Water Supply Assessments

Water Supply Assessments

While official water supply assessments and verifications were first required in 2002 due to the passage by the California State Legislature of of SB 610 (Costa) and SB 221 (Kuehl), IRWD has always proactively planned for the future. Water supply assessments closely tie land use planning and water supply reliability. 

Water supply assessments, under SB 610, determine water supply sufficiency for a 20-year projection in addition to the demand of existing and other planned future uses, including, but not limited to, agricultural and manufacturing uses. They are required for any project that is subject to the California Environmental Quality Act and proposes commercial development of more than 250,000 square feet of floor space, a retail center with more than 500,000 square feet of floor space or more than 500 dwelling units.

Under SB 221, approval by a city or county of residential subdivisions of 500 dwelling units or more requires a written verification of sufficient water supply from the water supplier. The verification is prepared prior to the adoption of the final subdivision map and ensures that the sufficient water supply is available to serve a new subdivision before construction begins. The verification can use information from the water supply assessment prepared for the project.

 Current IRWD Water Supply Assessments/Verifications


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