NATURAL TRACERS AS TOOLS TO ADDRESS MANAGEMENT ISSUES RELATED GROUNDWATER – SURFACE WATER INTERACTIONS

Two water management issues of increasing interest in the Upper Midwest include siting of new high capacity wells and underground storage of water using a technology known as aquifer storage recovery (ASR). Both of these issues have created recent challenges for regulators and water managers in Wisconsin. Increased public appreciation of the importance of groundwater discharge to aquatic ecosystems led to passage of new legislation in 2004 that requires regulatory review of new wells that may have significant impact on high volume springs. Proposals by water utilities to employ ASR as a cost effective way of meeting increasing peak demand without expanding treatment plant capacity prompted a reassessment and revision of the regulations governing injection wells. Assessing the impacts of new wells on surface water features such as springs and of subsurface storage of surface water on groundwater quality requires a good understanding of hydrostratigraphy and of ground water – surface water interactions at the regional and local scale. The potential usefulness of natural geochemical and isotopic tracers as tools to improve this understanding will be illustrated with case studies from several areas in Wisconsin where new wells are being sited or ASR systems have been proposed.