U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5291

Groundwater Resources Program

Water-Level and Storage Changes in the High Plains 

Aquifer, Predevelopment to 2011 and 2009–11

105° 97° 96° 104° 103° 102° 101° 100° 99° 98°

43°

42°

41°

40°

39°

38°

37°

36°

35°

34°

33°

32°

Canadian River

Arkansas River

South Platte River

Republican River

North Platte River

Platte River

OKLAHOMA

NEW MEXICO

COLORADO

KANSAS

WYOMING

SOUTH DAKOTA

TEXAS

NEBRASKA

U

U

U

U

U

U

U

10 to 25

 5 to 10

25 to 50

More than 50

Area of little or no saturated thickness

Area of water-level changes with few 

predevelopment water levels—(Lowry 

and others 1967; Luckey andothers, 1981; 

University of Nebraska–Lincoln, 

Conservation and Survey Division, 2012)

County boundary

Faults—U, upthrown side U

EXPLANATION

Water-level change—In feet

More than 150

100 to 150

50 to 100

25 to 50

10 to 25

 5 to 10

Decline

No substantial change

Rise

-5 to +5

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

Water-Level and Storage Changes in the 

High Plains Aquifer, Predevelopment to 

2011 and 2009–11

By V.L. McGuire

Groundwater Resources Program

Scientific Investigations Report 2012–5291

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

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

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Suggested citation:

McGuire, V.L., 2013, Water-level and storage changes in the High Plains aquifer, predevelopment to 2011 and 2009–

11: U.S. Geological Survey Scientific Investigations Report 2012–5291, 15 p. (Also available at http://pubs.usgs.gov/

sir/2012/5291/.)
iii

Contents

Acknowledgments........................................................................................................................................iv

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

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

Data and Methods .........................................................................................................................................3

 Characteristics of Raster Datasets....................................................................................................3

Characteristics of Water-Level Data.................................................................................................4

Characterizing Water-Level Changes, Predevelopment to 2011 ..................................................4

Characterizing Water-Level Changes, 2009–11 ...............................................................................5

Characterizing Specific Yield..............................................................................................................6

Calculation of Area-Weighted, Average Water-Level Changes, Predevelopment to 2011 ......6

Calculation of Area-Weighted, Average Water-Level Changes, 2009–11...................................6

Calculation of Total Water in Storage and Change in Water in Storage.....................................7

Characterizing Change in Saturated Thickness, Predevelopment to 2011 .................................7

Water-Level Data...........................................................................................................................................7

Water-Level Changes, Predevelopment to 2011.......................................................................................8

Water-Level Changes, 2009–11....................................................................................................................9

Water in Storage, Predevelopment, 1980, 2000, 2009, and 2011.............................................................9

Change in Water in Storage, Predevelopment to 2011 and 2009–11...................................................10

Percent Change in Saturated Thickness, Predevelopment to 2011 ....................................................11

Summary........................................................................................................................................................13

References Cited..........................................................................................................................................13

Figures

1. Map showing water-level changes in the High Plains aquifer, predevelopment 

to 2011.............................................................................................................................................2

2. Map showing change in saturated thickness of the High Plains aquifer,

predevelopment to 2011.............................................................................................................12

Tables

1. Number of wells used in this report for 2009 and 2011 water levels, and for the

water-level comparison periods, predevelopment to 2011 and 2009–11, by State

and in total for the High Plains aquifer......................................................................................3

2. Area-weighted, average water-level changes in the High Plains aquifer, not

including areas of little or no saturated thickness, predevelopment to 2011 and

2009–11, by State and as an overall total, and by comparable methods from this

report and previous reports ........................................................................................................8

3. Change in water in storage in the High Plains aquifer, predevelopment to 2011

and 2009–11, by State and as an overall total, and by comparable methods from

this report and previous reports...............................................................................................10
iv

Conversion Factors and Datum

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

Area

acre 4,047 square meter (m2

)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

)* 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3

) 

cubic foot (ft3

) 0.02832 cubic meter (m3) 

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

)

million acre-foot (Macre-ft) 4,047,000,000 square meter-ft (m2

-ft)

*There are 640 acres in a square mile (mi2).

**One acre-foot of water is equivalent to the volume of water that would cover one acre 

(43,560 ft2) to a depth of 1 foot (325,851 gallons or 43,560 ft3).

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

Acknowledgments

Most of the water-level data used in this report were provided by the following local, State, and 

Federal entities: Colorado: Division of Water Resources (also known as the Office of the State 

Engineer); Kansas: Department of Agriculture–Division of Water Resources and the Kansas 

Geological Survey; Nebraska: Central Nebraska Public Power and Irrigation District, Natural 

Resources Districts, and University of Nebraska–Lincoln, Conservation and Survey Division; 

New Mexico: Office of the State Engineer; Oklahoma: Water Resources Board; South Dakota: 

Department of Environment and Natural Resources; Texas: Groundwater Conservation Districts 

and the Water Development Board; Wyoming: State Engineer’s Office; and Federal: Bureau of 

Reclamation and U.S. Fish and Wildlife Service. The author thanks the above entities for providing the water-level data and for their responsiveness regarding questions about the data.
Water-Level and Storage Changes in the High Plains 

Aquifer, Predevelopment to 2011 and 2009–11

By V.L. McGuire

Abstract

The High Plains aquifer underlies 111.8 million acres 

(175,000 square miles) in parts of eight States—Colorado, 

Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, 

Texas, and Wyoming. Water-level declines began in parts of 

the High Plains aquifer soon after the beginning of substantial 

irrigation with groundwater in the aquifer area. This report 

presents water-level changes in the High Plains aquifer from 

the time before substantial groundwater irrigation development began (generally before 1950, and termed “predevelopment” in this report) to 2011 and from 2009–11. The report 

also presents total water in storage, 2011, and change in 

water in storage in the aquifer from predevelopment to 2011. 

The methods to calculate area-weighted, average water-level 

changes; change in water in storage; and total water in storage 

for this report used geospatial data layers organized as rasters 

with a cell size of about 62 acres. These methods were modified from methods used in previous reports in an attempt to 

improve estimates of water-level changes and change in water 

in storage.

Water-level changes from predevelopment to 2011, by 

well, ranged from a rise of 85 feet to a decline of 242 feet. 

The area-weighted, average water-level changes in the aquifer 

were an overall decline of 14.2 feet from predevelopment to 

2011, and a decline of 0.1 foot from 2009–11. Total water in 

storage in the aquifer in 2011 was about 2.96 billion acrefeet, which was a decline of about 246 million acre-feet since 

predevelopment.

Introduction

The High Plains aquifer underlies 111.8 million acres 

[175,000 square miles (mi2)] in parts of eight States—Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South 

Dakota, Texas, and Wyoming (Qi, 2010). In the High Plains 

aquifer, groundwater generally occurs under unconfined conditions and the water body, from a regional perspective, has a 

water table at which the water pressure is atmospheric (Weeks 

and Gutentag, 1981). The saturated thickness of the aquifer, 

which is the distance from the water table to the base of the 

aquifer, ranges from less than 50 feet (ft) to about 1,200 ft 

(McGuire and others, 2003). Gutentag and others (1984) 

reported that, in a few parts of the aquifer area, the water table 

is discontinuous; these areas total about 6.0 million acres 

(10,780 mi2) and are labeled in figure 1 as “area of little or 

no saturated thickness.” Wells drilled in areas of little or no 

saturated thickness (see fig. 8 in Gutentag and others, 1984) 

likely will not yield water unless the well penetrated saturated 

sediment in buried channels or depressions in the bedrock.

