By Chris Hancock 

Water is essential for California, supporting households, agriculture, ecosystems, and the state’s economy. Yet across the state, rivers, streams, and aquifers are stressed from overuse, and climate change and continued growth are increasing pressure on water resources. Understanding water use patterns and environmental flows is critical to informing policy and planning across the state. 

The analysis highlights five key findings: 

1. Environmental flows are a critical part of California’s water system, but difficult to define and measure. 

Environmental flows support aquatic ecosystems and human well-being. Determining how much water is truly dedicated to environmental purposes is difficult due to limited direct measurement, reliance on assumptions, and inconsistent or unclear definitions. 

2. Environmental flows are unevenly distributed across California, spatially and temporally.  

Environmental flows vary widely across regions and between wet and dry years, closely tracking precipitation and dropping sharply during droughts. Over half of environmental flows occur in the North Coast, a region that makes up just 12% of the state’s land area and only 2% of its population, highlighting a stark geographic imbalance.  

3. Water use has decoupled from population and economic growth. 

California’s population more than doubled and the economy grew since the 1960s, while total urban and agricultural water use increased by less than 20%, reflecting a clear decoupling of water use from growth. 

4. Agriculture accounts for most developed water use. Urban water use has declined across hydrologic regions. 

Agricultural water use accounts for 80% of developed water supply and is influenced by weather, irrigated acreage, and crop type. Urban water use has declined across hydrologic regions. 

5. Better data and reporting are needed. 

Much of the available water use data is based on modeled estimates rather than direct measurement, with inconsistent or unclear definitions. Strengthening measurement and reporting systems and improving terminology and classification would help inform more effective decision-making. 

Learn more in the Pacific Institute issue brief “Water for Nature and People: Trends in California, 1960–2022.”