Limnological data from selected lakes in the San Francisco Bay region, California

Abstract

Limnological data were compiled on 21 lakes in the San Francisco Bay area. The data were obtained from regulating agencies and from recent surveys made by the U.S. Geological Survey. The history of each lake and of its respective regulating agency is presented, along with methods used for data collection and analyses. The largest reservoir, Lake Berryessa, has a volume of 1,600,000 acre-ft (1,975 hm 3 ), with a drainage. area of 576 mi 2 (1,490 km 2 ). Pilarcitos Lake is one of the smallest reservoirs, with a volume of 3,100 acre-ft (3. 8 hm 3 ) and a drainage area of 3. 80 mi 2 (9.84km 2 ). Eleven of the 21 reservoirs are open to the public for recreation. The most intensive shoreline development and use is at Lake Berryessa and Lake Merced. All but three of the 21 reservoirs (not including Upper Crystal Springs Reservoir) were thermally stratified during the summer. Eight of the reservoirs showed evidence of dissolvedoxygen depletion during the summer. Lafayette Reservoir and Loch Lomond are mechanically aerated in order to increase the dissolved-oxygen concentration and lower the surface water temperature. The lake waters ranged from the hard (320 mg/1 CaC0 3 ) of Calero Reservoir, to the soft (27 mg/1 CaC0 3 ) of Upper Crystal Springs Reservoir. Drainage from abandoned mercury mines in Santa Clara County has resulted in mercury concentrations in Calero and Lexington Reservoir fish which exceed U.S. Food and Drug limitations (0.5 μ /g) for acceptability of mercury in fish used for human food. In Loch Lomond, four major production periods of the blue-green algae, Anabaena sp . , occurred from May to October, 1967-69. Blue-green algae were the most numerous algae in Lake Del Valle from March through July 1971, with 5,400 blue-green algal organisms per millilitre collected in April.