Streamflow Response of a Southern Plains Watershed to Decade-Scale Precipitation Variations

The sensitivity of streamflow response to decade-long variations in precipitation was investigated for the Little Washita River Experimental Watershed (LWREW) in southwestern Oklahoma. Understanding the dynamics of this precipitation - streamflow interplay is important for long-term strategic planning of adequate water supplies to meet the demands of a growing society. This study showed that trends in annual streamflow leaving the LWREW are sensitive to trends in average annual precipitation. About half of the additional precipitation amount produced by an increasing trend above the long-term average leaves the watershed in the form of surface runoff. The converse is true for a decreasing trend in precipitation. The sensitivity of streamflow in the LWREW to decade-long variations in precipitation was between 4 and 6, meaning that, at decade scales, a 10% increase or decrease in precipitation leads to a 40% to 60% increase or decrease in streamflow, respectively. This high sensitivity emphasizes the need to consider such decade-scale precipitation and streamflow in the planning of water resources infrastructure and development of long-term management strategies for efficient utilization of water resources.