Revised Shallow and Deep Water-Level and Storage-Volume 

Changes in the Equus Beds Aquifer near Wichita, Kansas, 

Predevelopment to 1993

Scientific Investigations Report 2013–5170

U.S. Department of the Interior

U.S. Geological Survey

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K96

HARVEY COUNTY
-25

EXPLANATION

(cover illustration)

Line of equal water-level change in the shallow layer of the 

Equus Beds aquifer, predevelopment to 1993. Contour 

interval 5 feet.

Boundary of study area

Boundary of pre-2012 study area

Boundary of basin storage area

Boundary of central part of the study area

! Index monitoring well and identifier

Monitoring well in the shallow layer of the Equus Beds aquifer,

1993—Well identifier shown in italic type

Monitoring well in the shallow layer of the Equus Beds aquifer,

predevelopment, and identifier

807

EB245A

IW35

Area of water-level change:

Decline of 40 feet or more

Decline of 30 to less than 40 feet

Decline of 20 to less than 30 feet

Decline of 10 to less than 20 feet

Decline of zero to less than 10 feet

Rise of zero to 10 feet

Rise of greater than 10 feet

Front cover illustration: Static water-level changes in the shallow layer of the Equus Beds 

aquifer, predevelopment to 1993. (Fig. 6 from this report.)

Back cover photograph: Aerial photograph of city of Wichita Aquifer Storage and Recovery 

phase II facility (photograph by Tom Mason, city of Wichita, February 1, 2012).
Revised Shallow and Deep Water-Level 

and Storage-Volume Changes in the 

Equus Beds Aquifer near Wichita, Kansas, 

Predevelopment to 1993

By Cristi V. Hansen, Jennifer L. Lanning-Rush, and Andrew C. Ziegler

Scientific Investigations Report 2013–5170

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Hansen C.V., Lanning-Rush J.L., and Ziegler A.C., 2013, Revised shallow and deep water-level and storage-volume 

changes in the Equus Beds Aquifer near Wichita, Kansas, predevelopment to 1993: U.S. Geological Survey Scientific 

Investigations Report 2013–5170, 18 p., http://pubs.usgs.gov/sir/2013/5170/.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................2

Hydrogeology of the Study Area ........................................................................................................3

Previous Studies ...................................................................................................................................5

Methods..................................................................................................................................................5

Aquifer Layers ..............................................................................................................................5

Water Levels.................................................................................................................................5

Data Quality and Limitations .............................................................................................6

Water-Level Altitudes..................................................................................................................6

Water-Level Difference and Change........................................................................................7

Specific Yield................................................................................................................................8

Aquifer Storage Volume..............................................................................................................8

Aquifer Storage-Volume Change ..............................................................................................8

Water-Level Altitude Maps ..........................................................................................................................9

Shallow Aquifer Layer, Predevelopment...........................................................................................9

Deep Aquifer Layer, 1993 ...................................................................................................................10

Shallow Aquifer Layer, 1993 ..............................................................................................................10

Water-Level Altitude Differences and Storage-Volume Changes.......................................................10

Difference between Shallow and Deep Aquifer Layers, 1993.....................................................10

Change in Shallow Aquifer Layer, Predevelopment to 1993........................................................11

Summary........................................................................................................................................................15

References Cited..........................................................................................................................................16

Figures

1. Map showing location of study area near Wichita, south-central Kansas........................4

2. Map showing predevelopment water-level altitudes in the shallow layer of the 

Equus Beds aquifer.......................................................................................................................9

3. Map showing static water-level altitudes in the deep aquifer layer of the Equus

Beds aquifer, 1993.......................................................................................................................10

4. Map showing static water-level altitudes in the shallow aquifer layer of the Equus

Beds aquifer, 1993.......................................................................................................................10

5. Map showing difference between the shallow and deep static water-level 

altitudes of the Equus Beds aquifer, 1993...............................................................................12

6. Map showing static water-level changes in the shallow layer of the Equus Beds 

aquifer, predevelopment to 1993 ..............................................................................................14
iv

Tables

1. Measured and interpolated water levels in wells in the Equus Beds aquifer, predevelopment and 1993 .........................................................................................................................10

2. Comparison of computations of average differences between static water-level 

altitudes in the shallow and deep aquifer Equus Beds aquifer layers, 1993, for various 

parts of the study area...............................................................................................................11

3. Total aquifer storage volume and comparison of computations of average water-level 

and storage-volume changes from previously published mixed stressed water-level 

change map and from static water-level change maps of the shallow layer of the 

Equus Beds aquifer, predevelopment to 1993, for various parts of the study area .........13

Conversion Factors

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2

)

section (640 acres or 1 square 

mile)

259.0 square hectometer (hm2

) 

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

acre-foot (acre-ft) 1,233 cubic meter (m3

)

Flow rate

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 

(NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
v

Acknowledgments

The authors acknowledge the invaluable assistance of Tim Boese and Daniel Clement of the 

Equus Beds Groundwater Management District Number 2 and of Tara Lanzrath and Andrew Lyon 

of Kansas Department of Agriculture, Division of Water Resources for providing expertise and 

consensus in evaluating which wells and water levels to use for the 1993 water-level altitude 

map of the deep layer of the Equus Beds aquifer. 

The authors acknowledge the assistance of Debra Ary and Michael Jacobs of the city of Wichita 

and Tim Boese of Groundwater Management District Number 2 for providing water-level data 

and for their technical reviews, which contributed to improved technical and editorial clarity of 

the report.

Technical reviews by U.S. Geological Survey employees Brian Klager, Brian Kelly, and Geoffrey 

Delin also contributed to improved technical and editorial clarity of the report.

Abstract

Beginning in the 1940s, the Wichita well field was 

developed in the Equus Beds aquifer in southwestern Harvey 

County and northwestern Sedgwick County to supply water to 

the city of Wichita. The decline of water levels in the aquifer 

was noted soon after the development of the Wichita well field 

began. Development of irrigation wells began in the 1960s. 

City and agricultural withdrawals led to substantial water-level 

declines. Water-level declines enhanced movement of brines 

from past oil and gas activities near Burrton, Kansas and 

enhanced movement of natural saline water from the Arkansas River into the well field area. Large chloride concentrations may limit use or require the treatment of water from the 

well field for irrigation or public supply. In 1993, the city of 

Wichita adopted the Integrated Local Water Supply Program 

(ILWSP) to ensure an adequate water supply for the city 

through 2050 and as part of its effort to effectively manage 

the part of the Equus Beds aquifer it uses. ILWSP uses several 

strategies to do this including the Equus Beds Aquifer Storage 

and Recovery (ASR) project. The purpose of the ASR project 

is to store water in the aquifer for later recovery and to help 

protect the aquifer from encroachment of a known oilfieldbrine plume near Burrton and saline water from the Arkansas 

River.

As part of Wichita’s ASR permits, Wichita is prohibited 

from artificially recharging water into the aquifer in a Basin 

Storage area (BSA) grid cell if water levels in that cell are 

above the January 1940 water levels or are less than 10 feet 

below land surface. The map previously used for this purpose 

did not provide an accurate representation of the shallow water 

table. The revised predevelopment water-level altitude map of 

the shallow part of the aquifer is presented in this report.

The city of Wichita’s ASR permits specify that the January 1993 water-level altitudes will be used as a lower baseline 

for regulating the withdrawal of artificial recharge credits from 

the Equus Beds aquifer by the city of Wichita. The 1993 water 

levels correspond to the lowest recorded levels and largest 

storage declines since 1940. Revised and new water-level 

maps of shallow and deep layers were developed to better represent the general condition of the aquifer. Only static water 

levels were used to better represent the general condition of 

the aquifer and comply with Wichita’s ASR permits. To ensure 

adequate data density, the January 1993 period was expanded 

to October 1992 through February 1993. Static 1993 water 

levels from the deep aquifer layer of the Equus Beds aquifer 

possibly could be used as the lower baseline for regulatory 

purposes.

Previously, maps of water-level changes used to estimate 

the storage-volume changes included a combination of static 

(unaffected by pumping or nearby pumping) and stressed 

(affected by pumping or nearby pumping) water levels from 

wells. Some of these wells were open to the shallow aquifer 

layer and some were open to the deep aquifer layer of the 

Equus Beds aquifer. In this report, only static water levels 

in the shallow aquifer layer were used to determine storagevolume changes.

The effects on average water-level and storage-volume 

change from the use of mixed, stressed water levels and a 

specific yield of 0.20 were compared to the use of static water 

levels in the shallow aquifer and a specific yield of 0.15. This 

comparison indicates that the change in specific yield causes 

storage-volume changes to decrease about 25 percent, whereas 

the use of static water levels in the shallow aquifer layer 

causes an increase of less than 4 percent. Use of a specific 

yield of 0.15 will result in substantial decreases in the amount 

of storage-volume change compared to those reported previously that were calculated using a specific yield of 0.20. Based 

on these revised water-level maps and computations, the 

overall decline and change in storage from predevelopment 

to 1993 represented a loss in storage of about 6 percent 

(-202,000 acre-feet) of the overall storage volume within the 

newly defined study area.

Introduction

Beginning in the 1940s, the Wichita well field was 

developed in the Equus Beds aquifer in southwestern Harvey 

County and northwestern Sedgwick County to supply water 

to the city of Wichita, the largest city in Kansas (Williams and 

Lohman, 1949; Gibson, 1998; U.S. Census Bureau, 2012). 

