U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2016–1078

Prepared in cooperation with the Washington County Water Conservancy District 

Assessment of Managed Aquifer Recharge at Sand Hollow 

Reservoir, Washington County, Utah, Updated to Conditions 

through 2014 
Cover photograph: View of Sand Hollow Reservoir looking 

north towards the town of Hurricane, Utah. Photo by Tom M. 

Marston, April 2015.
Assessment of Managed Aquifer Recharge 

at Sand Hollow Reservoir, Washington 

County, Utah, Updated to Conditions 

through 2014 

By Thomas M. Marston and Victor M. Heilweil 

Prepared in cooperation with the Washington County Water 

Conservancy District 

Open-File Report 2016–1078

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, Director 

U.S. Geological Survey, Reston, Virginia: 2016 

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Suggested citation:

Marston, T.M., and Heilweil, V.M., 2016, Assessment of managed aquifer recharge at Sand Hollow Reservoir, Washington County, Utah, updated to conditions through 2014: U.S. Geological Survey Open-File Report 2016–1078, 35 p., 

http://dx.doi.org/10.3133/ofr20161078. 

ISSN 2331-1258 (online) 
iii

Contents

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

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

Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir .........................................3

Data Collection Methods and Results ..............................................................................................3

Production-Well Withdrawals ..................................................................................................3

Drain Discharge ..........................................................................................................................3

Groundwater-Level Data and Reservoir Altitude ..................................................................3

Surface-Water Inflow to and Outflow from Sand Hollow Reservoir ..................................9

Meteorological Data ..................................................................................................................9

Estimates of Managed Aquifer Recharge from Sand Hollow Reservoir...................................18

Changes in Reservoir Storage ................................................................................................19

Reservoir Evaporation ..............................................................................................................19

Estimates of Total Volume of Managed Aquifer Recharge from Sand Hollow 

Reservoir .......................................................................................................................19

Groundwater and Surface-Water Quality in Sand Hollow ...................................................................22

Water-Quality Results ........................................................................................................................22

Summary .......................................................................................................................................................34

References Cited .........................................................................................................................................35

Figures

1. Map showing the location of the Sand Hollow study area, Washington County, Utah ......... 2

2. Map showing the location of monitoring and production wells, weather stations, 

drains, and reservoir sampling sites in Sand Hollow, Washington County, Utah ............... 4

3. Graph showing Washington County Water Conservancy District production-well 

withdrawals in Sand Hollow, Washington County, Utah, 2004–14 ........................................ 5

4. Graph showing monthly reported discharge from the North and West Dam drains, 

and West Dam Spring drain in relation to reservoir altitude, Sand Hollow, Washington 

County, Utah, 2003–14 ................................................................................................................... 6

5. Graph showing water-level altitude in monitoring wells and Sand Hollow Reservoir 

altitude, Sand Hollow, Washington County, Utah, 1995–2014 ................................................ 7

6. Map showing potentiometric surface of the Navajo aquifer in December 2014, Sand 

Hollow, Washington County, Utah .............................................................................................. 8

7. Graph showing monthly precipitation at Sand Hollow, Washington County, Utah, 

1998–2014 ...................................................................................................................................... 18

8. Graph showing monthly estimated evaporation, groundwater recharge, and 

reservoir altitude, Sand Hollow Reservoir, Washington County, Utah, 2002–14 ............... 20

9. Graph showing monthly calculated groundwater recharge rates beneath Sand 

Hollow Reservoir, Washington County, Utah, 2002–14 ......................................................... 20

10. Graph showing estimated annual inflow, evaporation, and groundwater recharge, 

Sand Hollow Reservoir, Washington County, Utah, 2002–14 ................................................ 21
iv

Tables

1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand 

Hollow Reservoir, Washington County, Utah, 2002–14 .......................................................... 10

2. Field water-quality parameters, total dissolved-gas pressure, dissolved organic 

carbon, tritium, chlorofluorocarbons, and sulfur hexafluoride in groundwater and 

surface water from Sand Hollow, Washington County, Utah ............................................... 23

3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water from selected sites in Sand Hollow, 

Washington County, Utah ........................................................................................................... 28
v

Conversion Factors, Datums, and Abbreviated Water-Quality Units 

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d) 

Hydraulic gradient

foot per foot (ft/ft) 0.3048 meter per meter (m/m) 

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) can be converted to degrees Celsius (°C) as follows:

°C=(°F–32)/1.8

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

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

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

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).

Total dissolved-gas pressure is reported in millimeters of mercury (mm Hg), where 760 mm Hg equals 

one atmosphere.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or 

micrograms per liter (μg/L).

Stable isotope (oxygen and deuterium) concentrations are reported as permil, which is equivalent to parts 

per thousand. 

Tritium units (TU) are used to report tritium concentration, where 1 TU equals tritium concentration in 

picoCuries per liter divided by 3.22. 

Chlorofluorocarbon (CFC) concentrations are reported as picomoles per kilogram (pmol/kg). 

Sulfur hexafluoride (SF6) concentrations are reported as femtomoles per kilogram (fmol/kg). 
vi

Acronyms and Abbreviations

CFCs chlorofluorocarbons

Cl/Br chloride to bromide ratio

DO dissolved oxygen

DOC dissolved organic carbon

MAR managed aquifer recharge

NRCS Natural Resources Conservation Service

SCAN Soil Climate Analysis Network

TDG total dissolved gas

USGS U.S. Geological Survey

WCWCD Washington County Water Conservancy District

WD water district
Assessment of Managed Aquifer Recharge at Sand 

Hollow Reservoir, Washington County, Utah, Updated to 

Conditions through 2014

By Thomas M. Marston and Victor M. Heilweil 

Abstract 

Sand Hollow Reservoir in Washington County, Utah, 

was completed in March 2002 and is operated primarily for 

managed aquifer recharge by the Washington County Water 

Conservancy District. From 2002 through 2014, diversions of 

about 216,000 acre-feet from the Virgin River to Sand Hollow 

Reservoir have allowed the reservoir to remain nearly full 

since 2006. Groundwater levels in monitoring wells near the 

reservoir rose through 2006 and have fluctuated more recently 

because of variations in reservoir stage and nearby pumping 

from production wells. Between 2004 and 2014, about 

29,000 acre-feet of groundwater was withdrawn by these 

wells for municipal supply. In addition, about 31,000 acre-feet 

of shallow seepage was captured by French drains adjacent 

to the North and West Dams and used for municipal supply, 

irrigation, or returned to the reservoir. From 2002 through 

2014, about 127,000 acre-feet of water seeped beneath the 

reservoir to recharge the underlying Navajo Sandstone aquifer. 

Water quality continued to be monitored at various wells 

in Sand Hollow during 2013–14 to evaluate the timing and 

location of reservoir recharge as it moved through the aquifer. 

Changing geochemical conditions at monitoring wells WD 4 

and WD 12 indicate rising groundwater levels and mobilization of vadose-zone salts, which could be a precursor to the 

arrival of reservoir recharge.

Introduction 

Sand Hollow Reservoir (fig. 1) in Washington County, 

Utah, was completed in March 2002 and is operated primarily 

for managed aquifer recharge (MAR) by the Washington 

County Water Conservancy District (WCWCD). The reservoir 

is an off-channel facility that receives water diverted from 

the Virgin River near the town of Virgin, Utah. Sand Hollow 

has been the subject of interdisciplinary, cooperative investigations of groundwater hydrology and geochemistry since 

1999. Previous Sand Hollow reports document pre-reservoir 

vadose-zone and groundwater conditions prior to March 2002 

(Heilweil and Solomon, 2004; Heilweil and others, 2006; 

Heilweil and others, 2007; Heilweil and McKinney, 2007; 

Heilweil and others, 2009b), pond and trench infiltration 

studies adjacent to the reservoir (Heilweil and others, 2004; 

Heilweil and Watt, 2011), and post-reservoir groundwater 

conditions, water budgets, and estimates of groundwater 

recharge from the reservoir from March 2002 through December 2012 (Heilweil and others, 2005; Heilweil and Susong, 

2007; Heilweil and others, 2009a; Heilweil and Marston, 

2011; Marston and Heilweil, 2013). These reports also contain 

monitoring-well and production-well completion information, as well as historical water-quality and precipitation data. 

The objectives of this report are to present and interpret (1) 

groundwater levels, reservoir altitude, well withdrawals, drain 

discharge, meteorological data, reservoir water temperature, 

and inflows/outflows from March 2002 through December 

2014 for estimating monthly amounts of MAR from Sand 

Hollow Reservoir to the Navajo Sandstone, and (2) groundwater and surface-water chemical data collected prior to the 

construction of the reservoir through April 2014 for evaluating groundwater flow paths and travel times of this MAR. 

This study is a cooperative effort by the WCWCD and the 

U.S. Geological Survey (USGS). Funding for this work was 

provided by both the USGS and the WCWCD.
2 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Hurricane Fault Bar and ball on downthrown side

Virgin River

Virgin River

Sand

Hollow

Reservoir

 Quail

Creek

Reservoir

15

9

15

Base from U.S. Geological Survey digital data, 1:100,000, 1980

Universal Transverse Mercator projection, Zone 12

R. 14 W.

0 2 4 MILES

0 2 4 KILOMETERS

R. 13 W.

T. 42 S.

T. 43 S.

Sand Hollow

Boundary

of study area

Hurricane

Treatment 

Plant

T. 41 S.

Virgin River

diversion to

Sand Hollow

Reservoir

approximately

3 miles east

La Verkin

113°15' 113°22' 30''

37°07'30"

37°15'

St George

approximately

10 miles

southwest

Sand

Hollow

Resort

Salt Lake

City

Utah

Location of

map area

Figure 1. Location of the Sand Hollow study area, Washington County, Utah.
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 3

Assessment of Managed Aquifer 

Recharge from Sand Hollow Reservoir 

Many different types of data have been collected to investigate recharge processes, quantify recharge from Sand Hollow 

Reservoir, and to evaluate hydraulic and geochemical changes 

in the underlying Navajo Sandstone aquifer (Navajo aquifer). 

These data include production-well withdrawals near the 

reservoir, amounts of pumpage from drains capturing shallow 

groundwater discharge adjacent to the reservoir, reservoir and 

monitoring-well water levels, inflows and outflows through the 

pipeline connecting Sand Hollow Reservoir with the Virgin 

River and Quail Creek Reservoir and treatment plant, meteorological parameters, and reservoir water temperatures (fig. 1).

Data Collection Methods and Results 

Data collection methods are described in detail in Heilweil 

and others (2005) and briefly summarized in the following 

sections. 

Production-Well Withdrawals 

The WCWCD has 13 production wells completed in the 

Navajo Sandstone that are available to capture both preexisting groundwater (natural recharge) in Sand Hollow and 

recharge from Sand Hollow Reservoir (fig. 2). The WCWCD 

and other water users have withdrawn natural recharge in Sand 

Hollow for many years. The WCWCD groundwater withdrawals are recorded monthly from inline magnetic flow meters 

installed at each well. Since August 2004, monthly withdrawals by the WCWCD have generally exceeded 150 acre-feet 

(acre-ft), except for several months during the winters of 

2004–05, 2005–06, 2008–09, and 2010 (fig. 3). The majority of this pumping was from wells 8 and 9 through late 2012 

(fig. 3), both located adjacent to the North Dam. Starting in 

early 2013, some of the pumping has been shifted to wells 

19, 21, and 23 (fig. 3). From 2004 through 2006, there were 

minimal withdrawals from these wells during the winter. 

Since 2006, withdrawals have been more constant yearround. Monthly withdrawals from production wells averaged 

about 250 acre-ft from March 2006 through December 2014. 

Smaller amounts have been sporadically withdrawn from 

wells 1, 2, and 17 (fig. 3). Approximately 29,000 acre-ft were 

pumped from the WCWCD production wells from January 

2004 through December 2014 (fig. 3). Through 2014, withdrawals by the WCWCD at Sand Hollow have been permitted 

by the Utah Division of Water Rights as natural recharge in 

Sand Hollow. These withdrawals are governed by different water rights than recharge from Sand Hollow Reservoir; 

withdrawal rights for this artificial recharge have not yet been 

exercised.

Drain Discharge 

Because of the steep gradients associated with the hydraulic connection between the reservoir and the underlying 

Navajo aquifer, some land-surface areas downgradient of the 

North and West Dams became saturated following construction of the reservoir. In response, three French drains (North 

Dam drain, West Dam drain, and West Dam Spring drain) 

were constructed for capturing this shallow groundwater 

(fig. 2). Timing of excavation and spatial dimensions for the 

three drains can be found in Heilweil and Marston (2011).

Amounts of discharge pumped from these drains are measured with a Tigermag totalizing flow meter (Sparling Instruments in El Monte, California). Discharge from the North 

Dam drain has been pumped relatively consistently since 

September 2003 (fig. 4); about 8,000 acre-ft were pumped 

from the North Dam drain between 2003 and 2014. Initially, 

all of this water was returned to the reservoir, but since 2007, 

the majority of the water has been used by Sand Hollow 

Resort (fig. 1) to meet irrigation demands. About 2,100 acre-ft 

of water were pumped from the West Dam drain back into 

the reservoir from 2005 through 2014. Beginning in October 

2006, pumping of discharge from the West Dam Spring drain 

was initiated and has largely replaced the need for pumping of the West Dam drain. From 2006 through 2014, about 

21,000 acre-ft were pumped from the West Dam Spring drain 

for municipal use or returned back to Sand Hollow Reservoir. 

Although drainage to the West Dam Spring drain likely does 

not vary greatly, pumping from this drain has been intermittent. The intermittent pumping schedule results in high variability in the monthly reported discharge from the West Dam 

Spring drain (fig. 4).

Groundwater-Level Data and Reservoir Altitude 

Groundwater levels measured in an extensive monitoringwell network surrounding Sand Hollow Reservoir were used 

to document changes in the potentiometric surface associated 

with recharge from Sand Hollow Reservoir. The WCWCD 

measures water levels monthly in 20 monitoring wells completed in the Navajo Sandstone (fig. 2; the WD RJ monitoring 

well was removed in 2013). These wells were constructed with 

either 1- or 2-inch (in.) diameter PVC casing, with perforations along the bottom 5- to 20-foot (ft) length of the casing. 

Three locations have nested pairs of water district (WD) 

monitoring wells: WD 15 and WD 16, WD 17 and WD 18, 

and WD 19 and WD 20. The vertical distance between well 

screens for the nested-pair wells are 243 ft, 79 ft, and 227 ft, 

respectively. Water levels were measured by the WCWCD 

using electric-tape water-level indicators. Annual independent 

check measurements are performed by USGS personnel for 

quality assurance to ensure accurate and repeatable instrument 

measurements. 

Daily reservoir water-level altitude (stage) was recorded 

from January 2005 through December 2014 by using a pressure transducer installed by the WCWCD in the reservoir 
4 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

0 0.5 1 1.5 MILES

0 0.5 1 1.5 KILOMETERS

Base from State of Utah 25-centimeter aerial imagery, 2006

Universal Transverse Mercator projection, Zone 12

North American Datum of 1983

113°23'45" 113°22'30" 113°21'15"

37°8'45"

37°7'30"

37°6'15"

WCWCD pump

station

Inflow/outflow pipeline

Sand

Mountain

North Dam 3A 

WD 17

WD 18

WD 19

WD RJ WD 20

WD 1

WD 2

WD 4

WD 5

WD 9

WD 12

WD 13

WD 14

WD 15

WD 3

WD 6

WD 7

WD 8

WD 10

WD 11

WD 16

Well 2

Well 1

Well 4 Well 3

WCWCD

weather

station

NRCS

SCAN

station

Well 8

Well 9

Well 17

Well 18

Well 19

Well 20

Well 21

Well 22

Well 23

SH1-18

Boat Ramp

North Dam

West Dam

Haul Road

Sand

Hollow

Reservoir

Washington County Water Conservancy District (WCWCD)

Natural Resources Conservation Service (NRCS)

Soil Climate Analysis Network (SCAN)

WD 7

EXPLANATION

Well 17

SH1-18

Monitoring well—Dot indicates nested wells. 

Number indicates well identifier

Production well—Number indicates well identifier

Surface-water site—Number indicates well identifier

Weather station

Drains (approximate location)

North Dam drain

West Dam drain

West Dam Spring drain

Figure 2. Location of monitoring and production wells, weather stations, drains, and reservoir sampling sites in Sand Hollow, 

Washington County, Utah.
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 5

Jan-04Jan-05Jan-06Jan-07Jan-08Jan-09Jan-10Jan-11Jan-12Jan-13Jan-14Jan-15

Well 8 and Well 9

All well withdrawals

0

50

100

150

200

250

300

350

400

450

500

Total monthly pumping, in acre-feet

Figure 3. Washington County Water Conservancy District production-well withdrawals in Sand Hollow, Washington County, Utah, 

2004–14.

along the North Dam. Because of periods of transducer 

malfunction from 2005 through 2007, and from August 2011 

to December 2011, daily reservoir stage was interpolated on 

the basis of monthly measurements recorded at the boat ramp 

by WCWCD and Sand Hollow State Park personnel, and then 

correlated with trends from the transducer data. 

