U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5209

Prepared in cooperation with the U.S. Army Corps of Engineers–Fort Worth District, the Texas 

Water Development Board, the Guadalupe-Blanco River Authority, and the Edwards Aquifer 

Authority

A Preliminary Assessment of Streamflow Gains and Losses 

for Selected Stream Reaches in the Lower Guadalupe River 

Basin, Texas, 2010–12
Cover, Photograph looking downstream from U.S. Geological Survey (USGS) streamflow-gaging 

station 08169840 Guadalupe River at Oak Forest, Texas, August 9, 2011. Photograph by Mark A. 

Warzecha, USGS.
A Preliminary Assessment of Streamflow 

Gains and Losses for Selected Stream 

Reaches in the Lower Guadalupe River 

Basin, Texas, 2010–12

By Loren L. Wehmeyer, Karl E. Winters, and Darwin J. Ockerman

Prepared in cooperation with the U.S. Army Corps of Engineers–Fort Worth 

District, the Texas Water Development Board, the Guadalupe-Blanco River 

Authority, and the Edwards Aquifer Authority

Scientific Investigations Report 2013–5209

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

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

Suggested citation:

Wehmeyer, L.L., Winters, K.E., and Ockerman, D.J., 2013, A preliminary assessment of streamflow 

gains and losses for selected stream reaches in the lower Guadalupe River Basin, Texas, 2010–12: U.S. 

Geological Survey Scientific Investigations Report 2013–5209, 30 p., http://dx.doi.org/10.3133/20135209. 

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

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

ISBN 978 1 4113 3725 1
iii

Contents

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

Introduction ....................................................................................................................................................2

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

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

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

Streamflow Gains and Losses ..................................................................................................................17

Streamflow Gains and Losses during March 15–21, 2010 ..........................................................22

Streamflow Gains and Losses during April 10–16, 2011 ..............................................................22

Streamflow Gains and Losses during August 19–25, 2011 ..........................................................25

Streamflow Gains and Losses during September 22–28, 2012 ...................................................25

Summary .......................................................................................................................................................28

References Cited .........................................................................................................................................28

Figures

1. Map showing U.S. Geological Survey streamflow-gaging stations and stream 

reaches defined for assessment of streamflow gains and losses in the lower 

Guadalupe River Basin, south-central Texas ..........................................................................3

2. Map showing surficial geology and U.S. Geological Survey streamflow-gaging 

stations in the lower Guadalupe River Basin, south-central Texas ....................................6

3. Map showing aquifer systems and U.S. Geological Survey streamflow-gaging 

stations in the lower Guadalupe River Basin, south-central Texas ....................................7

4. Map showing location of inflow sites and U.S. Geological Survey streamflowgaging stations used in the lower Guadalupe River Basin gain and loss study .............13

5. Map showing water right permit locations and U.S. Geological Survey 

streamflow-gaging stations, lower Guadalupe River Basin, south-central Texas .........14

6. Map showing streamflow gains and losses, March 15–21, 2010, lower 

Guadalupe River Basin, south-central Texas ........................................................................23

7. Maps showing streamflow gains and losses, April 10–16, 2011, lower 

Guadalupe River Basin, south-central Texas ........................................................................24

8. Maps showing streamflow gains and losses, August 19–25, 2011, lower 

Guadalupe River Basin, south-central Texas ........................................................................26

9. Map showing streamflow gains and losses, September 22–28, 2012, in a reach 

of the Guadalupe River from Seguin, Texas, to Gonzales, Tex., lower Guadalupe 

River Basin, south-central Texas ............................................................................................27
iv

Tables

1. Selected U.S. Geological Survey streamflow-gaging stations in the lower 

Guadalupe River Basin, south-central Texas ..........................................................................4

2. Stream reaches for which streamflow conditions were analyzed in the lower 

Guadalupe River Basin, south-central Texas ..........................................................................8

3. Daily streamflow statistics for water years 1987–2011 for selected U.S. 

Geological Survey streamflow-gaging stations in the lower Guadalupe River 

Basin, south-central Texas .......................................................................................................10

4. Inflow sites used for gain and loss computations in the lower Guadalupe River 

Basin, south-central Texas .......................................................................................................11

5. Outflow sites used for gain and loss computations in the lower Guadalupe River 

Basin, south-central Texas .......................................................................................................12

6. Base-flow periods in 2010 and 2011 selected for computing streamflow gains 

and losses in the lower Guadalupe River Basin, south-central Texas .............................15

7. Streamflow gains and losses computed for 21 stream reaches in the lower 

Guadalupe River Basin, south-central Texas, March 15–21, 2010 ....................................18

8. Streamflow gains and losses computed for 21 stream reaches in the lower 

Guadalupe River Basin, south-central Texas, April 10–16, 2011 ........................................19

9. Streamflow gains and losses computed for 21 stream reaches in the lower 

Guadalupe River Basin, south-central Texas, August 19–25, 2011 ....................................20

10. Streamflow gains and losses computed for a stream reach on the Guadalupe 

River from Seguin, Texas, to Gonzales, Tex., September 22–28, 2012 ...............................21
v

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in) 2.54 centimeter (cm)

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

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

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per second per square 

mile [(ft3/s)/mi2]

 0.01093 cubic meter per second per 

square kilometer [(m3/s)/km2]

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

°C=(°F-32)/1.8

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

(NAVD 88).

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

A water year is the 12-month period October 1 through September 30 designated by the 

calendar year in which it ends.

A Preliminary Assessment of Streamflow Gains and 

Losses for Selected Stream Reaches in the Lower 

Guadalupe River Basin, Texas, 2010–12 

By Loren L. Wehmeyer, Karl E. Winters, and Darwin J. Ockerman

Abstract

The U.S. Geological Survey, in cooperation with the 

U.S. Army Corps of Engineers–Fort Worth District, the Texas 

Water Development Board, the Guadalupe-Blanco River 

Authority, and the Edwards Aquifer Authority, investigated 

streamflow gains and losses in the lower Guadalupe River 

Basin during four selected base-flow periods in March 2010, 

April 2011, August 2011, and, for a stream reach between 

Seguin, Tex., and Gonzales, Tex., in September 2012. Major 

sources of streamflow in this basin include releases from 

Canyon Lake, inflow from major springs (Comal Springs, 

San Marcos Springs, and Hueco Springs), and base flow 

(groundwater seeping to streams). Streamflow and springflow data were collected at 35 streamflow-gaging stations 

(including 6 deployed for this study) during the base-flow 

periods. This report describes streamflow in the lower 

Guadalupe River Basin, which consists of the Guadalupe 

River drainage basin downstream from Canyon Lake to the 

Guadalupe River near Tivoli, Tex.

Streamflow conditions in the lower Guadalupe River 

Basin were analyzed by computing surface-water budgets for 

reaches of the lower Guadalupe River and tributary streams. 

Streamflow gains and losses were mapped for reaches where 

the computed gain or loss was greater than the uncertainty in 

the computed streamflow at the upstream and downstream 

ends of the reach.

During the March 15–21, 2010, base-flow period, five 

reaches had gains greater than the uncertainty in the computed 

streamflow, including reach 1 on the Guadalupe River, which 

gained 130 cubic feet per second (ft3/s), and reach 3 on the 

Comal River, which gained 359 ft3/s. Streamflow gains during 

March 2010 primarily were derived from (1) inflow from 

the Edwards aquifer outcrop, including Hueco Springs and 

Comal Springs; (2) flow conveyed through the alluvium of the 

streambed; (3) inflows from the Carrizo-Wilcox aquifer and 

the Yegua Jackson aquifer; and (4) groundwater inflows from 

the Gulf Coast aquifer, which are enhanced by seepage losses 

from Coleto Creek Reservoir. During this base-flow period, 

none of the reaches had a loss greater in magnitude than the 

uncertainty in the computed streamflow.

During the April 10–16, 2011, base-flow period, three 

reaches had gains greater than the uncertainty in the computed 

streamflow. Among these three reaches were reach 1 on the 

Guadalupe River, which gained 40.7 ft3/s, and reach 3 on 

the Comal River, which gained 271 ft3/s—reaches where 

streamflow gains were also measured in March 2010. 

Streamflow gains during April 2011 primarily were derived 

from (1) inflow from the Edwards aquifer outcrop, including 

Hueco Springs and Comal Springs; and (2) inflows from the 

Carrizo-Wilcox aquifer. During this base-flow period, three 

reaches had losses greater in magnitude than the uncertainty 

in the computed streamflow. A reach of the Blanco River near 

Kyle, Tex. (reach 10), lost 18.7 cubic feet per second (ft3/s). 

Much of this loss likely entered the groundwater system 

through the numerous faults that intersect the stream channel 

northwest of Kyle. The reach that included the confluence of 

the Guadalupe and San Marcos Rivers (reach 17) lost 155 ft3/s, 

likely as recharge to the Sparta and Queen City aquifers.

During the August 19–25, 2011, base-flow period, 

three reaches had gains greater than the uncertainty in the 

computed streamflow, including reach 3 on the Comal River 

(168 ft3/s gain), which was one of the reaches where gains 

in streamflow also were measured in March 2010 and April 

2011. Streamflow gains in August 2011 were primarily from 

(1) inflows from Comal Springs, (2) inflows from the Yegua 

Jackson aquifer, and (3) groundwater inflows from the Gulf 

Coast aquifer, which are enhanced by seepage losses from 

Coleto Creek Reservoir. During this base-flow period, five 

reaches had losses greater in magnitude than the uncertainty in 

the computed streamflow. The reach including the confluence 

of the Guadalupe and Comal Rivers lost 82.8 ft3/s. Much of 

that loss likely seeped into the local groundwater system. 

The reach of the Guadalupe River south of New Braunfels, 

Tex., to Seguin, Tex., lost 53.5 ft3/s. Part of that loss may have 

been from seepage through streambed alluvium. Reaches 9 

and 10 of the Blanco River near Kyle lost 2.20 and 6.60 ft3/s, 

respectively, likely as infiltration through numerous faults 

intersecting the stream channel northwest of Kyle. Plum Creek 

between Lockhart, Tex., and Luling, Tex., lost 2.11 ft3/s, likely 

as recharge to the Carrizo-Wilcox aquifer. A base-flow period 

during September 22–28, 2012, was studied for the reach of 
2 A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin

the Guadalupe River between Seguin and Gonzalez, including 

flows from San Marcos River and Plum Creek. During this 

period, for the Guadalupe River reach between Seguin and 

Oak Forest, no computed gains or losses were greater in 

magnitude than the uncertainty in the computed streamflow.

Introduction

In south-central Texas, the lower Guadalupe River and 

its tributaries provide water for municipal water supplies, 

farms, ranches, industries, recreational activities, wildlife, and 

wastewater assimilation. The Guadalupe River Basin includes 

multiple springs that help sustain streamflow in some stream 

reaches and provides habitat for several endangered and 

threatened species (Ockerman and Slattery, 2008).

Streamflow conditions in the lower Guadalupe River 

Basin are affected by rainfall-runoff processes, outflows 

(withdrawals) for water supplies, point-source inflows, 

reservoir operations, spring flows, and infiltration. During 

normal base-flow conditions, releases from Canyon Lake and 

inflows from major springs (Comal, San Marcos, and Hueco 

Springs) (fig. 1) account for most of the streamflow in the 

lower Guadalupe River. A better understanding of streamflow 

conditions in the basin, including how gains, losses, outflows, 

and inflows affect downstream flows, can help resource 

managers to design watershed-management and operation 

strategies that improve utilization of available water resources 

in this basin.

In a previous study, the U.S. Geological Survey (USGS), 

in cooperation with the Edwards Aquifer Authority (EAA), 

evaluated streamflow conditions in the Guadalupe River 

Basin for the period 1987–2006 and described streamflow 

gains and losses and relative contributions of major springs to 

streamflow (Ockerman and Slattery, 2008). That report used 

historical streamflow data and available outflow and inflow 

data to evaluate streamflow characteristics of reaches in the 

Guadalupe River Basin and to estimate the contributions of 

major springs to streamflow in the lower part of the basin 

(downstream from Canyon Lake) for long-term (20-year 

average) conditions and selected short-term base-flow periods.

Purpose and Scope

The purpose of this report is to provide a preliminary 

assessment of streamflow gains and losses in the lower 

Guadalupe River Basin downstream from Canyon Lake. 