The area overlying the High Plains aquifer is one of the 

primary agricultural regions in the Nation; in parts of the area, 

farmers and ranchers began extensive use of groundwater for 

irrigation in the 1930s and 1940s. Estimated irrigated acreage in the area overlying the High Plains aquifer increased 

from 1940 to 1980, but did not change greatly from 1980 to 

2005: 1949—2.1 million acres, 1980—13.7 million acres, 

1997—13.9 million acres, 2002—12.7 million acres, and 

2005—15.5 million acres (Heimes and Luckey, 1982; Thelin 

and Heimes, 1987; U.S. Department of Agriculture, 1999 and 

2004; Kenny and others, 2009). In 2005, irrigated acres overlaid 14 percent of the aquifer area, not including the areas with 

little or no saturated thickness (Kenny and others, 2009).

About every 5 years, groundwater withdrawals for irrigation and other uses are compiled from water-use data and 

reported by the U.S. Geological Survey (USGS) and State 

agencies. Groundwater withdrawals from the High Plains 

aquifer for irrigation increased from 4 to 19 million acre-feet 

(acre-ft) from 1949 to 1974; groundwater withdrawals for 

irrigation in 1980, 1985, 1990, and 1995 were 4 to 18 percent less than withdrawals for irrigation in 1974 (Heimes and 

Luckey, 1982; U.S. Geological Survey, 2008). Groundwater 

withdrawals from the aquifer for irrigation were 21 million 

acre-ft (Macre-ft) in 2000 and 19 Macre-ft in 2005 (Maupin 

and Barber, 2005; U.S. Geological Survey, 2008; Kenny and 

others, 2009).

Water-level declines began in parts of the High Plains 

aquifer soon after the onset of substantial irrigation using 

groundwater in the area—about 1950 (Gutentag and others, 1984). By 1980, water levels in the High Plains aquifer 

in parts of Texas, Oklahoma, and southwestern Kansas had 

declined more than 100 ft (Luckey and others, 1981).
2 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

Figure 1. Water-level changes in the High Plains aquifer, predevelopment to 2011.

105° 97° 96° 104° 103° 102° 101° 100° 99° 98°

43°

42°

41°

40°

39°

38°

37°

36°

35°

34°

33°

32°

Canadian River

Arkansas River

South Platte River

Republican River

North Platte River

Platte River

OKLAHOMA

NEW MEXICO

COLORADO

KANSAS

WYOMING

SOUTH DAKOTA

TEXAS

NEBRASKA

U

U

U

U

U

U

U

10 to 25

 5 to 10

25 to 50

More than 50

Area of little or no saturated thickness

Area of water-level changes with few 

predevelopment water levels—(Lowry 

and others 1967; Luckey and others, 1981; 

University of Nebraska–Lincoln, 

Conservation and Survey Division, 2012)

County boundary

Faults—U, upthrown side U

EXPLANATION

Water-level change—In feet

More than 150

100 to 150

50 to 100

25 to 50

10 to 25

 5 to 10

Decline

No substantial change

Rise

-5 to +5

Aquifer boundary from Qi (2010); areas of little 

or no saturated thickness and faults from 

Gutentag and others (1984) and Cederstrand 

and Becker (1999a, 1999b)

Base from U.S. Geological Survey digital data, 2001, 1:2,000,000

Albers Equal-Area Conic projection

Standard parallels 29o 30' and 45o 30', central meridan -101o

North American Datum of 1983 (NAD 83)

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS
Data and Methods 3

Long-term water-level changes in the aquifer result from 

an imbalance between discharge and recharge. Discharge 

from the High Plains aquifer primarily consists of groundwater withdrawals for irrigation, but also includes groundwater 

withdrawals for public supply and other uses, evapotranspiration where the water table is near land surface, and seepage 

to streams, springs, and other surface-water bodies where the 

water table intersects the land surface (Maupin and Barber, 

2005). Recharge to the aquifer primarily is from precipitation, 

but other sources of recharge include seepage from streams, 

canals, and reservoirs, and irrigation return flows (Luckey and 

Becker, 1999). Water-level declines may result in increased 

costs for groundwater withdrawals because of increased 

pumping lift and decreased well yields (Taylor and Alley, 

2001). Water-level declines also can affect groundwater availability, surface-water flow, and near-stream (riparian) habitat 

areas (Alley and others, 1999).

In response to water-level declines, Congress, under 

the authority of Title III to the Water Resources Research 

Act (U.S. Public Law 98-242, 99-662), directed the USGS to 

monitor water levels in the aquifer; in 1987–88, the USGS, in 

collaboration with numerous Federal, State, and local waterresources entities, compilied water levels for 1987 and 1988 

from more than 7,000 wells screened in the High Plains aquifer. Water levels for 2009 were based on measurements from 

9,178 wells, and water levels for 2011 were based on measurements from 8,410 wells (table 1).

Purposes of this report are (1) to present water-level 

changes in the High Plains aquifer from the time before substantial development of groundwater for irrigation to 2011 and 

from 2009–11, and (2) to publish the raster dataset depicting 

water-level changes, predevelopment to 2011. The time period 

before substantial development of groundwater for irrigation is 

termed “predevelopment” in this report; predevelopment generally is before about 1950, but in some areas (for example, in the 

north-central part of the Texas Panhandle), predevelopment is 

the late 1990s, and in other areas (for example, in north-central 

Nebraska), groundwater has not yet (2012) been developed substantially for irrigation. Water levels used in this report generally 

were measured in winter or early spring, when irrigation wells 

typically were not pumping, and water levels generally had 

recovered from pumping during the previous irrigation season.

This report also describes drainable water in storage in 

the High Plains aquifer in 2011 and changes in both drainable 

water in storage and saturated thickness of the aquifer from 

predevelopment to 2011. Drainable water in storage is the 

fraction of water in the aquifer that will drain by gravity and 

can be withdrawn by wells. The remaining water in the aquifer 

is held to the aquifer material by capillary forces and generally 

cannot be withdrawn by wells. Drainable water in storage is 

termed “water in storage” in this report.

Area-weighted, average water-level changes; change in 

water in storage, predevelopment to 2011; and total water in 

storage, 2011, were calculated for this report using geospatial 

data organized as rasters, including available raster datasets 

for saturated thickness, 2009, and specific yield (Gutentag and 

others, 1984; Cederstrand and Becker, 1998; McGuire and 

others, 2012). The methods used for these calculations were 

modified from methods used for previous reports (McGuire, 

2009, 2011) in an attempt to improve estimates of water-level 

changes and change in water in storage.

Table 1. Number of wells used in this report for 2009 and 2011 water levels, 

and for the water-level comparison periods, predevelopment to 2011 and 

2009–11, by State and in total for the High Plains aquifer.

