Publication Date:
1959-05-01
Description:
Alternating wet and dry periods, each of several years' duration, are suggested by the records of precipitation at several localities in the southwestern United States, and they are indicated also by the records of natural streamflow. In some regions, the precipitation and runoff since 1930 have been at a significantly lesser rate than in the quarter-century prior to 1930, and in most of the Southwest drought has been prevalent since about 1945. A large proportion of the precipitation stations and stream-gaging stations in the Southwest have been established subsequent to 1930, and records from them are likely to be too short to indicate the climatic norm. Reservoirs, both surface and subsurface, can smooth out the marked daily, seasonal, and annual variations in water supply from precipitation, and can furnish water at rates more nearly in accordance with human needs. Many ground-water reservoirs, and some surface reservoirs, after being well filled during years of abundant precipitation and runoff, have provided an adequate supply of water during several successive years of drought. In the protracted drought periods that have been recorded in the Southwest, however, storage in most reservoirs has been depleted seriously, and the actual yield of some of them has been significantly less than the computed long-term average yield. Maintenance of a relatively constant yield throughout protracted wet and dry periods would require reservoirs having large storage capacity and losing as little water as possible by evaporation or other natural discharge; accurate evaluation of the long-term average inflow is a prerequisite to successful utilization of the reservoirs.
Print ISSN:
0003-0007
Electronic ISSN:
1520-0477
Topics:
Geography
,
Physics
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