A water-quality reconnaissance of Big Bear Lake, San Bernardino County, California, 1972-1973
A water-quality reconnaissance study of the Big Bear Lake area in southern California was made by the U.S. Geological Survey from April 1972 through April 1973. The primary purpose of the study was to measure the concentration and distribution of selected primary nutrients, organic carbon, dissolved oxygen, phytoplankton, and water temperature in the lake. Estimates of the nitrogen, phosphorus, and silica loading to the lake from surface-water tributaries and precipitation were also made. Results of the study indicate that Big Bear Lake is moderately eutrophic, at least in regard to nitrogen, phosphorus, and organic content. Nitrate was found in either trace concentrations or below detectable limits; however, ammonia nitrogen was usually detected in concentrations greater than 0.05 milligrams per liter. Orthophosphate phosphorus was detected in mean concentrations ranging from 0.01 to 0.05 milligrams per liter. Organic nitrogen and phosphorus were also detected in measurable concentrations. Seasonal levels of dissolved oxygen indicated that the nutrients and other controlling factors were optimum for relatively high primary productivity. However, production varied both seasonally and areally in the lake. Primary productivity seemed highest in the eastern and middle parts of the lake. The middle and western parts of the lake exhibited severe oxygen deficits in the deeper water during the warmer summer months of June and July 1972.