State

Number of wells 

measured 

Number of wells used in water-level 

comparison for indicated period

2009 2011 Predevelopment 

to 2011 2009–11

Colorado 343 512 325 291

Kansas 1,745 1,439 530 1,313

Nebraska 3,772 3,346 1,504 3,132

New Mexico 71 113 55* 33

Oklahoma 140 152 90 125

South Dakota 106 105 67 101

Texas 2,731 2,689 734 2,330

Wyoming 270 54 17 51

High Plains aquifer 9,178 8,410 3,322 7,376

*

For 24 wells in the predevelopment-to-2011 water-level comparison period, 2007, 2008, 

2009, or 2010 water levels were used instead of 2011 water levels because many wells in 

New Mexico were measured only once every 5 years or because the 2011 water level was 

not a static water level.

Data and Methods

Characteristics of Raster Datasets

The water-volume data for this report are 

presented as raster datasets (hereinafter, “rasters”), 

which were generated using a geographic information system; the specific geographic information 

system used was ESRI® ArcInfoTM Workstation, 

version 10.0 (Environmental Systems Research 

Institute, 1992, 2010), which will hereinafter be 

referred as “GIS.” The rasters are georeferenced 

to map coordinates on an Albers equal-area conic 

projection and using the North American Datum 

of 1983 (NAD 83). The cell size for all rasters was 

about 62 acres [500 meters (m) by 500 m]. The 

water-level change values were stored in units of 

feet. The units for change in water in storage were 

square meter-feet (m2

-ft); and water in storage was 

summarized in this report in units of Macre-ft. In 

this report, rasters, which are presented as maps 

and summarized with statistics, include water-level 

changes, predevelopment to 2011, and percent 

changes in saturated thickness, predevelopment to 
4 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

2011; an additional raster for water-level changes, 2009–11, is 

discussed and summarized with statistics, but not shown.

Characteristics of Water-Level Data

Water-level data used in this report generally were from 

wells measured with an electric or steel tape using methods similar to those described by Cunningham and Schalk 

(2011). The wells were measured by numerous Federal, 

State, and local water-resources agencies, and the measurement results were loaded through the USGS Groundwater 

Site Inventory System (GWSI) into the USGS National 

Water Information System (NWIS) (U.S. Geological Survey, 

2012a, 2012b).

Most of the wells were measured manually one to two 

times per water year. The water year starts with October of 

the prior year and ends with September of the given year. 

Generally, if a well was measured one time per water year, 

the well was measured in the winter or early spring; if a 

well was measured two times per water year, the well was 

measured in winter or early spring and in the late fall. Some 

wells were measured nearly continuously by using instrumentation (data recorders with sensors or floats) installed in 

the well that recorded the water level periodically (generally 

every 15 to 60 minutes) (Cunningham and Schalk, 2011). 

Water-level data used to map water-level changes were compiled for the specified water years (U.S. Geological Survey, 

2012a, 2012b). Available water-level data for each well were 

reviewed to select a water level that (1) best represents the 

static water level for each applicable water year (that is, a 

water level that has recovered from pumping in the previous 

irrigation season) and (2) that is consistent with water levels 

in nearby wells. If a static water level was not available for a 

given well for the specified water year, the water-level data 

for that well for the specified water year were not used in this 

report, except as noted in table 1.

Most of the measured wells supply water for irrigation; 

water-level accuracy in irrigation wells can be adversely 

affected by excess oil used to lubricate the well’s pump. The 

thickness of the excess oil and the depth to the oil-water 

interface can be measured with specialized water-level tapes; 

however, often these specialized tapes cannot be used in 

irrigation wells because opening(s) in the well casing for 

the measurement tape generally are not adequate. Using 

standard water-level tapes, the depth-to-water measurement 

may be underestimated as the depth to the oil floating on the 

water surface. Therefore, in this report, it is assumed that the 

accuracy of the water-level measurements ranges from 0.01 

to 1 ft.

In all eight States underlain by the High Plains aquifer, 

available water levels for predevelopment and 1980 were 

compiled by Weeks and Gutentag (1981) and McGuire and 

others (2003). The predevelopment water level in a given 

well is defined as the water level in the aquifer before 

extensive groundwater pumping. The predevelopment water 

level generally was estimated by using the earliest waterlevel measurement available for more than 20,000 wells. The 

median measurement year in the predevelopment period was 

1957 (McGuire and others, 2003). The 1980 water levels are 

static water levels generally measured after the irrigation 

season in 1979 and before the irrigation season in 1980 (that 

is, in water year 1980), but some were measured 1 or 2 years 

earlier.

In seven of the eight States that are underlain by the 

High Plains aquifer—Colorado, Kansas, Nebraska, Oklahoma, South Dakota, Texas, and Wyoming—most waterlevel data used in this report were from wells measured 

annually. In areas underlain by the High Plains aquifer in 

New Mexico, a substantial number of wells are measured 

only once every 5 or more years.

In Colorado, Kansas, Nebraska, Oklahoma, South 

Dakota, Texas, and Wyoming, the water levels used to map 

water-level changes, predevelopment to 2011, were from 

wells with a static water level for predevelopment and for 

2011. In New Mexico, the water levels used to map waterlevel changes, predevelopment to 2011, were from wells 

with a static water level for predevelopment, and a static or 

estimated water level for 2011. A total of 24 water levels 

were estimated for 2011 for wells in New Mexico, which 

were not measured in 2011; these estimates used water levels 

measured in 2007 for 7 wells, in 2008 for 2 wells, in 2009 

for 7 wells, and in 2010 for 8 wells.

In the eight States that are underlain by the High Plains 

aquifer, the water levels used to map water-level changes, 

2009–11, were from wells with a measured static water level 

for 2009 and 2011. Estimated water levels were not used to 

map water-level changes, 2009–11.

Characterizing Water-Level Changes, 

Predevelopment to 2011

The raster of water-level changes from predevelopment to 2011 was developed by first using the GIS command 

“topogrid” to interpolate from point measurements to a raster 

of water-level changes, and then modeling the topogridoutput raster as a contoured surface using the GIS command 

“contour.” The results of this first cut at mapping water-level 

changes are referred to as the initial contours. The data inputs 

to the GIS command “topogrid” were the water-level-change 

values from wells measured in the predevelopment and 2011 

periods, and the contours of water-level changes, predevelopment to 2009 (McGuire, 2011). The contours of water-level 

changes, predevelopment to 2009, were input to the topogrid 

process to preserve information from discontinued waterlevel monitoring in areas with few measured wells.

The initial water-level-change contours and supplemental water-level-change data from water-level measurements in other wells and from published maps were used 

to create the final water-level-change contours for the 
Data and Methods 5

predevelopment-to-2011 period. The supplemental waterlevel-change data were from the following sources:

1. Wells measured in the predevelopment period and, 

for New Mexico only, in at least one year of the 

2007–10 period, but not in the 2011 period;

2. Wells measured before June 15, 1978 (but not during 

or before the predevelopment period for the area), 

and in the 2011 period;

3. Wells measured in 1980 and 2011; and 

4. For parts of the aquifer in Nebraska and Wyoming 

with few predevelopment water levels, published 

maps of water-level changes since predevelopment 

(Lowry and others, 1967; Luckey and others, 1981; 

University of Nebraska–Lincoln, Conservation and 

Survey Division, 2012).

