Halfmoon Lake TMDL


The Wisconsin Department of Natural Resources (WDNR) developed one phosphorus Total Maximum Daily Load (TMDL) for one segment in the lower Chippewa River Basin, Half Moon Lake, Eau Claire, Wisconsin. The TMDL addresses the phosphorus impacts and impairments which were identified on the Wisconsin 1998 and 2002 303(d) lists.


Half Moon Lake (Hydrologic Unit Code 070500006) is a small, shallow eutrophic lake that formed as an oxbow of the Chippewa River. The lake is geographically located within the City of Eau Claire and the Lower Chippewa River Basin. The lake is highly eutrophic and exhibits excessive algae and aquatic macrophyte growth (Borman, 1990; Brakke, 1995; Konkel and Borman, 1996; James et. al., 2001, 2002). Half Moon Lake was originally listed on Wisconsin’s 303(d) impaired waters list in 1998 for eutrophic conditions and sedimentation and listed as a high priority for TMDL development on the October 2002 303(d) list.


WDNR will consider Half Moon Lake to meet the narrative water quality standard when the mean summer in lake chlorophyll a concentration in the lake is 30 ug/l. To achieve this goal, WDNR has determined a total load capacity of phosphorus to be 102 kg seasonally (June-August). The total load capacity proposed by Wisconsin of 102 kg/season represents a 65 percent reduction of phosphorus. WDNR has determined that this reduction of phosphorus will achieve the water quality target of establishing the appropriate designated use in the lake.

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Halfmoon Lake TMDL