Rainfall and Tree Growth in the Great Basin

Rainfall and Tree Growth in the Great Basin

Rainfall and Tree Growth in the Great Basin

Rainfall and Tree Growth in the Great Basin

Excerpt

In the autumn of 1931 the writer collected data bearing on rainfall fluctuations in the northwestern part of the Great Basin since the first settlement of the region by white men. The study was suggested by Dr. Isaiah Bowman, and the expenses of the field work were defrayed by the Carnegie Institution of Washington. Officials and long-time inhabitants were interviewed, newspaper files and libraries consulted, lake levels observed and samples of lake sediments collected, and radial samples were sawed from stumps of trees growing on mountain slopes near the desert. Later, relevant literature was consulted in the Library of Congress and the library of the American Geographical Society. The Great Salt Lake region is included in this survey, although no field work was done there.

Because of the supreme importance of water in the deserts and semideserts of the Great Basin, explorers, emigrants, settlers, and historians made notes on the precipitation, on the water supply of rivers and lakes, and on crops and grazing conditions long before systematic instrumental observations were begun. Since official records of rainfall and runoff have been kept, settlers have observed and newspapers have recorded facts and conditions that are often more telling than the statistical figures. These traditional and historical data are especially valuable because they emphasize and date the extreme conditions, such as unusual floods and runoffs, high lake levels, severe droughts and economic catastrophies, and thereby help in determining the existence and trend of fluctuations in precipitation. However, these data are also sporadic, local, subjective, and inaccurate or misleading. Least reliable are the narratives about early emigrant trains to the West. Statements by settlers are usually correct as to facts but not always as to time. Average conditions and gradual changes have been given little thought, and therefore the data are notoriously incomplete. In some regions occurrences and conditions have been recorded or remembered by observant inhabitants; elsewhere no comparable information may be available for entire decades.

It seemed possible that the lake sediments might record stages of high and low water or complete desiccation. The exceptional opportunity offered by the partial or complete desiccation of most of the lakes in the northwestern Great Basin in 1931 was therefore used to study and sample their deposits. However, the results of the study were either negative or indefinite. The surface crusts of salt or clay that form when most of the lakes dry up are not preserved when the lake bottoms are . . .

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