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OPERATIONS UPDATE Maintenance Update Projects Offer Hope for Weed Problems Fish Screens Installed During the past winter NCWCD staff have installed molor driven rotary fish screens In the South Platte Supply Canal west of Erie. Fish screens became necessary !ollowlng the introduclfOn 01 grass carp In 1984. Grass carp have proven 10 be an effective method for controlling weed growth in canals eating up to twice their welghl in aquatic weeds daily. -.,. Installed Fish Screen on South Plane Supply Canal With the placement of the carp came the dilemma 01 keeping them confined to the designated canal sections. Otherwise the carp could end up outside the C.BT system altogether. At hrsl. bar screens were placed on both the upstream and downstream sections of canal. While this was an effective means for controlling the carp, this required considerable labor expense as a person was required to clean the bar screens of weed and trash almost hourly. The District and U.S. Bureau of Reclamation. under whose supervision the grass carp program was implemented. began looking for alternative ways to control the fish without such labor intenSive screens. The Dlstnct and the Bureau contacted the Florida Wafer Conservancy District near Durango about a pair 01 rotary screens that were not belOg used. After Inspecting the screens and determlOlOg they would meet the C-8T needs. plans were made to haul the TwO 6.000 pound screens and lrames across the mountalOS. NCWCD staff installed the screens in early 1990. In addition to setting the screens in place. bridges and handrails were installed and backfilled. rip rap placed and flOal canal alignment made pnor to the water delivery season. The motor driven screens elimlOate the need for constant surveillance by operation and maintenance personnel by Iiltmg trash and other debns up and over the screens and on down the canal. Shadow Mountain Drawdown Shadow Mountain ReservOir will be lowered thIS fall in an effort to control the burgeoning weed growth situation. The growth 01 aquatic vegetation has become an IOcreaslOg problem in recent years and the fall drawdown Will determrne if this is a feasible method for control Cooperatrng organizations rnclude the NCWCD and U S Bureau of Reclamation which operale the reservOir as part of the C-BT ProJect. the Western Area Power Admrnlstratlon whIch markets the power generated from the C.BT. the U S Forest Service. which manages . Shadow Mountain Reservoir the Arapahoe NallOnal Recreation Area In which Shadow Mountain is IOcluded. Grand County. the Town of Grand Lake, and local landowners. The five-foot drawdown will allow local homeowners. marina operators. and county officials to clear out weeds in approximately 140 acres (10.5% of the surface area) of land normally under water. . To lower Shadow Mountarn by fIVe feet. a coffer dam will have to be utilized between Grand lake and Shadow Mountain. This will separate the two lakes and keep Grand Lake at Its mandated histone lake level. The coffer dam is formed by inserting stop logs Into the existing structure that constItutes the foolbrldge at the passageway between the two lakes. The plan will lower the reservOir elevation for two weeks la allow night freezes to kill the exposed weeds. local landowners and Grand County will then be responsible far removing the dead and dying vegetation. II this method proves successful II wilt alleViate a problem that has grown worse In recent years. . 6 WATERNEWS SUMMER 1990