Three aquifers of diverse lithology and hydraulic character form the ground-water reservoir in the Roswell basin. The main aquifer, the carbonate aquifer, is developed in carbonate rocks of Permian age. It is the source of about two-thirds of the ground water pumped in the basin and receives more than 90 percent of the recharge to the basin. The second most important aquifer is the shallow aquifer which lies near the Pecos River in beds of sand and gravel of both Permian and Holocene age. About one-third of the ground water pumped in the basin comes from the shallow aquifer. Prior to pumping, the main source of recharge to the shallow aquifer was probably ground water leaking upward from the carbonate aquifer. Since pumping began, the main source of recharge to the shallow aquifer is probably return flow of irrigation water pumped from the carbonate aquifer. Natural discharge of ground water from the shallow aquifer into the Pecos River causes a gain in th.e base flow of the Pecos River in the Roswell basin. The third aquifer, the shallow-artesian aquifer, is in red beds and evaporite beds of Permian age. This aquifer overlies the carbonate aquifer and underlies the shallow aquifer. The shallow-artesian aquifer acts as a minor aquifer and also as a semi-permeable unit which partly confines ground water in the carbonate aquifer. Vertical permeability of the shallow-artesian aquifer is variable and depends on the lithology and thickness of the aquifer. Hydraulic head in the shallow-artesian aquifer also varies quite widely depending on the depth to which a well penetrates the aquifer. All ground-water aquifers in the basin transect formational boundaries and are therefore not closely related to the named geologic formations. A flow net analysis of the carbonate aquifer and of the shallow aquifer imply that geologic structure is important in the movement of ground water in the basin by limiting the transmissivity of the shallow and carbonate aquifers, by forming the present pattern of surface water drainage, and possibly by the contamination of fresh ground water by highly saline ground water. The flow net analysis also shows areas of recharge to the shallow and carbonate aquifers, and areas where the carbonate aquifer looses water to the shallow-artesian aquifer and to the shallow aquifer.