Historical and Potential Groundwater Drawdown in the Bruneau Area, Owyhee County, Southwestern Idaho.

摘要

Geothermal seeps and springs in the Bruneau area in southwestern Idaho provide a vital but disappearing habitat for the Bruneau hot springsnail (Pyrgulopsis bruneauensis). In order to aid in conservation efforts, a two-part study was conducted (1) to determine trends in groundwater levels over time and (2) to simulate drawdown in aquifers that contribute to the geothermal seeps and springs along the Bruneau River. Seasonal and Regional Kendall tests for trends were used to determine waterlevel trends over a 20-year monitoring (19902010) period. Seasonal Kendall tests were used to calculate trends in groundwater-levels in 22 monitoring wells and indicated statistically significant changes in water level with trends ranging from 0.21 to 1.0 feet per year. Regional Kendall tests were used to calculate drawdown in categories of wells based on five criteria (well depth, distance from Indian Bathtub Spring, geologic unit, regional topographic valley, and temperature). Results from Regional Kendall tests indicate that slope of the trend (in feet per year) increased as a function of well depth; trends in water level as a function of other categories did not exhibit an obvious pattern based on distance from Indian Bathtub Spring, geologic unit, topographic valley, or temperature.