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WATER RESOURCES RESEARCH, VOL. 41, W06006, doi:10.1029/2004WR003677, 2005

Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams

Richard G. Niswonger

Department of Land, Air and Water Resources, University of California, Davis, California, USA


David E. Prudic

U.S. Geological Survey, Carson City, Nevada, USA


Greg Pohll

Desert Research Institute, Reno, Nevada, USA


Jim Constantz

U.S. Geological Survey, Menlo Park, California, USA


Abstract

Seepage losses along numerous mountain front streams that discharge intermittently onto alluvial fans and piedmont alluvial plains are an important source of groundwater in the Basin and Range Province of the Western United States. Determining the distribution of seepage loss along mountain front streams is important when assessing groundwater resources of the region. Seepage loss along a mountain front stream in northern Nevada was evaluated using a one-dimensional unsteady streamflow model. Seepage loss was incorporated into the spatial derivatives of the streamflow equations. Because seepage loss from streams is dependent on stream depth, wetted perimeter, and streambed properties, a two-dimensional variably saturated flow model was used to develop a series of relations between seepage loss and stream depth for each reach. This method works when streams are separated from groundwater by variably saturated sediment. Two periods of intermittent flow were simulated to evaluate the modeling approach. The model reproduced measured flow and seepage losses along the channel. Seepage loss in the spring of 2000 was limited to the upper reaches on the alluvial plain and totaled 196,000 m3, whereas 64% of the seepage loss in the spring of 2004 occurred at the base of the alluvial plain and totaled 273,000 m3. A greater seepage loss at the base of the piedmont alluvial plain is attributed to increased streambed hydraulic conductivity caused by less armoring of the channel. The modeling approach provides a method for quantifying and distributing seepage loss along mountain front streams that cross alluvial fans or piedmont alluvial plains.

Received 22 September 2004; accepted 14 March 2005; published 9 June 2005.

Keywords: modeling; mountain front streams; seepage loss; unsteady surface flow; variably saturated flow.

Index Terms: 1830 Hydrology: Groundwater/surface water interaction; 1838 Hydrology: Infiltration; 1847 Hydrology: Modeling; 1849 Hydrology: Numerical approximations and analysis; 1860 Hydrology: Streamflow.

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Citation: Niswonger, R. G., D. E. Prudic, G. Pohll, and J. Constantz (2005), Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams, Water Resour. Res., 41, W06006, doi:10.1029/2004WR003677.