Changes in Groundwater Levels and Storage in the Equus Beds Aquifer, Northwest of Wichita, Kansas

 

Index

• Map of Study Area
  
  

• Map of Well Locations

• Water-Level Change Maps

• Water-Level Altitude Maps

• Water-Level Change Data

• Publications

The Wichita well field was developed in the Equus Beds aquifer northwest of Wichita, Kansas, to supply water to the city beginning in 1940. For many years the U.S. Geological Survey (USGS) in cooperation with the city of Wichita has been monitoring the changes in water levels in the Equus Beds aquifer and the associated changes in the amount of groundwater stored in the Equus Beds aquifer. Groundwater level changes are important because they can have large economic impacts. Water-level declines may cause shallow wells to go dry and pumping costs to lift water from greater depths to increase. As water levels decline, the amount of water available for use and well yields generally decline too, which may reduce the amount of water available for use by cities, industries, or agriculture. If water-level declines are large enough, the direction of groundwater flow may change and poor-quality water may migrate from natural or human-caused sources into the aquifer, causing the water to become unusable.

The change in the volume of water stored in the Equus Beds aquifer in the study area since pumping began by the city of Wichita is shown in the graph above. The change in groundwater storage is defined here as the change in the saturated aquifer volume multiplied by the specific yield of the aquifer. The change in the saturated aquifer volume is computed using the aquifer volume from areas inside water-level-change contours for a selected time period (see water-level change maps). The water-level-change contours are based on the differences in the depths to water observed in wells in 1940, when significant pumpage began, and the end of the selected time (for example, August 1940 to January 2002). The specific yield of the Equus Beds aquifer, which is the ratio of the volume of water that the saturated aquifer material would yield by gravity to the volume of the aquifer material, is estimated here as 20 percent.

Declines in groundwater levels and associated decreases in groundwater storage can be attributed to pumpage from the Equus Beds aquifer by the city of Wichita and by local irrigation water users. Irrigation water use was greatly exceeded by city water use up until the 1970's and is now similar. Increased reliance on surface water from Cheney Reservoir for city water supplies since 1965 and decreased city pumpage from the Equus Beds aquifer in recent years have moderated the water-level declines. During years with above-normal precipitation, recharge to the aquifer increases and demand for water--including groundwater pumpage from the Equus Beds aquifer--is generally less and the rate of water-level declines in the aquifer slows or reverses. However, in years with below-normal precipitation, recharge to the aquifer decreases and water demand and groundwater pumpage generally increase and contribute to accelerated water-level declines.

Phase I of the Equus Beds Aquifer Storage and Recovery (ASR) Project was completed in 2006 and is designed to add millions of gallons of water to the aquifer that would be available for city use during times of need. The water added to the aquifer will come from the Little Arkansas River (from bank-storage wells along the river) when streamflow is greater than base flow as defined by Kansas Permit No. KS-05-079-001.