressing Nitrate in California's Drinking Water

One in 10 people living in California’s most productive agricultural areas is at risk of exposure to harmful levels of nitrate contamination in their drinking water, according to a report released today by the University of California, Davis. The report was commissioned by the State Water Resources Control Board.

The report, “Addressing Nitrate in California’s Drinking Water,” is the first comprehensive scientific investigation of nitrate contamination in the Tulare Lake Basin, which includes Fresno and Bakersfield, and the Salinas Valley, which includes Salinas and areas near Monterey. It defines the extent of the problem, suggests promising solutions and outlines possible funding mechanisms.


California’s complex water management system often defies comprehensive analysis. We summarize the results of a decade of quantification and analysis of this system from a hydro-economic perspective using the CALVIN Model.

The general approach taken dates back to Roman times, when Frontinus (97 AD) began his oversight of Rome’s water system with a systematic inventory and quantification of its water infrastructure. 

This approach has been formalized and expanded in the modern era as economists, planners, and engineers have sought to grapple with complex water management systems and problems.

In California water supply and demand is inconvenient in both space and time. Most water availability is in northern California from winter precipitation and spring snow-melt; whereas water demands are more in the south during the dry summer. Major floods and seasonal and multiyear droughts further complicate water resource management in California. The Sacramento-San Joaquin Delta is the major north-south hub for this water network.

Population growth, climate change, a vulnerable Delta, and decentralized water governance pose opportunities and challenges to water management in California. Portfolios of water management activities, including diverse general policy tools, demand management, and operations and supply expansion options, are available to manage competing demands in complex situations.

Exploring promising portfolios of actions is the main intent of the CALVIN model. The CALVIN model is an economic-engineering optimization model of California developed at the University of California – Davis. CALVIN’s major innovations are its statewide (rather than project) scale, representation of a broad range of water management options, explicit integration of broad economic objectives, and its consequent applicability to a wide variety of policy, operations, and planning problems.



Water resource management in California is often extensive and complex and deserves a comprehensive data and modeling approach. The Hobbes Project is a new effort to provide a venue for modelers in California and elsewhere to create an open, organized and documented quantitative representation of the state's intertied water resources system. Geocoded elements in this database can be interactively converted into tiered networks able to be solved by multiple modeling platforms depending on user preferences, with the appropriate translators. Many Hobbes tools will be web-based with exporting capabilities to the most common analytical and modeling software.

The Hobbes Project will include:

  • Database standardization and data documentation

  • Geocoded data element representations

  • Open platform with web access

  • Ability to transform database elements into documented model inputs via co-development

  • Focus on data and database structure, organization, documentation, not specific models

As shown in Figure 1, users of the Hobbes Project will be able to visualize different documented elements in a common web-based mapping application, run specific modeling networks using either the Hobbes basic database, network managers scenario manager software pieces and visualize model outputs in tabular form, chart templates, maps or simply exporting the modeling network, its input data and/or its modeling output to be used in other platforms.

For more information, please see the project website at


Yolo Bypass: Managing a floodplain for multiple uses

This study will present a decision-making framework for balancing ecosystem and economic goals on the Yolo Bypass, a promising site for habitat restoration in the San Francisco Bay-Delta system. The bypass's primary purpose is to provide flood control for Sacramento, but it's also used for farming, duck hunting and bird-watching. We're developing an optimilization model to explore when, where and how floodwaters might most economically be applied to manage all the diverse activities.


The video (above) demonstrates our application of a newly developed flood simulation software (HEC-RAS-2D) to the Yolo Bypass. The model will help us determine whether solutions from the optimization analysis are realistic. If an optimal solution calls for engineered modifications to the floodplain, we can use the model to test the effects of those potential changes. The decision-making framework and tools we develop will be applicable to other floodplain restoration efforts in California and elsewhere.


