The Influence of Hillslope Hydrology and Intermittent Tributaries on Hyporheic and Stream Temperatures in a Coastal Headwater Stream

As environmental temperatures rise, understanding the factors and mechanisms that help moderate stream and hyporheic zone temperatures will assist in the protection of fragile ecosystems. The stream temperature structure of a first order coastal New England stream was finely measured and analyzed to understand the components of the hydrologic system responsible for the moderation of temperature in a 500-meter study reach. An energy balance analysis coupled with the detailed geomorphic and temperature measurements of the stream, tributaries, groundwater and hyporheic zone illustrates the importance of groundwater, intermittent seeps, small wetlands and springs to stream temperature moderation and may shed light on the resulting nutrient loading in this and other similar coastal streams. Fiber Optic Distributed Temperature Sensing (FO-DTS) using a fiber optic cable was used as a survey tool in combination with discrete temperature measurements using thermocouple and thermistor sensors, and traditional hydrologic evaluation, to provide a description of the stream and hyporheic zone longitudinally and with depth along the 500-meter stream reach. LIDAR is also being used to map the watershed so that catchment, hillslope and stream geomorphology can be closely linked with the detailed temperature measurements. An analysis of 2007 field campaign data and 2008 NCALM LIDAR data will be presented.