Stanley W. Trimble | USGS Science

USGS2010

Reclaiming freshwater sustainability in the Cadillac Desert

Increasing human appropriation of freshwater resources presents a tangible limit to the sustainability of cities, agriculture, and ecosystems in the western United States. Marc Reisner tackles this theme in his 1986 classic Cadillac Desert: The American West and Its Disappearing Water . Reisner's analysis paints a portrait of region-wide hydrologic dysfunction in the western United States, suggesting that the storage capacity of reservoirs will be impaired by sediment infilling, croplands will be rendered infertile by salt, and water scarcity will pit growing desert cities against agribusiness in the face of dwindling water resources. Here we evaluate these claims using the best available data and scientific tools. Our analysis provides strong scientific support for many of Reisner's claims, except the notion that reservoir storage is imminently threatened by sediment. More broadly, we estimate that the equivalent of nearly 76% of streamflow in the Cadillac Desert region is currently appropriated by humans, and this figure could rise to nearly 86% under a doubling of the region's population. Thus, Reisner's incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method. We close with a prospectus for reclaiming freshwater sustainability in the Cadillac Desert, including a suite of recommendations for reducing region-wide human appropriation of streamflow to a target level of 60%.

Proceedings of the National Academy of Sciences of↗

USGS1984

Sediment characteristics of Tennessee streams and reservoirs

Suspended sediment and reservoir sedimentation data have been analyzed to determine sediment yields and transport characteristics of Tennessee streams Data from 31 reservoirs plus suspended sediment data from TVA sampling efforts in the 1930’s and 1960’s, and U.S. Geological Survey efforts from 1975-82 have been used. Results of the analyses show that the measured suspended-sediment is mostly silt and clay-size material even in the sand bed channels of western Tennessee. Samples of suspended sediment rarely exceed 25 percent sand. Computed unmeasured load is less than 10 percent of the total sediment load in western Tennessee. Unmeasured load has not been computed for middle and eastern Tennessee streams because the bed material is generally coarse and quite variable. However, unmeasured load in these streams is believed to be less than 5 percent of total load. Transport curves show that when flow is less than about 1 cubic foot per second per square mile, western Tennessee streams have higher concentrations than middle or eastern streams. When flow exceeds about 10 cubic feet per second per square mile, however, concentrations in middle and eastern streams can equal or exceed those in western streams. The more efficient sediment-delivery processes operating in middle and eastern Tennessee basins are responsible for the rapid increases in suspended sediment concentrations with increasing flow. Sediment yields for middle and eastern Tennessee basins generally are less than 800 tons per square mile per year, however, heavily strip-mined basins can have yields from 1,000 to 3,000 tons per square mile per year. Yields for the heavily agricultural and channelized basins of western Tennessee generally range from 700 to 1,000 tons per square mile per year.

Tennessee↗