Impacts of climate change on water yield in the Upper Wind River Basin

The potential impacts of climate change on water yield are examined in the Upper Wind River Basin. This is a high-elevation, mountain basin with a sno wfall/snowmelt dominated streamflow hydrograph. A variety of physiographic conditions are represented in the rangeland, coniferous forests, and high-e levation alpine regions. The Soil Water Assessment Tool (SWAT) is used to m odel the baseline input time series data and climate change scenarios. Five hydroclimatic Variables (temperature, precipitation, CO2, radiation, and h umidity) are examined using sensitivity tests of individual and coupled var iables with a constant change and coupled variables with a monthly change. Results indicate that the most influential Variable on annual water yield i s precipitation; and, the most influential variable on the timing of stream flow is temperature. Carbon dioxide, radiation, and humidity each noticeabl y impact water yield, but less significantly. The coupled variable analyses represent a more realistic climate change regime and reflect the combined response of the basin to each variable; for example, increased temperature offsets the effects of increased precipitation and magnifies the effects of decreased precipitation. This paper shows that the hydrologic response to climate change depends largely on the hydroclimatic variables examined and that each variable has a unique effect (e.g., magnitude, timing) on water y ield.