Status of ground-water levels and storage volume in the Equus Beds aquifer Near Wichita, Kansas, January 2003-January 2006

Abstract

The Equus Beds aquifer northwest of Wichita, Kansas, was developed to supply water to Wichita residents and for irrigation in south-central Kansas. Groundwater pumping for city and agricultural use from the aquifer caused water levels to decline in a large part of the aquifer northwest of Wichita. Irrigation pumpage in the area increased substantially during the 1970s and 1980s and accelerated water-level declines. A period of water-level rises associated with greater-than-average precipitation and decreased city pumpage from the area began in 1993. An important factor in the decreased city pumpage was increased use of Cheney Reservoir as a watersupply source by the city of Wichita; as a result, city pumpage from the Equus Beds aquifer during 1993-2005 decreased to quantities similar to those pumped in the 1940s and went from being about 60 percent to about 40 percent of Wichita's water usage. Since 1995, the city also has been investigating the use of artificial recharge in the study area to meet future water-supply needs and to protect the aquifer from the intrusion of saltwater from sources to the west. During January 2006, the direction of groundwater 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 2003-January 2006 ranged from a decline of more than 36 feet to a rise of more than 2 feet. Almost all wells in the area had small cumulative water-level rises from January 2003 to January 2006 and larger rises from October 1992 (period of maximum storage loss) to January 2006. The water-level rises from October 1992 to January 2006 probably are due principally to decreases in city pumpage, with increases in recharge due to increased precipitation during the period also a contributing factor. Irrigation pumpage increased during the period, so irrigation did not contribute to the rises in water levels between the beginning and end of the period.

Revised shallow and deep water-level and storage-volume changes in the <i>Equus</i> Beds Aquifer near Wichita, Kansas, predevelopment to 1993

“…As noted by Kelly and others (2013), previous studies include those by Williams and Lohman (1949), Stramel (1956Stramel ( , 1962aStramel ( , 1962bStramel ( , 1967, Petri and others (1964), Sophocleous (1983), Spinazola and others (1985), Pruitt (1993), Myers and others (1996), , Aucott and others (1998), others (1999, 2010), Hansen and Aucott (2001, 2004, 2010, and Hansen (2007Hansen ( , 2009aHansen ( , 2009bHansen ( , 2011aHansen ( , 2011bHansen ( , 2012. In addition, Burns and McDonnell Engineering, Inc. (Kansas City) has worked with the city of Wichita to determine the location and amount of the ASR recharge credits the city of Wichita is allowed to pump from the aquifer as part of the annual accounting required by DWR.…”

“…The change in aquifer storage volume is estimated in this manner instead of the computing the difference between two total aquifer storage volumes because of the large uncertainty in the total aquifer storage volume and because the amount of storage-volume change to date (2013) is small compared to the total aquifer storage volume. For example, the -255,000 acre-ft of storage-volume change from August 1940 to January 1993 estimated by is the largest recorded storagevolume change to date; however, it only represents about 12 percent of the 2,100,000 acre-ft of total storage volume of the Equus Beds aquifer in the pre-2012 study area as estimated by Hansen (2007).…”

“…This resulted in an estimate of total aquifer storage volume of 2,100,000 acre-ft (Hansen, 2007). In this report, the aquifer storage volume was estimated using the recently published groundwater flow model of Kelly and others (2013).…”

“…The approximately 700-ft-thick Permian-age Wellington Formation underlies the Equus beds in the study area and forms the bedrock confining unit below them (Bayne, 1956;Myers and others, 1996). Total storage volume (the amount of water available for use) of the Equus Beds aquifer in the pre-2012 study area was estimated at about 2,100,000 acre-ft by Hansen (2007). Using the groundwater flow model of Kelly and others (2013), the total storage volume was estimated at about 2,776,000 acre-ft for the pre-2012 area and about 3,192,000 acre-ft for the current study area (Brian Kelly, written commun., June 10, 2013).…”

“…Aquifer storage volume was previously estimated by Hansen (2007) as the estimated average thickness of the aquifer of 100 ft multiplied by the area of the pre-2012 study and the estimated specific yield of 0.2. This resulted in an estimate of total aquifer storage volume of 2,100,000 acre-ft (Hansen, 2007).…”