The initial contours of water-level changes, predevelopment to 2011, were modified manually in areas with few 

water-level-change values to make the interpolation more realistic. Then, polygons of water-level changes, predevelopment 

to 2011, were constructed using the modified contours. These 

polygons were converted to a raster using the GIS command 

“polygrid.”

The GIS command “topogrid” was used again to regenerate a raster of water-level changes, predevelopment to 2011. 

Inputs to the second topogrid process included the same point 

dataset of water-level change from predevelopment to 2011, 

which was input to the initial “topogrid” process, and the 

modified contours of water-level change, predevelopment to 

2011. This raster was modified further (using the GIS commands “setnull” and “con”) to change the cell values to “missing data” in areas where the aquifer is not present (Gutentag 

and others, 1984); to change the cell values to zero in areas 

where water-level change ranges from a decline of less than 

5 ft to a rise of less than 5 ft; to change the cell values to 

“missing data” in the areas of little or no saturated thickness, 

as described by Gutentag and others (1984); and to examine 

the cell values within the polygons of water-level change to 

re-assign the cell, if appropriate, either (1) to the minimum 

value of the corresponding range for the polygon, if the cell 

value was less than the polygon’s minimum value, or (2) to the 

maximum value of the corresponding range for the polygon, 

if the cell value was greater than the polygon’s maximum 

value. The mapped areas between a decline of less than 5 ft 

to a rise of less than 5 ft were termed areas of no substantial 

change and were assigned a value of zero water-level change 

rather than using the GIS interpolation of water-level change 

values in these areas. GIS interpolation of water-level changes 

in these areas were not used because there was an insufficient 

density of wells with predevelopment and 2011 measurements for a reasonable interpolation in some of these areas. To 

determine the ramifications of the decision to set cells to zero 

in the areas of no substantial change, area-weighted, average water-level change and change in water in storage were 

calculated twice—once with and once without so assigning 

the areas between a decline of less than 5 ft and a rise of less 

than 5 ft. The final raster of water-level changes, predevelopment to 2011, was used to represent cartographically waterlevel changes from predevelopment to 2011 and to calculate 

area-weighted, average water-level change in this report. The 

interpolation process used in this report results in cell values, 

for cells collocated with a measured well, that are generally 

similar to, but commonly not equal to, the corresponding values based on those water-level measurements.

The method used to characterize water-level changes 

since predevelopment in previous reports (McGuire, 2009, 

2011) was to contour water-level changes by specified ranges 

and, for statistical purposes, to estimate the water-level change 

value at a given location in the map as the midpoint of the 

contour interval, which could be an over- or under-estimate of 

the location’s value. To allow an assessment of the magnitude 

of method-attributable differences on the results between the 

method used in previous reports and the method used in this 

report, the method used in previous reports also was used to 

produce a third characterization of water-level change, predevelopment to 2011.

Characterizing Water-Level Changes, 2009–11

The raster of water-level changes from 2009–11 was 

developed by first using a GIS implementation of inversedistance weighting to interpolate from point measurements 

of water-level change at wells measured in the 2009 and 

2011 periods to an initial raster of water-level changes (using 

the GIS command “IDW”). Then, using the GIS command 

“contour,” modeling the initial raster as a contoured surface to 

generate initial contours of water-level change ranges from a 

decline of less than 1 ft to a rise of less than 1 ft.

The initial contours of water-level changes, 2009–11, 

which were of the area where the change ranged from a 

decline of less than 1 ft to a rise of less than 1 ft, were modified manually in areas with few water-level-change values 

to make the interpolation more realistic. Then, polygons of 

water-level change, 2009–11, were constructed from these 

modified contours. These polygons were converted to a raster 

using the GIS command “polygrid.”

The GIS command “topogrid” was used again to regenerate a revised raster of water-level changes, 2009–11. Inputs to 

the second topogrid process included the same point dataset 

of water-level change from 2009–11, which was input to the 

initial “topogrid” process, and the modified contours of waterlevel change, 2009–11. This topogrid-output raster was modified further (using the GIS commands “setnull” and “con”) 

to change the cell values to “missing data” in areas where the 

aquifer is not present (Gutentag and others, 1984); to change 

the cell values to zero in areas where water-level change 

ranges from a decline of less than 1 ft to a rise of less than 1 ft 

(in recognition of estimated water-level accuracy for irrigation 

wells); and to change the cell values to ”missing data” in the 
6 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

areas of little or no saturated thickness, as described by Gutentag and others (1984).

The method used herein for characterizing water-level 

change, 2009–11, was selected to generate a water-levelchange surface that would be more realistic across the aquifer 

area than the corresponding results from the method used in 

previous reports (McGuire, 2009, 2011). The interpolation 

process used in this report results in cell values, for cells collocated with a measured well, that are generally similar to, but 

commonly not equal to, the corresponding values based on 

those water-level measurements.

Thiessen’s method (Thiessen, 1911), which was used to 

characterize annual water-level change in previous reports 

(McGuire, 2009, 2011), determines an area around each well 

and assigns a single value to each well’s area. In Thiessen’s 

method (Thiessen, 1911), hereinafter referred to as the “Thiessen-polygon” method, the size and shape of a well’s area 

are determined by the proximity of neighboring wells, and 

water-level change measured at the well is the polygon value 

assigned to the well’s area. In areas with widely spaced wells, 

the water-level change value for a given well can be assigned 

to a large area of the aquifer and may misrepresent water-level 

change for at least part of the assigned area.

Characterizing Specific Yield

Specific yield of the aquifer is used to calculate water in 

storage. Specific yield of a rock or soil, with respect to water, 

is the ratio of the volume of water, which the saturated rock or 

soil will yield by gravity, to the rock or soil volume (Meinzer, 

1923). Specific yield was mapped for the High Plains aquifer 

from point estimates of area-weighted, average specific yield 

derived from lithologic logs for selected wells or test holes 

generally drilled to the base of the aquifer; the area-weighted, 

average specific yield of the High Plains aquifer ranges from 

near 0 to 30 percent. The area-weighted, average specific 

yield, not including the areas of little or no saturated thickness, ranges by State, from 8.1 percent in Wyoming to 18.5 

percent in Oklahoma and is 15.1 percent overall for the aquifer 

(Gutentag and others, 1984; McGuire and others, 2012).

A specific-yield raster was created from a contour map 

of specific-yield ranges in the High Plains aquifer (Gutentag 

and others, 1984; Cederstrand and Becker, 1998). The GIS 

command “polygrid” was used to convert the average of the 

assigned range for the specific-yield polygons to a raster of the 

area (McGuire and others, 2012). The specific-yield value of 

cells in this raster of specific yield is hereafter referred to as 

the “average-mapped” specific-yield value.

Calculation of Area-Weighted, Average WaterLevel Changes, Predevelopment to 2011

In this report, area-weighted, average water-level 

changes, predevelopment to 2011, were calculated directly 

from the final raster of water-level changes, predevelopment 

to 2011. This method for calculating area-weighted, average water-level changes was selected for the final calculation 

because the interpolated value assigned for many cells using 

this report’s method is more realistic than the polygon-average 

value assigned to cells using the previous method (McGuire, 

2009, 2011), and the final raster can be used to easily calculate 

statistics for additional subareas of the aquifer.

