INVESTIGATION OF HYDROLOGICAL CONNECTIVITY IN THE UPPER DRY CREEK WATERSHED

The quality and quantity of water in a stream is controlled primarily by the hydrological processes that occur in hillslopes of a watershed. These hydrological processes are governed by the hillslope connectivity. Hydrologic connectivity depends on the lateral subsurface water flow connecting the different isolated regions on the hillslope between the ridge and the valley. Reasons for the lack of hydrologic connectivity include the low antecedent moisture conditions on hillslopes in semiarid regions. However, with heavy precipitation, and high antecedent soil moisture, the mid-slope region reaches saturation and the watershed is connected hydrologically. Here, we are investigating the timing of hillslope-stream in a semi-arid, snowmelt driven watershed. We are applying chemical tracers before snowmelt in the spring so as to map the subsurface flowpaths, and calculate the subsurface water residence time. The stream transient time is calculated by applying a tracer in the stream. We also attempt to measure the extent of growth of the saturation wedge in the riparian zone when the stream changes from being a gaining to losing stream. Understanding flowpaths and hillslope water residence time could lead to further understanding to the sources and mechanisms of solutes’ transport from the land to streams.