Here, we summarize our assessment of the impact of unconventional oil and gas exploration and development on groundwater supply sustainability in the San Juan Basin (SJB). The measurement of actual water use in the SJB is difficult, so we tackle this problem using three indirect approaches. First, we evaluate the amount of groundwater that could be used by the petroleum industry in the basin by tabulating the water rights/permits that have been allocated to a variety of stakeholders by the Office of the State Engineer. The largest allocations in the SJB are assigned to mining (coal and uranium, 31.1 %), domestic users and municipalities (28.2%), and food production (24.7%). The petroleum industry owns 6.3% of the groundwater rights, totalling ca. 6674 acre-ft/year (afy). Second, using data from the Oil Conservation Division, we tracked the amount of water reportedly used in hydraulic fracturing of both vertical and horizontal oil and gas wells since 2005. Vertical wells drilled into the Mesaverde Group, Gallup Sandstone, and the Dakota Sandstone account for 83% of hydraulically fractured completions since 2005. Mesaverde Group (Cliff House Sandstone, Menefee Formation, Point Lookout Sandstone) vertical wells averaged 150,000 gallons/well (0.46 acre-ft (af)), vertical Gallup wells averaged 207,000 gallons/well (0.63 af) and vertical Dakota wells used 105,000 gallons/well (0.33 af). The water usage for horizontal wells in the SJB averages 3.13 af/well. Operators in the SJB are using produced water, foam, and nitrogen as hydraulic fracturing agents to reduce water use. Third, we used formation top data from scout cards and well logs to create structure contour and isopach maps of the ten major aquifers in the San Juan Basin.