Robert C. Averett Walter G. Hines Richard H. Fuller 1975 <p><span>Lopez Reservoir is a multipurpose impoundment that was filled during a </span><span>30-week period following a series of intense storms during the winter 1968-69. </span><span>The reservoir is used for flood control, water supply, and recreation, </span><span>including swimming, fishing, and boating. At full pool Lopez Reservoir has </span><span>a surface area of 974 acres (394 square hectometres), a maximum depth of </span><span>145 feet (44.2 metres), and a shoreline of 22 miles (35.4 kilometres). </span></p><p><span>Nuisance algal blooms have been a frequent occurrence in the reservoir since the first summer after filling (1969). The dominant bloom species was the blue-green alga Anabaena unispora. Cospecies were the diatoms <i>Stephanodiscus astraea</i> and <i>Cyclotella operculata</i> and the green algae <i>Pediastrum duplex</i> and <i>Sphaerocystis schroeteri</i>. During a bloom of <i>A. unispora</i> in May 1972, the total cell count at the lake surface was almost 100,000 cells per millilitre of water.</span></p><p><span>Lopez Reservoir is thermally stratified from April until November. Dissolved-oxygen stratification closely parallels the thermal stratification. Anoxic conditions begin to develop in mid-May, and by early July all water below a depth of 40 feet (12 metres) is oxygen deficient.</span></p><p><span>The application of copper sulfate (CuSO₄) to reduce algal production has met with little success. Possible application rates and methods of determining application rates based upon water chemistry are presented.</span></p> application/pdf 10.3133/wri7447 en U.S. Geological Survey Problems related to water quality and algal control in Lopez Reservoir, San Luis Obispo County, California reports