On January 14, 2026, a California Court of Appeal upheld the Environmental Impact Report (EIR) certified by the City of American Canyon (American Canyon) and the accompanying water supply assessment (WSA) in City of Vallejo v. City of American Canyon. The California Environmental Quality Act (CEQA) requires a WSA to be prepared for certain large-scale development projects as part of the environmental review process to prove that adequate water supplies will be available for the project once complete. Legal challenges related to the availability of water to supply large developments are becoming increasingly common. The Vallejo case provides some new insights into the scope and details required for a valid WSA under CEQA.