Large chloride concentrations in Arkansas River water may degrade water quality in the adjacent Equus beds aquifer. A ground-water flow-model program (MODFLOW) was used to simulate hydrologic interaction of the Arkansas River and the Equus beds aquifer. A particle-tracking program (MODPATH) was used to simulate the movement of chloride from the river through the aquifer. Model-simulation results indicate that declining water levels in the Equus beds aquifer have caused net base-flow gains in the Arkansas and Little Arkansas Rivers to decrease from about 21 and 67 ft3/s (cubic feet per second), respectively, in 1940 to about -52 and 27 ft3/s, respectively, by the end of 1989. In hypothetical simulations (1990-2019) where only pumpage varied, net base-flow loss from the Arkansas River ranged from about 59 to 117 ft3/s for no increase in pumpage and a 3-percent per year increase in pumpage since 1989, respectively. Estimated chloride discharge from the Arkansas River Iassuming a chloride concentration of 630 milligrams per liter) to the aquifer increased from about 21 ton/d (tons per day) in 1940 to about 100 ton/d by the end of 1989 and was estimated to range from about 110 to 200 ton/d by 2019, depending on pumpage and climate conditions. Particle-tracking simulations show that the distribution of particles representing chloride from the Arkansas River expanded from relatively narrow bands near the river to a wider distribution within the aquifer, and may have reached the edge of the Wichita well field by 1963.
Additional publication details
USGS Numbered Series
Hydrologic and chemical interaction of the Arkansas River and the Equus Beds aquifer between Hutchinson and Wichita, south-central Kansas
Water-Resources Investigations Report
U.S. Geological Survey
viii, 100 p.; 2 Plates: 27.30 x 41.80 inches and 34.95 x 36.18 inches