Streamflow gains and losses for certain stream reaches 

were evaluated for four selected periods of base flow during 

2010–12—March 2010, April 2011, August 2011, and 

September 2012. The assessment of streamflow in September 

2012 was limited to the Guadalupe River between Seguin, 

Tex., and Gonzales, Tex., and the San Marcos River between 

Luling, Tex., and Gonzales, Tex. Streamflow and spring-flow 

data were collected at 35 streamflow-gaging stations in the 

study area (fig. 1; table 1), including 6 deployed for this study, 

during the selected base-flow periods from 2010–11, and at 2 

partial-record stations in September 2012.

The study results presented in this report do not constitute 

a comprehensive assessment of streamflow gains and losses in 

the lower Guadalupe River Basin because many factors were 

not incorporated in the assessment; for example, the effects 

of hydropower generation on streamflow, gains or losses to 

bank storage, interaction of surface water and groundwater, 

underflow in the streambed alluvium, and evapotranspiration 

losses are addressed only in part. Also, the extent of possible 

unpermitted withdrawals is unknown and therefore not 

included in the assessment.

Description of the Study Area

The headwaters of the Guadalupe River are in 

southwestern Kerr County, Tex. From there, the river flows 

easterly to southeasterly for about 250 miles (mi) to Gonzalez, 

Tex., then southeasterly for another 150 mi to join the San 

Antonio River about 11 mi upstream from the San Antonio 

Bay on the Gulf of Mexico (fig. 1). The study area for this 

report is the lower Guadalupe River Basin, which includes the 

basin downstream from Canyon Lake to the Guadalupe River 

near Tivoli, Tex. The entire Guadalupe River Basin includes 

about 10,100 square miles (mi2). The lower Guadalupe River 

Basin study area includes approximately 8,690 mi2.

The Blanco River, San Marcos River, and San Antonio 

River are principal tributaries of the Guadalupe River. The two 

major reservoirs in the Guadalupe River Basin are Canyon 

Lake and Coleto Creek Reservoir. Canyon Lake impounds 

the Guadalupe River in Comal County, Tex., about 12 mi 

northwest of New Braunfels, Tex. Canyon Lake impounds 

runoff from 1,432 mi2 of drainage area and has 382,000 acrefeet (acre-ft) of authorized conservation storage (GuadalupeBlanco River Authority, 2007a). Construction of the dam and 

reservoir at Canyon Lake began in 1958 and impoundment 

began in 1964. Coleto Creek Reservoir impounds Coleto 

Creek and Perdido Creek, about 12 mi southwest of Victoria, 

Tex. The dam for that reservoir was completed in 1980 and 

impounds runoff from 507 mi2 of drainage area. Conservation 

storage for that reservoir is 35,060 acre-ft (Guadalupe-Blanco 

River Authority, 2007b). The primary purpose of that reservoir 

is to provide cooling water for electric power generation. 

Daily regulation of streamflow for power generation affects 

much of the Guadalupe River downstream from Canyon Lake.

Major population centers in the Guadalupe River Basin 

include Kerrville, New Braunfels, San Marcos, Seguin, 

Lockhart, Gonzales, Cuero, Luling, and Victoria, Tex. The 

2009 population of the basin was approximately 646,000 

based on the 2009 estimated population of Kerr, Kendall, 

Comal, Hays, Guadalupe, Caldwell, Gonzales, De Witt, 

Goliad, and Victoria Counties (U.S. Census Bureau, 2011). 

Agriculture is the primary land use in the study area (MultiResolution Land Characteristics Consortium, 2006).
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LAVACA

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WILSON COUNTY

DEWITT COUNTY

ATASCOSA

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KARNES COUNTY

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Upper Guadalupe 

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Lower Guadalupe 

River Basin

(study area)

GULF OF MEXICO

TEXAS

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Base modified from U.S. Geological Survey 1:100,000 scale digital dataUniversal Transverse Mercator, zone 14 North American Datum of 1983 

Blanco River

Guadalupe

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McQueeney

Coleto Creek

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Guadalupe River Dry Comal Creek

Sandies Creek

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Lower Guadalupe River BasinUpper Guadalupe River BasinU.S. Geological Survey streamflow-gaging  station and map identifier—Table 1Reach number—Table 2Spring

EXPLANATION

7

#

9

29

Figure 1. U.S. Geological Survey streamflow-gaging stations and stream reaches defined for assessment of streamflow gains and losses in the lowesouth-central Texas.
Table 1. Selected U.S. Geological Survey streamflow-gaging stations in the lower Guadalupe River Basin, south-central Texas. [--, not applicable; FM, Farm Road; a water year is the 12-month period from October 1 through September 30 designated by the calendar year in which it ends] Map identifier (fig. 1) Streamflow- gaging station number Station name County Period of record (water years) Latitude (degrees, minutes, seconds) 

1 08167800 Guadalupe River at Sattler, Tex. Comal 1960–present 29°51′32′′ 92 08168000 Hueco Springs near New Braunfels, Tex. Comal 2003–present 29°45′33′′ 93 08168500 Guadalupe River above Comal River at New Braunfels, Tex. Comal 1928–present 29°42′53′′ 94 08168710 Comal Springs at New Braunfels, Tex. Comal 1928–present 29°42′21′′ 95 08168797 Dry Comal Creek at Loop 337 near New Braunfels, Tex. Comal 2006–present 29°41′16.8′′ 96 08169000 Comal River at New Braunfels, Tex. Comal 1928–present 29°42′21′′ 97 08169500 Guadalupe River at New Braunfels, Tex. Comal 1915–98 29°41′52′′ 98 08169792 Guadalupe River at FM 1117 near Seguin, Tex. Guadalupe 2005–present 29°32′10.2′′ 99 08169840 Guadalupe River at Oak Forest, Tex. Gonzales 2010–12a 29°29′44.31′′ 9

10 08169860 Guadalupe River below H-5 Dam near Gonzales, Tex. Gonzales 2010–12a 29°28′12.11′′ 9

11 08170000 San Marcos Springs at San Marcos, Tex. Hays 1956–present 29°53′20′′ 9

12 08170500 San Marcos River at San Marcos, Tex. Hays 1915–present 29°53′20′′ 913 08170990 Jacobs Well Spring near Wimberley, Tex. Hays 2005–present 30°02′04′′ 914 08171000 Blanco River at Wimberley, Tex. Hays 1924–present 29°59′39′′ 915 08171290 Blanco River at Halifax Ranch near Kyle, Tex. Hays 2009–present 30°00′20′′ 916 08171300 Blanco River near Kyle, Tex. Hays 1956–present 29°58′45′′ 917 08171500 San Marcos River at FM 20 at Fentress, Tex. Caldwell 2010–11a 29°45′10.02′′ 918 08172000 San Marcos River at Luling, Tex. Caldwell 1939–present 29°39′58′′ 919 08172400 Plum Creek at Lockhart, Tex. Caldwell 1959–present 29°55′22′′ 920 08173000 Plum Creek near Luling, Tex. Caldwell 1930–present 29°41′58′′ 921 08173500 San Marcos River at Ottine, Tex. Gonzales 1915–43, 2010–11a 29°35′33.39′′ 922 08173900 Guadalupe River at Gonzales, Tex. Gonzales 1997–present 29°29′03′′ 923 08174600 Peach Creek below Dilworth, Tex. Gonzales 1959–present 29°28′26′′ 924 08174700 Guadalupe River at U.S. Highway 183 near Yoakum, Tex. DeWitt 2010–11a 29°18′52.08′′ 925 08174970 Sandies Creek near Smiley, Tex. Gonzales 2010–11a 29°17′30.32′′ 926 08175000 Sandies Creek near Westhoff, Tex. DeWitt 1930–present 29°12′54′′ 927 08175800 Guadalupe River at Cuero, Tex. DeWitt 1964–present 29°05′25′′ 928 08176500 Guadalupe River at Victoria, Tex. Victoria 1935–present 28°47′34′′ 929 08176550 Fifteenmile Creek near Weser, Tex. De Witt 1985–89 28°53′51′′ 930 08176900 Coleto Creek at Arnold Road Crossing near Schroeder, Tex. Goliad 1979–present 28°51′41′′ 931 08177300 Perdido Creek at FM 622 near Fannin, Tex. Goliad 1978–present 28°45′05′′ 932 08177500 Coleto Creek near Victoria, Tex. Victoria 1939–present 28°43′51′′ 933 08177520 Guadalupe River near Bloomington, Tex. Victoria 1999–present 28°39′43′′ 934 08188570 San Antonio River near McFaddin, Tex. Refugio 2006–present 28°31′52.5′′ 935 08188800 Guadalupe River near Tivoli, Tex. Refugio 2000–present 28°30′20′′ 9

aPartial-record site deployed for this investigation.
Methods 5

Three major springs are in the Guadalupe River Basin: 

Comal Springs, San Marcos Springs, and Hueco Springs 

(fig. 1). Comal Springs is the largest spring in the Southwest 

United States (Brune, 1975). Comal Springs discharges from 

several outlets and provides most of the flow in the Comal 

River, which joins the Guadalupe River at New Braunfels. The 

annual average (water years 1933–2010) discharge of Comal 

Springs was 291 cubic feet per second (ft3/s) (U.S. Geological 

Survey, 2012a). San Marcos Springs, also with several outlets, 

provides most of the base flow for the San Marcos River, 

which joins the Guadalupe River near Gonzales. The San 

Marcos Springs, collectively, are the second largest spring in 

Texas (Brune, 1975). The annual average discharge (water 

years 1957–2010) for San Marcos Springs was 175 ft3/s 

(U.S. Geological Survey, 2012a). Hueco Springs is on the 

west side of the Guadalupe River about 3 mi upstream from 

New Braunfels. The annual average discharge (water years 

2004–8) for Hueco Springs was 51.8 ft3/s (U.S. Geological 

Survey, 2012a).

The surficial geology of the lower Guadalupe River Basin 

ranges in age from the Lower Cretaceous to the Quaternary 

period (fig. 2). Aquifer outcrops include the Gulf Coast, 

Yegua Jackson, Sparta, Queen City, Carrizo-Wilcox, Edwards, 

Edwards-Trinity, and Trinity aquifers (fig. 3). These strata dip 

to the southeast and contain various interstitial chalk and clay 

layers (fig. 2). 

Numerous faults are present in the chalk and limestone 

formations in the upper part of the study area (fig. 2) (Hanson 

and Small, 1995; U.S. Geological Survey, 2012b). Many of 

these faults intersect the channels of the streams crossing 

the outcrops of the Edwards aquifer. Most losses observed 

in streams crossing the Edwards aquifer are the result of 

streamflow contributing to groundwater recharge through 

faults intersecting the channels (Slade and others, 1986; 

Pantea and Cole, 2004).

The climate of the study area is subtropical, subhumid 

and is characterized by hot summers and mild winters (Larkin 

and Bomar, 1983). Most rainfall in the area occurs in spring, 

early summer, and fall. Periods with relatively large or small 

amounts of rainfall are common, resulting in recurring floods 

and droughts. Average annual rainfall (1971–2000) at the 

National Weather Service station at New Braunfels was 

35.74 inches per year (National Oceanic and Atmospheric 

Administration, 2002). In the region, water-balance modeling 

indicates that more than 80 percent of rainfall might be 

evaporated and transpired (Lizárraga and Ockerman, 2010). 

Rainfall greater than 0.01 inch was measured, on average, 

for 77 days per year during 1971–2000. Average monthly 

low temperatures from 1971–2000 ranged from 35.5 degrees 

Fahrenheit (°F) in January to 70.6 °F in July. Average monthly 

high temperatures from 1971–2000 ranged from 61.7 °F 

in January to 95.3 °F in August (National Oceanic and 

Atmospheric Administration, 2012).

Methods

To help evaluate streamflow gains and losses, streamflow 

conditions in the lower Guadalupe River Basin were analyzed 

by computing surface-water budgets for reaches of the lower 

Guadalupe River and tributary streams during 1987–2011. 

The lower Guadalupe River Basin was divided into a network 

of 29 stream reaches (table 2), defined by locations of 31 of 

the 35 USGS streamflow-gaging stations shown in figure 1. 

Of the 31 streamflow-gaging stations used to define the 

reaches, 6 were partial-record stations established to provide 

streamflow data for the selected base-flow periods used for 

analysis in this report and thus do not have long-term data 

from which to compute streamflow statistics. Some stream 

reaches include more than one upstream streamflow-gaging 

station because they include the confluence of streams.

