Oregon Ground Water Quality And Its Relation To Hydrogeologic Factors PDF Download

An ASR metric and site rating index applied to over 120 municipal and agricultural locations across Oregon, combined with comparison to case study data from existing ASR sites, indicate that more than 50% of selected sites are hydrogeologically suitable for ASR. The ASR metric is a ratio of aquifer storage to the rate at which surface water is available for injection, with a result greater than one indicating sufficient aquifer storage. The site rating index evaluates aquifer hydraulic parameters as well as economic and engineering factors, and produces a percentage of ideal conditions. While economic and engineering factors can determine ASR feasibility, transmissivity, depth to static groundwater level and the desired injection rate are the controlling hydraulic parameters for hydrogeologic ASR suitability. However, these factors have a flexible relationship; for example, high transmissivity can compensate for small depth to groundwater and vice versa. In Oregon, most existing ASR sites target Columbia River Basalt interflow zones, where transmissivity is high and native groundwater quality is generally suitable for drinking water. These units are also prone to groundwater decline due to over-pumping, which essentially creates storage for ASR. Results show that suitable potential sites correspond predominantly with Columbia River Basalt, Quaternary and late Tertiary sediments. Potential aquifer storage identified by this study is approximately equal to Oregon's annual public water supply in the year 2000, or 5 x 108 m3 (160 billion gallons or 502,809 ac-ft). This suggests that ASR expansion in Oregon can significantly increase public supply and provide flexibility in the timing of water availability.