Recharge in the Northern Edwards Aquifer: Key to Sustainable Groundwater Supply for People and Wildlife

The Edwards aquifer is famous for its groundwater quantity, groundwater quality, unique animal life and its large groundwater-dependent human population. The Northern Edwards aquifer is experiencing rapid population growth with the resulting increased groundwater demands amid the need to support a unique environment. The key to sustainable management for these diverse demands lies in understanding recharge. The Northern Segment of the Edwards aquifer is different from the rest of the Edwards aquifer in the following ways. The Colorado River has eroded completely through the Edwards aquifer framework separating the Northern Segment from the remainder of the aquifer. The western boundary of the aquifer has little to no faulting and thins out due to erosion. The geologic units that comprise the aquifer framework are changing stratigraphically, lithologically and diagenetically toward the north. However, the Northern Segment is also similar to the rest of the Edwards in that it is comprised chiefly of limestone and its hydrogeological characteristics are dominated by fractures and dissolutioning. Recharge in the Northern Segment occurs as regionally lateral flow, direct infiltration on the outcrop, and as important isolated features that include losing stream segments, faults, and sinkholes. Extensive field work coupled with GIS tools refined the recharge quantitatively in ways that were previously only conceptual and qualitative. Sustainable management for diverse demands hinges on such quantitative recharge data.