DETERMINING GROUNDWATER CONTRIBUTIONS IN A HEADWATER CATCHMENT USING CHANGES IN STREAM WATER TEMPERATURE

The temperature of stream water is controlled by climatic variables, runoff/baseflow generation, and hyporheic exchange. Hydrologic conditions such as gaining/losing reaches and sources of inflow can vary dramatically along a stream on a small spatial scale. The objective of this work was to identify areas along a headwater stream with relatively high contributions of groundwater inflow, based on temperature changes. To do this, we deployed a dense array of stream temperature sensors along a perennial stream network in a 43 ha catchment with a complex land use history in Cullowhee, NC. Two water temperature sensors were placed along the stream network on opposite sides of the stream at 100-meter intervals and at several locations of interest (i.e. stream junctions). The forty total sensors recorded the temperature every 10 minutes for one month in the spring and one month in the summer. These thermal surveys were compared with descriptions of the contributing area at the sample sites, discharge at the catchment outlet, and air temperature in an effort to identify sections with elevated groundwater contributions. We anticipate this work will lead to a better understanding of temperature patterns and heterogeneity in headwater stream networks. A better understanding of the effects of small-scale differences in flow paths on water temperature may be able to inform watershed management decisions in the future.