Characterization of spatial heterogeneity of groundwater-stream water interactions using multiple depth streambed temperature measurements at the reach scale

Abstract

Abstract. Streambed temperatures can be easily, accurately and inexpensively measured at many locations. We obtained 140 vertical streambed temperature profiles along a 220 m section of a small artificial stream to characterize patterns of groundwater-stream water interaction with a high spatial resolution. Groundwater temperature at a sufficient depth remains nearly constant while stream water temperatures vary seasonally and diurnally. In summer, streambed temperatures of groundwater discharge zones are relatively colder than downwelling zones of stream water. Assuming vertical flow in the streambed, the observed temperatures can be correlated to the magnitude of water fluxes. The water fluxes can then be estimated by applying a simple analytical solution of the heat diffusion-advection equation to the observed vertical temperature profiles. The calculated water fluxes through the streambed ranged between 10.0 Lm−2 d−1 of stream water entering the streambed and 455.0 Lm−2 d−1 of groundwater discharging to the stream. The investigated reach was dominated by groundwater discharge with two distinct high discharge locations accounting for 50% of the total flux on 20% of the reach length.