December 14, 2018 - MARIPOSA -  By Michael Martin, Ph.D., Director, Merced River Conservation Committee - The State Water Resources Control Board on Wednesday adopted a plan designed to restore water flows through the Lower San Joaquin tributaries, including the Merced River.  This action concludes studies, hearings, and testimony from fisheries and agricultural experts conducted over the past nine years.

The plan sets a starting point for increased flows but also makes allowances for reduced river flows on tributaries where stakeholders have reached voluntary agreements to pursue a combination of flow and “non-flow” measures that improve conditions for fish and wildlife, such as habitat restoration and reducing predation.

A dramatic decline in the once-thriving populations of native fish species that migrate through and inhabit the Delta has brought some species to the brink of extinction. In 1984, for example, about 27,000 fall-run Chinook salmon adults returned to the Merced River.

The number of returning adults dropped to < 400 in 2007-2009 and just 3200 in 2017.  The native steelhead rainbow trout has been extirpated from the Merced River below the Merced Irrigation District project facilities, and now remains only in Yosemite National Park, in the South Fork of the Merced River.

The final Lower San Joaquin River/Southern Delta update includes improved instream flows February through June, the critical months for migrating salmon and steelhead on the Merced River.   These flows are measured as a percentage of “unimpaired flow,” the amount of water moving down river if there were no dams or other diversions.

A flow criteria report adopted by the State Water Board in 2010 concluded that an unimpaired flow requirement of 60 percent on the Lower San Joaquin River tributaries would be desirable to preserve the attributes of a natural variable system to which native fish species are adapted. That report did not consider impacts to other water users, however, which the Board has done in arriving at a lower flow requirement, adopted this week.

The plan update the Board adopted includes a requirement for 40 percent of unimpaired flow, within a range of 30 to 50 percent.

The Board’s proposal seeks to incentivize agreements that offer habitat restoration and other measures that can benefit fish and wildlife with less water, than just water alone.

The Merced River Conservation Committee appreciates the SWRCB’s actions to adopt a water quality control plan that provides restoration water flows to the Merced River, and pledges to pursue agreements and additional actions toward habitat restoration and fisheries management that will improve salmonid populations in the lower Merced River, and hopefully prevent the extinction of these two important keystone California species.
Source: Merced River Conservation Committee