Area-weighted, average water-level changes, predevelopment to 2011, were calculated a second time with the cell 

values in the area of water-level change from a 5-ft decline to 

a 5-ft rise unchanged from the value interpolated by GIS during the second topogrid process. The State and aquifer results 

from this second calculation were compared to the results 

obtained using this report’s method to qualitatively assess 

the effect on the final calculations of setting the water-levelchange value to zero where the water-level-change range is 

between a 5-ft decline and a 5-ft rise.

Area-weighted, average water-level changes, predevelopment to 2011, were calculated a third time using the methods from previous reports (McGuire, 2009, 2011), to allow 

comparison of State and aquifer results using the previous 

method with the results obtained using this report’s method. 

The method used in previous reports (McGuire, 2009, 2011) 

for calculating area-weighted, average water-level changes 

used the areas of the mapped polygons of intervals of waterlevel changes and the midpoint value of the interval or, for 

areas of declines greater than 150 ft or rises greater than 50 ft, 

the beginning value of the associated polygon’s water-level 

change interval (that is, either 150 or 50 ft, respectively).

Calculation of Area-Weighted, Average WaterLevel Changes, 2009–11

In this report, area-weighted, average water-level 

changes, 2009–11, were calculated directly from the final raster of water-level changes, 2009–11. This method for calculating area-weighted, average water-level changes was selected 

for the final calculation because the value assigned for many 

cells is more realistic than in the previous method (McGuire, 

2009, 2011), and the final raster could be used to calculate 

statistics for additional subareas of the aquifer.

Area-weighted, average water-level changes, 2009–11, 

were calculated a second time with the cell values in the 

area of water-level change from a 1-ft decline to a 1-ft rise 

unchanged from the value interpolated by GIS during the second topogrid process. The State and aquifer results from this 

calculation were compared to the results obtained using this 

report’s method to qualitatively assess the effect on the final 

calculations of setting the water-level-change value to zero 

where the water-level-change range is between a 1-ft decline 

and a 1-ft rise.

Area-weighted, average water-level changes, 2009–11, 

were calculated a third time using the methods from previous 

reports (McGuire, 2009, 2011), to allow comparison of State 

and aquifer results using the previous method with the results 
Water-Level Data 7

obtained using this report’s method. The method used in 

previous reports (McGuire, 2009, 2011) for calculating annual 

area-weighted, average water-level changes used the area and 

water-level change value of the Thiessen polygon.

Calculation of Total Water in Storage and 

Change in Water in Storage

Total water in storage, 2011, was calculated by summing 

the rasters of saturated thickness, 2009 (McGuire and others, 

2012), and the raster of water-level changes, 2009–11, and 

multiplying the result by the raster of average-mapped specific 

yield (Gutentag and others, 1984; Cederstrand and Becker, 

1998; McGuire and others, 2012) and by a conversion factor 

to convert m2-ft to Macre-ft. Total water in storage, 2011, 

is not recalculated for this report using alternative methods, 

however, results for other years from previous reports are 

presented.

Changes in water in storage in the High Plains aquifer for 

the predevelopment to 2011 and 2009–11 time periods were 

calculated in this report by applying “map algebra” techniques 

(Tomlin and Berry, 1979) to coregistered rasters sharing a 

common cell size and mesh orientation. The raster of waterlevel changes for each period was multiplied by the raster 

of average-mapped specific yield, which ranges from 2.5 to 

27.5 percent (Gutentag and others, 1984; Cederstrand and 

Becker, 1998; McGuire and others, 2012) and by a conversion 

factor to convert m2-ft to Macre-ft. Changes in water in storage from predevelopment to 2011 and from 2009–11, by State 

and as an overall High Plains aquifer total, were calculated by 

aggregating the applicable resultant raster.

Changes in water in storage, predevelopment to 2011 

and 2009–11, were recalculated a second time using areaweighted, average specific yield for the aquifer (15.1 percent). 

The State and aquifer results from these calculations were 

compared to the results obtain using this report’s methods to 

qualitatively assess the difference(s) in results by State and for 

the aquifer.

Change in water in storage, predevelopment to 2011 and 

2009–11, were recalculated a third time using the method 

from previous reports (McGuire, 2009, 2011). In a previous 

report (McGuire, 2011), change in water in storage in the High 

Plains aquifer since predevelopment was calculated using 

the area-weighted, average specific yield of the High Plains 

aquifer (15.1 percent) (Gutentag and others, 1984); change in 

saturated volume of the High Plains aquifer, predevelopment 

to 2000; and change in the saturated volume of the High Plains 

aquifer from the corresponding annual water-level-change 

maps from 2000 to 2009 (McGuire, 2003, 2004a, 2004b, 2007, 

2009, 2011). The State and aquifer results from these calculations were compared to the results obtained using this report’s 

methods to qualitatively assess the difference(s) in results by 

State and for the aquifer.

Characterizing Change in Saturated Thickness, 

Predevelopment to 2011

Change in saturated thickness, predevelopment to 2011, 

was mapped by contouring the ratio of water-level change, 

predevelopment to 2011, to predevelopment saturated thickness, using locations where this ratio was calculated for wells 

measured in the predevelopment and 2011 period. Predevelopment saturated thickness was calculated for each well by 

subtracting water-level changes, predevelopment to 2011, 

from calculated saturated thickness, 2011. A raster of saturated 

thickness, 2011, was generated by adding the raster of waterlevel change, 2009–11, to the raster of saturated thickness, 

2009 (McGuire and others, 2012). The contours of change in 

saturated thickness were constructed initially by using the GIS 

command “topogrid,” and then modeling the output grid as a 

contoured surface using the GIS command “contour.” The initial change-in-saturated-thickness contours were reviewed and 

manually modified using supplemental data to construct the 

final contours. The supplemental data for changes in saturated 

thickness, in percent, were from the following sources:

1. Wells measured in the predevelopment period and in 

at least 1 year of the 2006–10 period, but not in the 

2011 period;

2. Wells measured before June 15, 1978 (but not in the 

predevelopment period for the area), and in the 2011 

period;

3. Wells measured in 1980 and in the 2011 period; and

4. For parts of the aquifer in Nebraska and Wyoming 

with few predevelopment water levels, published 

maps of water-level changes since predevelopment 

(Lowry and others, 1967; Luckey and others, 1981; 

University of Nebraska–Lincoln, Conservation and 

Survey Division, 2012).

Water-Level Data

Water-level data used in this report were provided by the 

following Federal, State, and local entities through data files 

or downloads from Web sites (noted below), and loaded into 

the USGS NWIS (U.S. Geological Survey, 2012b) through the 

USGS GWSI for each State overlying the High Plains aquifer 

(U.S. Geological Survey, 2012a):

• Colorado: Division of Water Resources (also known as 

the Office of the State Engineer);

• Kansas: Department of Agriculture–Division of Water 

Resources and the Kansas Geological Survey (Kansas 

Geological Survey, 2012);

• Nebraska: Central Nebraska Public Power and Irrigation District, applicable Natural Resources Districts, 
8 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

and the University of Nebraska–Lincoln, Conservation 

and Survey Division;

• New Mexico: Office of the State Engineer;

• Oklahoma: Water Resources Board;

• South Dakota: Department of Environment and Natural 

Resources;

• Texas: Groundwater Conservation Districts and the 

Water Development Board (Texas Water Development 

Board, 2012);

• Wyoming: State Engineer’s Office; and 

• Federal: Bureau of Reclamation, U.S. Fish and Wildlife Service, and USGS offices in Colorado, Kansas, 

Nebraska, New Mexico, Oklahoma, South Dakota, 

Texas, and Wyoming.

The data used in this report were retrieved from the USGS 

GWSI System for each applicable State and from USGS 

NWIS (U.S. Geological Survey, 2012a, 2012b).

Water-Level Changes, Predevelopment 

to 2011

The map of water-level changes in the High Plains 

aquifer from predevelopment to 2011 (fig. 1) is based on water 

levels from 3,322 wells (table 1) and on other published data 

(Lowry and others, 1967; Luckey and others, 1981; University of Nebraska–Lincoln, Conservation and Survey Division, 2012). The other published data were used in areas in 

Nebraska and Wyoming with few predevelopment water levels 

(fig. 1). Water-level changes in wells from predevelopment 

to 2011 ranged from a rise of 85 ft in Nebraska to a decline 

of 242 ft in Texas; 99 percent of the wells had water-level 

changes from predevelopment to 2011 that ranged from a 

rise of 46 ft to a decline of 186 ft. The area-weighted, average water-level change from predevelopment to 2011 was 

a decline of 14.2 ft. When summarized by State, the areaweighted, average water-level change from predevelopment to 

2011 ranged from a decline of 39 ft in Texas to a rise of 0.3 ft 

in South Dakota (table 2).

From predevelopment to 2011, not including the areas 

of little or no saturated thickness, water levels declined 5 ft 

or more in 33 percent of the aquifer area, 10 ft or more in 

26 percent of the aquifer area, 25 ft or more in 19 percent of 

the aquifer area, and 50 ft or more in 11 percent of the aquifer 

area. In approximately 54 percent of the aquifer area, waterlevel changes ranged from a 5-ft decline to a 5-ft rise. From 

predevelopment to 2011, water levels rose 5 ft or more in 

12 percent of the aquifer area and 10 ft or more in 3 percent of 

the aquifer area.

The decision to set to zero the raster cells in areas where 

water-level change ranged from a 5-ft decline to a 5-ft rise was 

examined by recalculating area-weighted, average water-level 

change from predevelopment to 2011without altering the cell 

values from their topogrid-interpolated value. The resulting 

area-weighted, average water-level change for the aquifer 

Table 2. Area-weighted, average water-level changes in the High Plains aquifer, not including areas of little or no 

saturated thickness, predevelopment to 2011 and 2009–11, by State and as an overall total, and by comparable methods from 

this report and previous reports.

[Positive values for water-level rises; negative values for water-level declines; “no substantial change” defined as changes between a 5-foot decline 

and a 5-foot rise for predevelopment to 2011 and changes between a 1-foot decline and a 1-foot rise for 2009–11]

State

Area-weighted, average water-level change, in feet

Final values calculated for this 

report, with areas of no substantial 

change set to zero feet

Calculated in this report, with areas 

of no substantial change interpolated using the available data

Calculated using methods 

from previous reports1

Predevelopment 

to 2011 2009–11 Predevelopment to 2011 2009–11 Predevelopment to 2011 2009–11

Colorado -12.9 0.3 -12.9 0.2 -13.4 0.6

Kansas -23.6 -1.1 -23.5 -1.1 -23.5 -1.3

Nebraska 0.2 0.8 0.7 0.9 -0.6 1.4

New Mexico -14.9 -0.3 -15.2 -0.3 -15.1 -0.7

Oklahoma -11.1 -0.6 -11.0 -0.8 -12.1 -1.2

South Dakota 0.3 0.2 1.9 0.2 0.1 0.4

Texas -39.0 -1.2 -38.9 -1.2 -38.1 -1.7

Wyoming -0.9 0.2 -1.1 0.3 -0.4 1.1

High Plains aquifer -14.2 -0.1 -13.9 -0.2 -14.4 0.0

1

McGuire, 2009, 2011.
Water in Storage, Predevelopment, 1980, 2000, 2009, and 2011 9

overall was a decline of 13.9 ft, and area-weighted, average 

water-level changes by State ranged from a decline of about 

39 ft in Texas to a rise of 1.9 ft in South Dakota. These results 

indicate that the decision to substitute a water-level change of 

zero for those ranging from a 5-ft decline to a 5-ft rise did not 

substantially affect the area-weighted, average water-levelchange calculations for the aquifer or for most of the States 

(table 2). The exceptions were the results for South Dakota 

and Nebraska, where substitution of zero for small changes 

resulted in area-weighted, average water-level-change values 

that were 0.5 ft lower for Nebraska, and 1.6 ft lower for South 

Dakota, than the corresponding values obtained with no 

substitutions. These differences in Nebraska and South Dakota 

imply that topogrid-interpolated water-level changes were generally greater than zero, rather than an average of near zero, in 

the areas between declines less than 5 ft and greater than 5 ft. 

However, since a large part of these areas in Nebraska and 

South Dakota are without water-level measurements, there is 

uncertainty about the accuracy of these interpolations in these 

States. In this report, the selected approach for final values of 

water-level change was, for areas with changes ranging from a 

5-ft decline to a 5-ft rise, to substitute zero change, because of 

the inherent uncertainty in measuring water levels in irrigation 

wells (as much as +1 ft) and, especially for the predevelopment period, an insufficient data density to accurately characterize small water-level changes in parts of the area to which 

substitutions were applied.

Using the method from previous reports (McGuire, 2009, 

2011), area-weighted, average water-level change in the High 

Plains aquifer from predevelopment to 2011 was a 14.4-ft 

decline. Area-weighted, average water-level changes by State 

ranged from a decline of about 38 ft in Texas to a rise of 0.1 ft 

in South Dakota (table 2). These results using the method from 

a previous report (McGuire, 2011) do not vary substantially 

from the results obtained using this report’s method.

Water-Level Changes, 2009–11

Water levels were measured in 7,376 wells before the 

irrigation season in 2009 and 2011 (table 1). Water-level 

changes in the measured wells ranged from about a 26-ft 

decline in Texas to about a 16-ft rise in Colorado; 99 percent 

of the wells had water-level changes from 2009–11 that ranged 

from a decline of 13 ft to a rise of 10 ft. Water levels declined 

3 ft or more in 11 percent of the measured wells; water levels 

declined 6 ft or more in 4 percent of the measured wells. The 

area-weighted, average water-level changes from 2009–11 by 

State ranged from a 1.2-ft decline in Texas to a 0.8-ft rise in 

Nebraska (table 2). The area-weighted, average water-level 

change from 2009–11 for the aquifer was a 0.1-ft decline 

(table 2).

The decision to set to zero the water-level change values 

in the raster cells representing the area of no substantial 

change (changes ranging from a 1-ft decline to a 1-ft rise) was 

examined by recalculating area-weighted, average water-level 

change from 2009–11without altering the cell values from 

their topogrid-interpolated value (table 2). The resulting areaweighted, average water-level change for the aquifer was an 

overall decline of 0.2 ft, and changes by State ranged from a 

decline of 1.2 ft in Texas to a rise of 0.9 ft in Nebraska. These 

results indicate that the decision to set raster cells to zero for 

the areas of no substantial water-level change, 2009–11, did 

not substantially affect the area-weighted, average water-levelchange calculations. Assigning cell values of zero to the areas 

with interpolated water-level change between a 1-ft decline 

to a 1-ft rise was preferred for calculating the final values 

reported herein, partly because water-level measurement accuracy is estimated to be from 0.01 ft to 1 ft.