Recently measured (January 2008 through December 

2014) and previously reported (Heilweil and others, 2005; 

Heilweil and Susong, 2007; Heilweil and others, 2009; 

Heilweil and Marston, 2011; Marston and Heilweil, 2013) 

groundwater levels and reservoir water-level altitude are 

shown in figure 5. The reservoir stage rose from about 2,980 ft 

at the beginning of March 2002 to a maximum of about 

3,060 ft in May 2006, when the reservoir was first filled to 

capacity. The reservoir altitude receded to about 3,040 ft in 

December 2007 as a result of reduced inflows and evaporative 

losses, and then fluctuated between about 3,040 and 3,060 ft 

from 2008 through 2011. From 2012 through 2014, the reservoir altitude dropped to a fluctuating level between 3,030 and 

3,050 ft. 

On the basis of water-level measurements in the 20 monitoring wells, altitude of the water table (or potentiometric 

surface) near Sand Hollow Reservoir during December 2014 

ranged from 2,889 to 3,040 ft (fig. 6). The reservoir altitude 

during this same period was about 3,040 ft. The lines on figure 

6 represent estimated potentiometric contours in the aquifer, 

which indicate lines of equal groundwater-level altitude, 

and the arrows indicate generalized directions of horizontal 

groundwater movement away from the reservoir. Horizontal 

hydraulic gradients, calculated by dividing the difference 

in water-level altitude between two points by the distance 

separating these locations, indicate the potential horizontal 

direction of groundwater movement. The steepest horizontal 

hydraulic gradients are beneath the North and West Dams and 

generally decline with increasing distance from the reservoir. The steep gradients beneath the dams are the combined 

result of low-conductivity materials at the core of the dams 

and pumping in wells and drains at the base of both dams. 

For example, the horizontal hydraulic gradient between Sand 

Hollow Reservoir (reservoir altitude of 3,040 ft) and WD 1 

(groundwater-level altitude of 2,970 ft) in 2014 was 0.122 foot 

per foot (ft/ft), whereas the gradient between WD 6 (groundwater-level altitude of 2,958 ft) and WD 19 (2,898 ft) was 

0.015 ft/ft. In 2014, the broader regional gradient between WD 

9 (3,040-ft altitude) and WD 17 (2,918-ft altitude) was 0.019 

ft/ft. In comparison, the hydraulic gradient between these 

same two wells in 2004 was 0.017 ft/ft (fig. 7 of Heilweil and 

others, 2005). 
6 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

0

100

200

300

400

500

600

2,990

3,010

3,000

3,020

3,040

3,030

3,050

3,060

3,070

Reservoir altitude, in feet

Drain pumping, in acre-feet

Reservoir altitude

North Dam drain

West Dam drain

West Dam Spring drain

Aug-03

Feb-04

Aug-04

Feb-05

Aug-05

Feb-06

Aug-06

Feb-07

Aug-07

Feb-08

Aug-08

Feb-09

Aug-09

Feb-10

Aug-10

Feb-11

Aug-11

Feb-12

Aug-12

Feb-13

Aug-13

Feb-14

Aug-14

Feb-15

Figure 4. Monthly reported discharge from the North and West Dam drains, and West Dam Spring drain in relation to reservoir 

altitude, Sand Hollow, Washington County, Utah, 2003–14.
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 7

Jan-95Jan-96Jan-97Jan-98Jan-99Jan-00Jan-01Jan-02Jan-03Jan-04Jan-05Jan-06Jan-07Jan-08Jan-09Jan-10Jan-11Jan-12Jan-13Jan-14Jan-15

2,940

2,960

2,980

3,000

3,020

3,040

3,060

3,080

2,880

2,900

2,920

Water-level altitude, in feet above sea level

WD 1

WD 3

WD 5

WD 6

WD 8

WD 10

WD 12

WD 14

WD 16

WD 18

WD 20

WD 2

WD 4

WD RJ

WD 7

WD 9

WD 11

WD 13

WD 15

WD 17

WD 19

Reservoir altitude

Figure 5. Water-level altitude in monitoring wells and Sand Hollow Reservoir altitude, Sand Hollow, Washington County, Utah, 

1995–2014.
8 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

2900

2930

2940

2950

2960

2970

2980

2990

3000

3010

3040

3040

3030

3020

3020

2920

2910

2916.9

2917.9

2888.9

2994.6

2897.6

2926.3

2958.4

2961.67

2970.5

2994.8

3016.5

3039.64

3030.9

3024.1

2986.3

2999.7 3002.9

3025.8

3035.4

3020.4

1 MILE

1 KILOMETER

0 0.5

0 0.5

Base from State of Utah 25-centimeter aerial imagery, 2006

Universal Transverse Mercator projection, Zone 12

North American Datum of 1983

37°7'30"

113°22'30"

Sand

Hollow

Reservoir

Reservoir altitude 3,040

113°23'45" 113°21'15"

37°8'45"

37°6'15"

EXPLANATION

Monitoring well—Shows calculated 

water-level altitude, in feet, December 

2014. Black well symbol is for wells not 

in monitoring network. White dot

indicates nested wells

Potentiometric contour—Shows altitude 

at which water level would have stood 

in tightly cased wells, December 2014. 

Contour interval 10 feet

Arrow shows direction of groundwater 

movement 

3040

2917.9

Figure 6. Potentiometric surface of the Navajo aquifer in December 2014, Sand Hollow, Washington County, Utah.
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 9

Surface-Water Inflow to and Outflow from Sand 

Hollow Reservoir 

Surface water is pumped into and flows out of Sand Hollow Reservoir through a 60-in. diameter pipeline that enters 

through an inlet structure at the North Dam (fig. 2). This 

pipeline is part of a network of pipelines that connect the 

Virgin River, Sand Hollow Reservoir, Quail Creek Reservoir, 

and the Quail Creek Reservoir Water Treatment Facility. The 

WCWCD has the capability to move water within this network 

of pipelines by using gravity-induced flow and inline pumping. Sand Hollow Reservoir is currently managed to maximize groundwater recharge and little surface water has been 

removed from the reservoir. Monthly surface-water inflow to 

and outflow from Sand Hollow Reservoir is shown in table 1. 

The “Monthly pump station inflow or outflow” column in this 

table is the amount of Sand Hollow Reservoir surface water 

coming in from the Virgin River or going out to Quail Creek 

Reservoir, the Quail Creek Water Treatment Plant, or other 

facilities (fig. 1). These data were collected at the WCWCD 

pump station located about 1 mi north of the North Dam. Five 

pumps, each with Sparling Tigermag totalizing flow meters, 

are linked to a computer system that combines and records 

total daily discharge in gallons. The flow meters have electronic modules on which calibration diagnostics are performed 

monthly by the WCWCD. Each module is removed annually 

for factory recalibration.

The “Monthly drain and spring return flow to reservoir” 

column in table 1 is the portion of discharge to the three 

drains that is pumped back into Sand Hollow Reservoir. The 

“Monthly outflow to Sand Hollow Resort” column is the 

amount of water required by the resort that cannot be met by 

discharge to the North Dam drain and is fulfilled by outflow 

of stored water from Sand Hollow Reservoir. Therefore, the 

“Monthly total inflow or outflow to/from reservoir” column is 

a sum of the pump station inflow/outflow, the drain and spring 

return flow, and the outflow to Sand Hollow Resort (table 1). 

The “Monthly pump station inflow or outflow” column is 

unchanged from Heilweil and Marston (2011) and is comparable to the “Total surface-water inflow or outflow” column 

in table 7 of Heilweil and others (2005) from March 2002 to 

August 2004, the “Monthly surface-water inflow or outflow” 

column in table 2 of Heilweil and Susong (2007) from September 2004 to August 2006, and the “Monthly net surfacewater inflow/outflow” column in table 2 of Heilweil and others 

(2009) from September 2006 to December 2007. 

As in Heilweil and Marston (2011), both “Monthly drain 

and spring return flow to reservoir” and “Monthly outflow 

to Sand Hollow Resort” are included in calculations of total 

inflow to and outflow from the reservoir. These amounts are 

added to the “Monthly pump station inflow or outflow” and 

summed in the “Monthly total inflow or outflow to/from 

reservoir” column. Monthly total inflow/outflow amounts 

from March 2002 through December 2014 range from about 

−5,000 acre-ft to 6,600 acre-ft. Approximately 216,000 acre-ft 

of total net inflow were pumped into Sand Hollow Reservoir 

from the Virgin River from 2002 through 2014.

Meteorological Data 

Meteorological data have been collected at the WCWCD 

weather station (fig. 2) in Sand Hollow since January 1998. 

Beginning in 2010, a Soil Climate Analysis Network (SCAN) 

Sand Hollow weather station (http://www.wcc.nrcs.usda.gov/

nwcc/site?sitenum=2159) operated by the Natural Resources 

Conservation Service (NRCS), replaced the collection of data 

by the WCWCD weather station. The NRCS Sand Hollow 

SCAN station is located south of the reservoir within Sand 

Hollow basin near the WCWCD station (fig. 2). Data from 

both weather stations have been used for evaluating evaporation and precipitation, which are required for calculating 

monthly recharge from Sand Hollow Reservoir. Parameters 

measured include air temperature, wind speed, wind direction, 

precipitation, relative humidity, and incoming solar radiation. 

Instrumentation includes a temperature and relative humidity 

probe, a wind direction and speed monitor, a tipping bucket 

rain gage, and a solar radiometer. Sensors collect data every 

minute, and average hourly and daily values are computed and 

stored on a data logger, with the exception of precipitation, 

which is summed rather than averaged. The solar radiation 

and temperature data were used for calculating evaporation 

by using the version of the Jenson-Haise method found in 

McGuinness and Bordne (1971). The other data were collected 

to permit calculations of evaporation using other methods.

From January 13, 1998, to December 30, 2014, daily average air temperature ranged from -10 to 37 degrees Celsius 

(°C). The coldest temperatures during the year were typically 

in December and January, when minimum air temperatures 

occasionally were below −10 °C. The warmest temperatures 

were typically in July, when maximum air temperatures 

occasionally approached 45 °C. Daily average solar radiation 

ranged from 34 to 840 calories per square centimeter per day. 

The minimum daily averages are typically in December and 

January, and the maximum daily averages are typically in June 

and July. 

Monthly precipitation was recorded at the Sand Hollow 

weather station continuously from January 1998 through 

December 2011, except for two periods when malfunctioning 

instrumentation resulted in data loss: December 26, 2008, to 

January 3, 2009, and September 28 to November 16, 2009. 

Precipitation amounts during these two periods were estimated 

on the basis of data from the nearby St. George Southgate 

Golf Course weather station (#427516; http://www.wrcc.dri.

edu/cgi-bin/cliMAIN.pl?ut7516). From January 1998 through 

December 2014, monthly precipitation ranged from 0 to about 

4.3 in. (fig. 7) and averaged about 0.6 in. Average annual precipitation during the 14-year period was 7.4 in. 
10 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow Reservoir, Washington County, 

Utah, 2002–14. 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily values for each month; 

2ơ, 2 standard deviation; —, no data available]

Month

Reservoir 

altitude 

(feet)

Reservoir 

storage 

(acre-feet)

Monthly pump 

station inflow 

or outflow (-) to/

from reservoir 

(acre-feet)1

Monthly drain 

and spring 

return flow to 

reservoir 

(acre-feet)

Monthly 

outflow (-) to 

Sand Hollow 

Resort 

(acre-feet)

Monthly 

total inflow or 

outflow (-) to/

from reservoir 

(acre-feet)1

Monthly 

reservoir storage change 

(acre-feet)

Reservoir 

surface area 

(acres)

Monthly evaporation rate 

(feet)2

Mar.–02 3,001 3,090 6,620 0 0 6,620 3,090 260 0.24

Apr.–02 3,003 3,500 3,690 0 0 3,690 410 280 0.46

May–02 3,001 3,090 2,450 0 0 2,450 -410 260 0.68

June–02 2,999 2,480 0 0 0 0 -610 230 0.91

July–02 2,997 2,050 0 0 0 0 -430 210 0.90

Aug.–02 2,995 1,650 0 0 0 0 -400 180 0.81

Sept.–02 2,994 1,300 0 0 0 0 -350 140 0.47

Oct.–02 2,995 1,500 790 0 0 790 200 160 0.26

Nov.–02 3,006 4,220 3,590 0 0 3,590 2,720 320 0.11

Dec.–02 3,012 7,000 3,930 0 0 3,930 2,780 400 0.05

Jan.–03 3,017 9,760 4,580 0 0 4,580 2,760 590 0.09

Feb.–03 3,019 10,670 2,850 0 0 2,850 910 570 0.10

Mar.–03 3,020 10,930 1,930 0 0 1,930 260 580 0.24

Apr.–03 3,019 10,680 540 0 0 540 -250 570 0.37

May–03 3,018 9,930 0 0 0 0 -750 540 0.66

June–03 3,010 6,040 -3,120 0 0 -3,120 -3,890 390 0.89

July–03 3,002 3,200 -2,020 0 0 -2,020 -2,840 240 0.92

Aug.–03 2,999 2,540 0 0 0 0 -660 230 0.75

Sept.–03 2,997 2,100 0 30 0 30 -440 220 0.58

Oct.–03 2,996 1,850 0 20 0 20 -250 170 0.36

Nov.–03 2,994 1,560 0 20 0 20 -290 200 0.09

Dec.–03 3,007 4,700 3,590 10 0 3,600 3,140 330 0.06

Jan.–04 3,013 7,600 3,990 30 0 4,020 2,900 480 0.06

Feb.–04 3,016 8,840 2,320 40 0 2,360 1,240 600 0.08

Mar.–04 3,019 10,400 2,400 50 0 2,450 1,560 630 0.38

Apr.–04 3,025 15,070 5,620 60 0 5,680 4,670 750 0.42

May–04 3,026 15,830 2,050 0 0 2,050 760 780 0.72

June–04 3,025 14,400 0 70 0 70 -1,430 750 0.87

July–04 3,023 13,000 0 60 0 60 -1,400 680 0.94

Aug.–04 3,021 11,670 0 50 0 50 -1,330 680 0.78

Sept.–04 3,019 11,260 3

600 30 0 630 -410 630 0.53

Oct.–04 3,019 11,040 3

630 30 0 660 -220 610 0.25

Nov.–04 3,022 12,650 3

2,300 40 0 2,340 1,610 630 0.10

Dec.–04 3,023 13,390 3

1,400 0 0 1,400 740 670 0.06

Jan.–05 3,027 16,200 3

3,500 60 0 3,560 2,810 740 0.07

Feb.–05 3,032 20,280 3

5,200 70 0 5,270 4,080 780 0.11

Mar.–05 3,037 25,030 6,530 90 0 6,620 4,750 880 0.24

Apr.–05 3,041 29,220 6,180 60 0 6,240 4,190 960 0.39

May–05 3,044 32,370 5,140 90 0 5,230 3,150 1,020 0.70

June–05 3,048 35,750 6,100 110 0 6,210 3,380 1,080 0.75

July–05 3,049 37,280 3,600 90 0 3,690 1,530 1,120 0.97

Aug.–05 3,050 38,670 3,390 80 0 3,470 1,390 1,140 0.75

Sept.–05 3,051 39,580 3,010 160 0 3,170 910 1,160 0.54
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 11

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow 

Reservoir, Washington County, Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily 

values for each month; 2ơ, 2 standard deviation; —, no data available]

Month

Monthly 

evaporation 

(acre-feet)

Monthly 

precipitation

(acre-feet)

Monthly groundwater recharge

(acre-feet)

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(percent) 

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(acre-feet)

Groundwater 

recharge rate 

(feet/day)

Mar.–02 60 — 3,470 6.7 232 0.430

Apr.–02 130 — 3,150 5.9 187 0.383

May–02 180 — 2,680 6.6 176 0.330

June–02 210 — 400 12.6 50 0.058

July–02 190 — 240 13.1 31 0.040

Aug.–02 150 — 250 12.7 32 0.044

Sept.–02 70 — 280 11.7 33 0.070

Oct.–02 40 — 550 6.6 36 0.110

Nov.–02 30 — 840 7.2 61 0.090

Dec.–02 20 — 1,130 7.1 80 0.090

Jan.–03 50 — 1,770 7.0 123 0.097

Feb.–03 60 — 1,880 6.4 121 0.118

Mar.–03 140 — 1,530 6.5 99 0.085

Apr.–03 210 — 580 9.4 55 0.034

May–03 360 — 390 13.2 52 0.023

June–03 350 — 420 8.4 35 0.036

July–03 220 — 600 8.4 51 0.081

Aug.–03 170 — 490 12.0 59 0.069

Sept.–03 130 — 340 12.3 42 0.052

Oct.–03 60 — 210 11.9 25 0.040

Nov.–03 20 — 290 10.6 31 0.048

Dec.–03 20 — 440 7.4 32 0.043

Jan.–04 30 — 1,090 7.2 78 0.073

Feb.–04 40 — 1,080 6.9 74 0.064

Mar.–04 240 — 650 7.7 50 0.033

Apr.–04 310 — 700 7.6 53 0.031

May–04 560 — 730 8.6 63 0.030

June–04 650 — 850 13.1 112 0.038

July–04 640 — 820 13.1 108 0.039

Aug.–04 530 — 850 12.8 109 0.040

Sept.–04 330 — 710 10.2 73 0.038

Oct.–04 150 — 730 8.4 61 0.039

Nov.–04 70 — 660 7.3 48 0.035

Dec.–04 40 — 620 7.0 43 0.030

Jan.–05 50 — 700 7.3 51 0.031

Feb.–05 80 130 1,240 7.3 91 0.057

Mar.–05 210 100 1,760 7.4 130 0.065

Apr.–05 370 130 1,810 7.5 136 0.063

May–05 710 40 1,410 7.9 112 0.045

June–05 810 20 2,040 7.8 160 0.063

July–05 1,080 10 1,090 8.8 96 0.031

Aug.–05 850 40 1,270 8.5 108 0.036

Sept.–05 630 20 1,650 8.1 133 0.047
12 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow Reservoir, Washington County, 

Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily values for each month; 

2ơ, 2 standard deviation; —, no data available]

Month

Reservoir 

altitude 

(feet)

Reservoir 

storage 

(acre-feet)

Monthly pump 

station inflow 

or outflow (-) to/

from reservoir 

(acre-feet)1

Monthly drain 

and spring 

return flow to 

reservoir 

(acre-feet)

Monthly 

outflow (-) to 

Sand Hollow 

Resort 

(acre-feet)

Monthly 

total inflow or 

outflow (-) to/

from reservoir 

(acre-feet)1

Monthly 

reservoir storage change 

(acre-feet)

Reservoir 

surface area 

(acres)

Monthly evaporation rate 

(feet)2

Oct.–05 43,052 440,960 2,960 180 0 3,140 41,380 41,190 0.28

Nov.–05 3,055 44,310 5,160 210 0 5,370 4

3,350 1,230 0.11

Dec.–05 3,056 46,120 3,380 240 0 3,620 1,810 1,250 0.05

Jan.–06 3,059 49,590 4,660 290 0 4,950 3,470 1,290 0.08

Feb.–06 3,059 49,840 1,200 250 0 1,450 250 1,320 0.12

Mar.–06 3,058 48,700 60 210 0 270 -1,140 1,310 0.18

Apr.–06 3,059 49,450 2,060 100 0 2,160 750 1,300 0.45

May–06 3,060 51,280 3,650 110 0 3,760 1,830 1,320 0.76

June–06 3,059 49,520 10 130 0 140 -1,760 1,330 0.92

July–06 3,058 47,920 30 140 0 170 -1,600 1,310 0.88

Aug.–06 3,056 46,220 0 140 0 140 -1,700 1,280 0.80

Sept.–06 3,055 44,610 10 90 0 100 -1,610 1,260 0.52

Oct.–06 3,054 43,390 30 120 0 150 -1,220 1,230 0.22

Nov.–06 3,053 42,360 0 100 0 100 -1,030 1,220 0.07

Dec.–06 3,055 45,100 4,430 70 0 4,500 2,740 1,230 0.04

Jan.–07 3,058 48,230 4,190 100 0 4,290 3,130 1,270 0.05

Feb.–07 3,057 47,630 30 60 0 90 -600 1,290 0.13

Mar.–07 3,057 47,660 1,210 70 0 1,280 30 1,290 0.33

Apr.–07 3,057 46,720 50 80 0 130 -940 1,280 0.45

May–07 3,055 44,880 0 0 -110 -110 -1,840 1,220 0.74

June–07 3,054 43,390 0 0 -220 -220 -1,490 1,240 0.93

July–07 3,053 41,740 120 0 -200 -80 -1,650 1,210 0.92

Aug.–07 3,051 40,040 60 0 -210 -150 -1,700 1,180 0.81

Sept.–07 3,050 38,040 5

-750 0 -210 6-910 -2,000 1,160 0.57

Oct.–07 3,046 34,280 5

-2,660 0 -120 6-2,780 -3,760 1,120 0.32

Nov.–07 3,045 32,480 5

-750 0 -100 6-850 -1,800 1,060 0.16

Dec.–07 3,044 31,680 90 10 0 100 -800 1,040 0.05

Jan.–08 3,044 31,470 0 20 0 20 -210 1,030 0.06

Feb.–08 3,046 34,490 3,240 20 0 3,260 3,020 1,050 0.13

Mar.–08 3,050 38,460 4,420 0 -70 4,350 3,970 1,110 0.29

Apr.–08 3,053 42,670 4,950 0 -160 4,790 4,210 1,180 0.45

May–08 3,055 44,410 3,260 0 -120 3,140 1,740 1,230 0.61

June–08 3,053 42,540 0 0 -220 -220 -1,870 1,230 0.93

July–08 3,052 41,080 0 0 -180 -180 -1,460 1,180 0.95

Aug.–08 3,047 34,600 7

-5,000 0 -180 -5,180 -6,480 1,140 0.82

Sept.–08 3,045 32,960 0 0 -140 -140 -1,640 1,070 0.61

Oct.–08 3,044 31,890 0 0 -70 -70 -1,070 1,050 0.36

Nov.–08 3,043 31,160 0 0 -10 -10 -730 1,040 0.16

Dec.–08 3,046 34,490 4,100 40 0 4,140 3,330 1,050 0.06

Jan.–09 3,046 33,830 0 70 0 70 -660 1,080 0.09

Feb.–09 3,049 37,770 4,630 50 0 4,680 3,940 1,110 0.14

Mar.–09 3,052 41,320 4,800 0 -30 4,770 3,550 1,190 0.30

Apr.–09 3,055 44,030 3,920 0 -70 3,850 2,710 1,220 0.44
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 13

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow 

Reservoir, Washington County, Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily 

values for each month; 2ơ, 2 standard deviation; —, no data available]

Month

Monthly 

evaporation 

(acre-feet)

Monthly 

precipitation

(acre-feet)

Monthly groundwater recharge

(acre-feet)

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(percent) 

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(acre-feet)

Groundwater 

recharge rate 

(feet/day)

Oct.–05 4330 60 1,490 7.6 113 0.040

Nov.–05 140 40 1,920 7.2 138 0.052

Dec.–05 60 20 1,770 6.9 122 0.046

Jan.–06 100 10 1,390 7.3 101 0.035

Feb.–06 160 30 1,070 7.3 78 0.029

Mar.–06 240 60 1,230 11.4 140 0.030

Apr.–06 580 40 870 8.7 76 0.022

May–06 1,000 0 930 8.7 81 0.023

June–06 1,220 10 690 14.1 97 0.017

July–06 1,160 30 640 14.1 90 0.016

Aug.–06 1,020 0 820 13.8 113 0.021

Sept.–06 650 10 1,070 12.8 137 0.028

Oct.–06 270 30 1,130 11.6 132 0.030

Nov.–06 90 0 1,040 10.8 112 0.028

Dec.–06 60 10 1,710 7.0 120 0.045

Jan.–07 60 10 1,110 7.2 80 0.028

Feb.–07 170 30 550 11.9 65 0.015

Mar.–07 430 0 820 9.0 73 0.021

Apr.–07 580 50 540 13.4 73 0.014

May–07 900 0 830 13.3 110 0.022

June–07 1,150 0 120 14.4 17 0.003

July–07 1,110 110 560 13.5 76 0.015

Aug.–07 960 60 650 13.3 87 0.018

Sept.–07 660 80 510 10.8 55 0.015

Oct.–07 360 0 620 8.6 53 0.018

Nov.–07 170 100 880 9.3 82 0.028

Dec.–07 50 90 940 10.0 94 0.029

Jan.–08 60 50 220 11.9 26 0.007

Feb.–08 140 100 200 7.7 15 0.007

Mar.–08 320 10 70 7.8 5 0.002

Apr.–08 530 0 50 8.0 4 0.001

May–08 750 50 700 8.5 59 0.018

June–08 1,140 10 520 13.8 72 0.014

July–08 1,120 110 270 14.2 38 0.007

Aug.–08 940 10 370 8.7 32 0.010

Sept.–08 650 20 870 12.8 111 0.027

Oct.–08 370 60 690 12.5 86 0.021

Nov.–08 160 80 640 11.6 75 0.021

Dec.–08 60 50 800 7.4 59 0.025

Jan.–09 100 50 680 11.2 76 0.020

Feb.–09 150 60 650 7.5 49 0.021

Mar.–09 360 0 860 7.7 66 0.023

Apr.–09 530 20 630 8.0 50 0.017
14 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow Reservoir, Washington County, 

Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily values for each month; 

2ơ, 2 standard deviation; —, no data available]

Month

Reservoir 

altitude 

(feet)

Reservoir 

storage 

(acre-feet)

Monthly pump 

station inflow 

or outflow (-) to/

from reservoir 

(acre-feet)1

Monthly drain 

and spring 

return flow to 

reservoir 

(acre-feet)

Monthly 

outflow (-) to 

Sand Hollow 

Resort 

(acre-feet)

Monthly 

total inflow or 

outflow (-) to/

from reservoir 

(acre-feet)1

Monthly 

reservoir storage change 

(acre-feet)

Reservoir 

surface area 

(acres)

Monthly evaporation rate 

(feet)2

May–09 3,053 42,180 180 10 -170 20 -1,850 1,220 0.78

June–09 3,052 40,600 210 0 -130 80 -1,580 1,190 0.73

July–09 3,050 38,700 220 0 -170 50 -1,900 1,170 0.96

Aug.–09 3,049 36,960 210 0 -150 60 -1,740 1,140 0.80

Sept.–09 3,047 35,380 200 0 -150 50 -1,580 1,110 0.58

Oct.–09 3,046 33,940 200 10 -80 130 -1,440 1,090 0.30

Nov.–09 3,045 32,960 180 10 -20 170 -980 1,070 0.16

Dec.–09 3,044 32,320 200 40 0 240 -640 1,050 0.05

Jan.–10 3,044 31,890 0 50 0 50 -430 1,040 0.07

Feb.–10 3,044 31,470 0 40 0 40 -420 1,040 0.10

Mar.–10 3,047 35,490 5,100 90 -50 5,140 4,020 1,070 0.23

Apr.–10 3,050 38,930 5,280 70 -110 5,240 3,440 1,130 0.36

May–10 3,053 41,810 4,650 90 -160 4,580 2,880 1,180 0.56

June–10 3,054 43,660 3,890 80 -190 3,780 1,850 1,220 0.81

July–10 3,053 42,300 570 100 -240 430 -1,360 1,220 0.91

Aug.–10 3,051 40,240 0 80 -220 -140 -2,060 1,190 0.77

Sept.–10 3,050 38,350 0 80 -210 -130 -1,890 1,160 0.60

Oct.–10 3,049 37,310 0 100 -90 10 -1,040 1,140 0.29

Nov.–10 3,048 36,620 0 90 -40 50 -690 1,120 0.13

Dec.–10 3,051 40,240 4,290 90 -10 4,370 3,620 1,150 0.06

Jan.–11 3,054 43,960 5,650 60 -10 5,700 3,720 1,200 0.09

Feb.–11 3,057 47,750 4,540 40 -30 4,550 3,790 1,260 0.11

Mar.–11 3,059 50,270 3,780 20 -30 3,770 2,520 1,310 0.26

Apr.–11 3,058 49,110 0 10 -140 -130 -1,160 1,310 0.43

May–11 3,057 47,460 0 10 -150 -140 -1,650 1,290 0.59

June–11 3,056 45,680 0 80 -190 -110 -1,780 1,270 0.89

July–11 3,054 43,710 0 10 -200 -190 -1,970 1,240 0.89

Aug.–11 3,053 41,990 0 10 -190 -180 -1,720 1,220 0.93

Sept.–11 3,052 40,600 0 20 -150 -130 -1,390 1,190 0.61

Oct.–11 3,051 39,910 0 30 -70 -40 -690 1,170 0.35

Nov.–11 3,054 43,490 3,980 30 -30 3,980 3,580 1,200 0.15

Dec.–11 3,058 48,010 4,990 20 -10 5,000 4,520 1,260 0.07

Jan.–12 3,060 50,990 3,540 120 -20 3,650 2,980 1,320 0.10

Feb.–12 3,059 50,360 340 80 -20 400 -630 1,330 0.14

Mar.–12 3,059 50,070 1,010 110 -70 1,050 -300 1,320 0.29

Apr.–12 3,060 50,710 1,700 110 -110 1,700 640 1,330 0.49

May–12 3,058 48,740 0 110 -200 -90 -1,980 1,310 0.83

June–12 3,056 46,440 -330 100 -200 -430 -2,300 1,280 0.98

July–12 3,055 44,220 -750 120 -200 -830 -2,220 1,250 0.87

Aug.–12 3,053 41,920 -800 120 -190 -870 -2,310 1,220 0.81

Sept.–12 3,051 40,170 -310 130 -140 -320 -1,750 1,190 0.58

Oct.–12 3,049 37,280 -1,560 110 -100 -1,550 -2,880 1,150 0.38

Nov.–12 3,047 35,280 -1,190 60 -50 -1,180 -2,010 1,110 0.18
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 15

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow 

Reservoir, Washington County, Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily 

values for each month; 2ơ, 2 standard deviation; —, no data available]

Month

Monthly 

evaporation 

(acre-feet)

Monthly 

precipitation

(acre-feet)

Monthly groundwater recharge

(acre-feet)

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(percent) 

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(acre-feet)

Groundwater 

recharge rate 

(feet/day)

May–09 950 0 920 12.9 119 0.024

June–09 870 10 800 12.9 103 0.022

July–09 1,120 10 840 13.1 110 0.023

Aug.–09 910 0 890 12.8 114 0.025

Sept.–09 650 0 980 12.3 120 0.029

Oct.–09 320 8

0 1,320 11.1 147 0.039

Nov.–09 170 8

0 1,050 10.6 111 0.033

Dec.–09 60 100 920 9.6 88 0.028

Jan.–10 80 150 550 11.2 62 0.017

Feb.–10 110 220 570 11.5 65 0.018

Mar.–10 250 190 1,060 7.6 80 0.032

Apr.–10 400 40 1,440 7.6 109 0.041

May–10 660 10 1,050 8.0 84 0.029

June–10 990 0 940 8.6 81 0.025

July–10 1,100 0 690 12.7 88 0.018

Aug.–10 920 60 1,060 13.0 138 0.029

Sept.–10 690 0 1,070 12.7 136 0.030

Oct.–10 320 280 1,010 12.0 121 0.029

Nov.–10 150 80 670 11.6 78 0.019

Dec.–10 70 410 1,090 7.5 82 0.031

Jan.–11 100 10 1,890 7.1 135 0.051

Feb.–11 140 170 790 7.5 60 0.020

Mar.–11 340 110 1,020 7.7 79 0.025

Apr.–11 560 90 560 13.1 73 0.014

May–11 760 50 800 13.1 105 0.020

June–11 1,130 10 550 13.9 76 0.014

July–11 1,110 10 680 13.6 92 0.018

Aug.–11 1,130 20 430 13.9 60 0.011

Sept.–11 720 50 590 13.3 79 0.016

Oct.–11 420 120 350 13.4 47 0.010

Nov.–11 180 40 260 7.7 20 0.007

Dec.–11 90 50 440 7.5 33 0.011

Jan.–12 130 60 590 7.6 45 0.014

Feb.–12 180 150 1,010 10.1 102 0.024

Mar.–12 380 40 1,000 9.3 93 0.024

Apr.–12 650 60 450 9.4 42 0.011

May–12 1,090 0 800 13.6 109 0.020

June–12 1,260 40 650 12.8 83 0.016

July–12 1,090 200 500 11.7 58 0.013

Aug.–12 990 130 580 11.4 66 0.015

Sept.–12 690 110 850 11.9 101 0.023

Oct.–12 440 60 950 9.3 89 0.027

Nov.–12 200 0 630 8.8 56 0.018
16 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow Reservoir, Washington County, 

Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily values for each month; 

2ơ, 2 standard deviation; —, no data available]

Month

Reservoir 

altitude 

(feet)

Reservoir 

storage 

(acre-feet)

Monthly pump 

station inflow 

or outflow (-) to/

from reservoir 

(acre-feet)1

Monthly drain 

and spring 

return flow to 

reservoir 

(acre-feet)

Monthly 

outflow (-) to 

Sand Hollow 

Resort 

(acre-feet)

Monthly 

total inflow or 

outflow (-) to/

from reservoir 

(acre-feet)1

Monthly 

reservoir storage change 

(acre-feet)

Reservoir 

surface area 

(acres)

Monthly evaporation rate 

(feet)2

Dec.–12 3,046 34,370 -310 60 -20 -260 -910 1,090 0.07

Jan.–13 3,049 37,020 2,860 280 -10 3,130 2,650 1,100 0.06

Feb.–13 3,051 40,080 3,190 130 -10 3,310 3,060 1,140 0.13

Mar.–13 3,053 41,650 2,070 70 -100 2,040 1,570 1,190 0.34

Apr.–13 3,051 40,260 0 60 -150 -90 -1,390 1,190 0.49

May–13 3,050 38,820 0 60 -150 -90 -1,440 1,160 0.82

June–13 3,048 36,320 -820 60 -190 -950 -2,490 1,140 1.17

July–13 3,044 32,070 -2,940 60 -180 -3,050 -4,250 1,080 1.02

Aug.–13 3,040 27,830 -2,560 50 -150 -2,660 -4,240 1,000 0.89

Sept.–13 3,038 26,280 -540 70 -110 -580 -1,560 950 0.57

Oct.–13 3,038 26,090 1,020 50 -90 980 -190 930 0.36

Nov.–13 3,042 30,120 4,360 40 -50 4,360 4,030 980 0.17

Dec.–13 3,044 31,410 1,910 60 -10 1,970 1,290 1,030 0.06

Jan.–14 3,047 34,870 4,350 60 -20 4,390 3,460 1,070 0.12

Feb.–14 3,049 37,570 3,100 60 -20 3,130 2,700 1,120 0.17

Mar.–14 3,049 37,630 1,070 100 -90 1,090 60 1,140 0.35

Apr.–14 3,048 36,600 0 280 -110 170 -1,030 1,130 0.53

May–14 3,047 35,430 0 280 -160 120 -1,160 1,110 0.79

June–14 3,046 33,660 -400 280 -180 -300 -1,780 1,090 1.12

July–14 3,042 29,820 -2,350 270 -190 -2,270 -3,830 1,040 1.05

Aug.–14 3,039 26,650 -2,230 240 -130 -2,120 -3,170 970 0.83

Sept.–14 3,035 23,400 -2,120 280 -120 -1,960 -3,260 910 0.70

Oct.–14 3,035 22,720 0 230 -90 140 -680 880 0.46

Nov.–14 3,034 22,130 0 210 -40 170 -580 870 0.19

Dec.–14 3,038 26,090 4,290 190 -10 4,470 3,950 900 0.10

Total — — — — — 215,750 — — —

1

Negative (-) values indicate flows out of Sand Hollow Reservoir to Quail Creek Water Treatment Plant or to Quail Creek Reservoir. 

