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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L10403, doi:10.1029/2006GL025711, 2006

Trends in 20th century drought over the continental United States

Konstantinos M. Andreadis

Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA


Dennis P. Lettenmaier

Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA


Abstract

We used a simulated data set of hydro-climatological variables to examine for 20th century trends in soil moisture, runoff, and drought characteristics over the conterminous United States (U.S.). An increasing trend is apparent in both model soil moisture and runoff over much of the U.S., with a few decreasing trends in parts of the Southwest. The trend patterns were qualitatively similar to those found in streamflow records observed at a station network minimally affected by anthropogenic activities. This wetting trend is consistent with the general increase in precipitation in the latter half of the 20th century. Droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the country over the last century. The main exception is the Southwest and parts of the interior of the West, where, notwithstanding increased precipitation (and in some cases increased soil moisture and runoff), increased temperature has led to trends in drought characteristics that are mostly opposite to those for the rest of the country especially in the case of drought duration and severity, which have increased.

Received 9 January 2006; accepted 21 April 2006; published 25 May 2006.

Index Terms: 1812 Hydrology: Drought; 1833 Hydrology: Hydroclimatology; 1872 Hydrology: Time series analysis (3270, 4277, 4475).

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Citation: Andreadis, K. M., and D. P. Lettenmaier (2006), Trends in 20th century drought over the continental United States, Geophys. Res. Lett., 33, L10403, doi:10.1029/2006GL025711.