0 25 50 100 MILES

Colorado River

Colorado Plateau

Flagstaff

Sedona CottonwoodVerde River

Camp 

Verde

Salt River

Gila River

Extent of Northern

Arizona Regional

Groundwater-Flow

Model

Verde Valley

sub-basin

Phoenix

Arizona

Tucson

Yuma

0 25 50 100 Miles

T

Possible Effects of Groundwater Pumping on Surface 

Water in the Verde Valley, Arizona

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3108

2010

Figure 1. Verde River Greenway below Deadhorse Ranch State Park, Cottonwood, Arizona. (Photograph by Jeanmarie Haney, The Nature Conservancy.)

The Verde Valley sub-basin of north-central Arizona (figs.1, 2) is 

favored with year-round flowing streams. Although surface water is diverted 

from the Verde River for agriculture and landscaping, nearly all water for 

public, domestic, and industrial supplies comes from groundwater pumping 

(Blasch and others, 2006). Groundwater use in the sub-basin increased more 

than tenfold in the latter half of the 20th century. A growing awareness of 

sustainable water management recognizes that development of groundwater 

affects connected surface water. With increasing population and water use, 

sustainability of water resources and long-term health of the Verde River are of 

concern. 

Detailed information about surface-water and groundwater resources 

and their interconnections can help water managers and elected officials make 

good water-development decisions that minimize environmental impacts. 

A technique developed by the U.S. Geological Survey (USGS) allows use 

of a groundwater-flow model to map the effects of groundwater pumping or 

artificial recharge on surface water through time. This technique has been 

applied in the Verde Valley and a detailed scientific report is available on the 

Internet (Leake and Pool, 2010, http://pubs.usgs.gov/sir/2010/5147/). This 

fact sheet presents basic information from the scientific report to help water 

managers and others understand possible long-term effects of groundwater 

pumping or artificial recharge on the Verde River and adjacent groundwaterdependent vegetation. 

Overview of Groundwater and Aquifers in the Verde Valley

When useful amounts of water can be extracted from a well, the 

subsurface material that contains the water is called an “aquifer.” Aquifers 

may consist of loose materials, such as sand, gravel, silt, and clay, or 

of solid rock, such as sandstone, limestone, or siltstone. Water occupies 

the open space between grains and in fractures. Aquifers may be stacked 

one upon another. Water enters aquifers from rain and snowmelt that 

percolates to the water table. Water moves through the aquifer system 

Figure 2. Location of Verde Valley sub-basin and extent of the Northern 

Arizona Regional Groundwater-Flow Model.

he U.S. Geological Survey 

(USGS), in cooperation with

The Nature Conservancy, has 

applied a groundwater model to 

simulate effects of groundwater 

pumping and artificial recharge 

on surface water in the Verde 

Valley sub-basin of Arizona. 

Results are in two sets of maps 

that show effects of locations 

of pumping or recharge on 

streamflow. These maps will 

help managers make decisions 

that will meet water needs and 

minimize environmental impacts.
and eventually flows out at lower elevations. Where the land surface 

intersects water-filled sediments or fractures, groundwater becomes 

surface water and supports flow and habitat at a spring, river, or 

wetland.

In the Verde Valley, groundwater is present in several aquifer 

layers. The upper part of the Verde Formation consists mostly of 

limestone and siltstone, and the lower part mostly of sand and gravel. 

Beneath the Verde Formation and extending laterally under Sedona 

is the “C aquifer,” dominated by rocks of the Supai Group. Beneath 

the C aquifer is the “R aquifer,” dominated by rocks of the Redwall 

Limestone. 

How Groundwater Pumping Affects Surface Water and Riparian 

Vegetation

Under natural or “predevelopment” conditions, long-term average 

rates of inflow to and outflow from an aquifer system are equal. 

