With extremely dry conditions continuing throughout the Sacramento-San Joaquin Delta, the State Water Resources Control Board today sent notices of water unavailability to approximately 4,300 right holders in the watershed, urging them to stop diverting to preserve dwindling water supply for both this year and the next. The letters also inform approximately 2,300 water users with more senior rights that continued drought later this summer could impact their ability to divert.
“Due to severe drought in the West, the water supply in many parts of California, including the Delta watershed, is not enough to meet demands,” said Erik Ekdahl, deputy director of the Division of Water Rights. “We do not come to this decision easily. We are asking people to reduce their water use, and we recognize this can create hardships. However, it’s imperative that we manage the water we still have carefully as we prepare for months, perhaps even years, of drought conditions.”
California has experienced an unprecedented loss of runoff this spring as water was either absorbed by parched soils or evaporated amid unusually warm temperatures before reaching streams and reservoirs. High temperatures also prompted water users to use water earlier and in greater volumes than in previous critically dry years.
These developments resulted in the unexpected loss of nearly 800,000 acre-feet of water, enough to supply more than one million households for a year and nearly the entire capacity of Folsom Reservoir. In response, on May 10, Governor Gavin Newsom issued a drought proclamation that now covers 41 of 58 counties and encompasses 30 percent of the state’s population, including the entire Delta and its abundant wildlife, dozens of islands and levees, and miles of winding waterways.
Water users work together in the Delta to prevent salinity intrusion, minimize ecosystem stress, and preserve water in storage. Today’s notices are likely to remain applicable for many users until winter rains restore natural flows.
Under California law, a water right holder can use surface water for beneficial purposes such as agriculture, municipal supply, recreation, and protection and enhancement of the environment. The age and type of right, be it appropriative (acquired natural or abandoned water) or riparian (natural water connected to land), generally informs how water can be diverted during drought conditions. In times of shortage, those with more junior rights typically are required to stop diverting from rivers and streams before limitations apply to more senior right holders.
Today’s notices applied to more junior post-1914 appropriative rights holders. Current projections indicate that water is also likely unavailable this summer for a subgroup of more senior pre-1914 appropriative and possibly riparian water right claims.
The board encourages diverters to collaborate with each other on voluntary agreements that help local communities adapt to water shortages, prevent impacts to other legal water right users, and benefit fish and wildlife.
The board website contains additional information about drought, notices of water unavailability and an updated methodology used to determine when water in the Delta is unavailable. Staff held a public workshop May 21 on the methodology and demonstrated the Unavailability Visualization Tool.