2

Monthly evaporation rate from February 2007 through December 2009 was calculated with a correction factor to account for higher solar radiation measurements with new instrument. 

3

Because of problems with monitoring equipment, inflows from September 2004 through February 2005 are estimated based on previous inflow history and changes in reservoir 

altitude. 

4

Revised value based on refined reservoir altitude estimate for October 2005. 

5

Monthly pump station outflow was increased from amount reported in Heilweil and others (2009a) based on reservoir altitude relations. 

6

Monthly total outflow was increased from amount reported by Washington County Water Conservancy District based on reservoir altitude relations. 

7

Monthly pump station outflow was increased from amount reported in Heilweil and others (2009a) based on reservoir altitude relations. 

8

Sand Hollow rain gauge not functioning; values of 0 based on lack of precipitation from St. George precipitation station #427516. 

9

Monthly total inflow or outflow (-) to/from reservoir (acre-feet). 
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 17

Table 1. Reservoir data, evaporation, precipitation, and calculated recharge beneath Sand Hollow 

Reservoir, Washington County, Utah, 2002–14.—Continued 

[Reservoir altitude and Reservoir storage: value is from the last day of each month; Reservoir surface area: value is an average of the daily 

values for each month; 2ơ, 2 standard deviation; —, no data available]

Month

Monthly 

evaporation 

(acre-feet)

Monthly 

precipitation

(acre-feet)

Monthly groundwater recharge

(acre-feet)

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(percent) 

Monthly 

groundwater 

recharge 

uncertainty, 2σ

(acre-feet)

Groundwater 

recharge rate 

(feet/day)

Dec.–12 80 100 670 9.4 64 0.020

Jan.–13 70 90 500 7.6 38 0.015

Feb.–13 150 30 130 7.7 10 0.004

Mar.–13 400 40 110 8.5 9 0.003

Apr.–13 580 30 750 12.9 97 0.021

May–13 950 10 420 14.0 58 0.012

June–13 1,330 0 210 12.0 25 0.006

July–13 1,100 150 250 9.6 24 0.007

Aug.–13 890 80 760 9.5 73 0.025

Sept.–13 540 170 600 11.0 66 0.020

Oct.–13 340 20 860 8.9 77 0.030

Nov.–13 170 110 260 7.7 20 0.009

Dec.–13 60 50 660 7.3 48 0.021

Jan.–14 130 10 810 7.4 60 0.025

Feb.–14 190 120 350 7.8 28 0.010

Mar.–14 390 50 690 9.1 63 0.019

Apr.–14 600 50 650 13.6 89 0.019

May–14 880 110 520 14.1 73 0.015

June–14 1,210 0 260 13.0 34 0.008

July–14 1,100 10 480 9.9 47 0.015

Aug.–14 810 180 420 9.5 40 0.014

Sept.–14 640 140 800 9.3 75 0.029

Oct.–14 410 0 410 13.8 56 0.015

Nov.–14 160 20 600 12.1 73 0.022

Dec.–14 90 60 490 7.5 37 0.017

Total 70,140 — 126,510 — — —
18 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Monthly precipitation, in inches

Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09 Jan-10 Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 

Figure 7. Monthly precipitation at Sand Hollow, Washington County, Utah, 1998–2014.

Estimates of Managed Aquifer Recharge from 

Sand Hollow Reservoir 

Substantial amounts of surface water from Sand Hollow 

Reservoir infiltrate through the underlying sediments to 

recharge the Navajo aquifer. This recharge either is captured 

by production wells for municipal supply, or it moves northward through the aquifer towards the Virgin River. Through 

2014, withdrawals from production wells operated by the 

WCWCD at Sand Hollow have been permitted for the capture 

of natural recharge in Sand Hollow. These withdrawals are 

governed by different water rights than those associated with 

MAR from Sand Hollow Reservoir; withdrawal rights for this 

artificial recharge have not yet been exercised.

Recharge from Sand Hollow Reservoir is calculated as the 

residual with the following water-budget equation (modified 

from Heilweil and others, 2005):

R = Isw + Idr – Osw + P ± ΔS – E (1)

where 

R is recharge, 

Isw is surface-water inflow,

Idr is drain return flow,

Osw is surface-water outflow, 

P is the amount of precipitation falling directly 

on the reservoir, 

ΔS is change in surface-water storage, and 

E is evaporation.

All the variables in equation 1 are in units of acre-feet. 

The following equation was developed to evaluate the 

uncertainty for each monthly recharge estimate:

CU = Σ[(|Ci| / Σ|Ci|) * Ui] (2)

where 

CU is the composite uncertainty fraction (2 

standard deviation, 2σ),

|Ci| is the absolute value of each component of the 

water budget (acre-feet), 

Σ|Ci| is the sum of absolute values of all the waterbudget components (acre-feet), and

Ui is the uncertainty fraction (2σ) for each 

individual water-budget component. 

The smallest estimated uncertainty fraction is 0.05 

(5 percent) for Isw, Idr, and Osw because these flows are 

recorded using calibrated inline flow meters. The estimated 

uncertainty fraction for P is higher, at 0.10 (10 percent), 

because it is an indirect measurement made on the basis of 

nearby meteorological station data. Similarly, the estimated 

uncertainty fraction is also 0.10 (10 percent) for ΔS because 

changes in surface-water storage are based only on approximate reservoir water-level altitude/volume relations rather 
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 19

than direct measurements. The largest estimated uncertainty 

fraction is 0.20 (20 percent) for E, which is based on differences between alternative methods for estimating evaporation 

at Sand Hollow and in other areas (Heilweil and others, 2007; 

Rosenberry and others, 2007).

The first two reports documenting monthly groundwater 

recharge beneath Sand Hollow Reservoir through August 

2006 (Heilweil and others, 2005; Heilweil and Susong, 2007) 

did not include precipitation falling directly on the reservoir. 

Beginning with the third report (Heilweil and others, 2009a), 

and continuing in this report, an additional term for precipitation falling directly on the reservoir (P) was included in 

equation 1. The monthly amount of precipitation falling on 

the reservoir is calculated by multiplying the total monthly 

precipitation recorded by the Sand Hollow weather station by 

the average reservoir surface area for that month, based on 

reservoir water-level altitude to area relations for the reservoir 

(Washington County Water Conservancy District, written commun., 2006; RBG Engineering, written commun., 2002). The 

precipitation term in equation 1, however, does not account for 

precipitation runoff to the reservoir. Because of high evaporation rates and permeable surficial soils, precipitation events 

seldom produce runoff that reaches the lower part of Sand 

Hollow (L. Jessop, Washington County Water Conservancy 

District, oral commun., 2001), where the reservoir is situated.

Monthly water-budget values for Sand Hollow Reservoir 

are shown in table 1. Values are generally monthly averages 

or totals, except for reservoir altitude and storage, which are 

shown for the last day of each month. Values for “Monthly 

evaporation rate,” “Monthly evaporation,” and “Monthly 

groundwater recharge” from March 2002 through January 

2005 and from January 2008 through December 2011 are 

monthly averages; during February 2005 through December 

2007, however, the values are the sum of daily measurements. 

Summing of daily evaporation estimates was discontinued 

after 2007 because comparison of daily and average monthly 

calculations during 2008 and 2009 showed little difference, 

and the equation used for calculating evapotranspiration is 

more appropriate for calculating average evaporation over 

longer periods (McGuinness and Bordne, 1971). 

Changes in Reservoir Storage 

Changes in reservoir storage were calculated from daily 

reservoir water-level altitudes reported by the WCWCD 

by using altitude to volume relations (RBG Engineering, 

written commun., 2002). Since inception of the reservoir 

in 2002, surface-water storage increased to a maximum of 

about 51,000 acre-ft in May 2006. From the latter half of 

2006 through 2007, surface-water storage decreased to about 

32,000 acre-ft, and during 2008 through 2010, surface-water 

storage varied between about 31,000 and 44,000 acre-ft. 

Following the abnormally wet winter and spring of 2010–11, 

surface-water storage was kept at a high level during 2011 

through mid-2012, varying between 40,000 to 50,000 acre-ft 

but then declined to as little as 22,000 acre-ft in December 

2014 as a result of decreased flows in the Virgin River 

(table 1).

Reservoir Evaporation 

The McGuinness and Bordne (1971) version of the JensenHaise method was selected for calculating evaporation from 

Sand Hollow Reservoir during this study. A detailed comparison to results using other methods for estimating evaporation 

is given in Heilweil and others (2005). The McGuinness and 

Bordne (1971) version of the Jensen-Haise method is based on 

the following relation: 

PET = {[((0.01Ta) – 0.37)(Qs)]0.000673}2.54 (3)

where

PET is potential evaporation, in centimeters per 

day, 

Ta is air temperature, in degrees Fahrenheit, and 

Qs is solar radiation, in calories per square 

centimeter per day.

The units for PET can be converted to feet per day by multiplying by 0.0328.

By using air temperature and solar radiation from the 

nearby SCAN weather station (fig. 2), monthly evaporation rates were calculated with equation 3. These estimated 

evaporation rates ranged from 0.04 to 1.17 ft per month from 

March 2002 through December 2014 (table 1). Multiplying the 

estimated evaporation rates by average reservoir surface area 

yields monthly evaporation losses that ranged from about 20 

to 1,300 acre-ft between March 2002 and December 2014.

Estimates of Total Volume of Managed Aquifer 

Recharge from Sand Hollow Reservoir 

Monthly estimates of precipitation (P), evaporation (E), 

inflows (Isw and Idr), outflows (Osw), and changes in surfacewater storage (ΔS) were used in equation 1 to calculate 

recharge to the Navajo aquifer beneath Sand Hollow Reservoir. Monthly recharge rates from March 2002 through 

December 2014 ranged from about 50 to 3,500 acre-ft (fig. 8), 

with 2 standard deviation (2σ) composite uncertainties ranging 

from about 6 to 14 percent of the estimate (table 1). Higher 

composite uncertainties in the summer reflect the larger, 

weighted importance of evaporation losses, which have the 

highest uncertainty. 

Estimated average monthly recharge rates beneath Sand 

Hollow Reservoir ranged from about 0.001 to 0.43 foot per 

day (ft/d) between March 2002 and December 2014 (fig. 9). 

Although the graph shows large monthly fluctuations, recharge 

has generally stabilized at an average of about 0.02 ft/d during 

2011 through 2014. 

Net annual inflow, evaporation, and groundwater recharge 

from Sand Hollow Reservoir from 2002 through 2014 are 
20 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

4,000

3,000

3,500

2,000

2,500

1,000

1,500

0

500

Volume, in acre-feet

3,080

3,060

3,020

3,000

2,960

2,980

3,040

Reservoir altitude, in feet 

Groundwater recharge volume

Evaporation volume

Reservoir altitude

Error bars

Mar 02 

Sept 02 

Mar 03 

Sept 03 

Mar 04 

Sept 04 

Mar 05 

Sept 05 

Mar 06 

Sept 06 

Mar 07 

Sept 07 

Mar 08 

Sept 08 

Mar 09 

Sept 09 

Mar 10 

Sept 10 

Mar 11 

Sept 11 

Mar 12 

Sept 12 

Mar 13 

Sept 13 

Mar 14 

Sept 14 

Mar 15 

Figure 8. Monthly estimated evaporation, groundwater recharge, and reservoir altitude, Sand Hollow Reservoir, Washington County, 

Utah, 2002–14.

0

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Jan-02 Jan-04 Jan-06 Jan-08 Jan-10 Jan-12 Jan-14 

Recharge rate, in feet per day 

Figure 9. Monthly calculated groundwater recharge rates beneath Sand Hollow Reservoir, Washington County, Utah, 2002–14.
Assessment of Managed Aquifer Recharge from Sand Hollow Reservoir 21

0

10,000

20,000

30,000

40,000

50,000

60,000

Net inflow

Evaporation

Groundwater recharge

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Volume, in acre-feet

Figure 10. Estimated annual inflow, evaporation, and groundwater recharge, Sand Hollow Reservoir, Washington County, Utah, 

2002–14.

shown in figure 10. Total net inflow during this period was 

about 216,000 acre-ft, with annual inflow during this period 

ranging from about 800 acre-ft in 2007 to 56,000 acre-ft in 

2005. The general increase in reservoir water-level altitude 

and area from 2002 to 2007 resulted in a steady increase in 

the volume of annual evaporation from about 1,000 acre-ft 

in 2002 to about 6,600 acre-ft in 2006, and then leveled off 

from 2007 through 2014. Total estimated evaporative losses 

from 2002 through 2014 were about 70,000 acre-ft. Annual 

recharge ranged from a low of about 5,000 acre-ft in 2008 to a 

high of about 18,000 acre-ft in 2005. Total estimated recharge 

from 2002 through 2014 was about 127,000 acre-ft, with a 2 

standard deviation (2σ) uncertainty of 11,900 acre-ft. 
22 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Groundwater and Surface-Water 

Quality in Sand Hollow 

As MAR from Sand Hollow Reservoir moves into the 

underlying Navajo aquifer, it has an initial water-quality signature similar to the reservoir water, but this evolves as water 

moves through the subsurface. Along its flow path, the MAR 

initially moves from the reservoir through the organic-rich 

silt layer that has accumulated beneath the reservoir, and then 

through the pre-reservoir vadose zone (now saturated) where 

vadose-zone solutes had naturally accumulated and air was 

trapped prior to and during filling of the reservoir. This results 

in water quality that is different from native groundwater. As 

part of the monitoring of MAR from Sand Hollow Reservoir, 

water-quality samples from the reservoir and surrounding 

monitoring wells were collected and analyzed for both field 

water-quality parameters and laboratory chemical, isotopic, 

and dissolved-gas concentrations. 

Field water-quality parameters included water temperature, 

specific conductance, pH, dissolved oxygen (DO), and total 

dissolved-gas (TDG) pressure. TDG pressure is the combination of partial pressures of all dissolved gases in the water. 

Field parameters were measured with a multi-parameter sonde 

placed within the screened interval at the bottom of each 

2-in. monitoring well, and in the reservoir at water depths of 

approximately 2 ft. The multi-parameter sonde was too large 

to enter the 1-in. monitoring wells (North Dam 3A, WD 4, 

WD 5, and WD 12). Consequently, field measurements from 

these wells were made onsite with a flow-through chamber connected to the discharge line from either a Waterra or 

peristaltic pump; no TDG pressure measurements were made 

at these sites. Additional details regarding field parameter 

methods are given in Heilweil and others (2005) and Heilweil 

and Susong (2007).

Laboratory water-quality analyses of water from Sand 

Hollow Reservoir and groundwater from the Navajo aquifer included dissolved major and trace inorganic elements, 

dissolved organic carbon (DOC), tritium (3H), and industrial 

dissolved gases. The major inorganic ions included calcium, 

magnesium, sodium, potassium, bicarbonate, sulfate, chloride, 

fluoride, and nitrate. Trace elements included bromide, iron, 

manganese, arsenic, nitrite, ammonia, and orthophosphate. 

Dissolved gases included chlorofluorocarbons (CFC–11, 

CFC–12, CFC–113) and sulfur hexafluoride (SF6). 

Water samples were collected from 2-in. monitoring wells 

by using either a Grundfos or Bennett submersible pump; 

1-in. wells were sampled with a Waterra hand pump; production wells were sampled utilizing installed turbine pumps. 

Prior to water sample collection from monitoring wells, water 

was purged from each well until field parameters stabilized 

and a minimum of three casing volumes were removed. After 

purging each well, water was pumped into sample bottles and 

filtered as necessary. Since 2009, a set of replicate samples 

has been collected annually at one randomly selected site and 

separately analyzed for all constituents for quality assurance. 

Samples for major cations and trace elements were filtered 

through 0.45-micron disposable filters and collected in clean 

polyethylene bottles according to procedures described by 

Wilde and Radtke (1998); samples for major anion analysis 

were preserved with 7.7-normal nitric acid. Tritium samples 

were collected in 500-milliliter (ml) polyethylene bottles with 

polyseal caps and no head space. CFC and SF6 samples were 

collected in 250-ml and 1-liter (L) glass bottles, respectively, 

according to procedures described on the USGS Reston 

Groundwater Dating Laboratory website at http://water.usgs.

gov/lab/. 