Daily streamflow statistics were computed for 17 

USGS streamflow-gaging stations in the lower Guadalupe 

River Basin with at least 10 years of record during the 

25-year period from 1987–2011 (table 3). Those statistics 

include daily mean streamflow, 20 percent exceedance 

streamflow, 50 percent exceedance (median) streamflow, 80 

percent exceedance streamflow, and 90 percent exceedance 

streamflow. The percentage exceedance streamflow is defined 

as the daily mean streamflow that was exceeded for the 

specified percentage of time during a base-flow period. For 

example, the 90-percent exceedance streamflow represents 

a (relatively low) daily mean streamflow that was exceeded 

during 90 percent of the base-flow period. The period 1987–

2011 provides a long-term period of record for comparison 

among many streamflow-gaging stations in the lower 

Guadalupe River Basin.

Daily streamflow data from USGS streamflow-gaging 

stations used for analysis were obtained from the USGS 

National Water Information System (NWISWeb) (U.S. 

Geological Survey, 2012a). These data were collected by the 

USGS in cooperation with Federal, State, and local agencies, 

including the U.S. Army Corps of Engineers–Fort Worth 

District, the Texas Water Development Board (TWDB), the 

Guadalupe-Blanco River Authority, and the Edwards Aquifer 

Authority. Accuracy of the streamflow records vary in time 

and by streamflow-gaging station. The accuracy of streamflow 

records is considered “good,” excluding estimated values, if 

95 percent of the daily streamflows are within 10 percent of 

their true values (U.S. Geological Survey, 2012c).
TRAVIS COUNTY

GILLESPIE

CO

U

NTY

BLANCO

COUNTY

BASTROP COUNTY

HAYS COUNTY

FAYETT

COUN

KENDALL

COUNTY

CALDWELL COUNTY

COMAL

COUNTY

GUADALUPE

COUNTY

GONZALES

COUNTY

LAVACA

COUNT

WILSON COUNTY

DEWIT

KARNES COUNTY

VICTORI

GOLIAD

COUNTY

REFUGIO

COUNT

BEX

A

R

COUNTY

98°

30°

29°

Blanco River

Guadalupe

River

Lake

Dunlap

Lake

McQueeney

Colet

Res

Canyon

Lake

Fifteen Mile

Creek

C

C

San

Marcos

Springs

San Antonio River

Guadalupe River Dry Comal

Creek

Sandies Creek

Perdido Creek

Peach

Creek

Plum

Creek

San Marcos River

9

SYSTEM

QUATERNARY TERTIARY

TERTIARY UPPER

CRETACEOUS

LOWER

CRETACEOUS

 Cook Mountain Formation Sparta Sand Weches Formation Queen City Sand Recklaw Formation Carrizo Sand Wilcox Group Midway Group Navarro Group Pecan Gap Chalk Austin Chalk Buda Limestone Del Rio Clay Edwards Formation Glen Rose Limestone Lower Glen Rose Limestone Upper Fort Terrett FormationLower Guadalupe River Basin boundaryFaultU.S. Geological Survey streamflow-gaging station and map identifier

—Table 1

Surface geology Alluvium Fluviatile terrace deposits Leona Formation High gravel deposit Deweyville Formation Beaumont Formation (sand) Beaumont Formation (clay) Lissie Formation Willis Formation (Pleistocene) Willis Formation (Pliocene) Goliad Formation Fleming Formation Oakville Sandstone Catahoula Formation Whitsett Formation Manning Formation Wellborn Formation Caddell Formation Yegua Formation

EXPLANATION

Ewb

Kau

Kbu

Kdr

Ked

Kft

Kgru

Kgrl

Kpg

Qal

Qt

Qd

Qbs

Qbc

Ql

Qle

PoW

Mg

Mf

Mo

Ecd

Em

Eca

Ey

Ecm

Es

Ew

Eqc

Er

Ec

Ewi

Emi

Oc

Qw Kknm

Qhg

9

1

31

30 29

27

26

25

24

23

21

20

19

18

17

16

15

1112

8

14

13

7 5

4, 6 3

2

22

10

Kgru

Kknm

Eqc Er

Kpg

Es

Qal

Qle

Qt

Qt

Ked

Qal

Qt Ew

Ec

Qt

Er

Eqc

Ecm Ey

Eca

Oc

Mg

Ewb

Em

Mo

Mf

Qt

Qt

Ewi

Qw

Qle

Qw

Kgrl

Kft

Kau

Kbu

Kdr

Ecd

Emi

Qhg

0 10 20 MILES0 10 20 KILOMETERS

Base modified from U.S. Geological Survey 1:100,000 scale digital dataUniversal Transverse Mercator, zone 14 North American Datum of 1983 

Surficial geology modified f

Brown and others (1976, 1983), 

Figure 2. Surficial geology and U.S. Geological Survey streamflow-gaging stations in the lower Guadalupe River Basin, south-central Texas.
Methods 7

Lake Dunlap

Lake McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteenmile

Creek

Coleto

Creek

San Antonio River Dry

Comal C reek

Guadalupe River

Sandies Creek

Plum Creek

San Marcos River

Cypress Creek

Perdido Creek

Guadalupe River

Peach

Creek

H-5

DAM

H-4

DAM

NOLTE

DAM

Hueco

Springs

Comal

Springs

San

Marcos

Springs

LEE

COUNTY

GILLESPIE

COUNTY

BLANCO

COUNTY

BASTROP COUNTY

WASHIN

COUN

HAYS COUNTY

KERR

COUNTY

FAYETTE

COUNTY

CALDWELL COUNTY

COLORA

BANDERA

COUNTY

GUADALUPE

COUNTY

GONZALES COUNTY

MEDINA

COUNTY

LAVACA COUNTY

DEWITT COUNTY

JACKSON

COUNTY

ATASCOSA

COUNTY

VICTORIA

COUNTY

FRIO

COUNTY

GOLIAD COUNTY

LIVE OAK

COUNTY

CALHOUN

COUNTY

BEE

LA SALLE COUNTY

COUNTY

MCMULLEN

COUNTY

REFUGIO

COUNTY

TRAVIS COUNTY

BEXAR COUNTY

COMAL

COUNTY

KENDALL

COUNTY

WILSON COUNTY

KARNES COUNTY

9

1

35 34

33

32 31

30 29

28

27

26

25

24

23

21

20

19

18

17

16

15

11

12

8

14

13

7 5

4

6 3

2

22 10

97°

98°

30°

29°

Aquifer data from

George and others, 2011

Base modified from U.S. Geological Survey 

1:100,000 scale digital data

Universal Transverse Mercator, zone 14 

North American Datum of 1983 

7

7

7

EXPLANATION

Major aquifer system

 Gulf Coast

 Carrizo-Wilcox

 Edwards-Trinity

 Edwards

 Trinity

Minor aquifer system

 Yegua Jackson

 Sparta

 Queen City

Fault

Lower Guadalupe River Basin

U.S. Geological Survey streamflow-gaging 

 station and map identifier—Table 1

Spring

9

7

0 5 10 20 MILES

0 5 10 20 KILOMETERS

15

15

Figure 3. Aquifer systems and U.S. Geological Survey streamflow-gaging stations in the lower Guadalupe River Basin, south-central 

Texas.
Table 2. Stream reaches for which streamflow conditions were analyzed in the lower Guadalupe River Basin, south-central Texas.—Continued [--, not applicable because there is no upstream streamflow-gaging station; FM, Farm Road] Reach number (figs. 1, 7–9) Upstream streamflow-gaging stations Stream reach length (miles) Downstream streamflow-gaging stations 

Map identi- fier (fig. 1) Station number Station name Map identi- fier (fig. 1) Station number Station name 1 1 08167800 Guadalupe River at Sattler, Tex. 15 3 08168500 Guadalupe River above Comal Rive

Braunfels, Tex. 

2 -- -- -- 29 5 08168797 Dry Comal Creek at Loop 337 near 

Braunfels, Tex. 

3 5 08168797 Dry Comal Creek at Loop 337 near New Braunfels, Tex. 3.0 6 08169000 Comal River at New Braunfels, Tex4 3 08168500 Guadalupe River above Comal River at New Braunfels, Tex. 1.9 7 08169500 Guadalupe River at New Braunfels, 

6 08169000 Comal River at New Braunfels, Tex. 1.8 5 7 08169500 Guadalupe River at New Braunfels, Tex. 33 8 08169792 Guadalupe River at FM 1117 near S

6 8 08169792 Guadalupe River at FM 1117 near Seguin, Tex. 43 9 08169840 Guadalupe River at Oak Forest, Tex7 9 08169840 Guadalupe River at Oak Forest, Tex. 14 10 08169860 Guadalupe River below H-5 Dam n

zales, Tex. 

8 -- -- -- 60 14 08171000 Blanco River at Wimberley, Tex. 9 14 08171000 Blanco River at Wimberley, Tex. 12 15 08171290 Blanco River at Halifax Ranch near 

10 15 08171290 Blanco River at Halifax Ranch near Kyle, Tex. 5.1 16 08171300 Blanco River near Kyle, Tex. 

11 -- -- -- 4.4 12 08170500 San Marcos River at San Marcos, T

12 12 08170500 San Marcos River at San Marcos, Tex. 24 17 08171500 San Marcos River at FM 20 at Fentr

16 08171300 Blanco River near Kyle, Tex. 33 13 17 08171500 San Marcos River at FM 20 at Fentress, Tex. 42 18 08172000 San Marcos River at Luling, Tex. 

14 -- -- -- 22 19 08172400 Plum Creek at Lockhart, Tex. 15 19 08172400 Plum Creek at Lockhart, Tex. 23 20 08173000 Plum Creek near Luling, Tex. 16 18 08172000 San Marcos River at Luling, Tex. 14 21 08173500 San Marcos River at Ottine, Tex. 

20 08173000 Plum Creek near Luling, Tex. 12 Table 2. Stream reaches for which streamflow conditions were analyzed in the lower Guadalupe River Basin, south-central Texas. [--, not applicable because there is no upstream streamflow-gaging station; FM, Farm Road]
Table 2. Stream reaches for which streamflow conditions were analyzed in the lower Guadalupe River Basin, south-central Texas.—Continued[--, not applicable because there is no upstream streamflow-gaging station; FM, Farm Road]

Reach 

number 

(figs. 1, 

7–9)

Upstream streamflow-gaging stations Stream 

reach 

length 

(miles)

Downstream streamflow-gaging stations 

Map 

identifier 

(fig. 1)

Station 

number Station name

Map 

identifier 

(fig. 1)

Station 

number Station name

17 10 08169860 Guadalupe River below H-5 Dam near Gonzales, Tex. 12 22 08173900 Guadalupe River at Gonzales, Tex. 

21 08173500 San Marcos River at Ottine, Tex. 25

18 -- -- -- 46 23 08174600 Peach Creek below Dilworth, Tex. 19 22 08173900 Guadalupe River at Gonzales, Tex. 36 24 08174700 Guadalupe River at U.S. Highway 1

Yoakum, Tex.

23 08174600 Peach Creek below Dilworth, Tex. 19

20 -- -- -- 56 25 08174970 Sandies Creek near Smiley, Tex. 21 25 08174970 Sandies Creek near Smiley, Tex. 24 26 08175000 Sandies Creek near Westhoff, Tex. 22 24 08174700 Guadalupe River at U.S. Highway 183 near 

Yoakum, Tex.

32 27 08175800 Guadalupe River at Cuero, Tex. 

26 08175000 Sandies Creek near Westhoff, Tex. 21

23 27 08175800 Guadalupe River at Cuero, Tex. 53 28 08176500 Guadalupe River at Victoria, Tex. 24 -- -- -- 22 29 08176550 Fifteenmile Creek near Weser, Tex. 25 29 08176550 Fifteenmile Creek near Weser, Tex. 14 30 08176900 Coleto Creek at Arnold Road Crossi

Schroeder, Tex.

26 -- -- -- 8.4 31 08177300 Perdido Creek at FM 622 near Fann27 30 08176900 Coleto Creek at Arnold Road Crossing near 

Schroeder, Tex.

14 32 08177500 Coleto Creek near Victoria, Tex. 

31 08177300 Perdido Creek at FM 622 near Fannin, Tex. 15

28 28 08176500 Guadalupe River at Victoria, Tex. 24 33 08177520 Guadalupe River near Bloomington

32 08177500 Coleto Creek near Victoria, Tex. 19

29 33 08177520 Guadalupe River near Bloomington, Tex. 18 35 08188800 Guadalupe River near Tivoli, Tex. 

