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Diversion Dam, Fish Ladders, & Diversion Canal Fish Screen

Diversion Dam and Fish Ladders Project

Completed in 2003, The New Dam & Fish Ladders Project originated in 1997 as part of the Lower Mokelumne River Restoration Program. The project consisted of the replacement of the District’s existing 93-year old dam with a new dam and three fish ladders to improve irrigation reliability and conditions for fish passage. This involved constructing the new dam with three Obermeyer Gates, state of the art fish ladders, fish monitoring systems, and fish screening at the District’s canal diversion.
  

The design documents underwent technical peer review by the engineering team and permitting agencies as part of all improvements that were included within the Lower Mokelumne River Restoration Program. This included the United States Bureau of Reclamation, the Army Corps of Engineers, the National Marine Fisheries Services, the United States Fish and Wildlife Service, the California Department of Fish and Game, the Division of Safety of Dams and the California Regional Water Quality Control Board.  A fulltime resident engineer was onsite during all construction periods to manage and inspect construction activities, and ensure conformance with the contract documents.

Upstream and Downstream Control.  The primary function of the WID Dam is to provide a responsive Lodi Lake water surface elevation of up to 41 feet for operating the District’s diversions and fishery flows.  Water levels are automatically controlled via a Supervisory Control and Data Acquisition System (SCADA) that manipulates the height of the gates, allowing the maintenance of pre-determined lake levels and flows, both upstream and downstream.

The main fish passage ladder is the High Level Ladder, operated under full reservoir conditions.  The ladder consists of a series of stair-stepped pools, with a design flow is 75 CFS. An automatically controlled master control gate measuring 4 feet high and 7 feet wide is provided for maintaining the required ladder discharge and a constant surface elevation at the fish counting station.

A separate Low Level Ladder provides fish passage during any low-reservoir period with flow conditions of 15 to 20 CFS or less.  The low level ladder is controlled by weirs with one-foot wide vertical slots and operates at varying flows, and under submergence conditions.  The 4’ x 4’ gate will prevent water from entering the ladder when the reservoir is full and the ladder is not being used. The low ladder utilizes the same entrances as the high ladder providing for a common attraction pool below the dam for up-stream migrants.

The Pool and Chute Ladder is designed to operate under low level reservoir conditions only.  The pool and chute ladder passes up to 275 CFS and can be operated in conjunction with the lower ladder, dependent upon the reservoir level. Salmon and steelhead of all life stages, as well as approximately 50 other fish species, are directed to the ladder entrance(s) by the attraction flows.

The total cost of the New Dam & Fish Ladders Project was approximately $15.4 million; financed almost entirely by the District through its own funds with the exception of a $2.7 million grant from the CALFED Bay Delta Program that funded the feasibility studies, permitting, licensing, and legal work required during the design phase of the project.

Diversion Canal Fish Screen Project

Completed in 2008 as part of the Lower Mokelumne River Restoration Program and operating in conjunction with the WID Dam, the “V” type Fish Screen is located just off-stream in the WID Diversion Canal. It prevents fish from entering the WID canal system by a series of stainless steel screens with openings of 1.75 mm. Fish approaching the screen will be channeled into a 30” bypass pipeline (with an operating flow range of 8-20 CFS) that deposits them downstream of the dam.   The “V” screen is approximately 100 feet long and 10.6 feet tall. The screen has an operating range of 0-414 CFS under a full reservoir with an operating elevation of approximately 39.5 feet to 41.0 MSL. 

Two main control gates are located just downstream of the screens and regulate water height and flow into the canal system. Like the dam, SCADA maintains the gates depending on the desired settings.  A floating debris boom and a trash rack is located upstream from the screen to remove any large debris.  Two vertically mounted and horizontally traveling brushes sweep small debris that accumulate on the screen into the bypass pipeline.  All aspects of this state of the art “V” screen are designed to meet the California Department of Fish and Game, National Marine Fisheries Service, and United States Fish and Wildlife Service criteria.