Groundwater Flow Model of the Ozark Plateaus Aquifer System
The groundwater flow model for the Ozark Plateau aquifer system is complete and the U.S. Geological Survey has released the Ozark Final Model Report.
For more information on modeling efforts in this region, visit the 
United States Geological Survey Ozark Aquifer Information page.
For more information on the Ozark Plateau aquifers visit the Ozark Plateau Aquifers homepage.
Ozark Groundwater Model Results
U.S. Geological Survey developed a groundwater model for the Ozark Plateau aquifer system. The area covers 7,340 square miles for parts of Arkansas, Kansas, Missouri and Oklahoma. This article summarizes the model results. It also includes information from the final model report released by the U.S. Geological Survey. The model characterizes groundwater flow within the Ozark Plateaus aquifer system. It assesses the effect that increased water use may have on the long-term availability of groundwater.
The Ozark aquifer is recharged from two sources. The first is runoff. The second is river infiltration in outcrop areas where permeable parts of the aquifer outcrop, generally east of the model area, and from downward flow through the overlying confining unit. All municipal and industrial wells, and some residential wells, in the model area are open to the Ozark aquifer. It ranges 250 feet to more than 1,000 feet beneath the land surface. A confining unit varying in thickness from zero to about 100 feet overlies the Ozark aquifer. It generally impedes groundwater flow between the Springfield Plateau aquifer and the Ozark aquifer. The Springfield Plateau aquifer yields sufficient water for residential use. It was a source of water to many older domestic wells. Large mined zones contained within the Springfield Plateau aquifer were represented in the model as extensive voids. They had a larger hydraulic conductivity than the adjacent non-mined zones.
Water use data were compiled for the period from 1950 to 2006. In 2006, total water use from the Ozark aquifer for Missouri was 8,531,520 ft3/day (87 percent of the total water use for the model area). Kansas was 727,452 ft3/day (7 percent of total). Oklahoma had 551,408 ft3/day (6 percent of total). Groundwater flow within the model occurs generally from the highlands of the Springfield Plateau in the southwest Missouri toward the west. There is localized flow toward rivers and five pumping centers near Joplin, Carthage and Noel, Missouri; Pittsburg, Kansas; and Miami, Oklahoma.
Hypothetical scenarios involving various increases in groundwater pumping rates in the Ozark aquifer were analyzed. The groundwater model assessed possible changes in the flow system to the year 2057. Pumping rates were increased between 0 and 4 percent per year starting with the 2006 rates for all wells in the model. Sustained pumping at 2006 rates was feasible at the five pumping centers until 2057. Model cells in four of the pumping centers go dry (Carthage, Joplin and Noel, Missouri, and Miami, Oklahoma) in the increased pumping hypothetical scenarios, one as early as 2029 (Carthage, Missouri; 4 percent increase in pumping per year). Even under a 1 percent increase in pumping per year, model cells at Carthage and Noel, Missouri, go dry by years 2037 and 2057, respectively. This indicates that pumping at 2006 rates is the maximum rate that can be pumped without model cells in those pumping centers going dry. The occurrence of dry cells indicates that pumping is not sustainable at those rates.
Groundwater pumping causes substantial reductions in water in storage. It also induces flow through the Ozark confining unit for all hypothetical scenarios evaluated. Although flow from the Ozark confining unit is substantial, it is not uniformly distributed. It varies spatially based on the vertical hydraulic conductivity and gradient and the Ozark confining unit thickness. The largest component of flow into Kansas comes from downward flow from the overlying Ozark confining unit. It varies from 21 percent to 41 percent of the total flow into Kansas in the different scenarios. As pumping in Kansas increases, the amount of water released from storage increases and is consistent with the increased size in cones of depression in Kansas. The largest component of flow out of Kansas occurs as pumping from wells. It ranges from 39 percent to 61 percent for all the scenarios. The second largest flow component out of Kansas is flow from Kansas to Missouri. This flow rate is induced by pumping that occurs in Missouri. It ranges from 30 percent to 43 percent of the total flow out of Kansas. Net flow in 2057 from Kansas to Missouri ranges from 74,044 ft3/day for 2006 pumping rates to 625,319 ft3/day for a 4 percent increase in pumping per year. The net flow is the difference between flow into and flow out.
For more information on groundwater modeling visit the Hydrologic Modeling page.