34 08188570 San Antonio River near McFaddin, Tex. 14
Table 3. Daily streamflow statistics for water years 1987–2011 for selected U.S. Geological Survey streamflow-gaging stations in the lower Guadalupcentral Texas. [USGS, U.S. Geological Survey; a water year is the 12-month period from October 1 through September 30 designated by the calendar year in which it ends; mi2, square miles; --, not applicable] USGS station number USGS station name Available record (water years) Drainage area (mi2) Daily mean streamflow (ft3/s) 20 percent exceedance streamflow (ft3/s) 50 percent exceedance streamflow (ft3/s) 

e

08167800 Guadalupe River at Sattler, Tex. 1960–2011 1,436 567 580 204 08168500 Guadalupe River above Comal River at New Braunfels, Tex. 1928–2011 1,518 662 736 267 08168710 Comal Springs at New Braunfels, Tex. 1928–2011 -- 306 376 312 08169000 Comal River at New Braunfels, Tex. 1928–2011 130 325 384 315 08170000 San Marcos Springs at San Marcos, Tex. 1956–2011 -- 185 239 171 08171000 Blanco River at Wimberley, Tex. 1924–2011 355 186 201 68.0 08171300 Blanco River near Kyle, Tex. 1956–2011 412 182 200 47.0 08172000 San Marcos River at Luling, Tex. 1939–2011 838 497 577 231 08172400 Plum Creek at Lockhart, Tex. 1959–2011 112 49.4 18.0 1.10 08173000 Plum Creek near Luling, Tex.1 1930–2011 309 120 59.0 10.0 08173900 Guadalupe River at Gonzales, Tex.1 1997–2011 3,490 1,830 2,080 938 08174600 Peach Creek below Dilworth, Tex.1 1959–2011 460 146 34 6.75 08175000 Sandies Creek near Westhoff, Tex. 1930–2011 549 144 33.5 8.60 08175800 Guadalupe River at Cuero, Tex. 1964–2011 4,934 2,220 2,340 1,010 08176500 Guadalupe River at Victoria, Tex. 1935–2011 5,198 2,340 2,460 1,070 08176900 Coleto Creek at Arnold Road Crossing near Schroeder, Tex. 1979–2011 357 82.2 31.9 8.20 08177500 Coleto Creek near Victoria, Tex. 1939–2011 500 111 7.40 4.66 

1Missing record estimated using maintenance of variance extension type 1 (MOVE.1) (Hirsch, 1982) to calculate statistics for 1987–2011 period. Stations with missing record during water years 1987–2011 and stations used in MOVE.1 computations to estimate missing record in the lower Guadalupe Riv

Streamflow-gaging station with missing record Streamflow-gaging station from which daily mean streamflow obtained Correlation coef

08173000 Plum Creek near Luling, Tex. 08172400 Plum Creek at Lockhart, Tex. 0.86 08173900 Guadalupe River at Gonzales, Tex. 08175800 Guadalupe River at Cuero, Tex. 0.95 08174600 Peach Creek below Dilworth, Tex. 08175000 Sandies Creek near Westhoff, Tex. 0.82 
Methods 11

Three stations listed in table 3 had periods of 

missing record during water years 1987–2011 because of 

discontinuous streamflow-gaging station operation. Statistics 

in table 3 were computed by including estimates of missing 

daily streamflow record during the 25-year period when data 

were not collected. Those estimates were calculated using 

an implementation of the maintenance of variance extension 

type 1 (MOVE.1) method (Hirsch, 1982) described in Granato 

(2009) with data from nearby stations (table 3). Record 

extension and gap filling were only applied if the coefficient 

of determination (r2) (Helsel and Hirsch, 2002) between the 

streamflow-gaging station with missing data and a nearby 

streamflow-gaging station without missing data was greater 

than 0.8, and there were more than 3,650 concurrent daily 

streamflow values (10 years).

Daily average per month inflows and outflows were 

provided by the Texas Commission for Environmental 

Quality (table 4, Michael Beatty, written commun., 2011; 

table 5, Angela Sander, written commun., 2011) and the U.S. 

Environmental Protection Agency (2013). Inflows consist 

primarily of treated wastewater-treatment plant discharges 

(table 4). Outflows consist primarily of withdrawals for 

public water supply. Inflows and outflows were assigned to 

the appropriate stream reach and included in the gain and 

loss calculations. Daily average per month outflow is defined 

as “The arithmetic average of all determinations of the daily 

discharge within a period on one calendar month” (U.S. 

Environmental Protection Agency, 2004).

Streamflow data were obtained from 31 continuous 

USGS streamflow-gaging stations, including 6 partial-record 

stations established to collect data for this study. These stations 

were operated to collect streamflow data for the range of flows 

typical of base-flow periods. Three 7-day base-flow periods 

were selected for assessment: March 15–21, 2010, April 

10–16, 2011, and August 19–25, 2011. The primary selection 

criteria for the base-flow periods included the following 

considerations: (1) the streamflow was in a relatively steady 

state, that is, inflow to the lower Guadalupe River Basin 

was not affected by storm runoff, (2) desire to identify three 

periods with different streamflow and climatic conditions, 

and (3) streamflows were relatively small, compared with 

median streamflows. Because of interest in streamflow losses 

in the Guadalupe River between Oak Forest, Tex. (08169840), 

and Gonzalez, Tex. (08173900), an additional analysis was 

conducted for reaches 6, 7, 16, and 17 from September 22–28, 

2012 (table 2).

Table 4. Inflow sites used for gain and loss computations in the lower Guadalupe River Basin, south-central Texas.

[EPA, U.S. Environmental Protection Agency; WWTP, wastewater-treatment plant]

Map 

identifier 

(fig. 4)

EPA 

identifier Owner or facility

Reach 

(figs. 1, 

7–9)

1 TX0125288 A&M Heep WWTP 13

2 TXG130005 A E Wood fish hatchery 11

3 TX0023477 Aloe field WWTP 27

4 TX0077534 Balcones cement plant 2

5 TX0128201 Castletop capital hays ABC WWTP 13

6 TX0054623 City of Blanco WWTP 8

7 TX0024244 City of Cuero WWTP 22

8 TX0023183 City of Flatonia WWTP 17

9 TX0027243 City of Gonzalez WWTP 18

10 TX0119466 City of Kyle WWTP 13

11 TX0023868 City of Lockhart 14

12 TX0022764 City of Luling, north WWTP 15

13 TX0022772 City of Luling, south WWTP 15

14 TX0070785 City of Nixon WWTP 19

15 TX0047945 City of San Marcos WWTP 11

16 TX0034452 City of Waelder WWTP 17

17 TX0054631 City of Yorktown WWTP 23

18 TX0070068 Coleto Creek power station 26

19 TX0124958 Delhi iron removal facility 17

20 TX0025208 Dunlap WWTP 5

21 TXG110657 Fiver starr concrete plant 1 13

Map 

identifier 

(fig. 4)

EPA 

identifier Owner or facility

Reach 

(figs. 1, 

7–9)

22 TX0103535 Geronimo Creek WWTP 5

23 TX0100684 Goforth WWTP 13

24 TX0030970 Gonzalez Warm Springs WWTP 16

25 TX0070939 Gruene Road WWTP 1

26 TX0025216 Guadalupe-Blanco River Authority 5

27 TX0128741 Holmes Foods chicken hatchery 20

28 TX0113565 Lockhart WWTP 2 14

29 TXG130018 National fish hatchery 12

30 TXG110091 New Braunfels WWTP number 71 2

31 TX0088170 North Kuehler WWTP 5

32 TXG110020 Plant 3 5

33 TX0117676 Railyard WWTP 13

34 TX0005118 Sam Rayburn powerplant 22

35 TX0126021 Schertz/Seguin WWTP 19

36 TX0067881 South Kuehler WWTP 5

37 TX0003603 Victoria power station 27

38 TX0025186 Victoria regional WWTP 27

39 TX0025194 Victoria Willow Street WWTP 27

40 TX0006050 E. I. du Pont de Nemours and 

Company (Dupont)

28

41 TX0022365 Walnut Branch WWTP 5
12 A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin

For this report, a stream reach is defined as a stream 

channel extending from a downstream streamflow-gaging 

station to either the headwaters (defined as having no flow) 

or one or more upstream streamflow-gaging stations (fig. 1; 

table 2). Whereas each reach has a single downstream gaging 

station, branching (when present) of the stream within the 

reach at times resulted in multiple upstream gaging stations. 

Streamflow gains and losses were estimated by computing 

the difference in streamflow between the upstream and 

downstream ends of a reach minus any outflows from the 

reach plus any inflows into the reach. Streamflows at the 

upstream and downstream ends of each reach were determined 

from the continuous streamflow record of the streamflowgaging station(s) defining each stream reach (table 2). Because 

daily regulation (for power generation) affects streamflow in 

much of the study area, streamflows used for computing gains 

and losses were not solely based on discrete measurements. 

Additional sources of gains or losses in a reach that were not 

specifically accounted for included evaporation from streams, 

groundwater inflow or outflow through the streambed, and 

unknown inflows and outflows. Streamflow gain or loss in a 

reach was computed as:

G = QD – ∑QU + QO – QI, (1)

where

G = streamflow gain or loss;

QD = streamflow at the downstream streamflowgaging station;

	 ∑QU = sum of streamflow at all upstream 

streamflow-gaging stations;

QO = outflows from the reach; and

QI = inflows into the reach 

(Units of all variables in cubic feet per second).

When defined in this manner, positive values of G

indicate streamflow gains in a stream reach, whereas negative 

values indicate streamflow losses. The downstream and sum 

of the upstream streamflow values (QD and ∑QU, equation 

1, respectively) were based on the average of instantaneous 

streamflow computed every 15 minutes at the upstream 

and downstream streamflow-gaging stations of each reach 

during each 7-day base-flow period (March 15–21, 2010, 

April 10–16, 2011, and August 19–25, 2011). Outflows and 

inflows (QO and QI, respectively, in equation 1) were based 

on monthly average (U.S. Environmental Protection Agency, 

2004) inflows (table 4; Michael Beatty, Texas Commission on 

Environmental Quality, written commun., 2011) and outflows 

(table 5; Angela Sander, Texas Commission on Environmental 

Quality, written commun., 2011; U.S. Environmental 

Protection Agency, 2013). The locations of facilities providing 

inflow data are shown in figure 4. The locations of permitted 

water rights are shown in figure 5.

Table 5. Outflow sites used for gain and loss computations in the 

lower Guadalupe River Basin, south-central Texas.

Map 

identifier 

(fig. 5)

Name of entity or individual 

responsible for reporting outflows 

at the outflow site to the Texas 

Commission for Environmental Quality

Reach

(figs. 1, 

7–9)

1 Guadalupe-Blanco River Authority 5

2 Robert M Kiehn 16

3 San Marcos River Ranch, Limited 13

4 City of New Braunfels 3

5 New Braunfels Utilities 3

6 Canyon Regional Water Authority 6

7 Canyon Regional Water Authority 6

8 Seguin Municipal Utilities 5

9 Sara Darilek Rainwater 5

10 City of Gonzales 17

11 City of Gonzales 17

12 King Ranch, Incorporated 22

13 South Texas Electric Cooperative, 

Incorporated

23

14 E. I. du Pont de Nemours and Company 

(Dupont)

28

15 Texas Parks and Wildlife Department 12

16 City of Blanco 8

17 Canyon Regional Water Authority 12

18 Barbara Baugh 12

19 Tri Community Water Supply Corporation 12

20 City of Luling 13

21 Spencewood, Incorporated 14

22 John Scott Greene 12

23 Guadalupe-Blanco River Authority 13

24 City of Victoria 28

25 Victoria WLE LP1 28

26 Coleto Creek Power 27

1

Official company name; combinations of letters that do not form words are 

part of the official name and are not acronyms. 
Methods 13

LEE

COUNTY

GILLESPIE

COUNTY

BLANCO

COUNTY

BASTROP COUNTY

HAYS COUNTY

KERR

COUNTY

FAYETTE

COUNTY

CALDWELL COUNTY

BANDERA

COUNTY

GUADALUPE

COUNTY

GONZALES COUNTY

MEDINA

COUNTY

LAVACA COUNTY

DEWITT COUNTY

ATASCOSA

COUNTY

VICTORIA

COUNTY

FRIO

COUNTY

GOLIAD COUNTY

LIVE OAK

COUNTY

CALHOUN

COUNTY

BEE

LA SALLE COUNTY

COUNTY

MCMULLEN

COUNTY

REFUGIO

COUNTY

TRAVIS COUNTY

BEXAR COUNTY

COMAL

COUNTY

KENDALL

COUNTY

WILSON COUNTY

KARNES COUNTY

San

Marcos

Springs

Lake Dunlap

Lake

McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteenmile

Creek

Coleto Creek

San Antonio River Dry

Comal C reek

Guadalupe River

Sandies Creek

Plum Creek

San Marcos River

Cypress Creek

Perdido Creek

Guadalupe River

Peach

Creek

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

! !

