A PRELIMINARY ANALYSIS OF CLIMATIC AND ANTHROPOGENIC EFFECTS ON GROUNDWATER-STREAM FLOW INTERACTIONS IN ALPINE REGIONS; UNCOMPAHGRE RIVER WATERSHED, CO, USA

In the western United States, limited fresh water availability coupled with growing agricultural and urban demands, are causing large urban locations to be heavily dependant on alpine water resources as supplemental sources of water supply. Regrettably, alpine water resources are fragile and highly dependent upon persistent weather and climatic conditions. Heavy dependence on a single water resource places extreme vulnerability on water resources for urban environments. With current research indicating dramatic changes resulting from climate warming, water resources in alpine areas are approaching excessive liability. The problem of reduced water resources is being accelerated by the volume of readily available fresh water decreasing and populations increasing. Thus, predicting the impact of climate change and variability on water resources is necessary to ensure that demands for water for irrigation and municipal water supply can be met.

Although snowmelt is the primary hydrologic input to an alpine stream, there are other first-order controls affecting the spatial variability of the hydrologic response linked to climate forcing. Spatial differences in groundwater dynamics and topographic controls are likely to have equally significant influences on the response of stream-flow, as does the spatial relationship associated with snow accumulation and melt. To understand the hydrologic response related to climate change in alpine regions, it is necessary to ask: To what extent do geologic and geomorphic spatial variations in groundwater dynamics control/modify the impact of climate change on stream-flow patterns in alpine drainage basins?

The Uncompahgre Watershed covers ~ 258.54 hectares. Using a X² test, preliminary analysis focused on establishing a link between a warming climate and changes in alpine stream-flow regimes. USGS, BOR, and Colorado State historic stream-flow data were used to identify change in flow regimes that may reflect anthropogenic effects on stream-flow. Like other regions in the western U.S., it is thought that the Uncompahgre River will show a decrease in summer stream-flow and a shift in peak runoff into earlier spring as a result of earlier snowmelt. Additional work will focus on documenting the geomorphic linkage and determining the strength of the relationship.