Submitted to: Water Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 15, 2005
Publication Date: N/A
Interpretive Summary: Four variables that influence water flow through areas adjacent to streams (riparian areas)were calculated, mapped, and analyzed to determine if the size classification of the adjacent stream (stream order) will be an aid to locating vegetated buffers. Digital elevation data and stream-flow records, available throughout the nation, were used for the analysis. The variables tested include a wetness index, sediment-transport index, discharge index, and baseflow index. The wetness index showed that shallow groundwater could be intercepted along first-order streams more frequently than along larger streams. Values of the sediment transport index were smaller along first order streams reducing the potential to trap sediment. The baseflow index does not significantly vary among stream orders. The discharge index shows that riparian buffers along first order streams can intercept at least ten times more water than those occupying a similar reach along larger streams. Land owners, watershed planning organizations, and action agencies will be able to use these results to maximize the potential for contaminant removal by riparian buffers. Results of research on the water-quality response of specific buffer designs can be combined with analysis of these hydrologic variables to estimate the potential water quality improvement produced by buffers in various combinations of stream reaches.
Methods for mapping hydrologic variables to locate vegetated riparian buffers were explored using examples from the Deep Loess Region of the Midwest. Elevation and stream-flow data were used to define wetness, baseflow, sediment transport, and discharge indices. Groundwater dominates discharge in very small streams and through riparian areas in the region. All indices showed that riparian areas along first order streams have greater potential to intercept groundwater or runoff than similar areas along larger streams. A wetness index, used to indicate saturated soils, defined a significantly greater probability of saturation along smaller streams, enhancing the potential for groundwater interception. Significantly smaller values of the sediment transport index along smaller streams provide enhanced opportunities for deposition of sediment and associated contaminants. A discharge index shows that buffers along first order streams have orders of magnitude greater opportunities to intercept water passing through riparian areas than reaches of larger streams.