!

!

!

!

!

!

!

!

!

!

9

8

7

6

5

3

2

1

41

40

39

38

37

35

34

33

32

29

28

27

26

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

1

35 34

33

32 31

30 29

28

27

26

25

24

23

21

20

19

18

17

16

15

11

12

8

14

13

22 10

Base modified from U.S. Geological Survey

1:100,000 scale digital data

Universal Transverse Mercator, zone 14

North American Datum of 1983 

97°

98°

30°

29°

See inset 

7

7

7

7

7

0 5 10 20 MILES

0 5 10 20 KILOMETERS

15

15

COMAL

COUNTY

7

5

4

6

3

2

Comal

Springs

Inset

!

!

!

4

30

25

36

31

!!

Dry

Comal Creek

Guadalupe River

Hueco

Springs

7

7

77

EXPLANATION

Lower Guadalupe River Basin

U.S. Geological Survey streamflow-gaging

 station and map identifier—Table 1

Approximate disharge permit location

 and map identifier—Table 4

Spring

9#

9 !

Figure 4. Location of inflow sites and U.S. Geological Survey streamflow-gaging stations used in the lower Guadalupe River Basin 

gain and loss study.
14 A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin

Lake Dunlap

Lake McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteenmile

Creek

Coleto

Creek

San Antonio River Dry

Comal C reek

Guadalupe River

Sandies Creek

Plum Creek

San Marcos River

Cypress Creek

Perdido Creek

Guadalupe River

Peach

Creek

LEE

COUNTY

GILLESPIE

COUNTY

BLANCO

COUNTY

BASTROP COUNTY

HAYS COUNTY

KERR

COUNTY

FAYETTE

COUNTY

CALDWELL COUNTY

BANDERA

COUNTY

GUADALUPE

COUNTY

GONZALES COUNTY

MEDINA

COUNTY

LAVACA COUNTY

DEWITT COUNTY

ATASCOSA

COUNTY

VICTORIA

COUNTY

FRIO

COUNTY

GOLIAD COUNTY

LIVE OAK

COUNTY

CALHOUN

COUNTY

BEE

LA SALLE COUNTY

COUNTY

MCMULLEN

COUNTY

REFUGIO

COUNTY

TRAVIS COUNTY

BEXAR COUNTY

COMAL

COUNTY

KENDALL

COUNTY

WILSON COUNTY

KARNES COUNTY

San

Marcos

Springs

9

1

35 34

33

32

31

30

29

28

27

26

25

24

23

21

20

19

18

17

16

15

11

12

8

14

13

22 10

97°

98°

30°

29°

See inset 

Base modified from U.S. Geological Survey 

1:100,000 scale digital data

Universal Transverse Mercator, zone 14

North American Datum of 1983 

7

5

4

6

3

2

Comal

Springs

Dry

Comal Creek

Guadalupe River

Hueco

Springs

5

4

COMAL

COUNTY

Inset 

7

7

0 5 10 20 MILES

0 5 10 20 KILOMETERS

15

15

7

7

7

7

EXPLANATION

Lower Guadalupe River Basin

U.S. Geological Survey streamflow-gaging 

 station and map identifier—Table 1

Approximate water right permit location 

 and map identifier—Table 5

Spring

9

Figure 5. Water right permit locations and U.S. Geological Survey streamflow-gaging stations, lower Guadalupe River Basin, southcentral Texas.
Methods 15

For the three 7-day base-flow periods (table 6) during 

March 2010, April 2011, and August 2011, the starting and 

ending dates for each period were chosen retrospectively to 

maximize the total number of field measurements made by 

hydrologic technicians within the period, thereby minimizing 

the uncertainty (error) of the upstream and downstream 

computed streamflows used for gain and loss computations. If 

two or more 7-day intervals had the same maximum number 

of field measurements, the interval that minimized streamflow 

variability, as measured by the daily mean coefficient 

of variation (CV), was selected. The CV is the standard 

deviation of a dataset divided by the mean (Ott, 1988) and is 

a measure of the variability of the data. Table 6 lists the CV 

associated with base-flow periods in 2010 and 2011 selected 

for computing streamflow gains and losses. CV was not 

determined for the September 2012 base-flow assessment, 

which was made for a short reach of the river.

Streamflow at the downstream streamflow-gaging station 

and outflows and inflows (QD, QO, and QI, respectively, 

equation 1) were computed as the arithmetic mean of all 

15-minute instantaneous streamflow values during each 

7-day base-flow period. To account for the effects of 

unsteady streamflow, traveltime was estimated to account 

for the elapsed time it takes for water to travel from each 

upstream gage of a reach to the downstream gage. To estimate 

traveltimes, stream velocities were determined for each 

upstream and downstream streamflow-gaging station pair of 

a reach. When one or more discharge measurements were 

available for a streamflow-gaging station during a base-flow 

period, the field-measured stream velocity with the highest 

accuracy rating was used. For each measurement rating 

the error (estimated difference between measured and total 

discharge) ranges are (1) less than or equal to 2 percent, 

excellent; (2) more than 2 and less than 5 percent, good; 

(3) greater than or equal to 5 and less than 8 percent, fair; 

and (4) equal to or more than 8 percent, poor (Fulford, 1992; 

Turnipseed and Sauer, 2010). The accuracy rating assigned 

by the hydrologic technician is based on factors such as 

cross-section uniformity, velocity homogeneity, streambed 

conditions, and other factors that affect the accuracy of each 

streamflow measurement (Turnipseed and Sauer, 2010). If 

more than one discharge measurement had the same (highest) 

accuracy rating, the mean of the highest rated field-measured 

stream velocities was used. If no discharge measurements 

were made at a streamflow-gaging station during a baseflow period, velocity was determined from the most recent 

measurement within 5 percent of the period streamflow; 

if no discharge measurements were within 5 percent, the 

measurement closest in value to average streamflow of the 

base-flow period was selected. The effective traveltime for an 

upstream and downstream streamflow-gaging station pair was 

computed as:

T =D / VMEAN, (2)

where

T = effective traveltime between upstream and 

downstream gages, in hours;

D = distance between upstream and downstream 

gages, in miles;

VMEAN = mean of upstream and downstream flow 

velocities, in miles per hour.

Traveltime between each upstream and downstream station 

was accounted for by shifting the base-flow period in time 

at the upstream station by the effective traveltime. This 

procedure was applied individually for each upstream and 

downstream pair of streamflow-gaging stations in a given 

reach. The effects of storage were not considered in the 

computation of traveltime.

To test the sensitivity of traveltime on computed 

discharge and gains or losses, traveltime (T) for reach 9 on 

the Blanco River during the March 15–21, 2010, base-flow 

period, was varied by -50 percent and +50 percent. For reach 

9, T was estimated to be 19 hours during the March 15–21, 

2010, base-flow period. For values of T of 9.5 and 28.5 

hours, the flow of the downstream streamflow-gaging station 

(08171290) was within +1.2 and +2.1 percent, respectively, 

of the streamflow computed for T = 19 hours. The associated 

gain in streamflow for T = 19 hours was 28 ft3/s. For values 

of T = 9.5 and 28.5 hours, the gain in streamflow would be 

25 and 23 ft3/s, respectively. The gains of 25 and 23 ft3/s are 

within -11 and -18 percent, respectively, of the gain computed 

for T = 19 hours.

Streamflow uncertainties were assigned to the upstream 

and downstream flows used in equation 1 according to the 

accuracy rating reported in the USGS annual water data report 

for that streamflow-gaging station (U.S. Geological Survey, 

2012c). According to this scale, ratings of excellent, good, 

Table 6. Base-flow periods in 2010 and 2011 selected for 

computing streamflow gains and losses in the lower Guadalupe 

River Basin, south-central Texas.

[CV, coefficient of variation]

Baseflow 

period

Starting date1 Ending date

Total 

number 

of streamflowdischarge 

measurements

Mean daily 

streamflow 

variability 

(CV2, 

dimensionless)

1 March 15, 2010 March 21, 2010 14 21

2 April 10, 2011 April 16, 2011 16 19

3 August 19, 2011 August 25, 2011 30 16

1

Starting and ending dates are associated with the downstream end of each 

stream reach. Streamflow hydrographs at the upstream end of each stream 

reach precede those of the downstream end of the reach to account for streamflow traveltime within each reach. 

2

The coefficient of variation is the standard deviation of a dataset divided by 

the mean (Ott, 1988).
16 A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin

fair, and poor were given progressively increasing percentage 

uncertainties of 5, 10, 15, and more than 15 percent, 

respectively. Percentage uncertainty estimates using the 

annual water data report rating were based on Novak (1985), 

which states that 95 percent of the time an excellent rating 

corresponds to less than or equal to 5 percent error, a good 

rating corresponds to less than or equal to 10 percent error, a 

fair rating corresponds to less than or equal to 15 percent error, 

and a poor rating indicates less than fair accuracy. 

 Streamflow uncertainties, in units of cubic feet per 

second, were computed by multiplying the appropriate 

percentage uncertainty by the streamflow value used in the 

gain and loss computation. The uncertainties associated with 

downstream and upstream streamflows of each reach were 

summed to obtain a composite streamflow-measurement 

uncertainty (Turco and others, 2007). The uncertainties of 

within-reach outflows and inflows, QO and QI, were not 

evaluated.

For the studies conducted in 2010 and 2011, factors 

including evaporation, groundwater inflow or outflow 

through the streambed, and unknown withdrawals and 

return flows were not evaluated during the three baseflow periods. Evaporation from stream channels was not 

accounted for in the determination of streamflow gains and 

losses, but evaporation estimates from Lake Dunlap and 

Lake McQueeney (reach 5, fig. 1), downstream from New 

Braunfels, and Coleto Creek Reservoir (reach 27, fig. 1) are 

presented. Estimates of evaporation at these lakes were based 

on the surface area of each lake and monthly evaporation 

values published by the Texas Water Development Board 

(2013). Evaporation from Lake Dunlap was estimated as 2.1, 

3.1, and 4.6 ft3/s during March 2010, April 2011, and August 

2011, respectively. Evaporation from Lake McQueeney was 

estimated as 2.0, 3.0, and 4.5 ft3/s during March 2010, April 

2011, and August 2011, respectively. Evaporation from Coleto 

Creek Reservoir was estimated as 16, 23, and 29 ft3/s during 

March 2010, April 2011, and August 2011, respectively.

For streamflow gains and losses computed in the 

September 22–28, 2012, base-flow period, groundwater 

inflows and outflows from the streambed and unknown 

withdrawals and return flows were not directly measured, 

but Penman’s formula for evaporation from an open-water 

surface (Penman, 1948) was used to estimate evaporation 

from the stream channel for a similar period in 2011. For 

those computations, average air temperature and wind speed 

measured at a nearby weather station in New Braunfels, Tex., 

were acquired from the National Weather Service (National 

Oceanic and Atmospheric Administration, 2012). The average 

air temperature for selected periods was converted from 

degrees Celsius to atmospheric vapor pressure, in millimeters 

of mercury, using the relation between temperature and 

water vapor pressure (Oklahoma State University Chemistry 

Department, 2001). Hourly water temperature data from 

USGS streamflow-gaging station 08188060 San Antonio River 

near Runge, Tex., also were used (U.S. Geological Survey, 

2012a). The open-water surface area of that 14-mi reach of the 

Guadalupe River was calculated in ArcMap (Environmental 

Systems Research Institute, Inc., 2008) by using the editor 

function to create polygons on the river and summing of the 

areas of those polygons (about 0.497 mi2). Evaporation losses 

from the Guadalupe River between Oak Forest, Tex., and H–5 

dam for the weeks of August 12, 2011, August 19, 2011, and 

August 26, 2011, were 29.9, 51.2, and 8.4 ft3/s, respectively.

Possible influences of surficial geology (fig. 2) and 

aquifer outcrops (fig. 3) were considered in an evaluation 

of streamflow gains from or losses to groundwater. In 

calculating streamflow gains and losses, inflows and outflows 

were determined from daily average flow per month (U.S. 

Environmental Protection Agency, 2004).

Streamflows computed at Guadalupe-Blanco River 

Authority dams (Charlie Hickman, Guadalupe-Blanco 

River Authority, written commun., March 4, 2013) were not 

used in the computations of streamflow gains and losses; 

however, they qualitatively support the gain and loss survey. 

Comparisons to streamflows at the USGS streamflow-gaging 

stations downstream from each respective dam are presented. 

