Changes in Local Groundwater Elevation Following Stream Restoration in the Lower Red River Meadow, Idaho

The Lower Red River Meadow, located in north central Idaho, was hydraulically mined in the late 1940s and early 1950s. In-stream dredging straightened the Red River channel and deteriorated fish spawning and rearing habitat. The Lower Red River Meadow Restoration Project (LRRMRP) was initiated in 1994 to restore natural biological and physical processes in the channel. Another goal of the restoration efforts was to re-establish relationships within and among the river channel, riparian corridor, floodplain, wet meadow, and adjacent upland habitats. Regaining natural functions within the habitat types would prove beneficial for aquatic, wetland, and riparian dependent species (LRK Communications, Wildlife Habitat Institute, and Pocket Water Inc., 1999). The University of Idaho Ecohydraulics Research Group (ERG) became involved with the LRRMRP in 1997. Since that time, the ERG has primarily focused on collecting and analyzing Red River data. The monitoring program was established to measure, document, and evaluate the success of the restoration efforts. In addition, monitoring hydrologic, fish and wildlife population, habitat quality, and stream channel responses would allow for future adaptive management and improvements in restoration design, implementation techniques, and revegetation procedures. The purpose of this study was to analyze data from monitoring wells located within the LRRMRP to determine whether realigning and lengthening the Red River channel had raised the local groundwater elevation. This was accomplished through the use of an analytical solution based on Dupuit-Forchheimer theory that was applied to pre- and post-restoration data. The Dupuit-Forchheimer approximation is one of the most effective techniques for analyzing unconfined flows. Furthermore, it represents the only simple tool for solving these types of problems (Bear, 1972). In addition to the analytical solution, a three-dimensional analysis of the groundwater data was performed using Geographical Information System (GIS) software. The GIS software provided graphical output that identified areas conducive to native riparian plant survival based on depth to groundwater requirements. Finally, the ability to quantify changes in local groundwater elevation near realigned streams is highly dependent on the amount, type, and accuracy of available data. Therefore, recommendations for establishing effective well networks in the future, at the LRRMRP or similar projects, were developed and are presented