Hydroclimate Heterogeneity in the Upper Deschutes River Basin

Abstract

The Upper Deschutes Basin displays significant climatic, topographic, biotic, and pedolgic variability that contrasts markedly with the regular streamflow. Increasing demands on the quantity and quality of local and regional water supplies emphasize the importance of understanding the watershed’s hydroclimatic variability. Dividing the watershed into four units maximizing landscape homogeneity within each area provides a framework for analyzing hydroclimatic differences. Modeled monthly runoff for 108 months accurately estimates the total watershed monthly average runoff and standard deviation. Sector comparisons reveal greater diversity than suggested by either precipitation or runoff amounts. The Wickiup sector is clearly the dominant hydroclimatic component. The Little Deschutes sector is the largest, but it accounts for only 22 percent of the precipitation and 23 percent of the runoff. Differences in moisture exchange processes among the sectors reveal that évapotranspiration consumes 40 percent of precipitation in the Wickiup sector but 69 percent in Little Deschutes. The annual moisture deficit in the Benham Falls sector is 188 mm, or 9 times greater than the annual deficit in the Wickiup sector. Hydroclimatic variability represents a major challenge for land and water resource development in the watershed.