Revised Shallow and Deep Water-Level and StorageVolume Changes in the Equus Beds Aquifer near Wichita, 

Kansas, Predevelopment to 1993

By Cristi V. Hansen, Jennifer L. Lanning-Rush, and Andrew C. Ziegler
2 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

In addition to supplying drinking water for Wichita, the other 

primary use of water from the Equus Beds aquifer is crop 

irrigation in this agriculturally dominated part of south-central 

Kansas (Rich Eubank, Kansas Department of Agriculture, 

Division of Water Resources, oral commun., 2008). The 

decline of water levels in the aquifer was noted soon after the 

development of the Wichita well field began (Williams and 

Lohman, 1949). Large-scale development of irrigation wells 

began in the 1960s. City and agricultural withdrawals have led 

to substantial declines. As water levels in the aquifer decline, 

the volume of water stored in the aquifer decreases and less 

water is available to supply future needs. Water-level declines 

enhanced movement of brines from past oil and gas activities near Burrton, Kansas and enhanced movement of natural 

saline water from the Arkansas River into the well field area. 

Further movement into the well field area of these waters with 

large chloride concentrations may limit use or may require 

treatment of water from the well field area for irrigation or 

public supply (Ziegler and others, 2010). Since 1940, the U.S. 

Geological Survey (USGS), in cooperation with the city of 

Wichita, has monitored changes in water levels and the resulting changes in storage volume in the Equus Beds aquifer as 

part of Wichita’s effort to effectively manage this resource

In 1993, the city of Wichita adopted the Integrated Local 

Water Supply Program (ILWSP) to ensure an adequate water 

supply for the city through 2050 and as part of its effort to 

effectively manage the part of the Equus Beds aquifer it uses 

(City of Wichita, [2007?] and 2008; Warren and others, 1995). 

ILWSP uses several strategies to do this including: (1) greater 

reliance on other sources of water from outside the study area 

(for example, Cheney Reservoir on the North Fork of the Ninnescah River (fig. 1), the Bentley Wellfield southwest of the 

Arkansas River, and Wichita’s Local Wellfield at the confluence of the Arkansas and Little Arkansas Rivers (locations 

not shown on figures), (2) encouraging conservation, and 

(3) developing the Equus Beds Aquifer Storage and Recovery 

(ASR) project with a designed artificial-recharge capacity of 

as much as 100 million gallons a day (City of Wichita, [2007?] 

and 2008). The purpose of the ASR project is to store and later 

recover groundwater and to help protect the part of the aquifer 

used by the city from the encroachment of a known oilfieldbrine plume near Burrton and encroachment of saline water 

from the Arkansas River (Ziegler and others, 2010). In 2007, 

the city of Wichita began using the Phase I facilities of the 

Equus Beds ASR project to increase the long-term sustainability of the Equus Beds aquifer through large-scale artificial 

recharge (City of Wichita, [2007?]). The ASR project uses 

water from the Little Arkansas River—either pumped from the 

river directly or from wells in the riverbank that obtain their 

water from the river by induced infiltration—as the source of 

artificial recharge to the Equus Beds aquifer (City of Wichita, 

[2007?]). For Phase I (operational in 2007), the water pumped 

directly from the Little Arkansas River is treated to reduce 

sediment and remove atrazine before being recharged to the 

aquifer through recharge basins; water pumped from wells 

in the riverbank does not receive additional treatment before 

being recharged to the aquifer through recharge basins or wells 

(Debra Ary, city of Wichita, written commun., 2012). Phase 

II recharge facilities withdraw water from the Little Arkansas 

River and treat the water using ultrafiltration membranes and 

advanced oxidation techniques. The treated water can then be 

recharged into spreading basins or recharge wells throughout 

the area and stored in the aquifer for future use. The Phase II 

facilities began operation in April 2013. 

The previously published maps of August 1940 (predevelopment) and 1993 water-level altitudes (Aucott and Myers, 

1998; Hansen and Aucott, 2001) are no longer appropriate for 

use as baselines for computing changes in water levels and 

storage volume because they were made using a single set of 

wells in which some were open to the shallow layer of the 

Equus Beds aquifer and some were open to the deep layer. 

This requires that new predevelopment and 1993 water-level 

altitude maps be created that only include wells that are from 

a single aquifer layer. In addition, estimates of the predevelopment 1993 static water-level altitude at the Phase I and II 

monitoring sites are needed as part of the accounting of ASR 

recharge-credits.

Purpose and Scope

The purpose of this report is to (1) document measured 

and interpolated predevelopment water levels in the shallow layer of the Equus Beds aquifer, (2) document measured 

and interpolated 1993 static water levels in the shallow and 

deep aquifer layers for the set of wells used for regulating 

the withdrawal of ASR recharge credits from the Equus Beds 

aquifer by the city of Wichita, (3) document changes in the set 

of wells used for calculating the 1993 water-level and storagevolume changes, (4) document the change in method used to 

calculate storage volume changes in the Equus Beds aquifer, 

(5) compare average water-level differences for 1993 calculated using measured and interpolated water-levels from the 

current (2013) set of wells with previously published average 

water-level changes, and (6) compare the differences in waterlevel changes and storage volumes using static water levels 

from the shallow aquifer layer. Maps of related measured and 

interpolated groundwater levels and water-level changes are 

presented. Comparison of average water-level changes and 

storage-volume changes for several subareas are presented in 

tabular form. Information in this report can be used to document and improve understanding of the effects of climate, 

water use, and water-resource management practices on water 

supplies in the Equus Beds aquifer, which is an important 

source of water for the city of Wichita and the surrounding 

area.

Description of Study Area

The current study area covers approximately 189 square 

miles (mi2) and is located northwest of Wichita, Kansas in 

Harvey and Sedgwick Counties (fig. 1). It is mostly bounded 
Introduction 3

on the southwest by the Arkansas River and on the east by the 

Little Arkansas River. The land surface in the study area typically slopes gently toward the major streams from an altitude 

of about 1,510 feet (ft) above the North American Vertical 

Datum of 1988 (NAVD88) in the northwest to a low of about 

1,325 ft in the southeast. The study area represents about oneseventh of the 1,400-mi2 Equus Beds aquifer and about onethird of the pumpage from the aquifer occurs in the study area 

(Kansas Department of Agriculture, 2011). Pumpage from the 

Equus Beds aquifer in the study area is dominated by irrigation and city use (Hansen and Aucott, 2010). Pumpage from 

the study area in 2011 (latest year for which pumpage is available) was about 45,500 acre-feet (acre-ft) for irrigation and 

about 21,900 acre-ft for the city of Wichita (Kansas Department of Agriculture and Kansas Geological Survey, 2013). 

The current study area is an expansion of the 165-mi2

study area first used by Aucott and Myers (1998). In 2012, the 

study area of Aucott and Myers (1998) (referred to as the “pre2012 study area” in this report) was expanded north to the 

northern boundary of township 23 south, west to the eastern 

Reno County line, southwest of the Arkansas River in a small 

area south of Bentley, and south to the southern boundary of 

township 25 south (fig. 1). This current study area includes all 

the ASR Phase I and II wells and the ASR basin storage area 

(BSA) west of the Little Arkansas River. 

The approximately 141-mi2 BSA is defined by Wichita’s 

ASR permits as the recharge-credit accounting area and is 

used by the city of Wichita, Groundwater Management District Number 2 (GMD2), and Kansas Department of Agriculture, Division of Water Resources (DWR) to estimate the 

location of artificially recharged water in the aquifer and to 

determine where and how much of it can be withdrawn for use 

by Wichita (Kansas Department of Agriculture, 2005). 

The central part of the study area (fig. 1), which covers 

about 55 mi2 or less than one-third of the study area, is the historic center of pumping in the study area. The central part of 

the study area includes wells used to supply water to the city 

of Wichita and many wells used for irrigation (Kansas Department of Agriculture and Kansas Geological Survey, 2013). 

Pumpage from the central part of the study area in 2011 was 

about 12,100 acre-ft for irrigation and about 21,300 acre-ft 

was for the city of Wichita (Kansas Department of Agriculture 

and Kansas Geological Survey, 2013).

Hydrogeology of the Study Area

The Equus Beds aquifer is the easternmost extension of 

the High Plains aquifer in Kansas (Stullken and others, 1985; 

Hansen and Aucott, 2001). The Equus Beds aquifer covers 

about 1,400 mi2 in Kansas, or about 5 percent of the approximately 30,900 mi2

 covered by the High Plains aquifer in 

Kansas (fig. 1). The Equus Beds aquifer is an important source 

of water because of the generally shallow depth to the water 

table, the large saturated thickness, and generally good water 

quality. 

The Equus Beds aquifer primarily consists of Quaternary-age alluvial deposits, locally known as the Equus beds, 

with some dune sand and loess (Myers and others, 1996). 

The alluvial deposits are as thick as 250 ft in the study area 

(Leonard and Kleinschmidt, 1976). The Equus beds primarily 

consist of sand and gravel interbedded with clay or silt, but 

locally may consist primarily of clay with thin sand and gravel 

layers (Lane and Miller, 1965a; Myers and others, 1996). The 

middle part of the Equus beds generally has more fine-grained 

material than the lower and upper parts (Lane and Miller, 

1965b, Myers and others, 1996). Approximately north of U.S. 

Highway 50 (fig. 1) and south of the Little Arkansas River 

in the study area, an area of dune sands is underlain by thick 

clay layers that restrict the downward movement of water in 

the Equus Beds aquifer and create the confined to semiconfined conditions in the deep aquifer layer in this part of the 

area (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).

Near the Arkansas River and in the western part of the 

study area, the water table in the Equus Beds aquifer can be 

less than 10 ft below land surface. Farther from the Arkansas 

River and near the Little Arkansas River, the water table can 

be at a greater depth (as much as 50 ft below land surface in 

January 2012), depending on the altitude of the land surface 

and the amount of water-level decline that has been caused 

by groundwater withdrawals. The saturated thickness of the 

Equus Beds aquifer within the study area ranges from about 

75 ft near the Little Arkansas River to almost 250 ft near 

the Arkansas River where the lowest areas of the underlying bedrock surface occur (Spinazola and others, 1985). The 

Equus Beds aquifer is considered to be an unconfined aquifer, 

but the presence of clay layers has resulted in semiconfined 

conditions in some areas (Spinazola and others, 1985; Stramel, 

1967). These semiconfined conditions may have resulted in 

the substantial water-level and water-quality differences in 

the shallow and deep parts of the Equus Beds aquifer in some 

parts of the study area (Stramel, 1956; Whittemore, 2007, 

2012; and Ziegler and others, 2010). These substantial differences, along with a need to monitor the long-term effects of 

artificial recharge on the shallow and deep aquifer layers, led 

to development of separate potentiometric-surface maps of the 

shallow and deep layers of the aquifer. 
4 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

KANSAS

Map area

Equus Beds aquifer

Base from U.S. Geological Survey digital data, 1983, 1:100,000

Universal Transverse Mercator projection, Zone 14

97°30’ 97°20’

07143665

07144200

07143330

07143375

07143375

97°50’ 97°40’

38°05’

38°’

37°55’

37°50’

Burrton

Halstead

Hesston

Sedgwick

Buhler

Haven

Andale

Bentley

Colwich

Maize

Mount

Hope

Newton

Wichita

Cheney

 Reservoir

HARVEY COUNTY

RENO COUNTY

HARVEY COUNTY

SEDGWICK COUNTY

SEDGWICK COUNTY

RENO COUNTY

K15

K17

K96

50 50

135

0 2 4 6 MILES

0 2 4 6 KILOMETERS

EXPLANATION

Chloride concentrations in deep groundwater wells in this 

approximate area exceed the Environmental Protection 

Agency's National Secondary Drinking Water Regulation 

of 250 milligrams per liter (modified from Ziegler and 

others, 2010; Whittemore, 2007; and Myers and others, 1996)

Study area

Approximate extent of High Plains aquifer

Boundary of pre-2012 study area

Boundary of basin storage area

Boundary of central part of the study area

Approximate boundary of Equus Beds aquifer (modified from 

Juracek and Hansen, 1995; Stullken and others, 1985; and 

Stramel, 1967) 

Phase I U.S. Geological Survey (USGS) monitoring well

Phase II USGS monitoring well

! Index well

Diversion site

USGS streamflow-gaging station and identifier

River

Dry Creek

Middle Em

ma Creek

West Em

ma Creek

Mud Creek

Sand Creek

Jester Creek

Arkansas River

Kisiwa Creek

Arka nsas

Little Arkansas River

East Emma Creek

Little Arkansas River

Low-head dam at 

Harvey County 

West Park

Low-head 

dam at 

Halstead

Figure 1. Location of study area near Wichita, south-central Kansas (modified from Aucott and Myers, 1998).
Introduction 5

Previous Studies

The Equus Beds aquifer has been extensively studied 

because of its importance as a source of water for cities, 

agriculture, and industry. As noted by Kelly and others (2013), 

previous studies include those by Williams and Lohman 

(1949), Stramel (1956, 1962a, 1962b, 1967), Petri and others 

(1964), Sophocleous (1983), Spinazola and others (1985), 

Pruitt (1993), Myers and others (1996), Aucott and Myers 

(1998), Aucott and others (1998), Ziegler and others (1999, 

2010), Hansen and Aucott (2001, 2004, 2010), and Hansen 

(2007, 2009a, 2009b, 2011a, 2011b, 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.

Methods

Aquifer Layers

Wells used in this report were divided into two groups to 

describe differences between the water levels in the shallow 

and deep layers of the aquifer. For the purposes of this report, 

wells completed and screened in the Equus Beds aquifer were 

assigned to either the shallow or deep aquifer layer based on 

the layer in which the bottom of the well’s casing or screened 

interval occurred. These layer assignments were based on 

Equus Beds GMD2 aquifer zone designations and on well 

completion and screen depths. GMD2 has identified as many 

as four aquifer zones (designated AA, A, B, and C, in order 

of descending depth) within the Equus Beds aquifer where 

there are competent clay layers separating them (Tim Boese, 

Equus Beds Groundwater Management District Number 2, 

written commun., 2009). The A, B, and C zones are similar to 

the upper, middle, and lower aquifer units defined by Myers 

and others (1996); the AA zone is of more limited areal extent 

and would be considered part of the upper aquifer unit. GMD2 

monitoring wells generally are in clusters (closely spaced 

wells screened to different depths) with each well screened 

in a different aquifer zone. For this report, wells designated 

by GMD2 as completed in zones A or C were assigned to the 

shallow or deep aquifer layers, respectively; no wells designated as completed in zone AA were used in this study. A 

few wells designated by GMD2 as being in zone B that were 

deemed to be in the same zone as the nearby BSA deep index 

wells were used to supplement the interpretation of the deep 

1993 potentiometric map. 

The city of Wichita also measures water levels in clusters 

of monitoring wells. The shallower well in each city well 

cluster was assumed to be in and assigned to the shallow 

aquifer layer; the deeper well in each cluster was assumed to 

be in and assigned to the deep aquifer layer. Ziegler and others 

(2010) used a depth of 80 ft as the dividing point between 

the shallow and deep layers of the Equus Beds aquifer. An 

analysis of the GMD2 and city of Wichita well clusters in 

the study area by Hansen (2011b) indicated about 90 percent 

of the GMD2 zone A wells and shallower wells in city well 

clusters were completed and screened to a depth of 80 ft or 

less, and about 90 percent of the GMD2 zone C wells and 

deeper wells in city well clusters were completed and screened 

to a depth of greater than 80 ft. This indicates that, when no 

other information was available, the use of the 80 ft depth as 

the dividing point between shallow and deep aquifer layers 

was reasonable when assigning the city of Wichita monitoring 

wells not in clusters into either the shallow or deep layer of 

the Equus Beds aquifer. Examination of well and screen depth 

and of water-level hydrographs lead in a few cases to assigning more than one well in a cluster to the same aquifer layer. 

Most of these cases were where both wells measured less than 

80 ft deep and both wells were assigned to the shallow aquifer 

layer. 

Water Levels

The city of Wichita’s historic monitoring wells have been 

used for monitoring water levels in the Equus Beds aquifer 

for years, many since the late 1930s (Stramel, 1956). All of 

the historic monitoring wells are measured at least quarterly 

by the city of Wichita personnel; many of the historic wells 

in the central part of the study area are measured monthly by 

city personnel. Some of the historic wells in the central part 

of the study area were replaced in 2009 through 2010 as part 

of Phase II of the ASR project. The GMD2 monitoring wells 

were installed for GMD2 beginning in 1978, or are existing wells used by GMD2 to monitor the Equus Beds aquifer. 

Some of the GMD2 wells only are measured annually during 

the last 3 months of the year after the irrigation season has 

ended; other wells are measured by GMD2 on a quarterly or 

monthly frequency. 

Groundwater levels measured from August 1937 through 

August 1940 in 51 city of Wichita historic monitoring wells 

and 41 other wells in Harvey and Sedgwick Counties were 

used to represent predevelopment conditions in the study area. 

A range of years was used because of the limited amount of 

data available for either January 1940, the period mentioned 

in the ASR regulations as the highest baseline water levels 

(Kansas Department of Agriculture, 2005), or August 1940, 

the period that previously was used by Aucott and Myers 

(1998) to represent the time before substantial pumpage began 

in the study area. Other than the city of Wichita’s public-supply wells, some of which began pumping in September 1940, 

groundwater development in the study area was limited mostly 

to small-capacity wells; therefore, water levels measured 

before September 1940 were used. Most of the predevelopment water levels used in this report were the first water level 

measured at each well.

For the 1993 water-level altitude maps, the use of water 

levels for January 1993 is specified in the ASR permits; in 

addition, the water levels also are specified to be static water 
6 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

levels (Kansas Department of Agriculture, 2005). Static water 

levels are those unaffected by pumping; for example, no 

pumping in the previous 24 hours from wells within 300 ft of 

the measured well. Inspection of water-level data and hydrographs indicated many wells in the study area either were not 

measured in January 1993, or their January 1993 water levels 

were affected by pumping. To ensure the use of static water 

levels and increase the areal density of data, the period used to 

represent the static 1993 water levels was expanded from just 

January 1993 to October 1, 1992 (after the end of the irrigation 

pumping season) through February 1993 (before the beginning of the irrigation pumping season). If the January 1993 

water level was noted as affected by pumping, or inspection of 

the well’s hydrograph indicated the January 1993 water level 

was affected by pumping, it was not used. If the hydrograph 

indicated another water level in the October 1, 1992, through 

February 28, 1993, period was not affected by pumping, then 

that water level was used instead of the January 1993 water 

level. The October 1992 through February 1993 period is 

hereinafter referred to as 1993 in this report. DWR, GMD2, 

and USGS personnel examined and evaluated the water-level 

and construction data and hydrographs of the wells in the deep 

layer of the Equus Beds aquifer to arrive at a consensus of the 

set of wells and water levels to use for the deep static 1993 

water-level-altitude map that possibly could be used for regulating the withdrawal of ASR artificial recharge credit water 

from the Equus Beds aquifer by the city of Wichita. 

Groundwater levels measured from October 12, 1992, 

through February 1, 1993, at 124 city of Wichita historic monitoring or public-supply wells and 20 GMD2 monitoring wells 

were used to represent static water-level conditions in 1993 in 

the shallow layer of the Equus Beds aquifer in the study area. 

Water levels in the historic monitoring wells were measured 

by city of Wichita personnel, water levels in the GMD2 monitoring wells were measured by GMD2 personnel, and water 

levels from wells that were not part of either of these monitoring networks were measured by the USGS. All agencies used 

standard water-level measurement techniques that are similar to USGS methods described in Cunningham and Schalk 

(2011). The historic monitoring well data are on file, in paper 

and electronic form, with the city of Wichita’s Public Works 

and Utilities Department in Wichita, Kansas; the GMD2 monitoring well data collected by GMD2 are stored in the Kansas 

Geological Survey’s (KGS) Water Information Storage and 

Retrieval Database (WIZARD) (Kansas Geological Survey, 

2012); and well data collected by the USGS are stored in the 

USGS National Water Information System (NWIS) database 

(U.S. Geological Survey, 2012). All the measured water-level 

data used in this report also are stored in NWIS. 

Predevelopment and 1993 water levels for the ASR Phase 

I and II wells were interpolated from rasters generated from 

the measured water levels and the contours created from these 

measured data. A raster is an areal grid of cells with a value 

assigned to each cell. Each grid cell in the raster used for 

this report had an area of 10 meters by 10 meters. The BSA 

index (IW) wells were installed in 2001 and 2002 as part of 

Phase I of the ASR project to monitor the effects of artificial 

recharge on the water quality and water levels in the Equus

Beds aquifer across the study area and to determine if there are 

water-quality differences between the shallow and deep layers of the aquifer. The Phase II compliance-monitoring wells 

were installed to provide additional monitoring of the effects 

of artificial recharge within the central part of the study area. 

As part of Phase II of the ASR project, some of the historic 

public-supply wells and their associated monitoring wells 

were replaced with new wells.

Data Quality and Limitations

The data used in this report were collected for other purposes; most of the data were collected by the city of Wichita 

and GMD2 personnel. The quality of the water-level data for 

each well was evaluated by examining hydrographs of the all 

the water levels available for the well. If a water level looked 

questionable, it was not used. Because the water-level altitude 

maps are to represent static—not pumping—water-level conditions, water levels that were noted as being from pumping 

wells or near pumping wells or whose hydrographs indicated 

that the water levels were affected by pumping were excluded 

from use. 

Water-Level Altitudes

The predevelopment and 1993 water-level altitudes 

depicted in the water-level altitude maps of the shallow and 

deep layers of the Equus Beds aquifer were calculated by 

subtracting the depth to water below land surface in a well 

from the altitude of land surface at the well. Land-surface 

altitudes are those stored for the wells in NWIS or WIZARD 

or determined from Light Detection and Ranging (lidar) 

(Data Access and Support Center, 2013a, 2013b) or from the 

National Elevation Dataset (NED) (U.S. Geological Survey, 

2009). The land-surface altitudes referenced to the National 

Geodetric Vertical Datum of 1929 (NGVD 29) were converted 

to the North America Vertical Datum of 1988 (NAVD 88); all 

water-level altitudes are referenced to NAVD 88.

The predevelopment water-level-altitude contours of the 

shallow layer of the Equus beds aquifer were modified from 

the 1940–44 water-table contours and measured data from 

plate 1 of Williams and Lohman (1949). Examination of the 

wells used for these maps indicated that most of the wells were 

in the shallow aquifer and the water-level altitude contours 

were revised as needed. Historic wells that were previously 

determined to be in the deep layer of the Equus Beds aquifer 

or other wells that were greater than 80 ft deep were removed 

from the analysis. Comparison of the water levels displayed 

on plate 1 of Williams and Lohman (1949) with the data stored 

in NWIS indicated that many of the water levels were older 

than 1940; measurements from 1937 through 1939 were not 

uncommon and generally were the wells’ first measured water 

levels. The predevelopment contours and measured water 

levels were brought into ArcGIS (Environmental Systems 
Introduction 7

Research Institute, 2012) and were compared to the NED land 

surface; the contours were revised where needed to remain 

below the land surface. These predevelopment contours and 

measured water levels were used as input to create a raster of 

the predevelopment water-level surface of the shallow aquifer 

layer. The water-level altitudes of the raster cells that contain measured wells were modified, if needed, to ensure they 

exactly matched the measured water levels. The completed 

raster was used to interpolate the predevelopment water-level 

altitudes at ASR Phase I and II wells in the shallow layer of 

the Equus Beds aquifer. Only 164 wells used in this report 

had predevelopment and 1993 measurements. For those wells 

that had a shallow static 1993 water level used in this report 

that did not have a measured predevelopment water level, the 

well’s predevelopment water level was estimated as described 

in the ”Water Levels” section of this report.

For wells that were in existence in January 1993, no 

October 1992 through February 1993 water levels were 

interpolated. The measured 1993 static water-level altitudes of 

the wells were entered into ArcGIS, plotted on the water-level 

altitude map of their assigned aquifer layer, and converted to 

a raster using ArcGIS Spatial Analyst’s “Topo to Raster” command (http://resources.arcgis.com/en/help/main/10.1/index.

html#//009z0000006s000000). Each layer’s raster was then 

converted to contour data using the ArcGIS Spatial Analyst’s 

“Contour” command (http://resources.arcgis.com/en/help/

main/10.1/index.html#//009z000000ts000000) and plotted with 

the well data. Where needed, the machine-generated waterlevel altitude contours were modified to match the well data. 

Further constraints on the water-level altitude contours were 

that (1) all water-level altitude contours would remain below 

land surface; (2) the 1993 static water-level altitude contours 

of the deep aquifer layer would remain below those of the 

1993 static contours of the shallow aquifer layer, except where 

the measured water levels from well clusters indicated otherwise or at gaining streams; and (3) the 1993 static water-level 

altitude contours of the shallow layer would remain below 

those of the predevelopment contours, unless data indicated 

otherwise. A new raster was generated from the measured 

points and revised contours. 

After the shallow predevelopment and shallow and deep 

static 1993 water-level altitude contours and associated rasters 

were considered to appropriately represent their respective 

surfaces, they were used to interpolate the water-level altitudes at the ASR Phase I and II monitoring sites. This was 

done by intersecting the location of each well with the raster 

of the appropriate aquifer layer and applying the water-level 

altitude of the raster at that location to the well. Using the 

same method, a predevelopment water-level altitude was 

estimated for all wells with measured 1993 water levels used 

in this report that did not have a measured predevelopment 

water level. For wells in the shallow Equus Beds aquifer layer 

without a measured predevelopment water level, one was 

interpolated from the predevelopment water-level altitude 

map of the shallow aquifer layer that was based on measured 

values. For the ASR Phase I and Phase II monitoring wells, 

predevelopment water levels were interpolated only for those 

wells in the shallow aquifer layer; however, 1993 water-level 

altitudes were interpolated for Phase I and II wells in the shallow and deep aquifer layers of the Equus Beds aquifer.

Water-surface altitudes from four streamflow-gaging stations and two low-head dams (fig 1) were used as additional 

data points to manually adjust contours in the shallow aquifer 

layer. Median water-surface altitudes for October 1, 1992, 

through January 31, 1993, were obtained from NWIS (U.S. 

Geological Survey, 2012) for the streamflow-gaging stations; 

the altitudes of the tops of the low-head dams (Trudy Bennett, 

U.S. Geological Survey, written commun. 2009) were used as 

the surface-water altitude at the low-head dams.

Water-Level Difference and Change

Only 176 well clusters used in this report had measured 

1993 water levels in the shallow and deep wells in the cluster. 

At these well clusters, the measured water level from the 

well open to the deep aquifer layer was subtracted from the 

measured water level from the well open to the shallow layer 

in the same well cluster to determine the water-level difference between the aquifer layers. All wells used to develop the 

water-level-altitude change maps of predevelopment to 1993 

and between the shallow and deep Equus Beds aquifer layers 

in 1993 were historic or GMD2 monitoring wells. Only 164 

of the wells used in this report had measured predevelopment 

water levels. If a predevelopment water-level measurement did 

not exist for a well in the study area, one was estimated from 

the raster of the predevelopment water-level altitude map as 

described in the previous “Water Levels” section of this report.

The water-level difference and change maps in this report 

were developed using a different method than that used in 

the past. In the past, only the water-level changes measured 

or estimated at wells were used to develop the maps because 

water-level altitude maps were not always created for each 

time period. The method used in this report involved the 

subtraction of water-level altitude rasters developed from 

measured water-level altitudes for either separate time periods 

or for separate aquifer layers. The areal data density generally 

is greater for a single water-level altitude map than in sets of 

wells measured at two different time periods or in well clusters 

with static water levels in separate wells open to the shallow 

and deep Equus Beds aquifer layers. This allows for a waterlevel-altitude change map that is more consistent with the 

water-level altitude maps and potentially more accurate than 

one based only on wells with measured water-level altitudes. 

The results of the raster subtractions were converted to contour maps and the contours revised where necessary to honor 

the actual measured data and to make hydrologic sense.

The measured differences were determined from well 

clusters that had static 1993 water levels in wells in the shallow and deep aquifer layers. The measured and interpolated 

differences were determined from water-level altitudes in well 

clusters where either both wells in the cluster had measured 

static 1993 water-level altitudes or one or more wells in 
8 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

the cluster was missing a measured static 1993 water-level 

altitude. Where a 1993 static water-level altitude value was 

missing, one was interpolated for the well from the appropriate 

aquifer layer’s 1993 static water-level altitude raster. The raster differences were determined by subtracting the raster of the 

1993 static water-level altitude of the deep aquifer layer from 

the raster of the 1993 static water-level altitude of the shallow 

aquifer layer. The resulting raster of water-level altitude differences was summed and then divided by the number of cells in 

the raster to calculate the average water-level difference.

The average water-level change from predevelopment 

to 1993 was computed at wells with measured water levels 

in 1993 and measured or interpolated predevelopment water 

levels instead of using the average water-level altitude change 

of the resulting raster subtraction. Similarly, the average 

water-level change between the shallow and deep Equus Beds 

aquifer layers used water levels at well clusters where the 

water level from the deep well was subtracted from the water 

level in the shallow well in the cluster.

In previous studies (Aucott and Myers, 1998; Hansen and 

Aucott, 2001), the map of water-level changes from August 

1940 to January 1993 included a combination of static and 

stressed water levels from wells, some of which were open to 

the shallow aquifer layer and some open to the deep aquifer 

layer. To better represent the general condition in the aquifer, 

only static water levels from the shallow aquifer layer were 

used in this study for determining water-level changes and 

aquifer storage-volume changes.

Specific Yield

Specific yield is the ratio of (1) the volume of water 

which a rock or soil, after being saturated, will yield by 

gravity to (2) the volume of rock or soil (Lohman and others, 

1972). The specific yield of the Equus Beds aquifer has been 

estimated by many investigators using a variety of methods 

including aquifer tests, laboratory analyses of samples, lithologic descriptions from drillers’ logs, water-balance equations, 

and parameter estimation for groundwater models. Estimates 

of specific yield from these methods have ranged from less 

than 0.1 to more than 0.3 with most estimates in the range of 

0.15 to 0.2 (Williams and Lohman, 1949; Stramel, 1956, 1967; 

Kansas Water Resources Board, 1960; Bayne and Ward, 1969; 

Lohman, 1972; Gutentag and others, 1984; Reed and Burnett, 

1985; Spinazola and others, 1985; Stullken and others, 1985; 

Hansen, 1991; Cederstrand and Becker, 1998; David Stous 

and Patrick Higgins, Burns and McDonnell Engineering Consultants, written commun., 2000; and Kelly and others, 2013). 

A specific yield of 0.2 previously was used by Stramel (1956), 

who was the first to compute changes in storage volume in the 

Equus Beds aquifer. A specific yield of 0.2 continued to be 

used by scientists in Kansas through 2011. For this report, a 

value of 0.15 was used because it was within the range of most 

estimates and matched that used by a recent groundwater flow 

model of the Equus Beds aquifer (Kelly and others, 2013). The 

specific yield of 0.15 from the groundwater flow model was a 

product of the model calibration; that is, it was determined to 

produce simulated water levels that better matched observed 

water levels than did the specific yield of 0.20. Specific yield 

can be used with the aquifer volume to estimate the amount of 

water available from storage in the aquifer, referred to as storage in this report.

Aquifer Storage Volume

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). In this report, the aquifer storage volume was estimated 

using the recently published groundwater flow model of Kelly 

and others (2013). The model multiplies the predevelopment 

thickness of the aquifer by the area of each cell, sums the volume of all the cells within a specified area, and then multiplies 

the result by the specific yield of 0.15 that was used by the 

model.

Aquifer Storage-Volume Change

Aquifer storage-volume change for the purposes of this 

report is defined as the change in aquifer thickness multiplied 

by the area of the aquifer containing the change multiplied by 

the specific yield of the aquifer. 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 

Aucott and Myers (1998) 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). 

In recent reports (Aucott and Myers, 1998; Aucott and 

others, 1998; Hansen and Aucott, 2001, 2004, 2010; Hansen, 

2007, 2009a, 2009b, 2011a, 2011b, 2012), change in storage 

volume in the Equus Beds aquifer was computed using computer-generated Thiessen polygons (Thiessen, 1911) that were 

based on the measured water-level changes at wells and the 

manually drawn lines of equal water-level change. Thiessen 

polygons apportion the water-level change at each well and the 

estimated value at points representing the lines of equal waterlevel change to the area around the wells and points. The 

volume of storage change was computed by summing the area 

of each Thiessen polygon multiplied by the water-level-change 

value associated with the Thiessen polygon, and then multiplied by the specific yield. To determine the storage-volume 
Water-Level Altitude Maps 9

change since August 1940 in the whole study area and in the 

central part of the study area, the computation was done for 

the Thiessen polygons within each of these areas. 

The calculation of storage-volume change for this report 

uses a different method than was done in previous reports. In 

this report, the storage-volume change was calculated by subtracting the raster of the water-level altitudes at the beginning 

of the change period from the raster of the water-level altitudes at the end of the period. The resulting water-level change 

raster was converted to contours, plotted with the measured 

water-level changes at the wells, and the contours modified 

where needed to conform to the measured water-level changes 

and to make hydrologic sense. The revised contours and the 

measured water-level changes were used to create a new 

water-level change raster. The area of each cell in the revised 

raster was multiplied by the water-level change for that cell; 

the resulting value for each cell multiplied by a specific yield 

value of 0.15 yields the estimated storage-volume change in 

each raster cell. Storage-volume changes can be summed for 

all the cells within a particular area to get the storage-volume 

change for that area. 

Water-Level Altitude Maps

A water-level-altitude surface of an aquifer or of a layer 

within an aquifer indicates the height of the water surface 

above a datum (for example, NAVD 88) and the direction of 

flow within the aquifer or aquifer layer. Where an aquifer is 

unconfined, the water-level altitude surface is the same as the 

water-table. In general, water moves horizontally and vertically from areas of higher water-level altitudes towards lower 

water-level altitudes. Water moves perpendicularly to the 

water-level altitude contours in the horizontal direction. Where 

the water-level altitudes in the shallow aquifer layer are above 

those in the deep layer, water tends to move downward from 

the shallow layer into the deep layer. Where the water-level 

altitudes are higher in the deep aquifer layer than the shallow 

layer, the water tends to move upward from the deep layer 

into the shallow layer. Where an aquifer layer is confined or 

semiconfined, the water-level altitude in the deep aquifer layer 

may differ substantially from the water table in the shallow 

aquifer layer. 

Previously published water-level altitude maps for 

August 1940 and January 1993 (Williams and Lohman, 1949; 

and Aucott and Myers, 1998) were based on a mix of stressed 

and static water-level measurements made in Wichita’s historic 

monitoring wells, some of which were open to the shallow 

layer and some to the deep layer of the Equus Beds aquifer. In 

this report, the number of wells has been expanded to include 

other wells, especially monitoring wells measured by GMD2 

for the 1993 water-level altitude map. In addition, efforts were 

made to include only static water levels and for each map to 

include only wells from a single layer. 

Shallow Aquifer Layer, Predevelopment

An aquifer is considered to be in a predevelopment 

condition if large-scale pumpage from the aquifer has not yet 

begun. Large-scale pumpage from the Equus Beds aquifer 

in the study area began in September 1940 with the city of 

Wichita’s pumpage from the aquifer in the central part of the 

study area (fig. 1). Large-scale pumpage for irrigation, the 

other major use of water in the study area, did not begin until 

the 1960s and 1970s with the adoption of rolling sprinkler 

irrigation systems. For the purposes of this report, water levels 

before September 1940 are considered to represent predevelopment conditions, especially in the central part of the study 

area. 

Examination of the available predevelopment water 

levels indicated most were in the shallow part of the aquifer. 

A predevelopment water-level altitude map of the shallow 

aquifer layer was constructed using the measured water 

levels from the wells in the shallow aquifer layer (fig. 2, link 

to figure 2). The water-level altitude contours shown in 

figure 2 (link to figure 2) are a modification of the contours 

published by Williams and Lohman (1949), which are considered to represent predevelopment conditions in and near 

the study area. Except in the northern part of the study area, 

the contours are similar to those used by Aucott and Myers 

(1998). Most wells used by Aucott and Myers (1998) were 

open to the shallow aquifer layer; however, in the northern 

part of the study area (north of U.S. Highway 50), they were 

open to the deep aquifer layer. 

Figure 2 (link to figure 2) shows that in predevelopment 

time, water in the aquifer generally flowed from west to east 

and discharged to the Little Arkansas River and possibly to the 

Arkansas River. The large area of higher water-level altitudes 

in the northern part of the study area indicates an area of 

recharge associated with the porous dune sand deposits in this 

part of the study area (Kelly and others, 2013). Water-level 

altitudes in the study area range from about 1,470 ft in the 

northwest to about 1,330 ft in the southeast.

As part of the city of Wichita’s ASR permits, the city is 

prohibited from artificially recharging water into the aquifer in 

a BSA grid cell if water levels in that cell are above the January 1940 water levels or are less than 10 ft below land surface 

(Kansas Department of Agriculture, 2005). The map previously used for this purpose was the August 1940 water-level 

altitude map of Aucott and Myers (1998). As noted above, 

some of the wells used to construct this map were completed 

in the deep aquifer layer, especially in the northern part of the 

study area; water levels in the shallow aquifer layer in this 

area can be more than 30 ft higher than those in the deep aquifer layer. Therefore, the use of water levels from the deep part 

of the Equus Bed aquifer in the northern part of the study area 

would not provide an accurate representation of the shallow 

water table in this area. The revised predevelopment waterlevel altitude map of the shallow part of the aquifer that is 

presented in this report (fig. 2, link to figure 2) uses only water 

levels from wells open to the shallow part of the aquifer. This 

Figure 2. Predevelopment water-level altitudes in the shallow layer of the Equus Beds aquifer.
10 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

will enable the city of Wichita, DWR, and GMD2 to better 

manage the aquifer and meet regulatory requirements.

The raster created from the predevelopment map of the 

shallow aquifer was used to interpolate the predevelopment 

water-level altitudes for the ASR Phase I and II monitoring 

wells that are open to the shallow part of the aquifer. The 

water-level altitudes at the IW wells can be used as surrogates 

for the water levels in the BSA cells; however, as the IW 

wells were not installed until 2001–02, water-level altitudes, 

interpolated from the predevelopment map, must be used. The 

locations and names of these wells are shown on figure 2 (link 

to figure 2); the interpolated water-level altitudes for these 

wells are shown in table 1 (link to table 1). These interpolated 

water-level altitudes can be used for determining water-level 

changes since predevelopment at these wells and those waterlevel changes can be used to estimate the storage-volume 

changes since predevelopment. 

Deep Aquifer Layer, 1993

The ASR permits (Kansas Department of Agriculture, 

2005) specify that the January 1993 water-level altitudes will 

be used as a lower baseline for regulating withdrawals by the 

city of Wichita of artificial recharge credits from the Equus

Beds aquifer. January 1993 is used as the lower baseline 

because Aucott and Myers (1998) reported January 1993 was 

when record to near-record low water levels were measured 

in most wells. To better represent the general condition of 

the aquifer and to comply with Wichita’s ASR permits, only 

static (unaffected by pumping) water levels were used for this 

report. The January 1993 time period was expanded to October 1992 through February 1993 to ensure the use of static 

water levels and increase the areal density of data because 

water levels were not measured in many wells in January 

1993 and some of the measured water levels were affected by 

pumping. 

The ASR permits do not specify which aquifer layer to 

use as the lower baseline for regulating the withdrawal of 

recharge credits by the city of Wichita. After much consultation and discussion among personnel of the city of Wichita, 

GMD2, DWR, and USGS, the possibility exists of using the 

deep aquifer layer for this lower baseline. Using the deep 

aquifer layer for regulatory purposes would be helpful to 

stakeholders, in part, because most irrigation, city publicsupply, and artificial recharge wells are open to the deep layer 

of the aquifer. However, there are technical issues with using 

water levels from the deep aquifer layer to determine storage 

changes, especially in the more confined parts of the aquifer. 

Storage changes compared to predevelopment are computed 

using shallow water-level maps and are the most appropriate 

for assessing the depth to water below land surface and the 

overall storage changes in the aquifer. 

Measured water levels from October 1992 to February 

1993 were used to generate a static water-level altitude surface 

of the deep layer of the Equus Beds aquifer (fig. 3, link to 

figure 3) from which the 1993 water levels for the deep IW 

wells were interpolated. Use of the October 1992 to February 

1993 period also allowed the selection of the water level from 

each well that best represented static conditions. Water-level 

measurements were excluded from use if the hydrographs 

indicated that the measured wells or nearby wells were pumping or had recently been pumped for all measurements in the 

October 1992 through February 1993 period. For wells in the 

deep aquifer layer without measured 1993 water levels, waterlevel altitudes were interpolated from a raster of the map of 

static 1993 water-level altitudes in the deep Equus Beds aquifer layer and are shown in table 1 (link to table 1).

Water-level altitudes in 1993 in the deep Equus Beds 

aquifer layer indicate that groundwater generally moved from 

west to east. However, between the central part of the study 

area and the Little Arkansas River pumping from municipal 

and irrigation wells intercepted some groundwater flow and 

also diverted water from the Little Arkansas River. 

Shallow Aquifer Layer, 1993

Comparison of the shallow static water-level altitude 

maps for predevelopment and 1993 (figs. 2 and 4, link to 

figures 2 and 4) shows that groundwater during both time periods generally moved from the west to east. However, between 

the central part of the study area and the Little Arkansas River 

the direction of flow had changed by 1993. In this area, the 

direction of flow was from east to west in 1993, as water that 

formerly discharged to the Little Arkansas River was pumped 

out of the aquifer by wells in or near the central part of the 

study area. Interpolated static 1993 water levels for wells in 

the shallow aquifer layer without 1993 water levels are shown 

in table 1 (link to table 1). 

Water-Level Altitude Differences and 

Storage-Volume Changes

By comparing water-level altitude differences between 

the shallow and deep aquifer layers or changes between two 

time periods, the vertical and horizontal areas affected by 

water-level differences or changes can be determined. This 

difference or change also can be used to estimate the storagevolume of the aquifer within which water-level differences or 

changes have occurred. 

Difference between Shallow and Deep Aquifer 

Layers, 1993

Examination of 2011 water-level altitude maps of the 

shallow and deep aquifer layers (Hansen, 2011b and 2012) 

and figures 3 and 4 (link to figures 3 and 4) for 1993 show 

generally similar patterns of water-level altitudes. The only 

exception is in the area north of U.S. Highway 50 where semiconfined conditions exist in the deep aquifer layer that lies 

Table 1. Measured and interpolated water levels in wells in the Equus Beds aquifer, predevelopment and 1993.

Figure 3 . Static water-level altitudes in the deep aquifer layer of the Equus Beds aquifer, 1993.

Figure 4 . Static water-level altitudes in the shallow aquifer layer of the Equus Beds aquifer, 1993.
Water-Level Altitude Differences and Storage-Volume Changes 11

beneath thick clay-rich layers that are overlain by dune sands. 

The map of the shallow aquifer layer (fig. 4, link to figure 4) 

indicates an area of recharge that is not shown on the map of 

the deep aquifer layer (fig. 3, link to figure 3).

Differences between the shallow and deep aquifer waterlevel altitudes in 1993 were less than 5 ft in about two-thirds 

of the study area, indicating that unconfined conditions likely 

existed in those areas (fig. 5). The greatest differences were in 

the extreme northwestern part of the study area, centered near 

the IW01 cluster, where positive differences were as much 

as 60 ft. A positive value indicated that the water level in the 

deep aquifer layer was below the water level in the shallow 

aquifer layer and the vertical component of groundwater flow 

was downward. Near the IW09 well cluster was an area with 

positive differences of more than 10 feet; an area with positive 

differences of more than 15 ft was near and south of the IW26 

well cluster (fig. 5). There are several small areas where waterlevel differences were negative, but one of these areas in the 

western part of the study area is notably larger than the others. 

Where water-level differences were large and positive the deep 

Equus Beds aquifer layer was probably semiconfined, because 

water levels in the deep aquifer layer were substantially below 

those in the shallow aquifer layer. Areas with negative values 

indicated the water levels in the deep aquifer layer were above 

those in the shallow aquifer layer indicating water may have 

been moving from the deep aquifer layer upward into the shallow aquifer layer. None of the negative areas had differences 

as great as 5 ft, indicating only minor flow from the deep to 

the shallow aquifer layer (fig. 5). 

Table 2 shows the average differences between the static 

water-level altitudes in the shallow and deep Equus Beds 

aquifer layers in the four parts of the study area (fig. 1) using 

three different methods. Except in the pre-2012 study area, the 

average differences using measured and interpolated values 

are smaller than the differences from measured values only 

(table 2). The average differences from the raster are larger 

than the average measured differences and the average measured and interpolated differences (table 2), but are all within 

an average difference of 1.10 ft. 

Change in Shallow Aquifer Layer, 

Predevelopment to 1993

As noted by Kelly and others (2013), most of the waterlevel and storage-volume changes occur in the shallow layer 

of the Equus Beds aquifer. This is because most of the water 

that comes out of storage is from the unconfined part of the 

aquifer, which is typically the shallow aquifer layer. If the 

shallow and deep aquifer layers are unconfined, the water 

levels in both layers will be similar and use of specific yield to 

estimate the storage-volume change is appropriate. However, 

if the shallow aquifer layer is unconfined and the deep layer is 

semiconfined to confined, use of specific yield is appropriate 

for estimating the storage-volume change only for the shallow 

aquifer layer and storage coefficient for the deep aquifer layer. 

