Evaluation for the Development of a Jacob’s Well Groundwater Management Zone in Hays County, Texas

Jacob’s Well is a karst spring originating from the Lower Cretaceous, Middle Trinity Aquifer and is located in the Cypress Creek watershed near Wimberley, Texas. The Middle Trinity Aquifer is the primary groundwater resource for water supply in the region. Jacob’s Well flow responds to climatic variations of both short- and long-term cycles. Groundwater pumping from the Middle Trinity Aquifer also directly influences flow at Jacob’s Well. The combination of periodic drought cycles and increased groundwater pumping has significantly diminished springflow in recent years. The Hays Trinity Groundwater Conservation District (District) is charged with managing the groundwater resources within its jurisdictional boundaries. Jacob’s Well provides baseflow to Cypress Creek, which in turn provides ecological, hydrological, and financial benefits to the Wimberley region. Recognizing the importance of springflow from Jacob’s Well, the District’s Board of Directors formed the Scientific Technical Committee of groundwater scientists and tasked the committee with evaluating a potential groundwater management zone in collaboration with the Stakeholder Advisory Committee. The primary goal of this evaluation is to apply a scientificallybased approach to delineate an area in which strategies could be applied that lead to the preservation of springflow and baseflow in Cypress Creek during periods of drought. The Scientific Technical Committee identified three areas that have a strong hydrologic connection to Jacob’s Well (Figure ES-1). In other words, Jacob’s Well springflow is very sensitive to recharge and pumping influences in these areas. Each area has unique hydrologic and hydrogeologic features that influence the flow to Jacob’s Well. These features were considered as the basis for creating groundwater management zones. Evaluations indicate that most of the flow to Jacob’s Well can be explained by recharge occurring in an area defined as the Jacob’s Well Springshed, and that pumping in that area has direct effects on spring