Interactions Between Streams and Groundwater Along the River Continuum: Scaling up to a Stream Network

Oregon State University, Corvallis OR

Investigators

Abstract

9909564 Wondzell The objective of our study is to assess the relative importance of the factors controlling hyporheic exchange flow and provide the data needed to refine conceptual models that describe the extent of the hyporheic zone and its influence on stream ecosystems across scales ranging from individual stream reaches to entire stream networks. We will use extensive stream surveys to characterize the range of variability in channel and valley floor morphologic features in mountain stream networks, and use MODFLOW as a tool to explore the sensitivity of hyporheic exchange flows to morphologic features. MODFLOW simulations calibrated to existing study sites will serve as the starting point for these sensitivity analyses. A series of simulations will be analyzed to determine the sensitivity of exchange flows to the presence and absence of secondary channels, differing channel sinuosities, sediment depth, saturated hydraulic conductivity (k), and spatial heterogeneity of k, presence or absence of log jams, and different combinations of longitudinal channel gradient and pool-step structure. Model predictions will be verified using conservative tracer time of stream water to wells in a subset of the stream reaches we survey. We will examine the relative importance of these controlling factors in streams of different sizes and with differing degrees of channel constraint. Further, we will compare stream reaches in managed forests with those in wilderness areas to determine the effect of land management practices on the factors controlling hyporheic exchange flows.