California Water Supply and Demand: Technical Report

The California Water Supply and Demand Model (CWSD) assesses how climate change affects water availability and usage in California, focusing on the energy, urban, and agricultural sectors. The model evaluates scenarios with no adaptation, slow adaptation, and fast adaptation across different climate projections (B1 and A2). Key findings indicate that without adaptation, agricultural water demand will rise due to higher temperatures, particularly in the San Joaquin Valley. While slow adaptation may only marginally reduce use, fast adaptation—driven by higher water prices and technological efficiency—could significantly decrease demand. The report also extends its agricultural analysis to other Western U.S. states, noting a general increase in water demand by 2100.

• California's baseline annual agricultural water use is 24.9 MAF, with over 99 percent dedicated to crop irrigation.
• In a scenario with no adaptation, agricultural water demand is projected to increase to 28.7 MAF (115 percent of baseline) by 2100 under the A2 climate scenario due to rising temperatures.
• The San Joaquin Valley experiences the most significant absolute increase in water use without adaptation, ranging from 1.1 MAF by 2100 (B1 scenario) to 1.9 MAF by 2100 (A2 scenario).
• Slow adaptation in agriculture results in marginal reductions by 2050 (23.2 to 23.5 MAF), but by 2100, demand under the A2 scenario rises to 25.3 MAF, or 101 percent of the baseline.
• Fast adaptation leads to substantial demand decreases, with the lowest usage occurring in 2050 at 17.4 MAF (B1) and 17.6 MAF (A2); by 2100, overall reductions are between 24 and 26 percent compared to baseline.
• Baseline annual agricultural water use for the Western states is 52.8 MAF, projected to increase by 10 to 18 percent by 2100, reaching 58.3 MAF (B1) and 62.4 MAF (A2).
• California accounts for approximately 47 percent of the Western states' agricultural water demand; Idaho is the largest user outside of California, reaching 7.2 MAF by 2100 under the A2 scenario.
• Electricity generation in California requires only 1 percent of the total water supply, and projected increases under A2 climate assumptions would be a small fraction of 1 percent.
• Climate change is projected to cause adverse changes in the seasonal distribution of precipitation, potentially making existing reservoir capacity inadequate and causing winter rainfall to flow into the ocean unused.

APA

Stanton, E. A., & Fitzgerald, E. (2011). California Water Supply and Demand: Technical Report. Stockholm Environment Institute. https://www.sei.org/mediamanager/documents/Publications/Climate-mitigation-adaptation/Economics_of_climate_policy/sei-westernwater-cwsd-0211.pdf

Chicago

Stanton, Elizabeth A., and Ellen Fitzgerald. California Water Supply and Demand: Technical Report. Stockholm Environment Institute, 2011. https://www.sei.org/mediamanager/documents/Publications/Climate-mitigation-adaptation/Economics_of_climate_policy/sei-westernwater-cwsd-0211.pdf.

Wikipedia

{{cite report |last1=Stanton |first1=Elizabeth A. |last2=Fitzgerald |first2=Ellen |title=California Water Supply and Demand: Technical Report |publisher=Stockholm Environment Institute |date=February 2011 |url=https://www.sei.org/mediamanager/documents/Publications/Climate-mitigation-adaptation/Economics_of_climate_policy/sei-westernwater-cwsd-0211.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{stanton2011california, author = {Stanton, Elizabeth A. and Fitzgerald, Ellen}, title = {{California Water Supply and Demand: Technical Report}}, institution = {Stockholm Environment Institute}, year = {2011}, month = feb, url = {https://www.sei.org/mediamanager/documents/Publications/Climate-mitigation-adaptation/Economics_of_climate_policy/sei-westernwater-cwsd-0211.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }