THE RELATIONSHIP BETWEEN SOURCE WATERS AND GEOCHEMICAL PROCESSES ON THE CHEMISTRY OF RED CANYON CREEK, A 2ND ORDER STREAM IN WIND RIVER RANGE, WYOMING

We used a synoptic sampling of stream and ground water to identify different hydrologic sources to base flow and assess geochemical processes influencing stream chemistry in the Red Canyon Creek watershed. The 2nd order stream, located in the Wind River Range (Wyoming), is in a transitional climate region between the high peak region of the Wind River Range and adjacent arid deserts. We characterized the overall creek solute composition, which will help us to assess hyporheic exchange and nutrient dynamics at the watershed scale.

Red Canyon water evolves from a Ca-SO4-dominated to Ca-HCO3-dominated type water downstream. This change from sulfate to bicarbonate type water primarily reflects mixing of 1.) headwaters derived from irrigation, groundwater seepage, and overland flow through gypsum bearing clastic rocks and 2.) waters contributed to Red Canyon Creek by its tributaries, which are underlain by carbonate rock. After the initial dilution, sulfate increases downstream along a 4 km stretch of the creek by ~50%. This increase in sulfate may reflect additional groundwater discharge with higher sulfate concentrations, or perhaps dissolution of gypsum in channel sediments. Calcium and bicarbonate concentrations decrease as sulfate increases, suggesting that calcite may be precipitating places in the stream because of the common ion effect.