The Yakima River drainage is one of the most heavily irrigated regions in the state, and water use has been much contested and litigated. Due to this water demand and the increase in drilling of domestic wells, a moratorium on exempt well drilling was proposed in 2007. In this study geochemical data is used to evaluate the surface-groundwater interaction in the area around Cle Elum, WA. The hydrogeology of this area is poorly understood due to the complex stratigraphy where the valley floor meets the bedrock of the Cascade Range. It is important to understand the relationship between groundwater and surface water because more than the available surface water in the Yakima drainage is appropriated and many water rights holders depend on this water for their livelihood. This study began as a class project for an Environmental Geochemistry class at Central Washington University. Students collected samples from over 30 domestic wells and nearby surface water sources in the Cle Elum/Roslyn area. Trace element and major ion data are presented for these samples and are used along with geochemical analysis to draw conclusions regarding the different sub-surface water bearing units as well as the relationship between the surface and ground waters. This report concludes that exempt wells need monitoring and suggests the current policy of over-appropriation be reviewed
