Ground-water resources of the southeastern San Juan Basin
— William J. Stone

The availability of ground water varies considerably among four hydrogeologic provinces recognized in the southeastern San Juan Basin: the Nacimiento Uplift, Hogback Belt, Chaco Slope and Central Basin. In the Nacimiento Uplift province, the main aquifer is the Madera Formation (Pennsylvanian), which yields water with a total-dissolved-solids (TDS) content of <400 ppm at a rate of <1-200 gpm. The main aquifer in the Hogback Belt is Quaternary alluvium/pediment gravels. Rugged terrain and steep dips make extraction of water from Mesozoic and Cenozoic strata there impractical. However, this province serves as the recharge area for the Chaco Slope and Central Basin. In the Chaco Slope province, Cretaceous sandstones typically yield water with TDS contents of >300–> 10,000 ppm at a rate of 1-400 gpm. In the Central Basin province Tertiary sandstone units are the principal aquifers and are often artesian. Transmissivities on the order of 100 ft²/d have been reported. Water from these aquifers may have TDS contents of >4000 ppm, with elevated iron and/or sulfate content being special problems. Significant deep water resources exist that have not yet been seriously explored.