Related news and commentary:

Sacramento River Flood Control Project

California is looking to expand the Sacramento River Flood Control Project, partly as a defense against severe storms in a changing climate. This study creates a model of the Project for exploring various scenarios. Researchers are analyzing how the system's bypass channels and weirs interact during big storms and how expansions of these structures might reduce flood damage at various locations in the Sacramento Valley and the Delta. 



Water Modeling in Agricultural Production



This  technical workshop in collaboration with the California Water and Enviornmental Modeling Forum (CWEMF). This workshop presents various alternatives for modeling the economics of water use and water scarcity within an agricultural production setting, with a particular focus on California. This 6-hour workshop at UC Davis is intended to bring experts and interested water resources professionals from academia, industry and government agencies to talk and learn about various models and optimization tools that have been used to evaluate the economics surrounding agricultural water use  in California, Australia, Chile, and México. Applications using both mathematical programming and hedonic models will be presented.  A discussion about modeling needs and future applications for the California water modeling community will be encouraged.  



Drought's Economic Impact on Agriculture

UC Davis researchers forecast the socio-economic effects of the drought on California agriculture for 2014 and beyond. Economists use computer models and the latest estimates of water deliveries, well-pumping capacities and acres fallowed. The researchers exploit new satellite remote-sensing technologies to estimate fallowed acreage as the drought unfolds.

2016 Study Downloads


Economic Analysis of the 2016 California Drought for Agriculture (California Water Blog, August 15, 2016)

Estimates of Irrigated Cropland Idled due to the 2016 California Drought: Clarifications and Supplemental Information (NEW! Memorandum, September 1, 2016)


Collaborators: Duncan MacEwan

Daniel Sumner 

Integrated Environmental Modeling

Integrated Modeling for Adaptive Management of Estuarine Systems


May 21-22, 2015, UC Davis Campus

Like many estuarine systems, California’s Sacramento-San Joaquin Delta needs to revolutionize how models and data are developed and integrated to support adaptive management. Durable and adaptive solutions must account for a cascade of interacting social, economic, and ecological effects.

The National Science Foundation is sponsoring an Integrated Modeling Workshop to explore ways to improve the development and application of modeling for multipurpose management of changing estuarine systems. The two-day workshop will bring together experts from Europe, Asia and across the U.S. Potential solutions will be identified and discussed from multiple perspectives: government, academia, NGOs, consultants and stakeholders.

Approaches to be discussed include:

Community modeling leverages the expertise of many public, private, NGO, and academic researchers for understanding complex environmental problems and supporting adaptive management. Community modeling is a way to connect experts on each of the system components through a common framework. Community modeling requires a sustainable business model that works across agencies, universities, NGOs and the private sector.

Public domain models and data can include open source and more proprietary and controlled approaches to develop software and data. Such approaches are especially important where a broad common understanding must be developed among many interests and where alternatives must be compared with transparency and minimal cost.

Integrated Environmental Modeling (IEM) uses information technologies to couple independently developed models. Modular modeling components are assembled flexibly to explore, explain, and forecast the behavior of various system purposes. IEM systems around the world include diverse stand-alone applications and high performance computer clusters.

Workshop Program (Updated May 19, 2015)

  • Integrated Environmental Modeling
  • Decision support systems: science/modeling organizations that bridge the science-policy gap
  • Directions for improved integrated modeling of estuarine systems

The workshop is organized by the Delta Stewardship Council/Delta Science Program and UC Davis Center for Watershed Sciences. The National Science Foundation is sponsoring the event in partnership with the California Water and Environmental Modeling Forum and the International Association for Hydro-Environment Engineering and Research.


Student stipends are available on a first come first serve basis. Please fill out the student stipend request form. We can provide an stipend of $100 if located around 50 mi from Davis, $150 if located between 51 and 150 miles from Davis and $300 beyond 150 miles including out of state. 


This workshop was supported by the National Science Foundation under Award: A Workshop on Community Integrated Environmental Models (Grant Number 1464440).  The Organizing Committee acknowledges supplemental support by the Delta Stewardship Council through the Delta Science Program and the Center for Watershed Sciences. 


"Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation."

Collaborators: Christopher Enright

Peter Goodwin

Delta Consumptive Water Use Comparative Study

A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta

Principal Investigators 
Josué Medellín-Azuara, Kyaw Tha Paw U, Yufang Jin, and Jay R. Lund
Project Contact: Josue Medellin-Azuara or Jesse Jankowski (Delta CU Main Report) Kyaw Tha Paw U (Field Campaign Delta CU Study)

(Full list of authors and contributors below)

This research project was convened by the Center for Watershed Sciences at the University of California Davis with financial support from the California State Water Resources Control Board Office of the Delta Watermaster and other agencies. Its objective is to develop a better understanding of consumptive water use in the Delta by coordinating modeling, measurement, and other information from a variety of independent research and estimation efforts. 


Consumptive water use by crops, often referred to as evapotranspiration (ET), is frequently the largest component of an agricultural region’s water balance. This study investigates crop consumptive use in the Sacramento-San Joaquin Delta (“Delta”) of California using a comparative approach with several prominent methods for estimating crop ET, including estimates based on crop coefficients, water balances, energy balance using remote sensing, and field measurements.

Crop ET estimates are provided for both the Legal Delta and the Delta Service Area (DSA) for two water years (2015 and 2016) by seven methods:

  • CalSIMETAW: California Simulation of Evapotranspiration of Applied Water, by the California Department of Water Resources (DWR).
  • DETAW: Delta Evapotranspiration of Applied Water, by DWR.
  • DisALEXI:  Disaggregated Atmosphere-Land Exchange Inverse method, by the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS).
  • ITRC-METRIC: Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC), by the Irrigation Training and Research Center (ITRC) at California Polytechnic State University (Cal Poly).
  • SIMS: Satellite Irrigation Management Support System, by the National Aeronautics and Space Administration Ames Research Center (NASA-ARC) and California State University Monterey Bay (CSUMB).
  • UCD-METRIC: Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC), by the University of California (UC) Davis.
  • UCD-PT: Optimized Priestley-Taylor approach, by UC Davis.

In addition, field-based estimates and measurements of ET using eddy covariance and estimates with surface renewal stations were developed over bare soil during the fall of 2015 and over three predominant crops in the Delta (alfalfa, corn, and pasture) in the 2016 irrigation season. One direct ET measurement station was also deployed in 2016. Five additional California Irrigation Management Information System (CIMIS) stations were deployed in the Delta in 2016 to improve the spatial representation of weather variables and accuracy in input datasets of reference ET estimates. Two annual land use parcel surveys for 2015 and 2016 were conducted by Land IQ, Inc., which provided updated land use maps over the study area with more than 30 land use classes. A total of 26 agricultural classes were used for ET estimates and analysis.

Additional Funding and Research Support from

California State Water Resources Control Board, California Department of Water Resources, Delta Protection Commission, Delta Stewardship Council, North Delta Water Agency, Central Delta Water Agency, South Delta Water Agency, Center for Watershed Sciences, and UC Water. Project managemnt support from Cathryn Lawrence at the Center for Watershed Sciences is aknowledged.

Project Documents and Datasets





Full Authors and Contributors List

Principal Investigators
Josué Medellín-Azuara1,2, Kyaw Tha Paw U3, Yufang Jin3, and Jay R. Lund1

Report Preparation and Research Assistance
Jesse Jankowski, Eric Kent, Jenae' Clay, Andy Wong, Andrew Bell, Nicholas Santos, and Jessica Badillo, University of California, Davis

Other collaborators and research support from:
Commissioned by the Office of the Delta Watermaster
Michael George, Delta Watermaster, California State Water Resources Control Board

Field Campaign Group
Kyaw Tha Paw U3, Eric Kent3, Jenae’ Clay3, Michelle Leinfelder-Miles4, Jean-Jacques Lambert3, Megan McAuliffe3, David Edgar3, Sean Freiberg3, Ruolan Gong3, Megan Metz3, Cayle Little5, Bekele Temegsen

