Status of groundwater levels and storage volume in the Equus Beds aquifer near Wichita, Kansas, January 2006 to January 2010

A part of the Equus Beds aquifer in southwestern Harvey County and northwestern Sedgwick County was developed to supply water to residents of Wichita and for irrigation in south-central Kansas. Groundwater pumping for city and agricultural use caused water levels to decline in a large part of the aquifer northwest of Wichita. In 1965, the city of Wichita began using water from Cheney Reservoir in addition to water from the Equus Beds aquifer to meet the city's increasing demand for water. Irrigation pumpage in the area increased substantially during the 1970s and 1980s and contributed to the water-level declines. Water-level declines reached their maximum to date in October 1992.
Proposals to artificially recharge the aquifer have been made since the 1950s to meet future water-supply needs and to protect the aquifer from the intrusion of saltwater from sources to the south and west. In 2007, Wichita implemented Phase 1 of the Equus Beds Aquifer Storage and Recovery project for large-scale artificial recharge of the aquifer.
A period of water-level rises associated with greater-than-average precipitation and decreased city pumpage from the area began in 1993 and continued through January 2010. During January 2010, the direction of ground-water flow in the Equus Beds aquifer in the area was generally from west to east, similar to the direction prior to development of the aquifer. Water-level changes since 1940 for the period January 2006 to January 2010 ranged from a decline of more than 30 feet to a rise of more than 4 feet. Almost all wells in the area had cumulative water-level rises from October 1992 (period of maximum storage loss) to January 2010 and from January 2007 (beginning of large-scale artificial recharge) to January 2010. The average cumulative water-level change from October 1992 to January 2010 was a rise of about 8.7 feet and from January 2007 to January 2010 was a rise of about 3.2 feet.
The storage-volume change in the study area for the period October 1992 to January 2010 represented a recovery of about 183,000 acre-feet, or about 65 percent of the storage volume previously lost from August 1940 to October 1992, and was the largest recovery since October 1992 to date. Decreased city pumpage and artificial recharge during 1993-2009 and 2007-09 contributed to the recovery of storage volume in both periods, but artificial recharge's contribution was much smaller. Irrigation pumpage, because it increased during 1993-2009, did not contribute to the recovery of storage volume from October 1992 to January 2010. Recharge from excess precipitation contributed to the recovery of storage volume in both periods because precipitation averaged about 2 and 6 inches per year more than the annual long-term average of 31.52 inches during 1993-2009 and 2007-09, respectively.
Sustainable yield for the Equus Beds aquifer in the study area was estimated to be about 57,000 acre-feet per year using two different methods. The sum of permitted annual irrigation (about 45,600 acre-feet) and city (about 31,400 acre-feet) pumpage of 77,000 acre-feet per year greatly exceeds the estimated sustainable yield. Effective water management, including additions to the water budget such as those from the Equus Beds Aquifer Storage and Recovery project, can help produce the most water for beneficial use in a more sustainable way.