Nolte Dam is located about 4 mi upstream from USGS 

station 08169792 Guadalupe River at Farm Road 1117 near 

Seguin. The H–4 dam is about 2 mi upstream from 08169840 

Guadalupe River at Oak Forest, Tex. The H–5 dam is about 

0.2 mi upstream from USGS station 08169860 Guadalupe 

River below the H–5 Dam near Gonzales, Tex. Flows 

computed for the dams during the March 2010 base-flow 

period were within 10 percent of the streamflows recorded 

by the respective nearest USGS streamflow-gaging stations. 

Flows computed for the dams computed for the April 2011 

base-flow period were within 12 percent of the streamflows 

recorded by the respective nearest downstream USGS 

streamflow-gaging stations, except for the H–5 dam, for which 

flow was 34 percent lower than the flow recorded at USGS 

station 08169860. The reason for the difference in computed 

flows at the H–5 dam and station 08169860 during the April 

2011 base-flow period is not known but may be related to 

errors in the discharge ratings or to possible leakage under the 

dam. Flows computed for the dams during the August 2011 

base-flow period were within 15 percent of the streamflows 

recorded by the respective nearest downstream USGS 

streamflow-gaging stations, except for Nolte Dam, for which 

flow was 21 percent higher than the streamflow recorded at 

USGS station 08169792. Flows computed for the H–4 and 

H–5 dams during the September 2012 base-flow period were 

within 18 percent of the streamflows of the respective USGS 

streamflow-gaging stations.
Streamflow Gains and Losses 17

Streamflow Gains and Losses

Streamflow gains and losses were computed for 21 

reaches in the lower Guadalupe River Basin during March 

15–21, 2010, April 10–16, 2011, and August 19–25, 2011, 

base-flow periods (tables 7–9, respectively), and for reaches 6, 

7, 16, and 17 near Gonzales, Tex., during the September 2012 

base-flow period (table 10). Gains and losses are presented 

for each reach; the computed streamflow gain or loss per mile 

of stream reach are also presented to provide a sense of the 

relative magnitudes of gains or losses (tables 7–10). Only 

the gains or losses for the individual reaches are described. 

Streamflow gains or losses, which exceeded the sum of the 

associated streamflow uncertainties at the upstream and 

downstream ends of the reach (tables 7–10), are shown in 

figures 6–9. 

Differences in the computed gains and losses during 

each base-flow period may be related to antecedent rainfall, 

stream levels, ground-water levels, evaporation, or other 

factors. The March 2010 base-flow period was preceded 

by a month of near normal rainfall (National Oceanic and 

Atmospheric Administration, 2013); the April and August 

and 2011 base-flow periods were marked by extreme rainfall 

deficits; and the September 2012 base-flow period was 

preceded by a month of below normal to near normal rainfall 

in the study area. Streamflows on the main-stem Guadalupe 

River generally were well above normal during the March 

2010 base-flow period, below normal during the April 2011 

and September 2012 base-flow periods, and well below 

normal during the August 2011 base-flow period. The effects 

of drought on groundwater levels or evaporation during 2011 

and 2012 have not been quantified as they relate to this study. 

Additionally, although each base-flow period represents a 

specific set of streamflow rates within the study area, the 

effects of factors such as air temperature, groundwater-level 

altitudes, or evapotranspiration were not considered in the 

analyses; computed gains or losses may not be representative 

of streamflow conditions during the associated periods. 

The effects of undocumented withdrawals and 

unmeasured inflows on the streamflow gains and losses 

described in this report are unknown. In Texas, surface water 

belongs to the State, and a permit to withdraw water must 

be obtained from the Texas Commission on Environmental 

Quality (National Conference of State Legislatures, 2013). It is 

likely that not all withdrawals are permitted and documented, 

and these undocumented withdrawals might be an appreciable 

source of outflows (Wurbs and others, 1994). It is also likely 

that not all inflows contributing to streamflow in a reach could 

be measured; for example, in some reaches, unmeasured 

inflows from small streams and unmeasured irrigation return 

flows might represent an appreciable component of the 

streamflow. 
Table 7. Streamflow gains and losses computed for 21 stream reaches in the lower Guadalupe River Basin, south-central Texas, March 15–21, 2010. [Streamflow gain values are positive and streamflow loss values are negative. Bold green font indicates a streamflow gain that exceeded the measurement uncertainty for this reSurvey; hr, hour; ft3/s, cubic feet per second; mi, mile; --, data not available] Reach num- ber Upstream USGS streamflow- gaging station number Map identifier for upstream station1 Downstream USGS streamflow- gaging station number Map identifier for down- stream station Estimated traveltime (T) between upstream and downstream gaging stations (hr) Upstream streamflow2 (ft3/s) Down- stream streamflow (ft3/s) Estimated outflow3 between upstream and down- stream sites (ft3/s) Estimated inflow3 between upstream and downstream sites (ft3/s) Stream- flow gain or loss (ft3/s) 

1 08167800 1 08168500 3 10 529 660 0.0 0.72 130 3 08168797 5 08169000 6 5 7.0 366 0.0 0.0 359 4 08168500 08169000 3 6 08169500 7 12 661 366 999 0.0 0.0 -28 5 08169500 7 08169792 8 33 1,032 1,224 0.0 12.4 180 6 08169792 8 08169840 9 -- 1,237 -- 0.0 0.0 -- 7 08169840 9 08169860 10 -- -- 1,187 0.0 0.0 -- 9 08171000 14 08171290 15 19 242 270 0.0 0.0 28.0 

10 08171290 15 08171300 16 9 266 243 0.0 0.0 -23.0 12 08170500 08171300 12 16 08171500 17 21 43 255 233 554 0.00 8.84 57.2 13 08171500 17 08172000 18 46 552 617 2.85 0.0 67.9 15 08172400 19 08173000 20 34 23.9 45.4 0.0 1.70 19.8 16 08172000 08173000 18 20 08173500 21 15 15 616 42.0 628 0.0 0.72 -30.7 17 408169860 08173500 10 21 08173900 22 817 1,185 619 1,941 2.41 0.0 139 19 08173900 08174600 22 23 08174700 24 2324 1,943 14.5 1,771 0.0 1.82 -188 21 08174970 25 08175000 26 60 14.5 23.9 0.0 0.0 9.4 22 08174700 08175000 24 26 08175800 27 3626 1,772 21.7 1,853 0.0 0.0 59.3 23 08175800 27 08176500 28 54 1,868 1,831 0.0 1.53 -38.5 25 08176550 29 08176900 30 -- -- -- -- -- -- 27 08176900 08177300 30 31 08177500 32 19 37 24.3 0.58 41.1 0.0 0.0 16.2 28 08176500 08177500 28 32 08177520 33 2736 1,815 20.2 1,858 8.98 0.0 31.8 29 08177520 08188570 33 34 08188800 35 19 18 1,843 657 2,792 0.0 0.0 292 

1Second map identifier is for the second station listed in the “Upstream USGS streamflow-gaging station number” column. 2Computed streamflow was adjusted for traveltime to minimize effects of nonsteady-state streamflow. Hydrograph at upstream station adjusted for traveltime, in hours, prior t3Monthly average values for March 2010 (Texas Commission on Environmental Quality, 2011; U.S. Environmental Protection Agency, 2013). 4Station 08169860 has no data during March 18–21.
Table 8. Streamflow gains and losses computed for 21 stream reaches in the lower Guadalupe River Basin, south-central Texas, April 10–16, 2011.[Streamflow gain values are positive and streamflow loss values are negative. Bold red font indicates a streamflow loss that exceeded the measurement uncertainty for this reachstreamflow gain which exceeded the measurement uncertainty for this reach. USGS, U.S. Geological Survey; hr, hour; ft3/s, cubic feet per second; mi, mile; --, data not available

Reach 

number

Upstream 

USGS 

streamflowgaging 

station 

number

Map 

identifier

for 

upstream 

station1

Downstream 

USGS 

streamflowgaging 

station 

number

Map 

identifier 

for downstream 

station

Estimated 

traveltime (T) 

between 

upstream and 

downstream 

gaging stations 

(hr)

Upstream 

streamflow2

(ft3/s)

Downstream 

streamflow 

(ft3/s)

Estimated 

outflow3 between 

upstream and 

downstream 

sites 

(ft3/s)

Estimated 

inflow3

between 

upstream and 

downstream 

sites 

(ft3/s)

Streamflow gain 

or loss 

(ft3/s)

1 08167800 1 08168500 3 35 54.4 96.0 0.00 0.91 40.7 3 08168797 5 08169000 6 6 0.20 271 0.00 0.00 271 4 08168500 

08169000

3 6

408169500 7 2

1

96.2 

290

289 0.00 0.00 -97.2 

5 08169500 7 08169792 8 24 292 326 0.00 13.9 20.1 6 08169792 8 08169840 9 -- 344 -- 0.00 0.00 -- 7 08169840 9 08169860 10 -- -- 467 0.00 0.00 -- 9 08171000 14 08171290 15 44 28.2 22.6 0.00 0.00 -5.6 

10 08171290 15 08171300 16 17 23.0 4.3 0.00 0.00 -18.7 12 08170500 

08171300

12 16

408171500 17 30 

102

141 

6.84

155 0.00 6.96 7.16 

13 408171500 17 08172000 18 52 157 143 0.00 0.00 -14.0 15 08172400 19 08173000 20 99 1.74 6.99 0.00 2.01 3.24 16 08172000 

08173000

18 20

408173500 21 19 

44

144 

7.50

157 0.32 0.71 5.11 

17 08169860 

08173500

10 21

08173900 22 10 

74

443 161

449 0.00 0.00 -155 

19 08173900 

08174600

22 23

408174700 24 80 

72

490 

1.87

512 0.00 1.17 19.0 

21 08174970 25 08175000 26 -- -- -- -- -- -- 22 08174700

08175000

24 26

08175800 27 67 

36

500 

1.67

553 1.38 0.00 52.7 

23 08175800 27 08176500 28 95 588 503 0.00 1.58 -86.6 25 08176550 29 08176900 30 -- -- -- -- -- -- 27 08176900 

08177300

30 31

08177500 32 52 

82

6.25 0.03

5.15 0.00 0.00 -1.13 

28 08176500 

08177500

28 32

08177520 33 50 

57

519 

5.40

518 0.00 0.00 -6.4 

29 08177520 

08188570

33 34

08188800 35 44 

33

523 266

731 0.00 0.00 -58.0 

1Second map identifier is for the second station listed in the “Upstream USGS streamflow-gaging station number” column.2Computed streamflow was adjusted for traveltime to minimize effects of nonsteady-state streamflow. Hydrograph at upstream station adjusted for traveltime, in hours, prior t3Monthly average values for April 2011 (Texas Commission on Environmental Quality, 2011; U.S. Environmental Protection Agency, 2013).408169500 and 08174700 have no data for April 16. 08171500 and 08173500 have no data for April 15–16.
Table 9. Streamflow gains and losses computed for 21 stream reaches in the lower Guadalupe River Basin, south-central Texas, August 19–25, 2011[Streamflow gain values are positive and streamflow loss values are negative. Bold red font indicates a streamflow loss that exceeded the measurement uncertainty for this reachstreamflow gain which exceeded the measurement uncertainty for this reach. USGS, U.S. Geological Survey; hr, hour; ft3/s, cubic foot per second; mi, mile; N/A, not applicable

Reach Number Upstream USGS streamflow- gaging sta- tion number Map identifier for upstream station1 Downstream USGS streamflow gaging station number Map identifier for down- stream station Estimated traveltime (T) between upstream and downstream gaging stations (hr) Upstream streamflow2 (ft3/s) Down- stream streamflow (ft3/s) Estimated outflow3 between upstream and downstream sites (ft3/s) Estimated inflow3 between upstream and down- stream sites (ft3/s) Stream- flow gain or loss (ft3/s) 

1 08167800 1 08168500 3 36 63.9 60.9 0.00 0.69 -3.7 3 08168797 5 08169000 6 9 0.00 168 0.00 0.00 168 4 08168500 08169000 3 6 08169500 7 22 60.8 168 146 0.00 0.00 -82.8 5 08169500 7 08169792 8 26 147 106 0.39 12.9 -53.5 6 08169792 8 08169840 9 -- 130 -- 0.00 0.00 -- 7 08169840 9 08169860 10 -- -- 129 0.00 0.00 -- 9 08171000 14 08171290 15 34 8.84 6.64 0.00 0.00 -2.20 