Modeling Groups
CalSIMETAW: Morteza Orang5, Richard L. Snyder3,4, Quinn Hart1,3, Sara Sarreshteh5, and Simon Eching5
DETAW: Tariq Kadir5 and Lan Liang5
DisALEXI: Martha Anderson6
ITRC: Daniel Howes6
SIMS: Forest Melton8,9, Alberto Guzmán8,9, Lee Johnson8,9, Carolyn Rosevelt8,9, and Kirk Post8,9
UCD-METRIC: Nadya Alexander1, Nicholas Santos3, Andrew Bell1, Justin Merz1 and Quinn Hart1,3
UCD-PT: Yufang Jin3, Andy Wong3
Unmanned Aerial Vehicles: J. Andrés Morandé1, Ricardo Trezza5, Andreas Anderson2, Kyaw Tha Paw U3, Yufang Jin3, Josué Medellín-Azuara1,2, Jesse Jankowski1, Jessica Badillo1, Joshua H. Viers2, YangQuan Chen2
WRF-ACASA: Kyaw Tha Paw U3, Eric Kent3, Jenae’ Clay3, Rex David Pyles3

Peer Review Panel
Richard Allen10, Byron Clark11, Richard L. Snyder3,4 and Thomas Trout6


1 Center for Watershed Sciences, University of California, Davis
2 School of Engineering, University of California, Merced
3 Land, Air and Water Resources, University of California, Davis
4 University of California Cooperative Extension.
5 California Department of Water Resources
6 Agricultural Research Service, United States Department of Agriculture
7 Irrigation Training and Research Center, California Polytechnic State University, San Luis Obispo
8 NASA-Ames Research Center, Cooperative for Research in Earth Science and Technology
9 California State University, Monterey Bay
10 University of Idaho, Kimberly
11 Davids Engineering, Inc.

California Fourth Climate Change Assessment

Economic and Environmental Implications of California Crop and Livestock Adaptations to Climate Change and Climate Policy

To more accurately estimate the threat posed by sea level rise and intense storms to coastal infrastructure, this research will provide assess coastal flood risk accounting for changing climate patterns, erosion rates, shifting beach forms, and vertical land movement. Methods will be developed to support site-specific, project level assessments of coastal vulnerabilities to sea level rise through integration of models of projected sea level rise and climate scenarios, coupled with local and regional-scale erosion rates and vertical land motion estimates.

Collaborators: Daniel A. Sumner

SWAP Model

The Statewide Agricultural Production (SWAP) model is a multi-region, multi-input and output economic optimization model of the agricultural economy in California. The current model version covers over 93 percent of irrigated production in the state with primary regions in the Central Valley, Southern California, and the Central Coast. The model is currently used for policy analysis and planning by consultants and state and federal agencies. Some of the key features of the SWAP model include:

  • Self-calibrates using Positive Mathematical Programming (PMP)
  • Constant Elasticity of Substitution (CES) regional production functions
  • Exponential PMP cost functions
  • Groundwater pumping cost module including change in depth and electricity costs
  • Regional input constraints
  • Water broken out into 6 sources
  • Endogenous crop prices
  • Technological change and exogenous demand shift modules
  • 31 agricultural production regions based on homogenous hydrologic and agronomic conditions
  • Linkage to hydrologic, agronomic, and engineering models

The SWAP model is a fully calibrated optimization model which is well-suited to estimate spatially heterogenous commodity, resource, and input specific policies. Projects span a wide range of applications over many years. Some recent examples include: 

  • Costs of Central Valley salinity
  • Effects of Delta export restrictions
  • Nitrate externalities in the Salinas Valley
  • New CVP surface water storage feasibility analysis
  • South-of-Delta water markets
  • Yolo Bypass flood date and flow volume agricultural impact analysis
  • Climate change effects on California agriculture