Kelly and others (2013) used a specific yield of 0.15 for the 

Equus Beds aquifer where it was unconfined. Kelly and others 

(2013) used a storage coefficient of 0.0005 for the semiconfined to confined parts of the Equus Beds aquifer. Therefore, 

although water-level changes in the deep aquifer layer may 

be larger than those in the shallow aquifer layer in confined to 

semiconfined areas, the contribution of the deep aquifer layer 

to the amount of storage-volume change will be small. Kelly 

and others (2013) state:

“Use of groundwater level changes that do not 

include storage changes that occur in confined or 

semi-confined part of the aquifer will slightly underestimate storage changes; however, use of specific 

yield and groundwater level changes to estimate 

storage change in confined or semi-confined parts 

of the aquifer will overestimate storage changes. 

Using only changes in shallow groundwater levels 

will provide more accurate storage changes for the 

measured groundwater levels method.” 

Thus, the use of water-level changes in the shallow layer of 

the Equus Beds aquifer is more appropriate for determining 

storage-volume changes than the use of water-level changes in 

the deep aquifer layer, which includes semiconfined conditions 

in part of the area. 

The static shallow predevelopment to 1993 water-level 

change map shows that water-level declines occurred in most 

of the study area (fig. 6). Almost the entire central part of 

the study area and the northwest corner of the study area had 

declines of 10 ft or more and most of the central part of the 

study area had declines of 20 ft or more. Declines of more 

than 30 ft occurred in two areas in the central part of the study 

area. An area of more than 40 ft of decline from predevelopment to 1993 occurs on the eastern edge of the central part of 

the study area (fig. 6). This pattern of decline is similar to the 

pattern of August 1940 to January 1993 shown by Hansen and 

Table 2. Comparison of computations of average differences 

between static water-level altitudes in the shallow and deep 

aquifer Equus Beds aquifer layers, 1993, for various parts of the 

study area.

[Positive values indicate the water levels in the deep aquifer layer are below 

those in the shallow aquifer layer.]

Area

Average differences between static waterlevel altitudes in shallow and deep Equus

Beds aquifer layers, 1993 (feet)

Measured 

at wells

Measured and 

interpolated at 

wells

Raster

Study area 5.81 5.38 6.41

Pre-2012 study area 4.53 4.94 5.44

Basin storage area 5.11 5.07 6.16

Central part of study 

area

3.74 3.26 4.04
12 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

EB206C

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IW35 IW36 IW37

IW38

IW32 IW30 IW34 IW31

IW33

IW27 IW28

IW29 IW24 IW25

IW26

IW19

IW22 IW23 IW20 IW21 IW18

IW14

IW17 IW15 IW16 IW13

IW11

IW12 IW09 IW10

IW08

IW07

IW04

IW05 IW06

IW02 IW03

IW01 5

0

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55

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0

0

Base from U.S. Geological Survey digital data, 2012, 1:24,000

Universal Transverse Mercator projection, Zone 14

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83)

EXPLANATION

Area of water-level difference—Positive values indicate water levels in the deep 

aquifer layer are below those in the shallow aquifer layer and vertical flow is 

downward. Negative values indicate water levels in the deep aquifer layer 

are above those in the shallow aquifer layer and vertical flow is upward 

-10 to less than zero feet

Zero to less than 10 feet

10 to less than 20 feet

20 to less than 30 feet

30 to less than 40 feet

40 to less than 50 feet

50 to less than 60 feet

More than 60 feet

Line of equal water-level altitude difference between 

shallow and deep Equus Beds aquifer layers, 1993. 

Contour interval 5 feet 

0 1 2 3 MILES

0 1 2 3 KILOMETERS

97°40’ 97°35’ 97°30’ 97°25’

38°05’

38°

37°55’

37°50’

Boundary of study area

Boundary of pre-2012 study area

Boundary of basin storage area

Boundary of central part of the study area

! Index monitoring well and identifier

Monitoring well in the Equus Beds aquifer—Well identifier 

shown in black type indicates deep layer; well identifier 

shown in gray type indicates shallow layer. Datum is 

North American Vertical Datum of 1988 

Burrton

Halstead

Sedgwick

Bentley

Mount

Hope

Newton

Wichita

RENO COUNTY

HARVEY COUNTY

SEDGWICK COUNTY

SEDGWICK COUNTY

RENO COUNTY

50

135

Dry Creek

Middle Em

ma Creek

Mud Creek

Sand Creek

Arkansas River

Little Arkansas River

Little Arkan sas River

Jester Creek

Arkansas Riv er

West Em

ma Creek

East Emma Creek

Kisiwa Creek

K96

HARVEY COUNTY

EB245C

EB245A

IW35

Figure 5. Difference between the shallow and deep static water-level altitudes of the Equus Beds aquifer, 1993. 
Water-Level Altitude Differences and Storage-Volume Changes 13

Aucott (2001) that was constructed using a combination of 

stressed and unstressed January 1993 water levels. Pumping 

for municipal and irrigation purposes probably are the main 

reason for water-level declines in the central part of the study 

area. The area of water-level declines in the northwestern 

corner of the study area and the area of water-level rises of 

10 ft near the IW01 well cluster (fig. 6) were not reported by 

Hansen and Aucott (2001) because they were outside the pre2012 study area and probably because they used wells open to 

the deep aquifer layer in these areas. These areas of waterlevel rise and decline in the northwestern part of the study area 

may be associated with heterogeneity of the aquifer material 

within the dune sand area because there is little pumpage from 

the Equus Beds aquifer in this area (Kansas Department of 

Agriculture and Kansas Geological Survey, 2013). 

Estimates of total storage volume made using the recently 

published groundwater flow model of the Equus Beds aquifer 

(Kelly and others, 2013) and comparisons of average waterlevel and storage-volume changes for the method used in previous reports (for example, Aucott and Myers, 1998; Hansen, 

2012) are shown in table 3. The method used in this report and 

the effect on storage-volume change of using a specific yield 

of 0.15 instead of the previously used specific yield of 0.20 are 

also shown in table 3. Changing the specific yield from 0.20 

to 0.15 has a greater effect on the amount of storage-volume 

change than does the change from the use of mixed, stressed 

water-level altitudes to the use of static water-level altitudes 

from a single aquifer layer. For example, the use of mixed, 

stressed water-level altitudes with a specific yield of 0.20 for 

the pre-2012 study area resulted in a storage-volume change 

of -255,000 acre-ft. Retaining the 0.20 specific yield, but using 

static water-level altitudes in the shallow Equus Beds aquifer 

layer, caused the storage-volume change to increase by only 

2 percent to -261,000 acre-ft. Changing the specific yield to 

0.15 resulted in storage-volume change that was 25 percent 

less for use of the mixed, stressed water-level altitudes 

(table 3). The storage-volume change determined using the 

static, shallow water-level altitudes and a specific yield of 0.15 

(-196,000 acre-ft) was about 23 percent less than the storagevolume change determined using the mixed, stressed waterlevel altitudes and a specific yield of 0.20 (-255,000 acre-ft). 

Even in the central part of the study area, where many city 

public-supply wells are located, the effect on the storage-volume change from using mixed, stressed water-level altitudes 

to static water-level altitudes in the shallow aquifer layer 

was an increase in storage-volume change of less than 

4 percent (table 3). This indicates that use of static water-level 

altitudes in the shallow aquifer layer will not result in large 

changes in storage-volume calculations compared to those 

reported in previous reports. Instead, use of a specific yield 

of 0.15 will result in substantial decreases in the amount of 

storage-volume change compared to those reported in previous 

Table 3. Total aquifer storage volume and comparison of computations of average water-level and storage-volume changes from 

previously published mixed stressed water-level change map and from static water-level change maps of the shallow layer of the 

Equus Beds aquifer, predevelopment to 1993, for various parts of the study area.

[NA, not applicable]

Area and type of water 

levels used for water-level 

change map

Total aquifer 

storage volume, 

predevelopment, 

from model 

(acre-feet)

Average water-level change, 

predevelopment to 1993

(feet)

Storage-volume changes, 

predevelopment to 1993

(acre-feet)

Storage-volume changes, 

predevelopment to 1993 

(percent)

Specific yield 

0.15 Measured Measured and interpolated Raster Specific yield 0.20

Specific yield 

0.15

Specific yield 

0.15

Mix of shallow and deep stressed water levels

Study area NA -23.33 -16.73 NA -259,000 -194,000 NA

Pre-2012 study area NA -23.97 2

-16.07 NA 1-255,000 -192,000 NA

Basin storage area NA -24.58 -17.40 NA -250,000 -187,000 NA

Central part of study area NA -30.65 2

-24.09 NA 3-154,000 -116,000 NA

Shallow static water levels

Study area 3,192,000 -21.07 -15.16 -11.19 -270,000 -202,000 -6

Pre-2012 study area 2,776,000 -22.56 -16.17 -12.36 -261,000 -196,000 -7

Basin storage area 2,400,000 -25.87 -17.33 -13.97 -251,000 -188,000 -8

Central part of study area 1,025,000 -31.01 -24.56 -22.99 -160,000 -120,000 -12

1

 Storage-volume change previously reported by Aucott and Myers (1998).

2

 Storage-volume change previously reported by Hansen (2012a).

3

 Storage-volume change previously reported by Hansen and Aucott (2001).
14 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

IW35 IW36 IW37 IW38

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0

-25

Base from U.S. Geological Survey digital data, 2012, 1:24,000

Universal Transverse Mercator projection, Zone 14

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83)

EXPLANATION

Line of equal water-level change in the shallow layer of the 

Equus Beds aquifer, predevelopment to 1993. Contour 

interval 5 feet.

