Dam at McAarthur Lake to be Repaired

Lake Level Must be Lowered to Complete Project The Idaho Department of Fish and Game (IDFG) announced plans to repair the dam at the McArthur Lake Wildlife Management Area south of Naples and north of Elmira. Work is scheduled to begin September 11. Concerns about the structure were first indicated in February, 2006 when slumping of the earthen portion of the dike on the south side of the dam was discovered. The Idaho Department of Water Resources investigated the condition of the dam and determined that several cubic feet of material had been lost by water and soil movement through the dam. An engineering firm was then contracted to inject dye into the soil to ascertain where the soil was moving through the earthen dam. For repairs to be completed, the lake must be drawn down. The drawdown began on August 25. Periodic drawdown of any reservoir is beneficial to fish and wildlife. McArthur Lake was last drawn down in 2002 for wetland management purposes and would have been due for another drawdown in the not too distant future. Benefits of a drawdown include the facilitation of nutrient cycling, increased plant diversification, increased area occupied by emergent plants, and rendering of food items valuable to fish and wildlife. During the 2002 drawdown, a significant increase in selected habitat for shorebirds and loafing waterfowl was observed. The McArthur WMA property was obtained by IDFG in 1942, and the earthen dam was constructed in 1944 impounding about 200 acres. Further land acquisitions in 1964 allowed the IDFG to replace the original structure and in 1965 the dike was raised and major concrete spillway and a fish bypass were constructed increasing the reservoir to its current size of 600 acres.