Removal of groundwater by wells changes an aquifer system through 

time. Figure 3 shows the development of a “cone of depression” in 

the water table around a well and the later effects as that cone expands 

to a nearby stream and area of trees that use groundwater. Figure 4 

shows that when pumping starts, all of the pumped water comes from 

storage in the aquifer. As pumping time continues, however, a greater 

percentage of the pumping can come from “depletion,” which is reduced 

flow in the stream and reduced use of groundwater (evapotranspiration) 

by plants. At any time, the only sources of pumped water are aquifer 

storage and reduced streamflow and evapotranspiration. Percentages 

of these sources vary through time and are affected by distance to the 

surface water, as shown in figure 4, and by the properties of the aquifer.

The Northern Arizona Regional Groundwater-Flow Model 

(NARGFM)

Because the aquifer system underlying the Verde Valley subbasin is complex, a groundwater flow model is needed to understand 

the timing of effects of groundwater pumping on surface water and 

riparian vegetation. The USGS developed the Northern Arizona 

Regional Groundwater-Flow Model (NARGFM; Pool and others, in 

press)—the most comprehensive and up-to-date groundwater-flow 

model that includes the sub-basin. NARGFM simulates groundwater 

flow in an area much larger than the sub-basin, including parts of the 

Colorado Plateau, the Verde River Basin, and adjacent areas (fig. 2). 

In spite of the large extent of the model, it is well suited to simulate 

general conditions in the Verde Valley sub-basin.

NARGFM uses three distinct layers to simulate the different 

aquifers underlying the Verde Valley. The upper model layer (layer 1) 

represents the upper Verde Formation. The middle model layer (layer 

2) represents chiefly the lower Verde Formation and the C aquifer 

but also includes volcanic rocks. The lower model layer (layer 3) 

represents chiefly the R aquifer. For details on the model and attributes 

for streams and springs in the Verde Valley sub-basin, see Pool and 

others (in press). 

Possible Effects of Groundwater Pumping on Streamflow in the 

Verde Valley

Using NARGFM to estimate effects of groundwater pumping on 

surface water and riparian vegetation in the Verde Valley is a process that 

requires numerous steps and calculations. The results are presented in 

maps that show the total reduced streamflow as a percentage of pumping 

rate. Thus, estimated depletion for any pumping rate can be determined for 

any pumping location. Estimated streamflow enhancement from artificial 

recharge can also be determined, with certain caveats. For more details on 

the method, see Leake and Pool (2010). 

Because depletion of streamflow by groundwater pumping (or 

enhancement of streamflow by artificial recharge) is location and time 

dependent, a reference time period must be chosen to examine effects at any 

given location. Streamflow depletion also varies depending on the aquifer 

(model layer) in which pumping is occurring. Results at 10 and 50 years for 

pumping from model layers 1 and 2 are shown in figures 5 and 6. Simulated 

Figure 3. Diagram showing progressive effects of groundwater pumping on the water table, a nearby stream, and an area of trees that use 

groundwater (modified from Webb and others, 2007).

Water table

Direction of groundwater 

movement

Direction of groundwater 

movement

Aquifer

Aquifer

Stream

Stream

Direction of groundwater 

movement

Aquifer

Stream

A. When a well begins to pump, all of the water pumped comes from storage in the aquifer, creating

a “cone of depression.”

B. With time, the cone of depression can spread to areas of surface water and trees that use groundwater.

In this example, the pumping has taken all of the groundwater inflow to the stream in the area of the well

and has further caused the stream to lose water to the aquifer.

C. If the stream cannot supply the rate of water pumped, it may become disconnected

from the water table, resulting in an ephemeral stream. The lowered water table also may

result in loss of trees that depend on groundwater.

Cone of

depression

Cone of

depression

Cone of

depression Water table

Water table

depletion for layer 3 is not presented in this study. Results for layers 1 and 

2 are contoured as the percentage of the pumping rate that is derived from 

streamflow and evapotranspiration. Percentages are color-coded, as shown 

in the color bar at the bottom of figures 5 and 6. The procedure for using the 

maps to calculate depletion for a single well is shown in figure 7.