Inorganic and organic chemical analyses (major ions, trace 

elements, DOC) were analyzed by the U.S. Geological Survey 

at the National Water Quality Laboratory in Denver, Colorado. CFCs and SF6 (through 2012) were analyzed by the U.S. 

Geological Survey Chlorofluorocarbon Laboratory in Reston, 

Virginia. Tritium and SF6 (2013–2014) were analyzed at the 

University of Utah Dissolved Gas Service Center.

Water-Quality Results 

Detailed water-quality data and interpretations at Sand 

Hollow, including trends through 2012, have been previously 

published (Heilweil and others, 2005; Heilweil and Susong, 

2007; Heilweil and others, 2009a; Heilweil and Marston, 

2011; Marston and Heilweil, 2013). Tables 2 and 3 provide 

this previous data, along with additional data collected during 

2013 and 2014. The following discussion describes recent 

changes or the continuation of longer trends in water quality. 

Perhaps most significant are changes at wells WD 4 and WD 

12, located 2,600 and 1,000 ft from the reservoir, respectively. 

Although the low chloride to bromide (Cl/Br) ratios indicate 

that reservoir water has not yet arrived at these sites, increases 

in other constituents indicate a flush of naturally accumulating vadose-zone salts ahead of reservoir recharge. At WD 

4, specific conductance and dissolved-solids concentrations 

increased from 2011 through 2014 to values similar to those in 

the reservoir water. Although environmental tracers (tritium, 

CFCs, and SF6 ) have also increased, their concentrations are 

still lower than those in the reservoir water. At WD 12, specific 

conductance and dissolved-solids concentrations increased 

from 2011 through 2014 to higher values than those in the 

reservoir, indicating mobilization of naturally accumulating 

vadose-zone salts; however, Cl/Br ratios and environmental 

tracer concentrations (tritium, CFCs, and SF6) were still lower 

than those in the reservoir water.

At well WD 6, located 1,000 ft from the reservoir, the 

increase in the Cl/Br ratio from 2002 through 2014 towards 

ratios in the reservoir water indicates the arrival of recharge 

from the reservoir; specific conductance, dissolved-solids 

concentrations and concentrations of some environmental 

tracers (tritium, CFC-12, CFC-113) are also about the same 

as those in the reservoir and have remained relatively stable 

from 2012 through 2014. Other industrial gases (CFC-11, 

SF6) and DOC concentrations are substantially lower than 
Groundwater and Surface-Water Quality in Sand Hollow 23

reservoir concentrations, but this may indicate other processes 

such as microbial degradation and gas exchange with trapped 

air bubbles in the aquifer matrix. Although still elevated, the 

decrease in DO in water from WD 6 from 2009 through 2014 

may indicate the dissolution of some of this trapped air.

Although well WD 8 has had a slight increase in the Cl/Br 

ratio from 2002 through 2014, it is still much lower than the 

ratio in the reservoir water. Although located only 500 ft from 

the reservoir, this well is downgradient of an area of high natural recharge on Sand Mountain and may lie along a groundwater boundary between the two recharge mounds. The relatively 

high concentrations of modern environmental tracers may be 

caused by natural recharge. The recently observed concentration of DO, 26 mg/L, indicates a rapid rise in water level and 

entrapment of air bubbles. 

At wells WD 9 and WD 11, 55 and 160 ft away from the 

reservoir, respectively, the various field parameters, along with 

the results of chemical analyses and environmental tracers 

(with the exception of CFC-11 and CFC-113, which were possibly reduced by microbial degradation) indicate that reservoir 

recharge arrived several years prior to 2014. Recent declines 

in DO in the well may be due to a combination of dissolution 

of trapped air bubbles and chemical reduction as recharge 

infiltrates through carbon-rich sediment at the bottom of the 

reservoir.

At well WD 15, located 2,400 ft from the reservoir (fig. 2), 

specific conductance and dissolved-solids concentrations 

increased from 2010 through 2014, yet Cl/Br ratios and tritium 

concentrations remained much lower than those in the reservoir water. This may indicate vadose-zone salt mobilization, 

likely from rising water levels rather than a salt flush prior 

to the arrival of reservoir water. Elevated TDG pressure and 

DO similarly indicate air entrapment associated with rising 

water levels. WD 16, located at the same site but screened at a 

deeper interval, does not show an increase in salinity and has 

even lower Cl/Br ratios and tritium concentrations, supporting 

the interpretation of rising water levels rather than salt flushing 

prior to the arrival of reservoir recharge. Wells farther from the 

reservoir that were sampled in 2013 or 2014 (WD 5 located 

2,800 ft away and wells WD 17 and WD 18 located 5,900 ft 

away) show that reservoir recharge has not yet reached these 

locations. 

Arsenic concentrations have generally decreased at locations where reservoir recharge has already arrived or where 

there has been a water-table rise and flushing of vadose-zone 

salts, typically a precursor to the arrival of recharge. This 

decline may be attributable to an increase in oxidizing conditions, which facilitate the adsorption of arsenic on iron oxides 

within the aquifer matrix, in contrast to reducing conditions, 

which would mobilize arsenic. Wells WD 4, WD 6, WD 8, and 

WD 12 all show this trend of decreasing arsenic concentration 

with increasing DO.

Table 2. Field water-quality parameters, total dissolved-gas pressure, dissolved organic carbon, tritium, chlorofluorocarbons, and 

sulfur hexafluoride in groundwater and surface water from Sand Hollow, Washington County, Utah. 

[Analyzing agency: Dissolved organic carbon at U.S. Geological Survey (USGS) National Water Quality Laboratory in Denver, Colorado; Tritium at University of Utah Dissolved Gas 

Laboratory in Salt Lake City, Utah; CFC-11, CFC-12, CFC-113, and SF6 at USGS Chlorofluorocarbon (CFC) Laboratory in Reston, Virginia. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; mm Hg, millimeters of mercury; TU, tritium units; pmol/kg, picomoles per kilogram; fmol/kg, femtomoles per 

kilogram; —, no data available; E, estimated; >, greater than; <, less than]

Site name Date

sampled

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen 

(mg/L)

Total 

dissolved-gas 

pressure 

(mm Hg)

Dissolved organic carbon 

(mg/L) 

Tritium 

(TU)

Tritium 

precision 

(TU)

CFC-11 

(pmol/

kg)

CFC-12 

(pmol/

kg)

CFC-113 

(pmol/

kg)

SF6

(fmol/

kg)

Groundwater

North Dam 3A 10/8/02 15.9 4,430 8.0 5.0 — — 2.71 0.14 — — — —

12/18/02 14.7 2,830 8.0 10.8 — — — — — — — —

6/10/03 21.5 1,330 7.8 — — — — — — — — —

10/9/03 — 1,230 7.8 — — — — — — — — —

1/8/04 16.0 1,220 8.2 — — — — — — — — —

9/21/04 18.4 980 7.7 11.0 — — — — — — — —

10/29/04 15.9 910 7.9 11.1 — — — — — — — —

2/10/05 15.3 960 7.7 13.5 — — — — — — — —

4/5/05 16.5 960 7.8 12.6 — — — — — — — —

1/19/06 — 840 8.0 — — — — — — — — —

2/15/07 15.2 840 7.9 7.5 — — 2.53 0.31 — — — —

3/14/08 14.8 820 7.7 4.0 — — 3.45 0.44 — — — —

4/30/09 — 850 7.2 — — — 3.03 0.11 — — — —

3/16/10 22.8 860 7.6 1.3 — 1.91 3.05 0.12 0.54 2.0 0.10 —

3/10/11 20.3 830 7.4 0.8 — 1.93 2.87 0.12 0.60 1.93 0.09 —

2/6/12 11.3 820 7.8 — — 2.00 3.46 0.41 — — — —

4/15/13 25.7 870 — 2 — 2.09 3.10 0.10 0.54 2.01 0.09 1.85

4/29/14 23.6 912 8.0 0 — 2.02 3.04 0.15 — — — —
24 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 2. Field water-quality parameters, total dissolved-gas pressure, dissolved organic carbon, tritium, chlorofluorocarbons, and 

sulfur hexafluoride in groundwater and surface water from Sand Hollow, Washington County, Utah.—Continued

[Analyzing agency: Dissolved organic carbon at U.S. Geological Survey (USGS) National Water Quality Laboratory in Denver, Colorado; Tritium at University of Utah Dissolved Gas 

Laboratory in Salt Lake City, Utah; CFC-11, CFC-12, CFC-113, and SF6 at USGS Chlorofluorocarbon (CFC) Laboratory in Reston, Virginia. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; mm Hg, millimeters of mercury; TU, tritium units; pmol/kg, picomoles per kilogram; fmol/kg, femtomoles per 

kilogram; —, no data available; E, estimated; >, greater than; <, less than]

Site name Date

sampled

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen 

(mg/L)

Total 

dissolved-gas 

pressure 

(mm Hg)

Dissolved organic carbon 

(mg/L) 

Tritium 

(TU)

Tritium 

precision 

(TU)

CFC-11 

(pmol/

kg)

CFC-12 

(pmol/

kg)

CFC-113 

(pmol/

kg)

SF6

(fmol/

kg)

WD 4 4/2/99 21.0 360 8.2 — — — 0.22 0.10 — — — —

12/18/02 18.7 350 7.7 8.1 — — — — — — — —

1/19/06 — 350 8.0 — — — — — — — — —

2/15/07 19.0 340 7.9 8.7 — — — — — — — —

3/13/08 22.6 350 7.8 7.8 — — 0.25 0.10 — — — —

10/23/08 21.2 360 8.0 — — — 0.13 0.10 0.62 0.61 0.09 0.44

4/28/09 — 350 7.8 — — — 0.15 0.07 0.54 0.52 0.07 0.45

11/24/09 18.7 340 7.8 9.5 — 0.43 0.09 0.03 0.42 0.54 0.07 —

3/15/10 19.7 360 7.7 9.5 — E0.37 0.06 0.03 0.62 0.60 0.09 —

3/10/11 19.7 360 7.4 10.5 — 0.40 0.12 0.03 1.04 0.79 0.13 0.73

2/8/12 19.5 550 7.3 8.9 — 2.25 0.00 0.15 1.26 1.07 0.30 1.19

4/15/13 19.9 696 — 22.5 — 0.89 0.51 0.03 1.47 1.34 0.17 1.34

4/29/14 20.5 796 7.7 10.9 — 1.16 0.38 0.03 1.43 1.24 0.18 1.28

WD 5 4/3/99 15.0 540 8.3 — — — 0.19 0.03 — — — —

12/17/02 17.6 530 7.8 6.6 — — — — — — — —

1/18/06 — 530 7.9 — — — — — — — — —

2/15/07 18.3 530 7.8 8.3 — — — — — — — —

3/13/08 20.0 540 7.8 7.0 — — 0.05 0.10 — — — —

10/23/08 21.0 540 8.2 — — — 0.07 0.10 0.12 0.08 0.01 0.13

4/30/09 — 520 7.5 — — — 0.02 0.06 — — — —

11/24/09 16.9 510 8.5 7.2 — 0.45 0.09 0.05 0.20 0.07 0.02 —

3/15/10 21.0 540 7.7 8.1 — E0.44 0.09 0.10 0.19 0.10 0.03 —

3/10/11 19.5 510 7.4 8.0 — 0.72 0.00 0.03 0.12 0.07 0.03 0.10

4/16/13 19.8 502 7.6 9.1 — 0.89 0.51 0.03 1.47 1.34 0.17 1.34

4/30/14 20.1 522 7.4 — — 1.16 0.38 0.03 1.43 1.24 0.18 1.28

WD RJ 4/2/99 18.0 560 8.2 — — — 0.02 0.05 — — — —

12/17/02 18.2 530 7.7 6.4 — — — — — — — —

1/18/06 — 550 7.7 — — — — — — — — —

2/15/07 19.0 530 7.7 8.1 — — — — — — — —

3/12/08 19.3 540 7.3 6.8 — — 0.03 0.10 — — — —

4/28/09 — 550 7.5 — — — 0.04 0.02 — — — —

3/15/10 19.6 560 7.6 8.0 — 0.84 0.06 0.03 0.25 0.13 0.07 —

3/9/11 19.6 540 7.3 7.5 — — 0.00 0.03 0.34 0.15 0.06 —

WD 6 5/15/01 — 130 7.6 — — — 4.77 0.24 — — — —

8/28/01 19.7 190 7.7 6.1 710 — 6.88 0.34 — — — —

9/9/02 19.4 290 7.7 — 850 — — — — — — —

12/17/02 19.0 400 7.6 9.3 920 — — — — — — —

3/19/03 19.2 424 7.5 10.9 1,150 — — — — — — —

5/7/03 19.3 450 7.5 — 1,220 — — — — — — —

6/9/03 19.6 390 7.8 14.0 1,260 — — — — — — —

8/4/03 19.3 350 7.5 11.9 1,280 — — — — — — —

10/6/03 19.6 400 7.6 12.0 1,160 — — — — — — —

5/3/04 19.4 700 7.4 15.2 1,360 — — — — — — —

9/20/04 19.6 820 7.7 15.0 1,270 — — — — — — —

10/28/04 19.0 810 7.6 13.5 1,240 — — — — — — —

2/9/05 19.2 450 7.9 14.6 1,460 — — — — — — —

4/5/05 19.2 460 7.6 15.5 1,490 — — — — — — —

1/19/06 18.9 680 7.6 17.7 1

1,700 — — — — — — —

2/15/07 19.1 1,110 7.6 17.2 1

1,600 — — — — — — —
Groundwater and Surface-Water Quality in Sand Hollow 25

Table 2. Field water-quality parameters, total dissolved-gas pressure, dissolved organic carbon, tritium, chlorofluorocarbons, and 

sulfur hexafluoride in groundwater and surface water from Sand Hollow, Washington County, Utah.—Continued 

[Analyzing agency: Dissolved organic carbon at U.S. Geological Survey (USGS) National Water Quality Laboratory in Denver, Colorado; Tritium at University of Utah Dissolved Gas 

Laboratory in Salt Lake City, Utah; CFC-11, CFC-12, CFC-113, and SF6 at USGS Chlorofluorocarbon (CFC) Laboratory in Reston, Virginia. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; mm Hg, millimeters of mercury; TU, tritium units; pmol/kg, picomoles per kilogram; fmol/kg, femtomoles per 

kilogram; —, no data available; E, estimated; >, greater than; <, less than]

Site name Date

sampled

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen 

(mg/L)

Total 

dissolved-gas 

pressure 

(mm Hg)

Dissolved organic carbon 

(mg/L) 

Tritium 

(TU)

Tritium 

precision 

(TU)

CFC-11 

(pmol/

kg)

CFC-12 

(pmol/

kg)

CFC-113 

(pmol/

kg)

SF6

(fmol/

kg)

WD 6 3/13/08 19.2 1,300 7.5 14.4 11,590 — 2.11 0.14 — — — —

4/29/08 19.3 1,290 7.7 17.1 1

1,590 — — — — — — —

6/3/08 19.4 1,330 7.6 16.5 1

1,590 — — — — — — —

10/24/08 19.0 1,190 — 16.3 1

1,540 — 2.55 0.13 2.8 1.3 0.15 0.72

4/30/09 19.2 1,050 7.7 22.0 1

1,810 — 2.66 0.14 3.2 1.5 0.16 0.73

11/23/09 18.9 970 7.9 15.3 1

1,650 1.71 2.93 0.23 1.7 1.8 0.17 —

3/15/10 19.2 920 7.5 14.4 1,200 1.68 3.15 0.15 1.7 1.6 0.19 —

3/9/11 19.1 900 7.5 11.2 2

1,410 1.56 1.54 0.10 2.64 1.73 0.20 0.65

(replicate) 3/9/11 19.1 900 7.5 11.2 2

1,410 1.59 2.83 0.13 2.64 1.73 0.20 0.72

2/7/12 19.1 810 7.3 15.6 1

1,700 1.70 2.88 0.31 2.23 1.67 0.18 0.87

4/16/13 18.9 810 7.0 11.8 1

1,600 1.18 2.52 0.14 2.1 1.9 0.19 0.71

4/29/14 19.0 810 7.3 10.1 1

1,550 0.92 2.85 0.11 2.0 1.9 0.19 0.87

WD 8 5/21/01 — 300 7.7 — — — 4.13 0.38 — — — —

9/12/01 18.7 305 7.7 9.6 890 — 2.98 0.15 — — — —

9/9/02 18.9 305 7.9 — 840 — 3.89 0.19 — — — —

3/20/03 18.7 335 7.6 7.8 910 — — — — — — —

5/8/03 18.6 340 7.5 4.6 880 — — — — — — —

10/16/03 — 360 7.4 — — — — — — — — —

2/7/12 18.5 250 7.1 20.8 2

2,300 0.75 3.36 0.33 1.93 1.71 0.16 —

4/16/13 18.5 350 7.1 21.1 1

>2,290 0.52 3.14 0.16 2.02 1.69 0.16 0.42

4/30/14 18.7 380 7.8 25.9 1

1,620 0.64 3.07 0.15 2.00 1.80 0.18 0.21

WD 9 5/23/01 19.5 300 7.7 8.0 800 — 0.00 0.01 — — — —

9/14/01 19.4 280 7.4 — 790 — 0.20 0.15 — — — —

9/11/02 19.5 350 7.9 — 980 — — — — — — —

5/7/03 19.7 320 7.8 — 1

>2,250 — — — — — — —

6/9/03 19.5 350 7.7 24.4 1

>2,250 — — — — — — —

8/5/03 19.7 720 7.5 19.3 1

1,800 — — — — — — —

10/7/03 19.6 740 7.5 17.9 1

1,600 — — — — — — —

1/6/04 19.4 630 7.7 16.7 1

1,700 — — — — — — —

5/3/04 19.4 530 7.4 25.7 1

>2,250 — — — — — — —

9/20/04 18.5 750 7.8 22.6 1

>2,250 — — — — — — —

10/28/04 18.5 760 7.6 20.7 1

2,210 — — — — — — —

2/9/05 18.4 880 7.7 20.2 1

>2,250 — — — — — — —

4/5/05 18.5 820 7.4 23.2 1

>2,250 — — — — — — —

1/18/06 18.0 1,230 7.9 15.0 1

1,900 — — — — — — —

2/14/07 17.3 790 7.4 4.6 1

1,600 — — — — — — —

3/11/08 17.0 820 7.3 1.5 1,080 — 2.61 0.22 — — — —

4/27/09 16.6 830 7.4 1.8 840 — 2.99 0.12 1.2 2.2 0.19 2.15

3/15/10 16.4 840 7.3 1.7 920 1.23 3.20 0.14 0.8 2.2 0.21 —

(replicate) 3/15/10 16.4 840 7.3 1.7 920 1.17 2.90 0.12 0.8 2.2 0.18 —

3/8/11 16.1 900 7.3 0.5 900 1.36 3.34 0.16 1.33 2.10 0.17 —

2/7/12 16.3 830 7.1 0.4 720 1.77 3.56 0.28 0.76 1.85 0.13 —

4/15/13 16.1 860 7.3 0.6 790 1.30 3.23 0.15 0.91 2.01 0.14 2.64

4/28/14 16.1 880 7.0 0.16 1,010 1.29 2.78 0.11 0.52 1.78 0.08 3.59

WD 11 6/14/01 18.5 420 7.8 8.1 860 — — — — — — —

9/14/01 18.5 450 7.7 8.6 900 — 0.53 0.08 0.53 0.24 — —

9/12/02 18.5 465 7.6 — 873 — — — — — — —

12/16/02 18.2 455 7.6 8.1 890 — — — — — — —

5/7/03 18.4 620 7.7 — 1

1,770 — — — — — — —
26 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 2. Field water-quality parameters, total dissolved-gas pressure, dissolved organic carbon, tritium, chlorofluorocarbons, and 

sulfur hexafluoride in groundwater and surface water from Sand Hollow, Washington County, Utah.—Continued 

