Spatial and temporal variability in streamflow generation on the West Fork of Walker Branch Watershed

Spatially intensive measurements of streamflow were used to document the spatial and temporal variability in streamflow generation on the West Fork of Walker Branch Watershed, a 38.4 ha forested catchment in Oak Ridge, Tennessee. The study focused on a 300 m section of a small stream, and covered a wide range of flow conditions ( Q weir, streamflow at the basin outlet, varied from about 350 to 3500 l min −1). There was enormous spatial variability in the stream inflow, down to the finest scale investigated (reaches 20 m in length). Lateral inflow to longer reaches (60–130 m) was linearly correlated with Q weir over the full range of flows studied, making it possible to estimate the spatial pattern of stream inflow from measurement of Q weir alone. The heterogeneous nature of the karstic dolomite bedrock was the dominant control on the observed spatial variability in streamflow generation. This thesis is consistent with the results of field investigations using natural tracers, reported in a companion paper. Bedrock structure and lithology may affect streamflow generation directly (via water movement through fractured rock), and indirectly (by influencing the slope and thickness of the overlying soil). While the West Fork contains all the topographic and surface hydrologic features of larger basins (ridge tops, valleys, hollows, spurs, ephemeral and perennial stream channels), it covers an area which is relatively small with respect to the bedrock heterogeneity. Therefore, while the hydrologic processes observed on the West Fork are no doubt typical of those occurring elsewhere in karst terrain, the particular patterns of spatial and temporal variability observed are somewhat specific to the study site.