Results for layer 1 (for a well pumping from the upper Verde 

Formation at a constant rate) are shown in figure 5. At a pumping time 

of 10 years (fig. 5A), results indicate greatest percentages of streamflow 

depletion (yellow to red colors) along the Verde River between Clarkdale 

and Cottonwood and from several miles upstream of Camp Verde down to 

the sub-basin boundary. Depletion is also higher along Oak Creek upstream 

and downstream from Cornville. Values are lower along an 11-mile stretch 

of the Verde River below Cottonwood. Results for layer 1 for a well 

pumping at a constant rate for 50 years (fig. 5B) indicate similar patterns, 

but with higher overall percentages of streamflow depletion because of the 

additional pumping time. Numerous municipal and private water-company 

wells, and thousands of individually owned domestic wells, pump from this 

aquifer.

Results for layer 2 (C aquifer) are shown in figures 6A and 6B. 

Because layer 2 covers a greater extent of the Verde Valley than does 

layer 1, the maps in figure 6 show a larger area, nearly the entire subbasin, extending beyond Sedona and to the northwest of Flagstaff. 

Results indicate that for a pumping time of 10 years (fig. 6A), the greatest 

percentages of streamflow depletion (yellow to red colors) occur along 

the Verde River upstream from Cottonwood and downstream from Camp 

Verde, along reaches of Oak Creek, and along Wet Beaver Creek upstream 

from Rimrock. Results for layer 2 at a pumping time of 50 years (fig. 

6B) indicate general increases in effects along the streams and at greater 
distances from them. Many of the private water company wells in the 

Sedona area pump from this aquifer. 

Applicability and Limitations

The procedures used for the analysis described here depict 

responses to pumping or artificial recharge over large areas of 

an aquifer. The results are meant to give resource managers and 

the public a general understanding of areas in which pumping 

would result in faster or slower responses in surface-water flow 

and evapotranspiration. The distributions shown on figures 5 and 

6 do not mean that groundwater pumping is appropriate or even 

technically feasible at all locations. Responses shown are based 

on features represented in the part of the NARGFM underlying 

the Verde Valley sub-basin. Although NARGRM is the most 

comprehensive and up-to-date tool available to examine effects 

from groundwater pumping in the sub-basin, it is a regional model 

that cannot represent a high degree of local detail. For more 

information on these and other technical aspects of the results 

presented here, see Leake and Pool (2010).

References

Blasch, K.W., Hoffmann, J.P., Graser, L.F., Bryson, J.R., and Flint, 

A.L., 2006, Hydrogeology of the upper and middle Verde River 

watersheds, central Arizona: U.S. Geological Survey Scientific 

Investigations Report 2005–5198, 102 p., 3 plates, accessed July 

14, 2010, at http://pubs.usgs.gov/sir/2005/5198/.

Leake, S.A., and Pool, D.R., 2010, Simulated effects of groundwater 

pumping and artificial recharge on surface-water resources and 

Figure 4. Sources of pumped groundwater at two hypothetical well locations 

for pumping times of 10 and 50 years. 

When pumping

starts: 

After 10 years

of pumping:

After 50 years

of pumping:

Relative amount of groundwater

pumping rate coming from aquifer 

storage (falling water table) 

Relative amount of groundwater

pumping rate coming from

reduction in streamflow 

(depletion) 

Well A Well B

Stream

400000 420000

3820000 3840000

Verde

River

Oak

Creek

West Clear Creek

Wet

Beaver Creek

CLARKDALE

JEROME COTTONWOOD

CORNVILLE

RIMROCK

CAMP

VERDE

Verde

River

400000 420000

3820000 3840000

Oak

Creek

West Clear Creek

Wet

Beaver Creek

A B

UTM

ZONE 12

NAD 27 Verde River and major tributary streams

Major Roads

Verde Valley sub-basin

EXPLANATION 0 2.5 5 10 Miles

CLARKDALE

JEROME COTTONWOOD

CORNVILLE

RIMROCK

CAMP

VERDE

0 10 20 30 40 50 60 70 80 90 100

Total depletion (reduced ow and evapotranspiration)

as a percentage of pumping rate

After 10 years After 50 years

Figure 5. Depletion maps for a well pumping groundwater at a constant rate from model layer 1, the upper Verde Formation. A, Rate of total 

depletion after 10 years of pumping. B, Rate of total depletion after 50 years of pumping.

riparian vegetation in the Verde Valley sub-basin, central Arizona: 

U.S. Geological Survey Scientific Investigations Report 2010-5147, 

18 p., accessed October 1, 2010, at http://pubs.usgs.gov/sir/2010/5147/.