Using the Thiessen-polygon method from previous 

reports (McGuire, 2009, 2011), area-weighted, average waterlevel change in the High Plains aquifer during 2009–11 was 

0.0 ft. Area-weighted, average water-level change by State 

ranged from a decline of 1.7 ft in Texas to a rise of 1.4 ft in 

Nebraska (table 2). These results using the Thiessen-polygon 

method from previous reports (McGuire, 2009, 2011) do not 

vary substantially from the results obtained using methods 

described herein for the States of Texas, Kansas, or for the 

aquifer overall, but do vary substantially for the other States. 

Substantial variance occurs when there are relatively large 

areas with few water-level measurements, such as exist in 

Colorado, Nebraska, New Mexico, Oklahoma, South Dakota, 

and Wyoming. For such areas, the Thiessen-polygon method 

will generate large polygons around the wells and assign 

uniformly the applicable water-level-change value calculated 

from measured water levels at each well to its area(s).

Water in Storage, Predevelopment, 

1980, 2000, 2009, and 2011

The volume of water in storage in the High Plains 

aquifer has been estimated, using different methods, to have 

been about 3.25 billion acre-ft in 1980 (Gutentag and others, 1984), about 2.98 billion acre-ft in 2000 (McGuire and 

others, 2003), about 2.90 billion acre-ft in 2009 (McGuire, 

2011), and recalculated, as about 2.96 billion acre-ft in 2009 

(McGuire, 2012). Water in storage in the High Plains aquifer 

in 2011 is estimated in this report as 2.96 billion acre-ft. Water 

in storage, 2011, was calculated using the raster of water-level 

changes from 2009–11, which was generated for this report, 

and rasters of saturated thickness for 2009 and of averagemapped specific yield (Gutentag and others, 1984; Cederstrand and Becker, 1998; McGuire and others, 2012). Water in 

storage, predevelopment, was calculated as 3.20 billion acre-ft 

using the rasters of water-level change, 2009–11, and waterlevel change, predevelopment to 2011, which were generated 

for this report, and rasters of saturated thickness, 2009, and 

of average-mapped specific yield (Gutentag and others, 1984; 

Cederstrand and Becker, 1998; McGuire and others, 2012).
10 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

Previously reported values for water in storage in 2000 

(McGuire and others, 2003) were calculated using areal average values associated with mapped polygons of the aquifer’s 

saturated thickness and the area-weighted, average specific 

yield of the aquifer (15.1 percent). Previously reported values 

for water in storage in 2009 (McGuire, 2011) were calculated 

using areal average values associated with mapped polygons 

of saturated thickness in 2000, Thiessen polygons (Thiessen, 1911) of annual water-level changes from 2000 to 2009, 

and the area-weighted, average specific yield of the aquifer 

(15.1 percent). Water in storage, 2009, was recalculated 

(McGuire and others, 2012) using a raster of saturated thickness for 2009 and a raster of average-mapped specific yield 

(Gutentag and others, 1984; Cederstrand and Becker, 1998).

Advantages of the method used in this report to calculate 

water in storage, 2011, were that this report’s calculation for 

water in storage, 2011, uses the average-mapped specific yield 

raster and the interpolated values for the applicable rasters 

(saturated thickness and water-level change), instead of the 

average of the polygon ranges for associated cells. The use 

of average-mapped specific yield is preferred for calculating 

water in storage in this report because the average-mapped 

value better reflects the variability of aquifer characteristics 

than the aquifer average. The interpolated values for the applicable rasters (saturated thickness and water-level change) are 

preferred to an assigned average value because the interpolated value generally should be a more realistic reflection of 

the spatial variability in values than the polygon average.

Change in Water in Storage, 

Predevelopment to 2011 and 2009–11

Change in water in storage, predevelopment to 2011, 

which was calculated using average-mapped specific yield, 

was a decline of 246 Macre-ft for the aquifer overall or about 

an 8 percent decline in storage since predevelopment (Gutentag and others, 1984; Cederstrand and Becker, 1998; McGuire 

and others, 2012). Changes in storage, predevelopment to 

2011, by State, ranged from a decline of about 150 Macre-ft in 

Texas to a rise of 1.2 Macre-ft in Nebraska. Change in water 

in storage, 2009–11, was a decline of 2.8 Macre-ft overall; 

changes in storage from 2009–11 by State ranged from a 

decline of 4.5 Macre-ft in Texas to a rise of 4.7 Macre-ft in 

Nebraska (table 3).

Table 3. Change in water in storage in the High Plains aquifer, predevelopment to 2011 and 2009–11, by State and as an 

overall total, and by comparable methods from this report and previous reports.

[Positive values for increases in water in storage; negative values for decreases in water in storage; accumulated totals by State may differ from 

aquifer totals because of rounding]

State

Change in water in storage, in million acre-feet

Final values calculated for this 

report, with average-mapped specific 

yield (range of 2.5 to 27.5 percent)

Calculated for this report, with 

area-weighted, average specific 

yield of the aquifer (15.1 percent)

Calculated using methods 

from previous reports1

Predevelopment 

to 2011 2009–11 Predevelopment to 2011 2009–11 Predevelopment to 2011 2009–11

Colorado -16.9 0.4 -14.8 0.3 -18.7 0.7

Kansas -62.4 -2.8 -58.2 -2.7 -67.9 -3.2

Nebraska 1.2 4.7 1.1 4.8 -8.1 8.5

New Mexico -8.7 -0.1 -8.2 -0.1 -11.8 -0.4

Oklahoma -9.4 -0.5 -7.5 -0.4 -13.8 -0.8

South Dakota 0.1 0.1 0.2 0.1 -0.3 0.2

Texas -149.7 -4.5 -136.5 -4.1 -150.3 -5.8

Wyoming -0.4 0.0 -0.7 0.1 -1.7 0.9

High Plains aquifer -246.2 -2.8 -224.6 -1.9 -272.6 0.1

1

McGuire, 2009, 2011.
Percent Change in Saturated Thickness, Predevelopment to 2011 11

Changes in water in storage, predevelopment to 2011 

and 2009–11, were recalculated a second time using the same 

data and methods as were used in this report’s final calculations, except for using area-weighted, average specific yield of 

the aquifer (15.1 percent) instead of average-mapped specific 

yield (Gutentag and others, 1984). The change in water in storage results for the aquifer from the second calculation were a 

decline of about 225 Macre-ft, predevelopment to 2011, and 

a decline of 1.9 Macre-ft, 2009–11 (table 3). The differences 

in the change-in-water-in-storage value for the aquifer using 

area-weighted, average specific yield of the aquifer instead of 

average-mapped specific yield are 21.6 Macre-ft less decline 

from predevelopment to 2011 and 0.9 Macre-ft less decline 

from 2009–11. The use of average-mapped specific yield 

instead of area-weighted, average specific yield of the aquifer 

is preferred for the purposes of this report because averagemapped specific yield better reflects the variability of aquifer 

characteristics.