10 08171290 15 08171300 16 18 6.60 0.00 0.00 0.00 -6.60 12 08170500 08171300 12 16 08171500 17 29 N/A4 93.7 0.00 82.8 0.00 5.78 -16.7 13 08171500 17 08172000 18 67 84.3 73.7 0.00 0.00 -10.6 15 08172400 19 08173000 20 116 2.48 2.38 0.00 2.01 -2.11 16 08172000 08173000 18 20 08173500 21 18 25 73.8 2.72 78.9 0.00 0.67 1.71 17 08169860 08173500 10 21 08173900 22 13 40 131 79.2 178 0.00 0.00 -32.2 19 08173900 08174600 22 23 08174700 24 ---- ---- -- -- -- -- 21 08174970 25 08175000 26 N/A4 0.00 0.092 0.00 0.00 0.092 22 08174700 08175000 24 26 08175800 27 ---- ---- -- -- -- -- 23 08175800 27 08176500 28 120 201 186 0.00 1.51 -16.5 25 08176550 29 08176900 30 -- -- -- -- -- -- 27 08176900 08177300 30 31 08177500 32 N/A4 N/A4 0.00 0.00 1.98 0.00 0.00 1.98 28 08176500 08177500 28 32 08177520 33 110 98 173 1.88 176 0.00 0.00 1.1 29 08177520 08188570 33 34 08188800 35 109 117 184 88.1 281 0.00 0.00 8.9 

1Second map identifier is for the second station listed in the “Upstream USGS streamflow-gaging station number” column. 2Computed streamflow was adjusted for traveltime to minimize effects of nonsteady-state streamflow. Hydrograph at upstream station adjusted for traveltime, in hours, prior t3Monthly average values for August 2011 (Texas Commission on Environmental Quality, 2011; U.S. Environmental Protection Agency, 2013). 4Traveltime not applicable because of zero streamflow at the upstream station.
Table 10. Streamflow gains and losses computed for a stream reach on the Guadalupe River from Seguin, Texas, to Gonzales, Tex., September 22–28[Streamflow gain values are positive and streamflow loss values are negative. USGS, U.S. Geological Survey; hr, hour; ft3/s, cubic feet per second; mi, mile; --, data not availabl

Reach 

number

Upstream 

USGS 

streamflowgaging 

station 

number

Map 

identifier 

for 

upstream 

station1

Downstream 

USGS 

streamflowgaging 

station 

number

Map 

identifier for 

downstream 

station

Estimated 

traveltime (T) 

between upstream 

and downstream 

gaging stations 

(hr)

Upstream 

streamflow2

(ft3/s)

Downstream 

streamflow 

(ft3/s)

Estimated 

outflow3

between 

upstream 

and 

downstream 

sites 

(ft3/s)

Estimated 

inflow3

between 

upstream 

and 

downstream 

sites 

(ft3/s)

Stream

flow 

gain o

loss 

(ft3/s)

6 08169792 8 08169840 9 -- 424 -- 0.0 0.0 -- 

7 08169840 9 08169860 10 -- -- 330 0.0 0.0 -- 

16 

417

081698600817200008173000

10 18 20

08173900 22 10

6171

335 158

5.65

454 3.11 0.72 -42 

1Second and third map identifiers are for the second and third stations, respectively, listed in the “Upstream USGS streamflow-gaging station number” column.2Computed streamflow was adjusted for traveltime to minimize effects of nonsteady-state streamflow. Hydrograph at upstream station adjusted for traveltime, in hours, prior t3Monthly average values for September 2012 (Texas Commission on Environmental Quality, 2011; U.S. Environmental Protection Agency, 2013).4Station 08173500 San Marcos River at Ottine, Tex., (site 21) was not active during 2012, so reaches 16 and 17 were combined for September 2012 analysis period.
22 A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin

Streamflow Gains and Losses during March 

15–21, 2010

Streamflow gains greater than the uncertainty in the 

computed streamflow were measured during a period of 

elevated base flow from March 15–21, 2010, in reaches 1, 

3, 15, 21 and 27 (fig. 6; table 7). Reach 1 (fig. 1), on the 

Guadalupe River downstream from Canyon Lake, gained 

130 ft3/s. Groundwater inflows from the Edwards aquifer 

account for much of this gain, with discharges from Hueco 

Springs representing a primary source of these inflows. 

The average daily streamflow at USGS streamflow-gaging 

station 08168000 Hueco Springs near New Braunfels, Tex., 

was 76.4 ft3/s during March 15–21, 2010. Reach 3 on the 

Comal River gained 359 ft3/s, nearly all of which represents 

the inflow from Comal Springs. Reach 15 on Plum Creek 

between Lockhart and Luling gained 19.8 ft3/s, likely as 

inflows from the Carrizo-Wilcox aquifer (mostly from the 

Wilcox Group, the primary formation exposure of this aquifer 

in this reach), or from alluvial terrace deposits of the Leona 

Formation (figs. 2 and 3). Reach 21 on Sandies Creek gained 

9.4 ft3/s, which might be from inflows from the Yegua Jackson 

aquifer, which is composed primarily of the Yegua Formation 

(fig. 3). Reach 27 gained 16.2 ft3/s; this gain is likely from 

groundwater inflows from the Gulf Coast aquifer, which are 

enhanced by seepage losses from Coleto Creek Reservoir 

that contribute to groundwater recharge from the Gulf Coast 

aquifer (the interaction of surface water and groundwater 

at Coleto Creek Reservoir). During the period of elevated 

base flow in March 2010, streamflow losses greater than the 

uncertainty in the computed streamflow were not measured in 

any of the reaches.

Streamflow Gains and Losses during April 

10–16, 2011

During the April 10–16, 2011, base-flow period, reaches 

1, 3, and 15 recorded gains greater than the uncertainty in the 

computed streamflow (fig. 7; table 8). The sources of these 

gains were believed to be the same as during the March 15–21 

assessment of gains and losses for these reaches. Reach 1 on 

the Guadalupe River gained 40.7 ft3/s (table 8). Reach 3 on the 

Comal River gained 271 ft3/s, which was similar to the gain 

of 359 ft3/s recorded in this reach during March 15–21, 2010. 

Reach 15 on Plum Creek between Lockhart and Luling gained 

3.24 ft3/s (fig. 7). During this base-flow period, losses greater 

in magnitude than the uncertainty in the computed streamflow 

were measured in three reaches (fig. 7). Reach 4, on the 

Guadalupe River at New Braunfels, Tex., lost 97.2 ft3/s. There 

are no aquifer outcrops along reach 4, and the reason for this 

loss is not known. Puente (1978, p. 28) made the following 

observations pertaining to the Guadalupe River immediately 

upstream from reach 4: 

The Guadalupe River crosses the infiltration area of 

the Edwards aquifer [outcrop of the Edwards Formation, fig. 2 in this report], but does not contribute 

recharge in significant quantities. Although 48 

square miles of area in the Guadalupe River basin is 

within the infiltration area, seepage studies indicate 

that the net streamflow losses and gains in the area 

are small and insignificant. The potentiometric surface of the aquifer in the New Braunfels area is generally at the level of the streambed of the Guadalupe 

River and is relatively stable because of the large 

and almost perennial flow of Comal Springs.

Puente (1978) was referring to the reach of the Guadalupe 

River that crosses the outcrop of the Edwards aquifer, and 

reach 4 begins at USGS streamflow-gaging stations 08168500 

Guadalupe River above Comal River at New Braunfels, 

Tex (map identifier 3) and 08169000 Comal River at New 

Braunfels, Tex. (map identifier 6)—both of which are about 

1 mi downstream from the outcrop of the Edwards aquifer. If 

the Guadalupe River does not provide appreciable recharge to 

the Edwards aquifer when it flows over the Edwards aquifer 

outcrop, it is unlikely to provide appreciable groundwater 

recharge downstream from the outcrop; however, according to 

the U.S. Drought Monitor (University of Nebraska–Lincoln, 

2013), by April 2011, Comal, Guadalupe, and Gonzales 

Counties were in extreme drought. Hence, infiltration along 

the stream channel may have occurred in areas where this had 

not been previously documented. Reach 10, the Blanco River 

near Kyle, lost 18.7 ft3/s. Most of the losses in this reach are 

likely in the form of recharge to the Edwards aquifer, which 

occurs through the numerous faults intersecting the channel 

(fig. 7) (Hanson and Small, 1995; U.S. Geological Survey, 

2012b) northwest of Kyle (fig. 1). Reach 17, which includes 

the confluence of the Guadalupe and San Marcos Rivers 

(fig. 7, inset B), lost 155 ft3/s. Recharge to the outcrops of 

Sparta, Queen City, and Yegua Jackson aquifers along this 

reach likely accounts for much of the streamflow losses that 

occur in this reach.
Lake Dunlap

Lake McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteenmile

Creek

Coleto

Creek

San Antonio River Dry Comal C reek

Guadalupe River

Sandies Creek

Plum

Creek

San Marcos River

Cypress Creek

Perdido Creek

Guadalupe River

Peach Creek

LEE

CO

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NTY

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CO

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U

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CO

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DEWITT COUNTY

JACK

CO

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CO

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FRIO

CO

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BEXAR COUNTY

COMAL

COUNTY

KENDALL

COUNTY

WILSON COUNTY

KARNES COUNTY

San

Marcos

130 Springs

19.8

9.4

16.2

H-5

DAM

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DAM

NOLTE

DAM 9

1

35 34

33

32 31

30 29

28

27

26

25

24

23

21

20

19

18

17

16

15

1112

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13

97°

98°

30°

29°

Base modified from U.S. Geological Survey 1:100,000 scale digital dataUniversal Transverse Mercator, zone 14 North American Datum of 1983 

Aquifer data from

George and others, 2011

Comal

Springs

Dry Comal Creek

Guadalupe River Hueco Springs

COMAL

COUNTY

7

5

46

3

2

359

130

Inset A

5

4

3

1

1

See inset A

7

7

Guadalupe River

Inset B

Wood Lake

San Marcos River

H-5

DAM

22

10

17 19

17

See inset B

8

9 10

12 11

6

29

28

27

26

25

24

23

22

21

20

18

19

17

16

15

14

13

12

5

2

1

7

Mean daily streamflow measured at 

selected sites during March 15–21, 2010 

Map

identifier

8

22

Streamflow, 

in cubic feet 

per second

1,2301,950

U.S. Geological 

Survey station 

number

0816979208173900

0 5 10 20 MILES0 5 10 20 KILOMETERS

15

15

7

EXPLANAT

Major aquifer s Gulf Coast Carrizo-Wilco Edwards-Trini Edwards TrinityMinor aquifer s Yegua Jackso Sparta Queen CityFaultLower GuadaluStreamflow gai in cubic feet 

The only gain

 those larger  uncertainty i

U.S. Geological  station and mSpringReach number—

9

19.8

29

7

7

7

Figure 6. Streamflow gains and losses, March 15–21, 2010, lower Guadalupe River Basin, south-central Texas.
Lake Dunlap

Lake McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteenmile

Creek

Coleto

Creek

San Antonio River Dry Comal C reek

Guadalupe River

Sandies Creek

Plum

Creek

San Marcos River

Cypress Creek

Perdido Creek

Guadalupe River

Peach Creek

LEE

CO

U

NTY

GILLESPIE

CO

U

NTY

BLANCO

COUNTY

BASTROP COUNTY

WASH

CO

HAYS COUNTY

KER

R

CO

U

NTY

FAYETTE

COUNTY

CALDWELL COUNTY

COLO

BA

N

DERA

CO

U

NTY

G

U

A

D

ALUPE

CO

U

NTY

GONZALES COUNTY

MEDIN

A

CO

U

NTY

LAVACA COUNTY

DEWITT COUNTY

JACKS

CO

U

NT

ATASCOSA

CO

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VICTORIA

COUNTY

FRIO

CO

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GOLIAD COUNTY

LIVE O

A

K

CO

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COUNTY

BEE

LA SALLE CO

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CO

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ULLEN

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REFUGIO

COUNTY

TRAVIS COUNTY

BEXAR COUNTY

COMAL

COUNTY

KENDALL

COUNTY

WILSON COUNTY

KARNES COUNTY

San

Marcos

Springs

H-5

DAM

H-4

DAM

NOLTE

DAM 9

1

35 34

33

32 31

30 29

28

27

26

25

24

23

21

20

19

18

17

16

15

1112

8

14

13

97°

98°

30°

29°

Aquifer data from

 George and others, 2011

Base modified from U.S. Geological Survey 1:100,000 scale digital dataUniversal Transverse Mercator, zone 14 North American Datum of 1983 

