Water and energy resources are fundamentally connected and have created what some refer to as the energy-water or water-energy nexus. A common goal of water and energy management is to maximize the supply of one while minimizing the use of the other. Water management in Oklahoma has become an important issue not only because of recurring droughts and increased water demand, but because large volumes of saltwater are being co-produced with oil and gas and must be properly managed. Oklahoma’s statewide co-produced water volumes were estimated to range from 811–925 million barrels (MMbbl) from 2000–2011. In the last few years, an estimated 40–60% of Oklahoma’s co-produced water originated from oil and gas wells in the Mississippian play where median fluid production ratios of H2O:oil and H2O:gas were 7.4 and 9.8, respectively. Other practices, such as dewatering in the Hunton play of central Oklahoma, have resulted in high volumes of co-produced water and subsequently high volumes for saltwater disposal (SWD). Seismic activity from 2009–2014 far exceeds historic seismicity and, in a few cases, has been correlated to subsurface fluid injection in the midcontinent. Therefore, there is an urgent need to quantify volumes and pressures of injections by geologic zone of completion, and use this information to develop best management practices for water that is co-produced with oil and gas.