The State Water Board on Wednesday notified 930 junior water rights holders in the Upper Russian River basin to immediately reduce their water diversions to safeguard drinking water. The action cuts deliveries to a number of wineries and vineyards in Napa and Sonoma Counties but leaves out senior water rights holders for now.

“There is a real risk of Lake Mendocino emptying by the end of this year,” warned Erik Ekdahl, deputy director of the board’s Division of Water Rights.

He added that another dry winter could transform the river into a series of disconnected pools. The board noted that it is still early in the dry season and additional actions may be needed as conditions worsen.

On the Central Valley side, the Bureau of Reclamation officially cut all water allocations for agricultural contractors north and south of the Delta. The bureau had previously suspended the 5% allocation. Deliveries to municipal water users dropped from 55% of historic use to 25%.

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In response, the Westlands Water District banned landscape watering to conserve water for drinking, cooking and hygiene.

“Today’s announcement reflects the harsh realities of a second year of drought and the second driest year on record,” said Westlands General Manager Tom Birmingham. “Reclamation’s inability to make water available … is one more reminder that the state’s water supply infrastructure is inadequate.”

He said that added demands “from ineffective implementation of environmental laws” have led to basic human needs not being met.