Examination of Chronological Changes to Groundwater Flow Paths in the Upper Reaches of the Kimberly Watershed in Kimberly, Idaho

Irrigation has resulted in the development of the semi-arid Snake River Plain into a thriving agricultural region. Today, the eastern and central Snake River Plain is Idaho’s most productive agricultural area, which is only made possible due to irrigation (IDWR, 1999). However, this shift from a semi-arid climate which receives little summer rainfall to a agricultural area with continual summer water inputs has created a shift in the underlying aquifer. The Eastern Snake Plain Aquifer underlies much of the eastern and central areas of the Snake River Plain. Numerous studies have been done on the changes in aquifer storage, including a study done in 2012 that found that the Eastern Snake Plain Aquifer reached record levels in the early 20th century as a result of irrigation (Hipke et al.). While these studies have revealed the staggering effects irrigation can have on aquifer storage, they focus primarily on aquifer wide trends to storage. Little research has been done to better understand how irrigation affects groundwater storage on a watershed scale and how irrigation affects groundwater flow paths at this same scale. Analysis of groundwater flow paths was conducted for 1928, during which time when flood irrigation was the dominant irrigation method, and for 2008, during which sprinkler irrigation was the preferred method. The analysis was performed using both a triangulated irregular network (TIN) surface interpolation and a spline interpolation to determine potentiometric surfaces. From these potentiometric surfaces, groundwater flow paths were extrapolated. The analysis revealed that groundwater flow paths from 1928 were similar to 2008 flow paths. However, 2008 flow paths were determined to be more linear, suggesting the flood irrigation in 1928 may have resulted in variable recharge across the examined area. Contrary to expectation, the analysis also determined that water table levels were higher in 2008 than they were in 1928, which opposes the trends observed across the larger Eastern Snake Plain Aquifer. Further research on the chronological groundwater characteristics in the area should also examine the rate of agricultural expansion in Kimberly to better understand these trends. References Idaho Department of Water Resources, 1999. Feasibility of Large-Scale Managed Recharge of the Eastern Snake Plain Aquifer System, Idaho Department of Water Resources, December