Needed repairs of key valves in the Cherry Lake dam will require the reservoir to be drained down to a minimum pool by end of summer

            With many reservoirs receiving their highest flows of snowmelt in decades, it isn’t an ideal time to drain a giant reservoir before the rainy season next fall. But that is exactly what is needed at Lake Lloyd (known more broadly as “Cherry Lake”). Failing valves in the dam require the reservoir to be drawn down to an extremely small “minimum pool” in order for Hetch Hetchy Power and Water crews to do the necessary repairs.

            Almost all reservoirs have substantial shifts in water depth between the high levels of early summer (after the peak period of snowmelt) compared to low levels of water in the fall, so as to be capable of handling potential inflow from significant winter storms. But the degree to which Cherry Lake needs to be drained this year is far beyond normal drawdown levels.

           By late summer or early fall, only a small percentage of the reservoir area will still have water. The goal is to retain plenty of water for fish to survive and to maintain good water quality, while otherwise shrinking the reservoir to a minimum pool. Those who are used to seeing Cherry Lake’s miles of water stretch from the dam north toward the Emigrant Wildeness will see the bare landscape that was cleared in the 1950’s to create the reservoir.

           Due to high flow releases posing safety risk, recreational access is now being restricted downstream from the dam (starting mid July), and vehicle access over the dam as well as boating on the lake will both be restricted starting early September.

            Old timers have claimed that migratory deer paths were blocked by the filling of the reservoir, forcing strings of deer to migrate around the lake and dam. Perhaps this year, if the vast majority of the lake becomes dry and exposed, deer moving downslope from the Emigrant Wilderness and Northern Yosemite Park will once again move in groups and clusters across what is currently the deep water of Cherry Lake.

 

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