This just in … Water curtailment update: Extended curtailments for Merced River, Upper San Joaquin; also City of San Francisco

From the State Water Resources Control Board:

SWRCB logo water boardsWith drought conditions continuing into the summer months, the State Water Resources Control Board (State Water Board) extended curtailments on the Merced River for senior water rights dating back to 1858; and all pre-1914 and post-1914 appropriative rights on the Upper San Joaquin River.

The Upper San Joaquin River runs from upstream of Friant Dam to the confluence with the Merced River. Today’s announcement affects 16 water rights held by eleven owners.

A curtailment notice is also being sent to the City of San Francisco for four appropriative water rights on the Tuolumne River dating back to 1903, based on the notice sent on June 12. Those notices had omitted the San Francisco water rights because the city’s water right dates had been entered into the State Water Board’s database incorrectly.

The senior water rights affected by today’s notice add to the growing number of water rights limited by the State’s ongoing drought as demand far outstrips supply in key Northern California watersheds. As of this notice, a total of 8,721 junior water rights and 297 senior water rights in the Sacramento-San Joaquin River watersheds and Delta have been notified that there is insufficient water in the system to serve their rights.

To determine the need for curtailment by water right holders, the State Water Board uses monthly diversion data and sorts that data by watershed, water right type and priority date. Water flow used for power generation that is diverted and returned back to the water course is removed from the analysis. The demands for water use by type of right are summed and plotted graphically to display junior and senior water right needs. To assess supply, monthly and daily natural flow data from the Department of Water Resources (DWR) are plotted with DWR estimates of return flows and additional minor tributary flows. The resulting supply vs. demand curve indicates curtailment is needed when demand outstrips supply.

As supplies continue to decline through the summer, it is expected that more senior rights will be impacted by limited water availability. As supply increases in the fall or winter, the State Water Board will lift the curtailments, i.e. notify diverters that water is again available under their priority of right, as soon as appropriate using the same procedure.

Curtailment notices issued so far this year

June 26 – Senior appropriative water rights on the Merced River with a priority date of 1858 or later, and all appropriative water rights on the Upper San Joaquin River, affecting 16 water rights held by eleven right holders.  An additional four water rights on the Tuolumne River are being curtailed as well.

June 12 – Senior appropriative water rights with a priority date of 1903 or later in the Sacramento and San Joaquin river watersheds and the Delta, affecting 277 rights held by 114 right holders.

May 1 – Junior appropriative water rights back to 1914 in the Sacramento River watershed and the Delta. A total of 5,740 water rights held by 2,772 right holders are affected.

April 23 – Junior appropriative water rights to 1914 in the San Joaquin and Scott river watersheds. A total of 2,981 water rights held by 1,474 right holders in the San Joaquin River watershed and 162 water rights held by 137 in the Scott River watershed are affected.


California water rights law is based on seniority. In dry years, when there isn’t enough water in the system to serve all water right holders, those with more junior rights are required to stop diverting water from rivers and streams before restrictions are imposed on more senior right holders. The Water Commission Act of 1913, which took effect in 1914, created California’s system of water rights and the distinction between junior and senior appropriative water rights.

Senior water right holders are riparian water rights, and those claiming appropriative water rights established prior to the Water Commission Act. A riparian water right is the right to use natural flow on land abutting a stream or river. In most instances, riparian rights share equal priority to the available natural flow and have seniority over appropriative water rights (both pre-1914 and post-1914). For appropriative rights, the priority system is based on the concept of “first in time, first in right.”

The State Water Board administers California’s system of water rights and is authorized to prevent unauthorized diversions of water. Unauthorized diversions include taking water at times when there is insufficient water available under the priority of right held by the diverter.

The State Water Board issued two letters earlier this year warning all water-right holders that water may not be available to them under their priority of right (curtailment notices) due to drought conditions. Last year, the State Water Board issued curtailment notices to more than 5,000 diverters on five watersheds statewide.

This year the State Water Board approved a proposal from riparian water right holders in the Sacramento-San Joaquin River Delta on May 22 to voluntarily cut back water use in exchange for assurances that they would not face enforcement actions in the event that their riparian water rights require some reduction later during the June-September growing season. Riparian water right holders had until June 1 to elect to participate in the voluntary program.

The State Water Board maintains a webpage to assist water right holders in several key watersheds to plan for possible limits on water supply availability. The webpage, titled “Watershed Analysis,” details projected water supply, demand and availability for the watersheds most likely to face restrictions during the drought as demand outstrips available water supply.

A Curtailment Fact Sheet provides additional details on the curtailment process. Please visit our curtailment notification website to see what watersheds have received curtailment notices.

Information on the drought is available at the State Water Board’s drought website.

To learn about all actions the state has taken to manage our water resources and cope with the impacts of the drought, visit Drought.CA.Gov. Every Californian should take steps to conserve water. Find out how at




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