chapter  10
20 Pages

LAKE AND RESERVOIR RESTORATION

The water quality problems caused by eutrophication were briefly mentioned in Chapter 7, but will be reiterated here in more detail. Increased enrichment of lakes and reservoirs can have the following direct and indirect effects: increased biomass of planktonic algae, with usually a dominance of blue-greens, several of which produce unsightly surface scums; taste and odour problems, caused largely by excretory products of blue-green algae, that can taint drinking water supplies and fish flesh;

oxygen depletion, caused by decomposition of sinking algae, that may render the hypolimnion anoxic or low enough in DO to limit the production and even survival of cold-water fish; reduced transparency of the water; increased incidence of swimmer’s itch, as a result of increased production of algae and detritus eating snails, the intermediate host for the parasite; increased trihalomethane precursors resulting from the increased organic matter; and possible increased incidence of toxic bluegreen algal blooms.