Glacier Impacts on Summer Streamflow in the Wind River Range, Wyoming

Abstract

The Wind River Range (WRR) of Wyoming is host to approximately 63 glaciers. Extensive research has been conducted using remote imagery to estimate the recent area and volume changes of these glaciers with the goal of estimating the potential effects of these changes on watershed streamflow. Results show that the glaciers were mostly in recession since 1966, the beginning of the study period. The current research was performed to supplement results from the remote imagery analyses. In this paper, streamflows from glaciated and nonglaciated watersheds in the WRR for the period 1967–1992 were analyzed. The difference in July-August-September (JAS) watershed flow magnitude for the 26-year period between glaciated (Green River and Bull Lake Creek) and nonglaciated (East Fork River and Wind River) watersheds ranged between 8 and 23%. As expected, the effects of glaciers on local streamflows during JAS were shown to be much greater than that of ice melt alone. The influence of glaciers accounted for 23–54% of the late summer (JAS) flow in glaciated watersheds with approximately 2–12% because of loss of glacial mass, whereas the remainder of the increased flow was because of the glaciers decelerating the snowmelt runoff through internal storage/delayed release of liquid water. The glaciated watersheds provided a more stable source of streamflow because they displayed less year-to-year streamflow variability with coefficients of variation of 0.36 (Green River) and 0.29 (Bull Lake Creek) compared with the nonglaciated values of 0.55 (East Fork River) and 0.45 (Wind River).