LANDSLIDES IN THE LAKE IDAHO GLENNS FERRY FORMATION
Background Snake River water is pumped onto the Bruneau Plateau and distributed by canal systems to crops. Irrigation water percolates down through the unconsolidated sediments from canals, ponds and fields to form shallow perched ground water systems. The perched aquifers and slope failures are directly related to the land-use change and development of Bell Rapids Irrigation District in 1970 on the plateau adjacent to Hagerman Fossil Beds National Monument (Young 1984; Summer 1986; Riedel 1992; Vector 1994). The slope failures are located on the hillside of the Bruneau Plateau along the Snake River. They typically range in size from 300 to 800 feet wide and up to 1000 feet long and have occurred about every two years since 1979. In 1987, a slope failure destroyed a million-dollar irrigation pumping facility and nearly killed two workers. In November 2003, a bridge across the Snake River was closed due to a landslide affecting its stability. A conceptual hydrostratigraphic model was developed in an attempt to define the aquifer systems in the Lake Idaho Glenns Ferry Formation. The six-layer model provides clarification for the spatial distribution of perched aquifer discharge patterns on the hillsides and for identification of variable recharge areas to each system; which is needed to aid a mitigative plan to abate canal leakage.