Changes in water in storage, predevelopment to 2011 

and 2009–11, were recalculated a third time using methods 

from previous reports (McGuire, 2009, 2011). Change in 

water in storage, predevelopment to 2011, using methods 

from previous reports, was a decline of about 273 Macre-ft for 

the aquifer, or 26.4 Macre-ft more decline than was calculated as the final value for this report (table 3). A decrease of 

2.8 Macre-ft of water in storage in the High Plains aquifer, 

2009–11, was calculated using this report’s methods, whereas, 

using methods from previous reports (Thiessen polygons), the 

result was a 0.1 Macre-ft increase (table 3). These methodrelated differences in results for change in water in storage 

from predevelopment to 2011 and from 2009–11 are caused by 

two methods variations: (1) use of the spatially varying raster 

of average-mapped specific yield (2.5 to 27.5 percent) for this 

report instead of the area-weighted, average specific yield for 

the aquifer (15.1 percent); and (2) different methods for quantifying water-level change. In the method used for previous 

reports (McGuire, 2009, 2011), the maps of water in storage, 

2000; change in water in storage, predevelopment to 2000; and 

accumulated annual water-level changes since the year 2000 

were used to calculate the change in water in storage from 

predevelopment to the applicable year. An advantage of the 

method used in previous reports is that wells measured for the 

annual water-level change comparison periods from 2000 to 

the report year are included in the calculation. Disadvantages 

of the method used in previous reports are the use of areaweighted, average specific yield and a less straight-forward 

method for quantifying water-level change. In the methods 

used for this report, the 3,322 wells measured in the predevelopment and 2011 periods and the final contours of water-level 

changes, predevelopment to 2011, were used as inputs. Advantages of the methods used in this report are the use of averagemapped specific yield and a more straight-forward calculation 

method for water-level change. If a predevelopment water 

level could be estimated for the 5,088 wells measured in 

2011 and not measured in predevelopment (table 1), possibly 

the change in storage value reported herein (table 3) would 

be more similar to the value calculated in previous reports 

(McGuire, 2009, 2011).

Percent Change in Saturated 

Thickness, Predevelopment to 2011

The map of percentage change in saturated thickness 

(fig. 2) presents predevelopment-to-2011 water-level changes, 

as a percentage of predevelopment saturated thickness. This 

map (fig. 2) is similar in some areas to the water-level-change 

map (fig. 1); however, a large water-level change would not 

correspond to a substantial percentage change in saturated 

thickness if the predevelopment saturated thickness was large 

relative to the water-level change. Conversely, an area with 

small water-level change may correspond to a large percentage 

change in saturated thickness if its predevelopment saturated 

thickness was small. By 2011, 15 percent of the aquifer area 

had a saturated thickness decrease of more than 25 percent 

since predevelopment, 5 percent of the aquifer area had more 

than a 50-percent decrease in saturated thickness, and 1 percent of the aquifer area had more than a 10-percent increase in 

saturated thickness.
12 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

105° 96° 104° 103° 98° 97° 102° 101° 100° 99°

43°

42°

41°

40°

39°

38°

37°

36°

35°

34°

33°

32°

Canadian River

Arkansas River

South Platte River

Republican River

North Platte River

Platte River

TEXAS

OKLAHOMA

NEW MEXICO

COLORADO

KANSAS

WYOMING SOUTH DAKOTA

NEBRASKA

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

Aquifer boundary from Qi (2010); areas of little

or no saturated thickness and faults from

Gutentag and others (1984) and Cederstrand

and Becker (1999a, 1999b)

Base from U.S. Geological Survey digital data, 2001, 1:2,000,000

Albers Equal-Area Conic projection

Standard parallels 29o 30' and 45o 30', central meridan -101o

North American Datum of 1983 (NAD 83)

EXPLANATION

Saturated-thickness changes—In 

percent of predevelopment 

saturated thickness

More than 50

25 to 50

10 to 25

Areas of little or no saturated 

thickness

Faults—U, upthrown side

County boundary

10 to -10

10 to 25

More than 25

U

Decline

No substantial change

Rise

U

U

U

U

U

U

U

Figure 2. Change in saturated thickness of the High Plains aquifer, predevelopment to 2011.
References Cited 13

Summary

The High Plains aquifer underlies 111.8 million acres 

(175,000 square miles) in parts of eight States—Colorado, 

Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, 

Texas, and Wyoming. Water-level declines began in parts 

of the High Plains aquifer soon after the onset of substantial 

irrigation with groundwater (about 1950). In response to 

water-level declines, Congress directed the U.S. Geological 

Survey to monitor water levels in the aquifer; in 1987–88, the 

U.S. Geological Survey, in collaboration with numerous Federal, State, and local water-resources entities, began monitoring water levels in more than 7,000 wells. Water levels were 

measured in 9,178 wells in 2009 and 8,410 wells in 2011.

This report presents water-level changes in the High 

Plains aquifer from predevelopment (generally before 1950) 

to 2011 and from 2009–11. The water levels used in this 

report generally were measured in winter or early spring, 

when irrigation wells typically were not pumping, and after 

water levels generally had recovered from pumping during 

the previous irrigation season. The report also presents total 

water in storage, 2011, and changes in water in storage and in 

saturated thickness from predevelopment to 2011. The methods to calculate area-weighted, average water-level changes; 

changes in water in storage; and total water in storage for this 

report used geospatial data layers organized as rasters with 

a cell size of about 62 acres. These methods were modified from methods used in previous reports in an attempt to 

improve estimates of water-level changes and change in water 

in storage.

The map of water-level changes in the High Plains aquifer from predevelopment to 2011 is based on water levels from 

3,322 wells and other published data. Water-level changes 

from predevelopment to 2011, in individual wells, ranged 

from a rise of 85 feet (ft) in Nebraska to a decline of 242 ft in 

Texas. The area-weighted, average water-level change from 

predevelopment to 2011 was an overall decline of 14.2 ft.

Water levels were measured in 7,376 wells before the 

irrigation season in 2009 and 2011; water-level changes in the 

measured wells ranged from about a 26-ft decline in Texas 

to about a 16-ft rise in Colorado. The area-weighted, average 

water-level change in the High Plains aquifer during 2009–11 

was a decline of 0.1 ft.

Total water in storage in 2011 was about 2.96 billion 

acre-feet overall, which was a decline of about 246 million acre-feet (or about 8 percent) since predevelopment. By 

2011, 15 percent of the aquifer area had a saturated thickness 

decrease of more than 25 percent from its predevelopment 

saturated thickness, 5 percent of the aquifer area had more 

than a 50-percent decrease, and 1 percent of the aquifer area 

had more than a 10-percent increase.

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16 Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11

Publishing support provided by: 

Rolla Publishing Service Center 

For more information concerning this publication, contact:

Director, USGS Nebraska Water Science Center

5231 South 19th Street

Lincoln, Nebraska 68512

(402) 328–4100

Or visit the Nebraska Water Science Center Web site at:

http://ne.water.usgs.gov/

McGuire—Water-Level and Storage Changes in the High Plains Aquifer, Predevelopment to 2011 and 2009–11—SIR 2012–5291