The Water Report: Water Rights, Water Quality and Water Solutions in the West Issue 17

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Issue #17 The Water Report Fish & Farms Gravel Pits Bypass System Channel Capacity Restoration Flows Delta Water Delivery Flood Control For 30 miles or so below Friant Dam extensive gravel mining operations have been conducted for many years in the flood plain adjacent to the San Joaquin River (over 50 gravel pits in or immediately adjacent to the river; occupying approximately 198 acres). The existence of these gravel pits present formidable problems for restoration of the historical salmon fishery. They may increase evaporation and water temperatures. If the gravel pits are not isolated from the river, at high flows the river connects with ( "captures ") these abandoned gravel pits, thereby slowing river flows and causing sediment and gravel to be deposited into the pits. These geomorphological events can limit or prevent the development of spawning areas in the river channel. Predator fish that reside in the pits, such as largemouth bass, may decimate the young salmon population and compromise any restoration experiment. About 51 miles below Friant Dam, a concrete flood control structure known as the Chowchilla Bifurcation Structure diverts all flows above the flood capacity of the river channel into a bypass system that extends for many miles east of the river's natural channel. The flood control system was built by the State sometime in the 1950s or 1960s, to protect the riverside communities of Mendota and Firebaugh. The banks are maintained by the Lower San Joaquin Levee District, which is not a party to the case. Consistent with its operating criteria and statutory authorization, the Levee District manages the riparian vegetation along the banks to allow for maximum flood flow conveyance capacity. The channel between the Bifurcation Structure and the town of Mendota has a very small capacity, and the fragile levees that protect adjacent property are locally owned and maintained. The 50 -year flood capacity of that portion of the river channel was previously rated at only 2,500 cubic feet per second. In actuality, however, the river's capacity may be far less than that, perhaps no greater than 1,300 cubic feet per second, except during times of extreme flooding when Mendota Dam is fully open downstream and the flood flows are passing directly through Mendota Pool. Currently, flows in excess of about 1,300 cfs are diverted by the Lower San Joaquin Levee District to a system of bypasses. Diverted flows do not reenter the river channel until they reach a point about 80 miles downstream. The fish flow restoration hydrographs developed in connection with the Water Supply Study (published by plaintiffs) call for springtime releases in many years that are far in excess of either the actual or design capacity of the river channel as it exists today. If projected fish flows exceed the carrying capacity of the channel below the Bifurcation Structure, they will be diverted into the flood bypass system, where it is unlikely they will be of any use to the fish. Section 5937 does not authorize the conversion of flood control structures or facilities into substitute habitat for fish passage. To accomplish their purpose, flood control channels must be kept clear of the riparian vegetation that is needed for fish habitat. Further, flood easements from property owners downstream from the bypass do not provide for fish flows. Requiring flooding for fish flow purposes, therefore, may overburden those easements. Increasing flows in the bypass may also result in seepage problems for farms lining the bypass. At Mendota, 60 miles below Friant Dam and about 11 miles below the Bifurcation Structure, the San Joaquin River joins with the north fork of the Kings River, known as "Fresno Slough" or "James Bypass." Since the mid -to -late 19th Century, there has been a dam in existence at this location known as "Mendota Dam." For the past 50 years, water pumped from the Delta has been delivered to the Exchange Contractors and others by means of the Delta- Mendota Canal. The delivery of Delta water to the Exchange Contractors is pursuant to agreements (circa 1939) under which the Exchange Contractors refrain from exercising their historical water rights to divert the San Joaquin River thus making diversion at Friant possible. Water delivered from the Delta- Mendota Canal backs up behind Mendota Dam to form the Mendota Pool. The Mendota Pool furnishes Delta water for irrigation to a number of important, but unscreened, agricultural canals and pump facilities. Indeed, in addition to the four Exchange Contractors, about six other third - parties who are not before the Court take water from various facilities at the Mendota Pool. To restore the historic fishery, fish screens would have to be installed. Below Mendota Dam, the river meanders north through tree -lined banks for about 22 miles to the Sack Dam, a permanent concrete structure that extends across the river about 85 miles downstream of Friant Dam. In most years, the 22 mile stretch of the river channel between Mendota Dam and Sack Dam is fed entirely with Delta water delivered to the Delta- Mendota Canal and passed through Mendota Dam by the Exchange Contractors, who are not before the Court, to deliver water further downstream to one of their members. At Sack Dam, one of the Exchange Contractors (San Luis Canal Company) generally diverts the Delta water that has been bypassed at Mendota Dam into its Arroyo Canal. About 99 miles below Friant Dam is a structure called the Sand Slough Control Structure, which diverts any flow that has re- entered the San Joaquin River below Sack Dam into the Bypass System. The Sand Slough Control Structure is another feature of the State's flood control system for the San Joaquin Valley. It is owned by the California State Reclamation Board and operated pursuant to certain flood 22 Copyright© 2005 Envirotech Publications; Reproduction without permission strictly prohibited.