|Document Type:||Journal Article|
|Title:||Hydrologic spiralling: the role of multiple interactive flow paths in stream ecosystems|
|Author:||G. C. Poole, S. J. O'Daniel, K. L. Jones, W. W. Woessner, E. S. Bernhardt, A. M. Helton, J. A. Stanford, B. R. Boer, T. J. Beechie|
|Journal:||River Research and Applications|
|Keywords:||Hyporheic Zone, Floodplains, Groundwater, Surface Water, Biogeochemistry, Temperature, Alluvial Aquifer, Aquatic Habitat|
We develop and illustrate the concept of hydrologic spiraling using a detailed simulation of hyporheic hydrology in the upper Umatilla River of northeastern Oregon, USA. Across a 1.7 km2 section of the sand, gravel, and cobble floodplain aquifer, which is fully penetrated by hyporheic water, we developed a high spatial resolution model of groundwater movement within the alluvial aquifer. We parameterized the model using a continuous map of surface water stage derived from LIDAR remote sensing data, and compared empirical observations of water table elevation from 48 monitoring wells against water table elevations derived from a steady state model run. Results reveal the presence of complex spatial patterns of hyporheic exchange and a predominance of short flow paths within the model. We use this simulation of hyporheic hydrology to illustrate that streams can be viewed as a collection of hierarchically organized, individual flow paths that spiral across ecotones and knit together different components of stream ecosystems. Such a view underscores the importance of: 1) gross hyporheic exchange rates in rivers, 2) the differing ecological roles of short and long hyporheic flow paths, and 3) the downstream movement of water and solutes outside of the stream channel (e.g., in the alluvial aquifer). Application of this hydrologic spiraling concept reveals potentially important limitations in empirical measures of biotic uptake of solutes from streams and provides a needed hydrologic framework for emerging research foci in stream ecology such as hydrologic connectivity, spatial and temporal variation in the intensity of biogeochemical transformation rates, and the role of stream geomorphology as a dominant control on stream ecosystem dynamics.