Equus Beds Groundwater Quantity

Substantial pumping of the Equus Beds Aquifer began in September 1940 resulting in a gradual decrease of the aquifer's water level. Water-level declines, of up to 40 feet in some areas, occurred by 1993 as a result of increased city and irrigation pumpage and the 1988-92 drought. The water level declines resulted in a loss of storage of almost 300,000 acre feet that was no longer available for water supply. This trend in water-level decline and loss of storage prompted the City of Wichita to reduce pumpage of the Equus Beds aquifer and initiate the Integrated Local Water Supply Program (ILWSP). The ILWSP, now referred to as the Equus Beds Aquifer Storage and Recovery (ASR) Program was designed to ensure an adequate water supply for the city by increasing reliance on other sources outside the study area (for example, Cheney Reservoir), encouraging conservation, and developing the Equus Beds ASR project. The purpose of the Equus Beds ASR project is to take water from the Little Arkansas River and store it in the aquifer. The water stored in the aquifer increases the amount of groundwater available for later use and raises water levels in the aquifer. These higher water levels slow down or prevent the movement into the central part of the study area (where the city has its production wells) of an oil-field brine plume near Burrton, Kansas, and of naturally occurring saline water in the Arkansas River. Wichita plans to annually recharge into the aquifer about 11,000 acre-feet (about 3.6 billion gallons) of water.

The benefit of the ASR program to the Equus Beds aquifer was seen in winter 2013 at the end of the recent 2011-12 drought. In the central part of the study area, water levels in winter 2013 were about 10 feet higher and storage volume about 51,000 acre-feet greater than in 1993. These recoveries occurred despite precipitation that was 25 percent less than average in 2011 and 2012, irrigation pumpage that increased to new record amounts, and almost non-existent artificial recharge in 2011 and 2012. With the return to more normal rainfall 2013, water levels rose more than an average of 1 foot and storage volume recovered more than 5,000 acre-feet in the central part of the study area. These and other findings can be found at http://pubs.usgs.gov/sir/2014/5185/