Study region: A flat, large, semi-arid plateau in the southwest United States (west Texas and southeast New Mexico) underlain by a deep Paleozoic sedimentary basin, the tectonic Delaware Basin, host of intensive hydrocarbon production. Study focus: Impacts of injection of large volumes of water produced from oil and gas wells and injected through 1000 + disposal wells, in particular, pressure buildup, induced seismicity and their potential consequences, in a formation underlying fresh-water aquifers but separated from them by thick layers of evaporites. The target formation is the Delaware Mountain Group (DMG) of Permian age and consisting of up to 4500 ft (similar to 1400 m) of mostly fine-grained, deepwater siliciclastic slope and basin deposits (sandstones, siltstones, and minor limestones). A flow model was developed and calibrated from well log data, stratigraphic data, petrophysical analyses, and core data (123x170 mi(2) -1 x1 mi(2) grid size) complemented with dynamic injectivity information based on surface injection pressures and rates of the disposal wells. New hydrological insights for the region: Injection of 5.8 billion barrels (0.92 billion m(3)) of waste water has generated regional pressure increases in the DMG mostly in the 100-400 psi (0.7-2.8 MPa) range: (1) creating strong artesian conditions that, combined with the presence of numerous historical boreholes, could connect DMG and fresh-water aquifers; and (2) generating conditions leading to actually observed moderate induced seismicity.