The freshwater-saltwater interface migrates westward during periods of low rainfall. Chloride concentration also increases with depth. Chloride concentrations range from about 15 mg/kg in the unconfined area to as much as 7,000 mg/kg in an artesian well east of Roswell, N.M. Mineral content of the water rapidly increases in an eastward direction. Most down-gradient flow is intercepted by irrigation wells in the Artesian Basin. Decades of intensive pumping have caused substantial declines in hydraulic head in the aquifer, and by the mid-20th century it was estimated that withdrawals exceeded recharge. Recharge occurs by direct infiltration of precipitation and by runoff from intermittent losing streams flowing eastward across a broad area east of the Sacramento Mountains.Дuring the initial development of the artesian aquifer, many wells flowed to the surface and high volume springs fed the Pecos River. Secondary porosity is developed in vuggy and cavernous limestone, solution-collapse breccia, and solution-enlarged fractures. Some wells may penetrate as many as five water-producing zones.

Water-producing zones in the carbonate aquifer rise stratigraphically from north to south and from west to east. The carbonate aquifer is artesian to the east but under water-table conditions in the western outcrop area. The Roswell Artesian Basin consists of an eastward-dipping carbonate aquifer overlain by a leaky evaporitic confining unit, overlain in turn by an unconfined alluvial aquifer.

Eastward initial release date