Groundwater-surface water exchange within montane and alpine regions of the Front Range and Rocky Mountains, Colorado

Abstract

Climate-change modeling scenarios have projected that drought will be more likely to occur in dry regions of the world, surface-water and groundwater availability is likely to decrease, and water quality will be negatively impacted. Characterizing how excess nutrients and pollutants are naturally removed via groundwater and surface water exchange is a great topic of interest for ecologists, water managers, and agricultural researchers. The future timing of the water cycle becomes more important as air temperatures increase and precipitation occurs as rain instead of snow. This hydrologic change will diminish a crucial storage of water in mountainous regions and thus decrease water availability to Front Range communities and to agricultural regions in the Midwest. To characterize how water resources and quality will alter with time and with this hydrologic change, I have examined over 15 years of historical stream chemistry data within a subalpine creek within the Rocky Mountains and examined groundwater-surface exchange characteristics during low streamflow within a montane creek within the Front Range. An end-member mixing model was performed on Andrews Creek in Rocky Mountain National Park to look at changes in water source contributions over 15 years, while multiple stream tracer tests were performed in the Gordon Gulch catchment in the Boulder Creek Critical Zone Observatory. These tracer tests were paired with time-lapse electrical resistivity and modeled using OTIS to examine how solute transport and storage changed with decreasing stream discharge.