Document Type

Technical Report

Publication Date

1960

Publisher

United States Government Printing Office, Washington, D.C.

Abstract

Reservoirs are becoming an increasingly prominent feature of the American landscape. Built for flood mitigation and to change a fluctuating river into a dependable source of water for irrigation, power, and other purposes, they are predestined, like natural lakes, to be destroyed sometime following their creation. Sedimentation sooner or later robs most lakes and reservoirs of their capacity to store water. The significance of sedimentation in the life of Lake Mead, the largest artificial reservoir in the world, was realized when the plan for the reservoir was conceived, and an aerial survey of the floor was made in 1935 before the reservoir filled with water. The survey provided a base for the study of future sedimentation.

A casual view of the magnificent expanse of Lake Mead in its desert environment gives no more than a hint of the complex actions and interactions within and near the lake that are critical in relation to the long-term service for which the lake was impounded. The reservoir impounds sediment, dissolved salts, and heat as well as water. Each of these has important effects on the usefulness of the reservoir. Accurate appraisal of the magnitude of the impounded items is the key to longtime successful reservoir management. Such appraisals take the form of budgets, showing the balance between income, outgo, and storage. The sediment budget affects the life of the reservoir, the salt budget affects the chemical quality and usefulness of the impounded water, and the heat budget affects evaporation and the water balance. This report, although centered about the sediment budget, treats the other items to some extent, but each in time will require separate inquiry. The importance of evaporation already has led to a separate report on the heat budget. These problems relate to all reservoirs; but, because of the great size of Lake Mead, the importance and complexity of the problems there reach major proportions. The lake offers an opportunity to test and apply principles that can be derived from study of the sediment, salt, and heat balances. For these reasons the Bureau of Reclamation, the steward of the reservoir on behalf of the people of the country, asked the Geological Survey to lead a joint study by many scientists of the diverse and complicated aspects of Lake Mead. The resulting report is unique in its field because it represents a study by a diversified group of research scientists trained in several different fields of research, including oceanography, hydrology, and geology, working together on a common problem. Such pooling of talents promises to become more common in future hydrologic research because the results of this study have proved the synergistic value of collaboration.

The specific results of the study are food for speculation about future accumulations of sediment and the movement of salt. We have assurances that Lake Mead will not be filled with sediment for at least 350 years and that it will not become a salt lake. The wealth of information in this report undoubtedly will be useful in the operation, not only of Lake Mead, but of many other reservoirs already built or in prospect.

Keywords

Impoundments; Lake Mead (Ariz. and Nev.); Salinity; Sedimentation; Water quality; Water temperature

Disciplines

Biochemistry | Biology | Environmental Engineering | Environmental Monitoring | Geology | Hydrology | Natural Resources Management and Policy | Structural Engineering | Water Resource Management

Language

English