MODFLOW-NWT model used in simulation of groundwater availability in the Salt Fork Red River aquifer, southwestern Oklahoma, 1980-2015

The U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, constructed a finite-difference numerical groundwater-flow model of the Salt Fork Red River aquifer using MODFLOW with the Newton formulation solver (MODFLOW-NWT). The 1973 Oklahoma Water Law requires the Oklahoma Water Resources Board to conduct hydrologic investigations of the State’s aquifers to support a determination of the maximum annual yield (MAY) for each groundwater basin. The MAY is defined as the amount of fresh groundwater that can be withdrawn annually while ensuring a minimum 20-year life of the groundwater basin. For alluvium and terrace aquifers, the groundwater-basin-life requirement is satisfied if, after 20 years of MAY withdrawals, 50 percent of the groundwater basin retains a saturated thickness of at least 5 ft. When a MAY has been established, the amount of land owned or leased by a permit applicant determines the annual volume of water allocated to that permit applicant. The annual volume of water allocated per acre of land is known as the equal-proportionate-share (EPS) pumping rate. Because the MAY and EPS have not yet been established for the Salt Fork Red River aquifer, the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, conducted a hydrologic investigation and developed a calibrated numerical groundwater-flow model to evaluate the effects of potential groundwater withdrawals on groundwater availability in the Salt Fork Red River aquifer. The results of groundwater-availability scenarios run on the calibrated numerical groundwater-flow model could be used by the Oklahoma Water Resources Board to evaluate the maximum annual yield of groundwater from the Salt Fork Red River aquifer in Oklahoma. The numerical model was temporally discretized into 1 initial steady-state stress period representing average conditions during 1980-2015 and 432 monthly transient stress periods representing the period 1980-2015. This U.S. Geological Survey data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20215003).

[
  "010:12"
]

[
  "geospatial"
]