[Analyzing agency: Dissolved organic carbon at U.S. Geological Survey (USGS) National Water Quality Laboratory in Denver, Colorado; Tritium at University of Utah Dissolved Gas 

Laboratory in Salt Lake City, Utah; CFC-11, CFC-12, CFC-113, and SF6 at USGS Chlorofluorocarbon (CFC) Laboratory in Reston, Virginia. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; mm Hg, millimeters of mercury; TU, tritium units; pmol/kg, picomoles per kilogram; fmol/kg, femtomoles per 

kilogram; —, no data available; E, estimated; >, greater than; <, less than]

Site name Date

sampled

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen 

(mg/L)

Total 

dissolved-gas 

pressure 

(mm Hg)

Dissolved organic carbon 

(mg/L) 

Tritium 

(TU)

Tritium 

precision 

(TU)

CFC-11 

(pmol/

kg)

CFC-12 

(pmol/

kg)

CFC-113 

(pmol/

kg)

SF6

(fmol/

kg)

WD 11 6/9/03 18.4 650 7.9 22.5 11,600 — — — — — — —

8/5/03 18.6 700 7.8 12.4 1

1,520 — — — — — — —

10/7/03 18.5 800 7.8 19.4 1

1,700 — — — — — — —

5/3/04 18.4 680 7.7 21.5 1

1,900 — — — — — — —

9/20/04 18.0 920 8.2 23.5 1

>2,250 — — — — — — —

10/28/04 18.0 990 7.9 22.8 1

2,080 — — — — — — —

2/9/05 18.0 960 8.1 22.1 1

2,200 — — — — — — —

4/5/05 17.8 930 7.9 25.2 1

>2,250 — — — — — — —

1/18/06 17.6 980 7.9 23.0 1

>2,250 — — — — — — —

2/14/07 17.1 820 7.6 19.0 1

>2,250 — — — — — — —

3/11/08 17.0 840 7.6 14.9 1

>2,250 — 2.30 0.14 — — — —

4/30/08 17.0 840 7.7 17.4 1

>2,250 — — — — — — —

6/2/08 17.1 850 7.7 18.9 1

>2,250 — — — — — — —

10/22/08 16.7 840 8.0 15.9 1

>2,250 — 2.36 0.11 — — — —

4/30/09 15.9 840 7.7 19.4 1

2,160 — 3.06 0.14 2.0 3.0 0.34 3.5

11/23/09 16.3 840 7.9 13.2 12,160 1.46 2.75 0.12 0.8 3.0 0.30 —

3/15/10 16.2 840 7.7 10.3 2

1,700 1.35 2.81 0.13 0.8 2.9 0.30 —

3/8/11 16.0 890 7.7 9.9 2

1,940 1.45 2.76 0.14 1.24 2.76 0.24 —

2/7/12 15.4 800 7.4 9.5 2

1,850 1.57 2.52 0.21 0.76 2.60 0.18 —

4/15/13 16.1 830 6.7 11.4 1

2,160 1.32 2.66 0.09 0.63 2.31 0.11 1.85

(replicate) 4/15/13 16.1 830 6.7 11.4 1

2,160 1.50 2.63 0.13 0.59 2.27 0.11 —

4/28/14 16.2 820 7.3 3.1 1

>1,570 2.43 2.59 0.12 0.51 2.14 0.10 3.88

WD 12 4/30/99 — 330 — — — — 0.53 0.38 — — — —

9/12/02 — 335 7.9 — — — 0.02 0.06 — — — —

12/16/02 — 330 7.8 7.0 — — — — — — — —

3/9/11 19.9 1,670 7.1 13.4 — 2.17 0.96 0.06 2.34 2.20 0.25 0.68

2/8/12 19.3 2,100 7.2 9.2 — 3.81 1.01 0.13 2.27 2.04 0.28 1.10

4/16/13 19.0 2,390 7.3 17.8 — 2.93 1.49 0.10 2.58 2.26 0.28 0.77

4/28/14 20.5 2,380 7.4 — — 3.23 1.69 0.07 2.62 2.04 0.28 0.70

WD 15 10/25/08 18.8 720 — 14.2 1,300 — — — — — — —

4/28/09 18.9 710 8.0 17.6 1,490 — 0.77 0.04 2.3 1.9 0.23 1.4

11/23/09 18.8 730 8.3 14.5 1,410 2.47 0.68 0.05 1.0 1.9 0.22 —

3/16/10 19.1 730 7.9 11.5 1,320 2.49 0.72 0.05 1.2 2.1 0.25 —

3/8/11 19.1 820 8.0 12.5 1,400 2.50 0.55 0.06 2.56 2.27 0.28 1.56

2/7/12 19.1 820 8.0 18.8 2

1,450 3.15 0.15 0.13 2.36 2.14 0.27 1.48

4/17/13 18.9 900 — 17.8 1

1,780 2.44 0.60 0.02 2.24 2.21 0.26 1.23

4/29/14 18.8 970 7.7 11.7 1

1,560 2.75 0.63 0.03 2.16 2.23 0.27 1.18

(replicate) 4/29/14 18.8 970 7.7 11.7 1

1,560 2.72 0.50 0.04 2.14 2.20 0.27 1.25

WD 16 10/25/08 18.7 470 8.0 7.7 780 — — — — — — —

4/27/09 18.7 440 7.7 8.7 970 — 0.02 0.02 0.28 0.13 0.04 0.43

11/24/09 18.7 450 7.7 7.1 760 <0.66 0.03 0.04 0.12 0.01 0.01 —

3/16/10 18.7 440 7.6 5.1 770 <0.66 0.03 0.02 0.13 0.04 0.01 —

3/8/11 18.5 480 7.7 4.1 770 <0.15 0.04 0.03 0.07 0.01 0.02 0.2

4/17/13 18.7 430 — 8.1 830 <0.23 0.05 0.02 0.11 0.05 0.01 1.16

4/29/14 18.7 450 7.4 3.7 1,060 <0.23 -0.05 -0.15 0.20 0.15 0.01 0.27

WD 17 10/24/08 19.5 615 — 8.4 1,000 — — — — — — —

4/16/13 19.4 545 7.6 11.0 1,030 0.54 0.05 0.01 0.79 0.76 0.09 2.29
Groundwater and Surface-Water Quality in Sand Hollow 27

Table 2. Field water-quality parameters, total dissolved-gas pressure, dissolved organic carbon, tritium, chlorofluorocarbons, and 

sulfur hexafluoride in groundwater and surface water from Sand Hollow, Washington County, Utah.—Continued 

[Analyzing agency: Dissolved organic carbon at U.S. Geological Survey (USGS) National Water Quality Laboratory in Denver, Colorado; Tritium at University of Utah Dissolved Gas 

Laboratory in Salt Lake City, Utah; CFC-11, CFC-12, CFC-113, and SF6 at USGS Chlorofluorocarbon (CFC) Laboratory in Reston, Virginia. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; mm Hg, millimeters of mercury; TU, tritium units; pmol/kg, picomoles per kilogram; fmol/kg, femtomoles per 

kilogram; —, no data available; E, estimated; >, greater than; <, less than]

Site name Date

sampled

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen 

(mg/L)

Total 

dissolved-gas 

pressure 

(mm Hg)

Dissolved organic carbon 

(mg/L) 

Tritium 

(TU)

Tritium 

precision 

(TU)

CFC-11 

(pmol/

kg)

CFC-12 

(pmol/

kg)

CFC-113 

(pmol/

kg)

SF6

(fmol/

kg)

WD 18 4/28/09 19.7 500 7.4 7.5 870 — 0.04 0.02 0.21 0.16 0.03 1.46

3/16/10 19.3 470 7.4 4.9 740 E0.48 0.14 0.02 0.16 0.07 0.01 —

3/9/11 19.2 480 7.3 7.8 750 0.70 0.03 0.03 0.08 0.02 0.02 —

WD 19 10/23/08 18.9 1,070 — 9.2 910 — — — — — — —

3/10/11 19.1 2,030 7.5 9.8 920 4.61 2.70 0.10 3.25 2.03 0.31 —

2/7/12 18.6 1,900 7.5 6.8 820 4.87 2.99 0.30 3.17 1.82 0.30 1.55

(replicate) 2/7/12 18.6 1,900 7.5 6.8 820 5.65 2.84 0.29 3.21 1.85 0.29 1.54

WD 20 10/23/08 19.1 340 — 7.9 740 — — — — — — —

4/29/09 19.7 330 7.5 6.7 760 — 0.06 0.01 0.10 0.02 0.01 0.01

(replicate) 4/29/09 19.7 330 7.5 6.7 760 — 0.06 0.01 0.12 0.02 0.01 0.06

3/17/10 19.4 340 7.4 7.2 720 <0.66 0.03 0.04 0.11 0.04 0.01 —

3/10/11 18.9 330 7.3 7.2 710 0.23 0.01 0.04 0.15 0.07 0.02 —

Sand Hollow Reservoir water

Boat ramp 5/5/04 17.3 710 8.2 8.5 680 — — — — — — —

9/22/04 18.9 770 8.5 7.2 — — — — — — — —

2/10/05 8.3 860 8.4 11.3 — — — — — — — —

1/18/06 6.9 820 8.5 11.9 — — — — — — — —

2/14/07 5.1 760 8.1 11.6 — — — — — — — —

3/13/08 9.6 820 8.4 10.1 — — — — — — — —

10/21/08 18.3 820 8.7 8.9 700 — 3.59 0.18 2.3 1.5 0.22 1.49

4/29/09 16.1 790 8.4 7.0 — — 4.61 0.20 3.1 2.0 0.32 1.94

8/10/09 25.0 800 8.6 — — 2.85 — — — — — —

11/24/09 11.3 800 8.5 9.5 — 2.95 3.29 0.14 2.1 2.6 0.30 —

Boat ramp 3/1610 9.8 820 8.0 9.4 — 2.88 3.64 0.15 3.0 3.3 0.47 —

3/9/11 8.6 830 8.1 10.7 710 2.73 3.79 0.14 5.31 3.14 0.52 2.86

2/8/12 6.1 820 8.2 9.2 700 2.70 3.23 0.30 5.37 2.98 0.52 2.91

4/17/13 13.2 870 7.8 8.6 670 2.84 3.23 0.11 3.89 2.42 0.33 2.02

4/29/14 15.2 850 9.0 10.5 690 2.64 2.61 0.10 3.36 2.18 0.31 2.00

SH1-18 10/23/08 18.0 820 8.7 9.1 690 — 4.60 0.34 2.5 1.6 0.23 1.16

4/29/09 14.3 800 8.6 9.6 — — 2.55 0.22 3.4 2.1 0.26 1.98

8/10/09 25.3 800 8.7 9.1 — 5.67 — — — — — —

3/16/10 9.6 820 8.0 9.6 — 2.87 3.68 0.13 3.0 3.2 0.44 —

3/9/11 8.1 820 8.2 10.7 700 2.66 3.52 0.13 5.47 3.19 0.50 —

2/8/12 5.9 800 8.0 10.7 670 2.76 3.49 0.53 5.45 3.05 0.52 —

4/18/13 12.5 880 8.0 8.7 680 2.55 3.26 0.12 3.92 2.43 0.31 2.39

4/30/14 14.1 840 8.2 — 700 2.78 2.98 0.16 — — — —

1

Total dissolved-gas pressures greater than 1,500 mm Hg exceed the linear calibration of the multi-parameter sonde.

2

Total dissolved-gas pressure determined with advanced diffusion sampler. 

3

WD RJ monitoring well removed in 2013.
28 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water 

from selected sites in Sand Hollow, Washington County, Utah. 

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; Cl/Br, chloride to bromide ratio; μg/L, micrograms per liter; <, less than; 

E, estimated; —, no data available; ft, feet]

Site Name Date

Temperature

(oC)

Specific

conductance

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen

(mg/L)

Dissolvedsolids concentration

(mg/L)

Calcium

(mg/L as Ca)

Magnesium 

(mg/L as Mg) 

Sodium

(mg/L as Na)

Potassium 

(mg/L as K) 

Alkalinity as 

CaCO3

(mg/L)

Sulfate

(mg/L as SO4) 

Groundwater

North Dam 3A 10/8/02 15.9 4,430 8.0 5.0 3,020 150 160 590 2.0 148 1,020

12/18/02 14.7 2,830 8.0 10.8 1,890 110 110 340 3.6 155 584

3/16/10 22.8 864 7.6 1.3 554 65.8 38.0 51.2 3.0 177 187

3/10/11 20.3 834 7.4 0.82 538 68.0 36.7 59.0 3.40 170 181

2/6/12 11.3 820 7.8 — 523 64.8 35.9 58.0 3.36 180 174

4/15/13 25.7 870 — 1.60 571 68.6 39.4 63.7 3.67 181 201

4/29/14 23.6 912 8.0 0.32 572 68.8 39.1 64.0 3.67 183 193

WD 4 12/18/02 18.7 350 7.7 8.1 205 29 17 16 2.1 125 18.1

11/24/09 18.7 338 7.8 9.5 197 28.7 16.6 15.1 2.1 121 20.6

3/15/10 19.7 362 7.7 9.5 217 27.3 16.2 13.3 2.1 129 19.7

3/10/11 19.7 361 7.4 10.5 208 31.2 18.3 15.2 2.2 125 21.8

(

1

) 2/8/12 19.5 549 7.3 8.9 325 44.8 26.6 29.5 2.6 134 68.4

4/15/13 19.9 696 — 22.5 421 50.8 30.8 46.5 2.91 140 103

4/29/14 20.5 796 7.7 10.9 486 56.3 33.2 54.3 2.94 138 119

WD 5 12/17/02 17.6 530 7.8 6.6 311 45 22 29 1.8 138 46.8

11/24/09 16.9 512 8.5 7.2 298 43.1 21.4 27.2 1.8 136 46.4

3/15/10 21.0 543 7.7 8.1 313 43.3 22.2 24.9 2.0 136 45.8

3/10/11 19.5 510 7.4 8.0 298 45.7 22.1 26.9 2.0 141 43.8

4/16/13 19.8 502 7.6 9.1 298 43.7 22.9 27.2 1.92 139 47.6

4/30/14 20.1 522 7.4 — 319 44.5 22.8 29.8 1.92 136 49.7

WD 6 9/9/02 19.4 290 7.7 — 167 37 3.4 12 1.6 93 24

4/30/09 19.2 1,040 7.7 22.0 660 98.5 9.0 113 1.6 169 220

11/23/09 18.9 968 7.9 15.3 629 93.6 8.7 101 1.5 161 210

3/15/10 19.2 923 7.5 14.4 618 94.1 8.6 86.3 1.5 166 211

3/9/11 19.1 896 7.5 11.2 577 106 11.5 73.4 1.49 157 208

(replicate) 3/9/11 19.1 896 7.5 11.2 590 106 11.5 72.5 1.47 153 208

2/7/12 19.1 807 7.3 15.6 542 103 11.5 58.7 1.63 152 200

4/16/13 18.9 814 7.0 11.8 513 100 12.9 56.9 1.72 144 200

4/29/14 19.0 814 7.3 10.1 516 99 12.7 55.9 1.91 122 186

WD RJ 12/17/02 18.2 530 7.7 6.4 309 47 22 27 2.3 137 46

3/15/10 19.6 560 7.6 8.0 338 46.6 22.6 25.1 2.3 139 47.9

3/9/11 19.6 539 7.3 7.5 324 48.9 23.1 28 2.4 143 47.3

WD 7 9/10/01 18.8 380 7.8 9.8 — 37 12 25 1.9 137 28

WD 8 9/9/02 18.9 305 7.9 — 173 37 10 8.9 2.3 116 15

2/7/12 18.5 251 7.1 20.8 179 47.1 4.0 6.6 1.6 95 25.9

4/16/13 18.5 353 7.1 21.1 247 58.6 4.6 11.9 1.7 103 47.2

4/30/14 18.7 379 7.8 25.9 236 58.1 4.8 13.5 1.8 102 50.9

WD 9 9/11/02 19.5 335 7.9 — 189 36 7 22 1.6 120 18

4/27/09 16.6 832 7.4 1.8 549 78.2 30.9 53.7 3.4 157 200

3/15/10 16.4 842 7.3 1.7 543 71.8 31.0 52.2 3.3 157 200

(replicate) 3/15/10 16.4 842 7.3 1.7 545 67.4 28.8 51.0 3.2 155 198

3/8/11 16.1 902 7.3 0.5 531 73.8 33.9 60.9 3.58 161 188

2/7/12 16.3 826 7.1 0.4 533 66.4 34.2 56.6 3.45 162 185

4/15/13 16.1 855 7.3 0.60 545 67.0 38.4 62.1 3.73 167 207

4/28/14 16.1 877 7.0 0.16 570 67.7 38.5 63.4 3.72 151 191
Groundwater and Surface-Water Quality in Sand Hollow 29

