Paul Spring is the principal or sole discharge point of a perched localized aquifer of well defined boundaries. It is located on the western flank of the Roswell artesian basin, and conditions at Paul Spring are considered typical for a major portion of the basin. The recharge at Paul Spring could therefore provide insight into the recharge mechanisms controlling the basin’s groundwater supply. The geology of the area was mapped in detail. Springflow was measured over a span of 453 days. Precipitation records of many years were available from a NOAA weather station in the area. Tritium was measured in spring discharge and precipitation. Numerical and stochastic analysis and cross-correlation were performed on the data. The results suggest that a deep flow component plays an important role, hitherto underestimated, in the groundwater recharge to the basin. This deep component is transmitted by the Permian Yeso Formation and the Glorieta Sandstone Member of the San Andres Formation. At Paul Spring, this accounts for as much as 80% of the discharge. No clear results were obtained for the Paul Spring aquifer’s response time to precipitation events. The indications are that it is of the order of several months. This can be explained by the peculiar geologic structure, specifically the screening effect of the Glorieta sandstone, in combination with solution and collapse features in the Yeso formation which channel the recharge water. A longer series of springflow measurements under better controlled conditions is needed to clarify this problem. The measurements continue.

Project No. A-055-NMEX