Trends in runoff in the Pacific Northwest

The diminution in runoff in the Pacific Northwest, particularly the Columbia River Basin, during the past 50 years, and its hydrologic significance are discussed in this paper. An analysis of the rainfall‐runoff relations for the Basin is made in order to explain the different influence of short‐ and long‐term precipitation factors on the diminution of runoff. The indicated effects of long‐term precipitation may reflect the influence of ground‐water storage.