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The Lake Mead Monitoring Program has continued to develop information on the limnological condition of Lake Mead. We have significantly increased our analytical capabilities this year by developing a cooperative project with the U.S. Bureau of Reclamation and continuing our cooperative program with E.P.A. We also were able to derive significant benefit from the reviews of the Pollution Abatement Project written by Clair Sawyer and Charles Goldman. Partially as a result of these reviews we have had the opportunity to interpret and more fully explain the significance of our work to a wider public audience than would otherwise have been possible.
Among the important issues that have been of primary interest this
year are:
1. The significance, extent and effect on nutrient distribution of
a density current from Las Vegas Wash.
2. The significance of lake level on algal abundance and productivity
in Las Vegas Bay.
3. The probably effects of the AWT plant on algal abundance and
productivity in Las Vegas Bay.
This report more fully explains the data available on the density current and shows that the current becomes completely dissipated and mixed with waters of Las Vegas Bay, usually within the middle portion of the Bay. The influence of lake level on algal abundance is also examined with evidence supporting a hypothesis that higher lake levels result in lower algal populations. While we do not have accurate data on water volumes in Las Vegas Bay at various lake levels, rough calculations suggest that rising lake levels since 1972 have in fact resulted in a greater dilution of the inflowing nutrients from Las Vegas Wash. In effect the higher water levels have probably resulted in improved conditions in the lake because the nutrient inflows have actually become increasingly diluted in Las Vegas Bay since 1972. This is basically the same effect that would result by removing nutrients from an inflowing stream if lake level remained stable. A series of bioassays were performed to attempt a reasonable prediction of the probable effects of phosphorous removal on algal growth in Las Vegas Bay. Because of a number of variables, we did not obtain a quantitative estimate of the effect of phosphorous removal on algal growth in the bay. We did demonstrate however that reduction in phosphorous inflow will result in reduction of algal growth in Las Vegas Bay, if the bioassay procedures have approximately simulated conditions in Las Vegas Bay. Additional experimentation is necessary to approach a quantitative model of the effects of phosphorous removal on algal production in Lake Mead.
Again we believe the value of the monitoring program has been demonstrated. Without the long-term data base provided by the Lake Mead Monitoring Program, the public discussion that has resulted from the interest created by AWT construction would have been forced to rely on short-term investigations, interpretation by interested and concerned laymen or emotional argument by individuals or organizations with special interests.


Algae; Bacteria; United States--Lake Mead; Water quality--testing; Water treatment plants; Water--waste


Environmental Health and Protection | Environmental Monitoring | Fresh Water Studies | Water Resource Management