Pool, D.R., Blasch, K.W., Callegary, J.B., Leake, S.A., and Graser, L.F., in 
Stanley A. Leake (USGS) and 

Jeanmarie Haney (The Nature Conservancy)

Edited by

Peter H. Stauffer

Graphic design by

Stephen L. Scott

COOPERATING ORGANIZATION

The Nature Conservancy

For more information contact:

Stanley A. Leake 

U.S. Geological Survey

Arizona Water Science Center

520 N. Park Ave, Suite 221

Tucson, AZ 85719

Email: saleake@usgs.gov

This Fact Sheet and any updates to it are available online at: 

http://pubs.usgs.gov/fs/2010/3108/

0 10 20 30 40 50 60 70 80 90 100

EXAMPLE USE OF MAPS TO CALCULATE DEPLETION FOR A SINGLE WELL

Step 1-Select the right map

• Use figures 4A and 4B for wells open in

 the upper part of the Verde Formation.

• Use figures 5A and 5B for wells open

 in the lower part of the Verde Formation,

 the Supai Group, and volcanic rocks.

Well pumps an average of 10 acre-feet per year from the upper part of the Verde Formation for 50 years

Part of map showing depletion in model layer 1 (the 

upper part of the Verde Formation) at a pumping 

time of 50 years (fig. 4B)

Step 2-Find the location of the well on

the map

Step 3-Note the percent range on the

color bar corresponding to color at

well location on map

In this example the range is 60 to 70

percent.

Step 4-Multiply corresponding fraction

for color range by average well pumping rate to get average depletion rate

For the depletion range of 60 to 70

percent in this example, use a fraction of

0.65. Calculation is 0.65 x 10 acre-feet per

year = 6.5 acre-feet per year of depletion

at a pumping time of 50 years. Total depletion (reduced flow and evapotranspiration)

as a percentage of pumping rate

Figure 7. An example of the application of depletion maps such as shown in figures 4 and 5.

press, Regional groundwater-flow model of 

the Redwall-Muav, Coconino, and Alluvial 

Basin aquifer systems of northern and central 

Arizona: U.S. Geological Survey Scientific 

Investigations Report 2010-5180.

Webb, R.H., Leake, S.A., and Turner, R.M, 2007, 

The ribbon of green—change in riparian 

vegetation in the Southwestern United States: 

Tucson, University of Arizona Press, 480 p.

Figure 6. Depletion maps for a well pumping groundwater at a constant rate from model layer 2, the lower Verde Formation, the Supai Group, 

and volcanic rocks. A, Rate of total depletion after 10 years of pumping. B, Rate of total depletion after 50 years of pumping.

400000 450000

3850000 3900000

Verde

Oak

Sycamore

West

Clear Creek

WetBeaver Creek

Creek

Creek

River

FLAGSTAFF

400000 450000

3850000 3900000

Verde

Oak

Sycamore

West

Clear Creek

WetBeaver Creek

Creek

Creek

JEROME River

CAMP

VERDE

RIMROCK

CORNVILLE

CLARKDALE COTTONWOOD

SEDONA

JEROME

CAMP

VERDE

RIMROCK

CORNVILLE

CLARKDALE COTTONWOOD

SEDONA

FLAGSTAFF

A B

0 5 10 20 Miles UTM

ZONE 12

NAD 27 Verde River and major tributary streams

Major Roads

Verde Valley sub-basin

EXPLANATION

0 10 20 30 40 50 60 70 80 90 100

Total depletion (reduced ow and evapotranspiration)

as a percentage of pumping rate

After 10 years After 50 years