Table 3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water 

from selected sites in Sand Hollow, Washington County, Utah.—Continued 

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; Cl/Br, chloride to bromide ratio; μg/L, micrograms per liter; <, less than; 

E, estimated; —, no data available; ft, feet]

Site Name Chloride 

(mg/L as Cl) 

Fluoride 

(mg/L as F) 

Bromide 

(mg/L as Br) Cl/Br

Silica

(mg/L as 

SiO2) 

Iron

(μg/L as Fe) 

Manganese 

(μg/L as 

Mn) 

Arsenic 

(μg/L as As) 

Nitrogen

(nitrite + nitrate) 

(mg/L as N) 

Nitrogen, 

nitrite

(mg/L as N) 

Nitrogen, 

ammonia 

(mg/L as N) 

Phosphorus 

(orthophosphate)

(mg/L as P)

Groundwater

North Dam 3A 744 0.90 41.2 18 13.0 <30 <5 90.1 17.8 <0.008 0.03 0.030

476 0.79 2.44 195 14.0 <30 <5 63.9 14.3 <0.008 <0.04 0.030

55.2 0.43 0.06 882 15.7 <6 3.19 35.2 <0.04 E0.001 E0.01 0.035

58.3 0.45 0.06 936 15.5 <3.2 3.48 35.2 0.03 <0.001 0.07 0.033

55.4 0.39 0.07 778 16.3 12.6 17.3 34.0 0.07 <0.001 0.21 0.037

60.4 0.34 0.08 715 15.0 4.2 26.1 35.6 0.04 <0.001 0.31 0.038

60 0.37 0.06 938 15.0 <4 21.2 34.5 0.04 <0.001 0.38 0.038

WD 4 18.8 0.23 0.08 235 14 <10 <2 13.2 2.35 <0.008 <0.04 0.02

17.2 0.23 0.10 179 14.3 E3.8 <0.2 14.7 2.29 <0.002 <0.02 0.03

17.9 0.25 0.10 184 15.7 <6 <0.2 14.4 2.29 <0.002 <0.02 0.03

20.2 0.25 0.14 150 15.3 <3.2 0.19 13.7 2.25 <0.001 <0.01 0.03

(

1

) 54.5 0.20 0.42 128 15.7 4.5 0.37 11.9 2.21 <0.001 <0.01 0.02

72.9 0.19 0.54 135 14.5 7.2 0.75 12.2 2.16 <0.001 <0.01 0.025

93.6 0.21 0.63 149 14.5 <4.0 0.26 11.8 2.22 <0.001 <0.01 0.022

WD 5 44.8 0.29 0.16 280 13 <10 E1 9.1 4.18 <0.008 <0.04 E0.01

37.9 0.27 0.23 168 13.4 <6 <0.2 9.6 4.61 <0.002 <0.02 0.02

39.2 0.28 0.24 164 15 <6 <0.2 9.0 4.60 <0.002 <0.02 0.01

38.2 0.31 0.21 179 14.3 <3.2 0.19 9.3 4.60 <0.001 <0.01 0.01

40.3 0.24 0.22 187 13.6 4.8 0.41 9.2 4.73 <0.001 <0.01 0.012

42.8 0.26 0.23 189 13.7 <4.0 <0.02 9.4 4.73 <0.001 <0.01 0.010

WD 6 15.0 E0.08 0.16 94 13.3 <10 E2 2.0 E1.6 <0.008 <0.04 0.020

92.5 0.32 0.31 295 13.2 <4 0.23 3.3 1.20 <0.002 <0.02 0.011

80.3 0.30 0.28 286 12.2 <6 <0.2 3.3 1.06 <0.002 <0.02 0.012

77.9 0.32 0.24 322 13.4 20.8 0.32 3.0 0.97 <0.002 <0.02 0.013

63.5 0.30 0.14 457 13.5 6.3 0.40 2.8 0.71 <0.001 <0.01 0.010

 (replicate) 63.3 0.32 0.14 455 13.6 6.1 0.31 2.8 0.70 0.001 <0.01 0.009

54.8 0.22 0.08 684 13.9 17.6 0.75 2.3 0.47 <0.001 0.02 0.011

57.2 0.18 0.07 840 12.9 20.3 0.88 2.3 0.34 <0.001 <0.01 0.009

53.8 0.18 0.06 928 12.7 10.5 0.50 2.1 0.32 <0.001 <0.01 0.012

WD RJ 47.8 0.51 0.20 239 14 <10 <2 7.9 3.28 <0.008 <0.04 0.01

47.2 0.51 0.27 176 15.3 <6 <0.2 8.3 3.28 <0.002 E0.01 0.02

47.4 0.54 0.24 196 14.5 <3.2 0.18 8.5 3.34 <0.001 <0.01 0.01

WD 7 18.0 0.3 0.13 139 14 <10 <3 6.0 3.80 <0.008 <0.04 0.02

WD 8 10.1 0.1 0.07 144 14 <10 <2 6.0 3.90 <0.008 <0.04 0.02

13.6 0.1 0.08 173 13.8 7.4 0.99 11.5 3.33 <0.001 <0.01 0.02

19.4 0.07 0.12 169 13.4 11.7 2.25 10.6 3.52 <0.001 <0.01 0.014

20.5 0.07 0.10 199 13.5 9.3 2.07 10.0 3.60 <0.001 <0.01 0.015

WD 9 21.4 0.5 0.06 357 15 9 15 12.0 0.48 <0.008 <0.04 0.01

53.4 0.27 0.06 900 12.2 5 3.72 5.8 0.09 <0.002 <0.02 0.013

56.6 0.24 0.05 1,040 12.1 13.6 0.68 6.1 0.09 <0.002 <0.02 0.014

(replicate) 56.3 0.27 0.05 1,083 11.9 13.5 0.57 6.1 0.09 <0.002 <0.02 0.013

58.7 0.28 0.04 1,310 11.6 6.7 0.47 6.1 0.05 0.002 <0.01 0.011

55.6 0.27 0.06 927 11.3 26.3 2.53 5.9 0.06 <0.001 0.01 0.010

62.1 0.24 0.08 764 10.6 22.4 2.06 5.9 0.04 <0.001 0.01 0.011

60.7 0.25 0.06 1,029 10.7 16.6 2.64 5.9 <0.04 0.001 0.02 0.013
30 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water 

from selected sites in Sand Hollow, Washington County, Utah.—Continued 

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; Cl/Br, chloride to bromide ratio; μg/L, micrograms per liter; <, less than; 

E, estimated; —, no data available; ft, feet]

Site Name Date

Temperature

(oC)

Specific

conductance

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen

(mg/L)

Dissolvedsolids concentration

(mg/L)

Calcium

(mg/L as Ca)

Magnesium 

(mg/L as Mg) 

Sodium

(mg/L as Na)

Potassium 

(mg/L as K) 

Alkalinity as 

CaCO3

(mg/L)

Sulfate

(mg/L as SO4) 

WD 11 5/3/04 18.4 677 7.7 21.5 440 69.0 31.6 68.1 1.7 187 89.7

4/30/09 15.9 843 7.7 19.4 557 79.2 38.6 49.6 2.4 186 187

11/23/09 16.3 835 7.9 13.2 553 74.0 35.7 49.4 2.2 171 191

3/15/10 16.2 837 7.7 10.3 552 67.2 34.3 45.6 2.2 178 190

3/8/11 16.0 891 7.7 9.9 533 75.2 36.6 51.2 2.15 186 179

2/7/12 15.4 798 7.4 9.5 529 74.6 34.5 51.6 2.05 193 169

4/15/13 16.1 832 6.7 11.4 519 71.5 34.3 53.9 2.14 194 166

(replicate) 4/15/13 16.1 832 6.7 11.4 527 73.9 34.5 55 2.08 194 167

4/28/14 16.2 818 7.3 3.1 520 75.1 32.7 55.3 1.98 154 162

WD 12 9/12/02 — 335 7.9 — 202 37 13 9.0 1.6 115 19

(

1

) 3/9/11 19.9 1,670 7.1 13.4 1,150 132 57.3 150 3.0 116 440

(

1

) 2/8/12 19.3 2,100 7.2 9.2 1,510 173 75.0 188 3.5 124 665

4/16/13 19.0 2,390 7.3 17.8 1,730 192 83.7 237 3.62 131 802

4/28/14 20.5 2,380 7.4 — 1,750 178 77.1 249 3.59 115 783

WD 13 8/30/01 19.9 275 8.1 — — 24 16 8.4 1.5 109 12

WD 14 12/18/02 19.3 385 7.7 8.3 220 36 20 10 2.4 122 29

1

WD 15 4/28/09 18.9 707 8.0 17.6 414 41.0 35.9 48.0 2.1 191 71.4

(

1

) 11/23/09 18.8 729 8.3 14.5 436 43.3 33.6 57.5 2.1 184 80.4

(

1

) 3/16/10 19.1 734 7.9 11.5 458 42.0 33.8 51.6 2.1 188 84.7

(

1

) 3/8/11 19.1 816 8.0 12.5 469 45.9 39.3 60.6 2.1 182 91.3

(

1

) 2/7/12 19.1 821 8.0 18.8 473 42.2 38.2 67.8 2.1 169 102

4/17/13 18.9 895 — 17.8 531 50.2 36.7 82.1 2.3 170 122

4/29/14 18.8 969 7.7 11.7 583 52.4 38.0 88.4 2.3 169 132

(replicate) 4/29/14 18.8 969 7.7 11.7 560 52.2 38.0 88.5 2.34 167 128

WD 16 4/27/09 18.7 444 7.7 8.7 255 44.1 23.0 13.2 1.9 136 33.6

11/24/09 18.7 449 7.7 7.1 260 42.3 21.9 13.7 1.7 129 33.8

3/16/10 18.7 441 7.6 5.1 262 41.7 22.4 12.3 1.8 135 33.0

3/8/11 18.5 478 7.7 4.1 241 45.4 23.0 13.6 1.9 135 32.0

4/17/13 18.7 432 — 8.1 269 43.1 22.7 13.4 1.76 137 34.4

4/29/14 18.7 446 7.4 3.7 253 42.5 22.2 14.1 1.81 132 34.3

WD 17 4/16/13 19.4 545 7.6 11.0 332 51.3 20.5 34.0 2.0 141 56.1

WD 18 4/28/09 19.7 500 7.4 7.5 280 45.2 19.5 24.5 1.9 143 40.4

3/16/10 19.3 467 7.4 4.9 296 43.7 19.2 21.3 1.8 155 37.9

3/9/11 19.2 476 7.3 7.8 293 46.0 19.2 23.8 1.7 138 38.0

1

WD 19 3/10/11 19.1 2,030 7.5 9.8 1,120 120 41.6 216 2.8 210 282

(

1,2) 2/7/12 18.6 1,900 7.5 6.8 1,150 123 43.1 181 2.9 246 349

WD 20 4/29/09 19.7 331 7.5 6.7 188 30.2 17.4 11.7 2.1 120 20.8

3/17/10 19.4 344 7.4 7.2 214 28.0 16.1 10.5 1.9 120 19.6

3/10/11 18.9 332 7.3 7.2 181 31.5 17.7 12.1 2.0 116 18.9

Well 1 at 890 ft 5/6/03 — 350 7.8 — 216 31 21 7.4 2.9 130 19

Well 2 at 400 ft 10/10/02 — 365 8.0 — 208 30 21 9.0 2.1 129 20

Well 2 at 615 ft 10/10/02 — 365 8.1 — 190 30 21 6.5 2.5 131 16

Well 2 at 750 ft 10/10/02 — 370 8.1 — 196 30 22 6.8 2.7 134 18

Well 4 8/29/01 20.1 480 8.0 — — 36 19 38 2.0 128 58

9/11/02 19.1 495 8.1 — 297 36 19 35 2.0 124 56

Well 8 at 245 ft 10/8/02 19.0 550 7.5 — 323 49 20 35 2.1 141 70
Groundwater and Surface-Water Quality in Sand Hollow 31

Table 3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water 

from selected sites in Sand Hollow, Washington County, Utah.—Continued

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; Cl/Br, chloride to bromide ratio; μg/L, micrograms per liter; <, less than; 

E, estimated; —, no data available; ft, feet]

Site Name Chloride 

(mg/L as Cl) 

Fluoride 

(mg/L as F) 

Bromide 

(mg/L as Br) Cl/Br

Silica

(mg/L as 

SiO2) 

Iron

( g/L as Fe) μ

Manganese 

( g/L as μ

Mn) 

Arsenic 

( g/L as As) μ

Nitrogen

(nitrite + nitrate) 

(mg/L as N) 

Nitrogen, 

nitrite

(mg/L as N) 

Nitrogen, 

ammonia 

(mg/L as N) 

Phosphorus 

(orthophosphate)

(mg/L as P)

