According to a 2014 State Water Resources Control Board (SWRCB) report, there are more than 3,000 known in-Delta water rights and claims. However, evidence suggests that there are hundreds of additional water users in the Delta illegally diverting water.  In a 2004 U.S. Fish and Wildlife Service delta smelt 5 year review, it was estimated that local in-Delta diverters export up to 5,000 cubic feet per second (cfs) from the Delta – or almost half as much as the combined federal and state pumping plants maximum export rate of up to 11,000 cfs. Unlike the Central Valley Project (CVP) and State Water Project (SWP), pumping operations at these local diversions are not regulated to limit impacts on endangered species.


The number of agricultural in-Delta diversions has expanded over the past decade and therefore, the rate of unscreened and unregulated diversions has likely increased. Agencies and experts, including the U.S. fish and Wildlife Service, acknowledge that unscreened in-Delta diversions may impact the delta smelt through entrainment and hydrodynamic influence. However, State and federal regulators have expended little or no effort to date to determine the effects of these unscreened pumps, or to regulate or monitor these diversions in order to slow the decline of endangered species.

In February 2015, the SWRCB issued an order requiring senior water rights diverters in the Delta to provide detailed information regarding diverters’ water rights claims after receiving information of illegal diversions.  The order applied to 1,061 water rights claims held by about 450 individuals in the Delta and the Sacramento and San Joaquin watersheds.

Meanwhile, amid record drought the SWRCB issued historic curtailment notices in 2015.

  • April 23 2015 – 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.
  • May 1, 2015 – 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.
  • 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.
  • 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 11 right holders. An additional four water rights on the Tuolumne River are being curtailed as well.

In addition to the State and federal pumping operations, a number of municipalities operate diversions, including pumps, to serve municipal and industrial users in the Delta and Northern California, including the Bay Area. Together, these diversions directly impact the quantity and quality of water available for fisheries and the ecosystem.