Changes in Ground-Water Flow and Chemistry after Completion of Cattlemans Detention Basin, South Lake Tahoe, California— November 2001 to November 2003U

A study of the Cattlemans detention basin in South Lake Tahoe, California began in November 2000 to evaluate the effectiveness of the detention basin in reducing sediment and nutrient loads from urban runoff to nearby Cold Creek. Detention basins commonly are used to minimize sediment and nutrient loads from urban runoff in the Lake Tahoe Basin, but the effects of these detention basins on changes in ground-water flow and chemistry are largely unknown. This report summarizes changes in ground-water flow and chemistry for two years after completion of Cattlemans detention basin in October 2001. The report includes a comparison of dissolved nutrient loads from ground-water discharge to Cold Creek below the detention basin with dissolved loads in Cold Creek.