WD 11 49.8 0.40 0.25 199 14.5 <6 <0.8 15.3 3.06 <0.008 <0.04 0.020

49.6 0.35 0.07 687 14.0 <4 <0.2 9.6 0.99 <0.002 <0.02 0.014

49.8 0.31 0.07 711 13.1 <6 <0.2 10.3 0.67 <0.002 <0.02 0.013

51.8 0.32 0.07 781 14.3 18.6 0.26 10.0 0.70 <0.002 <0.02 0.016

53.6 0.31 0.07 811 14.7 4.4 0.26 9.6 0.48 0.001 <0.01 0.012

53.3 0.26 0.07 733 15.3 11.4 0.34 9.2 0.48 <0.001 <0.01 0.012

58.1 0.19 0.08 720 14.9 14.5 0.27 8.9 0.51 <0.001 <0.01 0.012

(replicate) 58.2 0.19 0.09 658 16.2 17.9 0.86 8.8 0.52 <0.001 <0.01 0.011

57.8 0.23 0.07 838 15.2 6.11 0.34 9.0 0.56 <0.001 <0.01 0.014

WD 12 20.0 0.2 0.08 250 15 <10 1 10.0 2.10 <0.008 <0.04 0.02

(

1

) 196 0.10 1.16 169 17.0 <3.2 0.35 8.2 1.89 <0.001 <0.01 0.009

(

1

) 264 0.12 1.54 171 17.1 14.5 <0.32 7.3 1.92 <0.001 0.01 0.008

290 0.09 1.69 172 16.8 <8 <0.32 6.9 1.66 <0.001 <0.01 0.008

265 0.14 1.46 182 16.9 <8 <0.4 7.2 1.43 <0.001 <0.01 0.007

WD 13 12.1 E0.1 0.05 258 12 <10 2 6.3 2.00 <0.006 <0.04 0.02

WD 14 28.3 0.25 0.11 257 13 <10 <2 15.6 2.18 <0.008 <0.04 0.02

1

WD 15 57.0 0.41 0.33 174 15 <4 0.7 28.3 3.32 E0.001 <0.02 0.02

(

1

) 63.5 0.41 0.36 178 14 <6 0.1 28.9 3.46 <0.002 <0.02 0.02

(

1

) 68.8 0.42 0.36 189 15 <6 <0.2 27.5 3.54 <0.002 <0.02 0.02

(

1

) 77.0 0.40 0.43 180 14.5 <3.2 <0.16 27.6 3.78 <0.001 <0.01 0.02

(

1

) 88.2 0.37 0.50 176 14.1 <3.2 2.08 26.7 4.32 <0.001 0.02 0.02

108 0.31 0.56 193 14.0 6.6 0.65 24.7 3.85 <0.001 <0.01 0.025

117 0.34 0.58 203 13.7 <4 0.23 24.9 3.80 <0.001 <0.01 0.021

(replicate) 114 0.34 0.58 196 13.7 <4 <0.2 25.0 3.82 <0.001 <0.01 0.020

WD 16 29.1 0.25 0.17 170 14 <4 <0.2 6.2 4.48 E0.001 <0.02 0.01

28.7 0.21 0.18 158 13 <6 <0.2 6.1 4.50 <0.002 <0.02 0.01

29.9 0.22 0.18 169 13.8 <6 0.79 5.9 4.44 <0.002 <0.02 0.01

29.4 0.28 0.18 166 13.6 <3.2 <0.16 6.0 4.43 <0.001 <0.01 0.01

30.8 0.19 0.19 164 12.9 <4 0.39 6.0 4.60 <0.001 <0.01 0.006

31 0.21 0.19 165 12.7 <4 <0.2 6.1 4.57 <0.001 <0.01 0.005

WD 17 55.2 0.34 0.30 187 15.0 20.8 0.57 12.8 3.06 <0.001 <0.01 0.015

WD 18 36.1 0.37 0.21 171 16 16 1 10.6 3.15 0.002 <0.02 0.01

34.1 0.33 0.22 154 15.8 <6 <0.2 10.0 3.14 <0.002 <0.02 0.02

35.1 0.36 0.22 163 15.3 <3.2 <0.16 10.2 3.12 <0.001 <0.01 0.01

1

WD 19 252 0.37 1.17 215 17.1 <3.2 <0.16 9.9 8.75 <0.001 <0.01 0.02

(

1,2) 192 0.34 0.89 216 17.5 5.2 0.16 9.3 9.38 <0.001 <0.01 0.03

WD 20 16.4 0.28 0.09 178 14 53 1 7.7 2.41 E0.001 <0.02 0.02

17.2 0.24 0.09 185 14.2 <6 0.53 8.0 2.40 <0.002 <0.02 0.02

16.9 0.22 0.09 197 14.3 <3.2 <0.16 7.6 2.37 <0.001 <0.01 0.02

Well 1 at 890 ft 16.9 1.08 — — 11 11 19 9.1 3.37 0.008 0.03 0.01

Well 2 at 400 ft 17.8 0.2 — — 11 10 12 2.6 3.41 0.008 0.10 0.02

Well 2 at 615 ft 13.2 0.23 — — 11 27 6 4.6 3.73 0.004 <0.04 0.02

Well 2 at 750 ft 14.3 0.23 0.10 143 12 19 3 5.9 3.84 <0.008 0.03 0.02

Well 4 44.4 E0.1 0.20 218 13 <10 <3 7.1 1.50 <0.006 <0.04 0.02

42.0 0.2 0.17 247 13 <10 <2 8.0 2.10 <0.008 <0.04 0.02

Well 8 at 245 ft 38.7 0.29 0.15 258 14 <10 5 16.6 1.72 0.03 0.18 0.01
32 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Table 3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water 

from selected sites in Sand Hollow, Washington County, Utah.—Continued

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; Cl/Br, chloride to bromide ratio; μg/L, micrograms per liter; <, less than; 

E, estimated; —, no data available; ft, feet]

Site Name Date

Temperature

(oC)

Specific

conductance

(μS/cm)

pH

(standard 

units)

Dissolved 

oxygen

(mg/L)

Dissolvedsolids concentration

(mg/L)

Calcium

(mg/L as Ca)

Magnesium 

(mg/L as Mg) 

Sodium

(mg/L as Na)

Potassium 

(mg/L as K) 

Alkalinity as 

CaCO3

(mg/L)

Sulfate

(mg/L as SO4) 

Well 9 8/30/01 20.7 285 7.9 — 179 27 16 7.0 1.9 115 13

9/11/02 19.5 740 8.2 — 458 53 28 52 2.3 124 126

3/10/11 15.3 777 7.6 3.8 535 60.2 36.1 54.2 3.32 151 175

Sand Hollow Reservoir water

Haul road 9/10/02 24.2 1,000 8.8 — 669 63 43 71 5.3 92 300

Boat ramp 5/5/04 17.3 710 8.2 8.5 442 63 26 45 3.3 161 122

4/29/09 16.1 790 8.4 7.0 503 54.3 37.4 53.7 4.0 147 189

11/24/09 11.3 797 8.5 9.5 502 40.9 39.8 62.9 4.3 108 212

3/16/10 9.8 817 8.0 9.4 534 43.5 38.4 57.6 4.6 120 211

3/9/11 8.6 827 8.1 10.7 534 60.2 39.2 62.2 4.5 142 212

2/6/12 6.1 821 8.2 9.2 534 53.6 39.8 61.3 4.3 138 213

4/17/13 13.2 874 7.8 8.6 562 56.5 42.7 66.0 4.89 149 223

4/29/14 15.2 846 9.0 10.5 535 52.0 40.8 66.2 4.66 134 207

SH 1-18 4/29/09 14.3 800 8.6 9.6 502 56.1 37.2 53.6 4.2 146 190

8/10/09 25.3 800 8.7 9.1 501 42.6 38.3 60.5 4.3 110 —

3/16/10 9.6 819 8.0 9.6 525 45.9 40.8 58.6 4.7 124 211

3/9/11 8.1 820 8.2 10.7 528 60.1 39.6 61.2 4.43 140 210

2/8/12 5.9 801 8.0 10.7 526 54.2 39.5 59.6 4.28 140 214

4/18/13 12.5 883 8.0 8.7 553 58.1 43.1 67.1 4.73 148 223

4/30/14 14.1 835 8.2 — 531 51.7 40.6 65.8 4.38 136 200

1

 High or increasing dissolved-solids concentrations but low Cl/Br ratios indicate groundwater is affected by flushing of naturally occurring solutes in vadose zone prior to reservoir 

construction. 

2

 Replicate sample not reported because submersible pump was re-installed for sample collection and dissolved-solids concentration differed by more than 10 percent. 
Groundwater and Surface-Water Quality in Sand Hollow 33

Table 3. Field measurements and major ions, selected trace elements, and nutrient concentrations in groundwater and surface water 

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; Cl/Br, chloride to bromide ratio; μg/L, micrograms per liter; <, less than; 

E, estimated; —, no data available; ft, feet]

Site Name Chloride 

(mg/L as Cl) 

Fluoride 

(mg/L as F) 

Bromide 

(mg/L as Br) Cl/Br

Silica

(mg/L as 

SiO2) 

Iron

( g/L as Fe) μ μ μ

from selected sites in Sand Hollow, Washington County, Utah.—Continued

Manganese 

( g/L as 

Mn) 

Arsenic 

( g/L as As) 

Nitrogen

(nitrite + nitrate) 

(mg/L as N) 

Nitrogen, 

nitrite

(mg/L as N) 

Nitrogen, 

ammonia 

(mg/L as N) 

Phosphorus 

(orthophosphate)

(mg/L as P)

Well 9 13.0 0.20 0.07 186 13 <10 <3 12.4 2.40 <0.006 <0.04 0.02

72.2 0.20 0.28 258 14.2 250 6.0 17.0 2.20 <0.008 <0.04 0.020

53.8 0.33 0.08 706 11.7 13.5 2.61 13.8 0.56 <0.001 <0.01 0.009

Sand Hollow Reservoir water

Haul road 76.0 0.30 0.02 3,800 4.9 <10 <2 2.0 0.04 <0.008 <0.04 0.02

Boat ramp 50.0 0.21 0.01 5,000 7.3 <6 1.3 1.1 — — — —

54.9 0.31 0.04 1,227 2.9 <4 0.3 1.4 0.04 0.002 <0.02 0.008

60.4 0.28 0.05 1,313 1.5 <6 0.2 1.6 <0.04 <0.002 <0.02 0.008

61.7 0.30 0.04 1,374 1.4 6.3 1.7 1.3 E0.03 <0.002 0.02 <0.008

57.0 0.30 0.04 1,390 4.0 <3.2 2.0 1.13 0.10 0.004 0.03 <0.004

58.3 0.27 0.05 1,108 4.2 <3.2 0.86 1.01 0.12 0.001 0.01 <0.004

65.8 0.25 0.08 875 2.9 5.2 1.22 <0.04 0.09 0.007 0.04 <0.004

65.3 0.27 0.05 1,280 1.2 <4 0.74 1.3 0.04 0.002 <0.01 <0.004

SH 1-18 54.6 0.27 0.04 1,318 3.0 <4 0.4 1.4 0.04 0.003 0.13 0.008

— 0.24 — — 1.3 3 0.3 1.6 <0.04 <0.002 <0.02 0.008

61.6 0.30 0.04 1,417 1.2 6.2 1.8 1.4 E0.02 <0.002 0.02 <0.008

57.2 0.30 0.04 1,546 3.9 <3.2 2.10 1.12 0.10 0.005 0.02 <0.004

56.5 0.27 0.05 1,060 4.1 <3.2 1.31 1.04 0.09 0.001 0.02 <0.004

65.3 0.25 0.07 898 2.8 2.1 0.82 1.2 0.09 0.007 0.03 <0.004

63.2 0.26 0.05 1,170 1.1 <4 0.45 1.2 0.04 0.001 <0.01 <0.004
34 Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah

Summary

Since its inception in 2002, diversions to Sand Hollow 

Reservoir from the nearby Virgin River generally have 

resulted in rising reservoir stage, ranging from about 

3,000 feet in 2002 to a maximum of about 3,060 feet in 2006, 

which then fluctuated between about 3,040 and 3,060 feet 

from 2008 through 2014. Similarly, groundwater levels 

in monitoring wells closest to the reservoir generally rose 

between 2002 and 2006, and then fluctuated with reservoir 

altitude and pumpage rate from nearby production wells. 

Water levels in monitoring wells farther from the reservoir 

were still rising through 2014.

About 29,000 acre-feet (acre-ft) of groundwater were withdrawn between 2004 and 2014 from production wells located 

near Sand Hollow Reservoir. French drains, installed to 

capture shallow seepage near the reservoir, were also pumped 

as they filled with water. About 8,000 acre-ft of groundwater 

were pumped from the North Dam drain between 2003 and 

2014. This water initially was returned to the reservoir, but 

since 2007, has been used by Sand Hollow Resort for irrigation. About 2,100 acre-ft of water were pumped from the 

West Dam drain back into the reservoir from 2005 through 

2014. In 2006, the West Dam Spring drain was constructed 

and has largely replaced the function of the West Dam drain. 

About 21,000 acre-ft were pumped from this drain from 2006 

through 2014 into the Washington County Water Conservancy 

District’s municipal supply system.

Total annual surface-water inflow to Sand Hollow Reservoir ranged from about 56,000 acre-ft in 2005 to 800 acre-ft 

in 2007. Total inflow from 2002 through 2014 was about 

216,000 acre-ft. The general increase in reservoir waterlevel altitude and surface area from 2002 to 2007 resulted in 

a steady increase in the volume of annual evaporation from 

about 1,000 to about 6,600 acre-ft through 2006, which then 

leveled off from 2007 through 2014. Total estimated cumulative evaporative loss from 2002 through 2014 was about 

70,000 acre-ft. During this same period, annual reservoir 

recharge to the underlying Navajo Sandstone aquifer fluctuated between about 5,000 and 18,000 acre-ft. Total calculated reservoir recharge from 2002 through 2014 was about 

127,000 acre-ft with a 2 standard deviation uncertainty of 

11,900 acre-ft. From 2002 through 2014, calculated monthly 

recharge volumes ranged from 50 to almost 3,500 acre-ft, 

and average daily recharge rates (calculated for each month) 

ranged from 0.001 to 0.43 feet. 

Annual water-quality sampling, including field parameters, 

chemistry, and environmental tracers (tritium, chlorofluorocarbons, sulfur hexafluoride) was continued during 2013 

and 2014. The most significant changes occurred at monitoring wells WD 4 (2,600 feet from the reservoir) and WD 

12 (1,000 feet away), where increases in salinity (specific 

conductance) and dissolved oxygen (and environmental tracer 

concentrations at WD 4) indicate rising groundwater levels 

and mobilization of vadose-zone salts, likely a precursor to the 

arrival of reservoir recharge. At wells WD 9 (55 feet away) 

and WD 11 (160 feet away), field parameters, and waterquality and environmental tracer data indicate that reservoir 

recharge arrived several years prior to 2014. At well WD 6 

(1,000 feet away), salinity, chloride to bromide ratios, and 

environmental tracer data all indicate the recent arrival of reservoir recharge. Although well WD 8 is located only 500 feet 

from the reservoir, it is downgradient of an area of high natural recharge on Sand Mountain and may lie along a groundwater boundary between the two recharge mounds; relatively 

high concentrations of modern environmental tracers may be 

caused by natural recharge. At WD 15 and WD 16 (nested 

wells located 2,400 feet from the reservoir), water-quality and 

environmental tracer data indicate a rising water table, but no 

arrival yet of reservoir recharge. 
References Cited 35

References Cited 

Heilweil, V.M., and Marston, T.M., 2011, Assessment of 

managed aquifer recharge from Sand Hollow Reservoir, 

Washington County, updated to conditions in 2010: U.S. 

Geological Survey Scientific Investigations Report 2011-

5142, 39 p.

Heilweil, V.M., and McKinney, T.S., 2007, Net-infiltration 

map of the Navajo Sandstone outcrop area in western Washington County, Utah: U.S. Geological Survey Scientific 

Investigations Map 2988.

Heilweil, V.M., McKinney, T.S., Zhdanov, M.S., and Watt, 

D.E., 2007, Controls on the variability of net infiltration 

to desert sandstone: Water Resources Research, v. 43, 

W07431, DOI:10.1029/2006WR005113, 15 p.

Heilweil, V.M., Ortiz, G., and Susong, D.D., 2009a, Assessment of managed aquifer recharge at Sand Hollow Reservoir, Washington County, Utah, updated to conditions 

through 2007: U.S. Geological Survey Scientific Investigations Report 2009-5050, 19 p.

Heilweil, V.M., and Solomon, D.K., 2004, Millimeter- to 

kilometer-scale variations in vadose-zone bedrock solutes: 

Implications for estimating recharge in arid settings, in

Phillips, F., Scanlon, B., and Hogan, J., eds., Groundwater 

recharge in a desert environment: The southwestern United 

States: Water Science and Application, v. 9, Washington, 

D.C., American Geophysical Union, p. 49–67.

Heilweil, V.M., Solomon, D.K., and Gardner, P.M., 2006, 

Borehole environmental tracers for evaluating net infiltration and recharge through desert bedrock: Vadose Zone 

Journal, v. 5, p. 98–120.

Heilweil, V.M., Solomon, D.K., and Ortiz, G., 2009b, Silt 

and gas accumulation beneath an artificial recharge spreading basin, southwestern Utah, U.S.A: Boletin Geologico y 

Minero, v. 120, no. 2, p. 185–195.

Heilweil, V.M., Solomon, D.K., Perkins, K.S., and Ellett, 

K.M., 2004, Gas-partitioning tracer test to quantify trapped 

gas during recharge: Ground Water, v. 42, no. 4, p. 589–600.

Heilweil, V.M., and Susong, D.D., 2007, Assessment of 

artificial recharge at Sand Hollow Reservoir, Washington 

County, Utah, updated to conditions through 2006: U.S. 

Geological Survey Scientific Investigations Report 2007-

5023, 14 p.

Heilweil, V.M., Susong, D.D., Gardner, P.M., and Watt, D.E, 

2005, Pre- and post-reservoir ground-water conditions and 

assessment of artificial recharge at Sand Hollow, Washington County, Utah, 1995–2005: U.S. Geological Survey 

Scientific Investigations Report 2005-5185, 74 p.

Heilweil, V.M., and Watt, D.E., 2011, Trench infiltration for 

managed aquifer recharge to permeable bedrock: Hydrological Processes 25, DOI:10.1002/hyp.7833, p. 141–151.

Marston, T.M., and Heilweil, V.M., 2012, Numerical simulation of groundwater movement and managed aquifer 

recharge from Sand Hollow Reservoir, Hurricane Bench 

area, Washington County, Utah: U.S. Geological Survey 

Scientific Investigations Report 2012-5236, 34 p.

Marston, T.M., and Heilweil, V.M., 2013, Assessment of managed aquifer recharge at Sand Hollow Reservoir, Washington County, Utah, updated to conditions in 2012: U.S. 

Geological Survey Scientific Investigations Report 2013-

5057, 40 p.

McGuinness, J.L., and Bordne, E.F., 1971, A comparison of 

lysimeter-derived potential evapotranspiration with computed values: U.S. Department of Agriculture Technical 

Bulletin 1472, Agricultural Research Service, Washington, 

D.C., 71 p.

Rosenberry, D.O., Winter, T.C., Buso, D.C., and Likens, G.E., 

2007, Comparison of 15 evaporation methods applied to a 

small mountain lake in the northeastern USA: Journal of 

Hydrology, v. 340, p. 149–166.

Wilde, F.D., and Radtke, D.B., 1998, National field manual for 

the collection of water-quality data―Field measurements: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6, 233 p. 
For additional information, contact:

Director, Utah Water Science Center 

U.S. Geological Survey

2329 Orton Circle

Salt Lake City, Utah 84119

http://ut.water.usgs.gov/

Marston and Heilweil—Assessment of Managed Aquifer Recharge at Sand Hollow Reservoir, Washington County, Utah, Updated to Conditions 

through 2014—OFR 2016–1078

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20161078