An examination of recharge and groundwater conditions of the western region of the Roswell basin is presented. Recharge mechanisms are proposed on the basis of several long record observation wells. Water levels with long trends are associated with recharge from areal precipitation. It is thought that several years of above average rainfall are necessary to increase groundwater storage significantly. A fluctuating cyclic response is associated with channel leakage from streams in the study area. This recharge mechanism was verified using a stochastic stream-aquifer model applied to the Rio Hondo and Rio Penasco drainages. With this model, channel leakage and aquifer parameters could be estimated.

The two types of water level response are associated with characteristic tritium levels. High tritium levels in wells near streams verify a fast recharge component indicated by the model. For wells not located near streams in the intake area and for wells in the Principal Aquifer, low tritium values are found. These wells indicate longer residence times than previously suggested. It seems likely that precipitation on the region outside the Principal Intake Area supplies a significant portion of total recharge to the Principal Aquifer.

Project No. A-055-NMEX