The Stanislaus River is paying for the sins of the Central Valley Water Project.
The Bureau of Reclamation 10 days ago significantly increased releases from the most drought-ravaged major dam in California — New Melones Reservoir — to meet state mandated salinity requirements at Vernalis just south of Manteca where the Stanislaus River joins the San Joaquin River.
The releases nearly doubled to 575 cubic feet per second in a bid to help dilute salinity at Vernalis caused by agricultural runoff primarily from the west side of the San Joaquin Valley south of Tracy.
It had the effect of lowering levels at New Melones as the outflow in the middle of winter significantly exceeded inflow. Outflow was running between14 and 108 cubic feet per second between Feb. 9 and Feb. 18 before being ramped up significantly to flows ranging from 366 cubic feet per second to 575 cubic feet per second. Releases from New Melones are expected to drop to 200 to 250 cubic feet per second today.
The salinity at Vernalis issue is in addition to effort to save native fish on the Stanislaus from low water flow this summer that will be detrimental to their survival due to temperature concerns. It is also separate from Delta salinity issues that could come into play and further drain New Melones given water releases from reservoirs farther south such on the Merced River may not reach Vernalis this summer due to extensive agricultural pumping from the river before water reaches Vernalis.
The South San Joaquin Irrigation District has been lobbying the Bureau to ask for relief from the salinity order from the Department of Water Resources for months. The Bureau just recently asked for such relief from the state due to the drought emergency. A decision is expected in the coming weeks.
The salinity problems started on the San Joaquin Valley’s Westside in the late 1940s. That’s when the federal government constructed Friant Dam that diverted relatively salt free water from the upper San Joaquin River into the Tulare Lake Basin and north to Madera County. The Central Valley Project had Westside farmers exchange their water rights for that water for water supplied via the Delta through the Delta-Mendota Canal that is west of Tracy. That water switch brought water from the Delta with a higher salinity content to the Westside. It triggered salinity issues for Westside farmland. High salinity can render soil sterile. The runoff from the Westside irrigated with Delta water drained into the San Joaquin River which in turn hurt fish.
The salinity standard order at Vernalis was designed to rectify that situation.
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SSJID, OID walking tight rope on Stanislaus
The releases for salinity from Vernalis may go counter to an agreement hammered out by the San Joaquin River Tributaries Group with environmental concerns for the restoration of the San Joaquin River as water to flush the San Joaquin River wasn’t supposed to touch New Melones water exclusively. But the other rivers — most notably the Tuolumne and Merced — also lack water plus their releases are being pumped downstream for farming before it reaches Vernalis.
The SSJID and their partner in the Tri-Dam Project — the Oakdale Irrigation District — are walking a tight rope trying to get the Bureau to look at biological research and water conditions to amend its operation of New Melones while trying to protect fish and keep water flowing to farms and the cities of Manteca, Lathrop, and Tracy while saving water for a potential fifth year of drought.
The SSJID and OID have invested $1 million annually since 2004 to study fish and improve fish habitat along the Stanislaus River.
The investment was designed so they could not only be good stewards of the river that they control senior water rights on but also to assure fish could stay healthy while water needs were met for farming and urban users.
SSJID General Manager Jeff Shields noted the districts’ two biggest concerns in regards to keeping water supplies flowing as the fourth summer of drought inches closer is salinity and water temperature.
A five degree increase in the water temperature on the Stanislaus River can prove lethal to fish.
It is behind the decision to drain the 67,000-acre-foot Tulloch Lake. It saves scarce water at New Melones to make sure there is water to prevent the Stanislaus from running dry this summer and fall. It also eliminates the lethal shocking of fish by having them move in warmer water to colder water at Tulloch and then back to warmer water as they continue on their journey to the Delta and the Bay.
The strategy of draining Tulloch was successfully used in 1991 to protect fish.