0 1 2 3 MILES

0 1 2 3 KILOMETERS

97°40’ 97°35’ 97°30’ 97°25’

38°05’

38°

37°55’

37°50’

Boundary of study area

Boundary of pre-2012 study area

Boundary of basin storage area

Boundary of central part of the study area

! Index monitoring well and identifier

Monitoring well in the shallow layer of the Equus Beds aquifer,

1993—Well identifier shown in italic type

Monitoring well in the shallow layer of the Equus Beds aquifer,

predevelopment, and identifier

Burrton

Halstead

Sedgwick

Bentley

Mount

Hope

Newton

Wichita

RENO COUNTY

HARVEY COUNTY

SEDGWICK COUNTY

SEDGWICK COUNTY

RENO COUNTY

50

135

Dry Creek

Middle Em

ma Creek

Mud Creek

Sand Creek

Arkansas River

Little Arkansas River

Little Arkan sas River

Jester Creek

Arkansas Riv er

West Em

ma Creek

East Emma Creek

Kisiwa Creek

K96

HARVEY COUNTY

807

EB245A

IW35

Area of water-level change:

Decline of 40 feet or more

Decline of 30 to less than 40 feet

Decline of 20 to less than 30 feet

Decline of 10 to less than 20 feet

Decline of zero to less than 10 feet

Rise of zero to 10 feet

Rise of greater than 10 feet

Figure 6. Static water-level changes in the shallow layer of the Equus Beds aquifer, predevelopment to 1993.
Summary 15

reports that were calculated using a specific yield of 0.20. 

Because the value of specific yield has such a large effect on 

storage-volume calculations and there is substantial range in 

values, more information on the distribution of specific yield 

in the study area would improve the accuracy of the estimates 

of storage-volume change.

Dividing the estimated storage-volume change by the 

estimated total predevelopment aquifer storage volume yields 

the percent of aquifer storage volume that has been lost. 

Approximately 12 percent of storage volume had been lost 

from August 1940 to January 1993 using the storage-volume 

change of -255,000 acre-ft from Aucott and Myers (1998) and 

the estimated aquifer storage volume of 2,100,000 acre-ft from 

Hansen (2007) for the pre-2012 study area. Table 3 shows that 

this previous estimate, which was made using a specific yield 

of 0.2, mixed, stressed water levels and an average aquifer 

thickness, may have overestimated the percentage of storage 

volume change and underestimated the amount of total aquifer 

storage volume. Based on the revised water-level maps and the 

methods used in this report, there was only a 7 percent loss of 

aquifer storage volume in the pre-2012 study area from predevelopment to 1993. The overall decline and change in storage 

from predevelopment to 1993 represented a loss in storage 

of about 6 percent of the overall storage volume in the newly 

defined study area. Even in the central part of the study area, 

where the declines were greatest, the loss of storage volume 

from predevelopment to 1993 was only 12 percent of the total 

aquifer volume. These revised estimates of storage changes in 

shallow and deep layers can be used by Wichita, GMD2, and 

DWR to manage, regulate, and preserve the water supply in 

this aquifer.

Summary

Beginning in the 1940s, the Wichita well field was 

developed in the Equus Beds aquifer in southwestern Harvey 

County and northwestern Sedgwick County to supply water to 

the city of Wichita. The decline of water levels in the aquifer 

was noted soon after the development of the Wichita well field 

began. Development of irrigation wells began in the 1960s. 

City and agricultural withdrawals have led to substantial 

water-level declines. Water-level declines enhanced movement of brines from past oil and gas activities near Burrton, 

Kansas and enhanced movement of natural saline water from 

the Arkansas River to migrate into the well field area. Further 

movement into the well field area of these waters with large 

chloride concentrations may limit use or require treatment of 

water from the well field area for irrigation or public supply. 

As water levels in the aquifer decline, the volume of water 

stored in the aquifer decreases and less water is available to 

supply future needs. In 1993, the city of Wichita adopted the 

Integrated Local Water Supply Program (ILWSP) to ensure 

an adequate water supply for the city through 2050 and as 

part of its effort to effectively manage the part of the Equus 

Beds aquifer it uses. The ILWSP uses several strategies to do 

this including the Equus Beds Aquifer Storage and Recovery (ASR). The purpose of the ASR project is to store water 

and later recover groundwater and to help protect the aquifer 

from the encroachment of a known oilfield-brine plume near 

Burrton and saline water from the Arkansas River.

As part of the Wichita’s ASR permits, Wichita is prohibited from artificially recharging water into the aquifer in a 

Basin Storage area (BSA) grid cell if the water levels in that 

cell are above the January 1940 water levels or are less than 

10 feet below land surface. The map previously used for this 

purpose was a previously published August 1940 water-level 

altitude map, which used water levels from wells in the deep 

and shallow Equus Beds aquifer layers, and did not provide an 

accurate representation of the shallow water table. The revised 

predevelopment water-level altitude map of the shallow part of 

the aquifer is presented in this report. A raster of the predevelopment map was used to interpolate predevelopment water 

levels for wells in the shallow layer of the Equus beds aquifer.

The city of Wichita’s ASR permits specify that the January 1993 water-level altitudes will be used as a lower baseline 

for regulating withdrawals by the city of Wichita of artificial 

recharge credits (water) from the Equus Beds aquifer. The city 

of Wichita is prohibited from withdrawing artificial recharge 

credits from the aquifer if water levels estimated in the BSA 

cells are below the lowest January 1993 water levels. To better 

represent the general condition of the aquifer and to comply 

with Wichita’s ASR permits, only static (unaffected by pumping) water levels were used. To ensure an adequate density 

of static water levels, the January 1993 period was expanded 

to October 1992 through February 1993. Static water levels 

from the deep aquifer layer of the Equus Beds aquifer possibly 

could be used as the lower baseline for the city of Wichita’s 

ASR permits because most city public-supply wells and artificial recharge wells, respectively, pump water from and inject 

water into the deep layer of the aquifer.

The 1993 water-level altitudes in the shallow and deep 

aquifer layers indicate that water generally flows from west 

to east across the study area but that pumping wells in the 

central part of the study area were intercepting some of the 

east to west flow and were also drawing water from the Little 

Arkansas River. Water-level altitudes in 1993 in the shallow 

Equus Beds aquifer layer were less than 5 feet above those in 

the deep aquifer layer in about two-thirds of the study area. 

Water-level altitude as much as 60 feet higher in the shallow 

aquifer layer than in the deep aquifer layer occurred locally in 

the northwest part of the study area, indicating downward 

flow and semiconfined conditions in this part of the study 

area. Small areas where water-level altitudes were less than 

5 feet lower in the shallow deep than the deep shallow aquifer 

layer indicate only minor flow upward from the deep to 

shallow aquifer layer. A comparison of average water-level 

altitude differences between the shallow and deep Equus Beds 

aquifer layers in 1993 shows those determined by the use of 

rasters were greater than those from either well clusters with 

measured water levels or wells clusters with measured and 

interpolated water levels.
16 Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas

Previously, maps of water-level changes used to estimate 

the storage-volume changes included a combination of static 

and stressed water levels from wells, some of which were 

open to the shallow part of the aquifer and some open to the 

deep part of the aquifer. In this report only static water levels 

in the shallow aquifer layer were used. This change was made 

because the use of water-level changes in the shallow layer of 

the Equus Beds aquifer is more appropriate for determining 

storage-volume changes than use of water-level changes in the 

deep aquifer layer, which includes semiconfined conditions 

in part of the area. The map of static water-level changes in 

the shallow aquifer layer from predevelopment to 1993 shows 

declines of 20 feet or more in most of the central part of the 

study area with declines of 40 feet or more along the eastern 

edge of the central part of the study area. Pumping for municipal and irrigation purposes probably are the main reason for 

these water-level declines. A small area of water-level rises in 

the northwestern part of the study area may be associated with 

heterogeneity of the aquifer material within the dune sand area 

because there is little pumpage from this area.

The effects on average water-level and storage-volume 

change from the use of mixed, stressed water levels and a 

specific yield of 0.20 (used in previous studies) were compared to the use of static water levels in the shallow aquifer 

and a specific yield of 0.15. This comparison indicates that 

the change in specific yield causes storage-volume changes to 

decrease about 25 percent, whereas the use of static shallow 

aquifer layer causes an increase of less than 4 percent. Use 

of a specific yield of 0.15 resulted in substantial decreases in 

the estimated amount of storage-volume change compared to 

those reported in previous reports that were calculated using a 

specific yield of 0.20. Based on these revised water-level maps 

and computations, the overall decline and change in storage 

from predevelopment to 1993 represented a loss in storage 

of about 6 percent (-202,000 acre-feet) of the overall storage 

volume within the newly defined study area. These revised 

estimates of storage changes in shallow and deep layers can 

be used by Wichita, Equus Beds Groundwater Management 

District Number 2 and Kansas Department of Agriculture, 

Division of Water Resources to manage, regulate, and preserve 

the water supply in this aquifer.

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Hansen and others—Revised Shallow and Deep Water-Level and Storage-Volume Changes in the Equus Beds Aquifer near Wichita, Kansas—Scientific Investigations Report 2013–5170