"Deer Lake is located in the southeastern portion of Stevens County, Washington. In recent years, nuisance algal blooms have appeared on the lake causing concern that water quality may be deteriorating. This study was undertaken to determine the source(s) of nutrient loading. Two in-lake stations, inflowing surface tributaries, and groundwater wells were monitored for selected physical, chemical and biological parameters. Temperature profiles revealed thermal stratification with an accompanying positive heterograde oxygen distribution, achieving bottom anoxia throughout the growing season. Comparison of study findings to previous studies suggested that Deer Lake is an oligo- mesotrophic system undergoing a progression towards a more eutrophic state. Surface inflow from the Northeast Meadows, where livestock grazing occurs, was found to be a significant source of nutrient loading. Nutrients entering the lake are detained because of Deer Lake's high retention time, approximately nine years. Reduction of nutrient appears to be an intregral factor in slowing down the eutrophication process in Deer Lake, specifically phosphorus, since it was found to be the major limiting nutrient to algal growth"--Document.