Regional assessment of groundwater vulnerability in the Snake river plain aquifer basin, USA

Abstract

The Snake River Aquifer System in eastern Idaho is one of the largest and most important regional water supplies within the United States. Safeguarding the Snake River Aquifer System from pollution underlying the Idaho National Engineering and Environmental Laboratory (INEEL) is of critical importance to the U.S. Department of Energy. The present paper contains the results of the investigations. Its tasks were: analyze the impact of natural factors on groundwater vulnerability; develop the map of groundwater vulnerability to contamination; indicate contaminated sites for risk of groundwater contamination using the map. Main attention was paid to vadose zone (aeration zone), that determines potential danger of contaminant penetration from the land surface to groundwater table. Assessment of vadose zone protection role was based on the following controlling factors: passive factors- depth to water and conduct properties of unsaturated medium; active factors- recharge, including its main parts: precipitation and irrigation. Vulnerability assessment was done step by step by compiling a series of maps. Combining vadose zone map and the map of groundwater recharge at Eastern Snake River Plain, the resulting map reflecting all above mentioned factors were received. The Point Count System was a main concept of vulnerability assessment. Influence of each factor was specified by different numbers (Rank), which were determined by expert assessment. The lesser the Rank, the more favorable situation is with relation to groundwater vulnerability. Groundwater vulnerability is characterized by Rank's sum that could vary from 8 to 40 in region under investigation. Total Rank sum characterizes groundwater vulnerability to contamination.