Guadalupe River

Dry Comal Creek

COMAL

COUNTY

7

5

46

3

2

Comal

Springs

Hueco

Springs

Inset A

271

40.7

–97.2

4

3

1

1

5

See inset A

7

7

Guadalupe River

Inset B

Wood Lake

San Marcos River

H-5

DAM

22

10

–155

17 19

17

See inset B

40.7

3.24

–155

–18.7

Mean daily stre

selected sites du

Map

identifier

8

22

U.S. Ge

Survey 

nu

081081

8

9 10

12 11

6

29

28

27

26

25

24

23

22

21

20

18

19

17

16

15

14

13

12

5

2

1

7

0 5 10 20 MILES0 5 10 20 KILOMETERS

15

15

7

EXPLANATI

Major aquifer sy Gulf Coast Carrizo-Wilcox Edwards-Trinity Edwards TrinityMinor aquifer sy Yegua Jackson Sparta Queen CityFaultLower GuadalupStreamflow gain  amount in cub

The only gains 

 those larger in  uncertainty in 

 Streamflow gai Streamflow losU.S. Geological S station and maSpringReach number—

9

40.7

–18.7

29

7

7

7

Figure 7. Streamflow gains and losses, April 10–16, 2011, lower Guadalupe River Basin, south-central Texas.
Streamflow Gains and Losses 25

Streamflow Gains and Losses during August 

19–25, 2011

The August 19–25, 2011, period represents base-flow 

conditions during the most severe drought conditions since 

the 1950s (Winters, 2013). During the August 19–25, 2011, 

base-flow period, three reaches had gains greater than the 

uncertainty in the computed streamflow (fig. 8; table 9). Reach 

3 on the Comal River gained 168 ft3/s; nearly all of this gain 

represents inflow from Comal Springs as in the March 2010 

and April 2011 base-flow periods. Reach 21 on Sandies Creek 

gained a small amount of flow (0.092 ft3/s). Reach 27, which 

includes Coleto Creek, Perdido Creek, and Coleto Creek 

Reservoir, gained 1.98 ft3/s, likely as a result of groundwater 

inflows from the Gulf Coast aquifer, which are enhanced along 

this reach by seepage losses from Coleto Creek Reservoir. 

During this period of extreme drought, five reaches had losses 

greater in magnitude than the uncertainty in the computed 

streamflow (fig. 8). Reach 4, including the confluence of the 

Guadalupe and Comal Rivers, lost 82.8 ft3/s. Reach 5 on the 

Guadalupe River lost 53.5 ft3/s, with part of that loss possibly 

occurring as infiltration to the alluvium of the streambed or 

as recharge to the Carrizo-Wilcox aquifer outcrop (figs. 2–3). 

Reaches 9 and 10 of the Blanco River lost 2.20 and 6.60 

ft3/s, respectively, likely as infiltration through numerous 

faults (Hanson and Small, 1995; U.S. Geological Survey, 

2012b) intersecting the stream channel northwest of Kyle 

(fig. 1). Whereas reach 15 on Plum Creek between Lockhart 

and Luling gained streamflow during the March 2010 and 

April 2011 assessments, reach 15 lost 2.11 ft3/s during the 

August 2011 assessment. Water levels in the Carrizo-Wilcox 

aquifer were likely much lower in August 2011 compared to 

March 2010 and April 2011, causing the stream to lose water 

to the Carrizo-Wilcox aquifer or to alluvial terrace deposits 

of the Leona Formation that by August 2011 were dried out 

compared to the previous assessments. 

Streamflow Gains and Losses during September 

22–28, 2012

Analysis of the September 22–28, 2012, base-flow period 

was only done for reaches 6, 7, 16, and 17 on the Guadalupe 

River between Seguin, Tex., and Gonzalez, Tex. Inflows from 

San Marcos River and Plum Creek (fig. 9) were included in 

this assessment. Because USGS streamflow-gaging station 

08173500 San Marcos River at Ottine, Tex., was not active 

during 2012, the streamflows for USGS streamflow-gaging 

stations 08172000 San Marcos River at Luling, Tex., and 

08173000 Plum Creek near Luling, Tex., were included in the 

assessment of the Guadalupe River reach between Seguin, 

Tex., and Gonzalez, Tex. During the September 22–28, 2012, 

base-flow period, no computed gains or losses were greater in 

magnitude than the uncertainty in the computed streamflow 

(table 10).
Lake Dunlap

Lake McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteenmile

Creek

Coleto

Creek

San Antonio River Dry Comal C reek

Guadalupe River

Sandies Creek

Plum

Creek

San Marcos River

Cypress Creek

Perdido Creek

Guadalupe River

Peach Creek

LEE

CO

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NTY

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CO

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COUNTY

BASTROP COUNTY

WAS

C

HAYS COUNTY

KER

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COL

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DEWITT COUNTY

JACK

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CO

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LIVE O

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ULLEN

CO

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COUNTY

TRAVIS COUNTY

BEXAR COUNTY

COMAL

COUNTY

KENDALL

COUNTY

WILSON COUNTY

KARNES COUNTY

San

Marcos

Springs

H-5

DAM

H-4

DAM

NOLTE

DAM

17

8

9 10

11 12

6

29

28

27 26

25

24

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7 9

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35 34

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27

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25

24

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21

20

19

18

17

16

15

1112

8

14

13

97°

98°

30°

29°

Aquifer data from

 George and others, 2011

Base modified from U.S. Geological Survey 1:100,000 scale digital dataUniversal Transverse Mercator, zone 14 North American Datum of 1983 

7

5

46

3

2

Comal

Springs

Hueco

Springs

Inset A

See inset A

Dry Comal Creek

Guadalupe River

COMAL

COUNTY

4

3

1

1

168

–82.8

5

4

3

5

7

7

Guadalupe River

See inset B

Inset B

Wood Lake

San Marcos River

H-5

DAM

22

10

17 19

17

–2.11

1.98

0.092

–6.60

–2.20

–53.5

EXPLA

Major aquifer s Gulf Coast Carrizo-Wilco Edwards-Trin Edwards TrinityMinor aquifer s Yegua Jackso Sparta Queen CityFaultLower GuadaluStreamflow gai amount in cu

The only gain

 those larger  uncertainty i

 Streamflow g Streamflow loU.S. Geologica station and mSpringReach number—

9

168

–82.8

29

7

7

7

7

0 5 10 20 MILES0 5 10 20 KILOMETERS

15

15

Mean daily streamflow measured at

selected sites during August 19–25, 2011

Map

identifier

8

22

Streamflow, 

in cubic feet 

per second

106181

U.S. Geological 

Survey station 

number

0816979208173900

Figure 8. Streamflow gains and losses, August 19–25, 2011, lower Guadalupe River Basin, south-central Texas.
Note: No gains or l magnitude than  computed strea September 22–2

"

"

"

"

"

"

"

"

"

"

TRAVIS COUNTY

GILLESPIE

CO

U

NTY

BLANCO

COUNTY

BASTROP COUNTY

HAYS COUNTY

KERR COUNTY

FAYETTE

COUNTY

KENDALL

COUNTY

CALDWELL COUNTY

COMAL COUNTY

BANDERA COUNTY

GUADALUPE

COUNTY

GONZALES

COUNTY

BEXAR COUNTY

LAVACA

COUNTY

WILSON COUNTY

DEWITT COUNTY

KARNES COUNTY

VICTORIA COUNTY

GOLIAD

COUNTY

CALHOUN

COUNTY

REFUGIO

COUNTY

Dilworth Oak Forest

Bloomington Fannin

Ottine

Sattler

Tivoli

Weser

Westhoff

97°

99° 98°

29°

30°

H-5

DAM

Wood Lake

Guadalupe River

22

10

17

19

17

17

7

Inset B

San Marcos River

See inset B

COMAL

COUNTY

Hueco

Springs

Comal Springs

Guadalupe River

4 7

5

6

3

2

Comal

River

7

7

5

4

3

1

1

Inset A

Dry Comal Creek

See inset A H-5

DAM

H-4

DAM

NOLTE

DAM

8

9 10

12

11

6

29

28

27

26

25

24 23

22

21

20

18

19

17

16

15

14

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5

2

1

7 9

1

35 34

33

32

31

30 29

28

27

26

25 24

23

21

20

19

18

17

16

15

1112

8

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7

7

7

0 10 20 40 MILES0 10 20 40 KILOMETERS

30

30

Base modified from U.S. Geological Survey 1:100,000 scale digital dataUniversal Transverse Mercator, zone 14 North American Datum of 1983 

Blanco River

Guadalupe

River

Lake

Dunlap

Lake

McQueeney

Coleto Creek

Reservoir

Canyon Lake

Fifteen Mile

Creek

Coleto

Creek

San  Antonio Bay

San

Marcos

Springs

San Antonio River

Guadalupe River Dry Comal Creek

Sandies Creek

Perdido Creek

Peach Creek

Plum

Creek

San Marcos River

EXPLANATION

Major aquifer syste

Gulf Coast

 Carrizo-Wilcox Edwards-Trinity Edwards TrinityMinor aquifer syste Yegua Jackson Sparta Queen CityFaultLower Guadalupe RBoundary for exten analysis for SepU.S. Geological Su station and map iSpringReach number—Ta

9

29

7

Aquifer data from

 George and others, 2011

Mean daily streamflow measured at

selected sites during September 22–28, 2012

Map

identifier

8

22

Streamflow, 

in cubic feet 

per second

426457

U.S. Geological 

Survey station 

number

0816979208173900

Runge

Figure 9. Streamflow gains and losses, September 22–28, 2012, in a reach of the Guadalupe River from Seguin, Texas, to Gonzales, Tex., lower Guadcentral Texas.
28 A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin

Summary

This report describes streamflow in the lower Guadalupe 

River Basin, consisting of the Guadalupe River drainage basin 

downstream from Canyon Lake to the Guadalupe River near 

Tivoli, Texas, during selected base-flow periods in 2010–12. 

The U.S. Geological Survey, in cooperation with the U.S. 

Army Corps of Engineers–Fort Worth District, the Texas 

Water Development Board, the Guadalupe-Blanco River 

Authority, and the Edwards Aquifer Authority, investigated 

streamflow gains and losses in the lower Guadalupe River 

Basin during four base-flow periods in March 2010, April 

2011, August 2011, and September 2012. Streamflow and 

springflow data were collected at 35 streamflow-gaging 

stations (including 6 deployed for this study) in the study 

area during the selected base-flow periods from 2010–11. The 

assessment of streamflow in September 2012 was limited to 

the Guadalupe River between Seguin, Tex., and Gonzales, 

Tex., and the San Marcos River between Luling, Tex., and 

Gonzales, Tex. 

During the March 15–21, 2010, base-flow period, five 

reaches had gains greater than the uncertainty in the computed 

streamflow. Reach 1 on the Guadalupe River downstream from 

Canyon Lake gained 130 cubic feet per second (ft3/s). This 

gain primarily is from groundwater inflow from the Edwards 

aquifer outcrop, which includes a large contribution from 

Hueco Springs. Reach 3 on the Comal River gained 359 ft3/s, 

nearly all of which represents the inflow from Comal Springs. 

Reach 15 on Plum Creek between Lockhart and Luling gained 

19.8 ft3/s, which likely represents inflow from the CarrizoWilcox aquifer or from alluvial terrace deposits of the Leona 

Formation. Reach 21 on Sandies Creek gained 9.4 ft3/s, which 

might be related to inflows from the Yegua Jackson aquifer 

that is composed primarily of the Yegua Formation. Reach 

27 gained 16.2 ft3/s, which likely is a result of groundwater 

inflows from the Gulf Coast aquifer that are enhanced by 

seepage losses from Coleto Creek Reservoir. During this 

period of elevated base flow in March 2010, streamflow losses 

greater than the uncertainty in the computed streamflow were 

not measured in any of the reaches.

During the April 10–16, 2011, base-flow period, three 

reaches had gains greater than the uncertainty in the computed 

streamflow. Reach 1 on the Guadalupe River gained 40.7 

ft3/s; this gain was likely caused by inflows from the Edwards 

aquifer and Hueco Springs. Reach 3 on the Comal River 

gained 271 ft3/s, nearly all of which represents the inflow 

from Comal Springs. Reach 15 on Plum Creek between 

Lockhart and Luling gained 3.24 ft3/s, which is likely related 

to inflows from the Carrizo aquifer or inflows from alluvial 

terrace deposits of the Leona Formation. During this base-flow 

period, losses greater in magnitude than the uncertainty in the 

computed streamflow were measured in three reaches. Reach 

4 on the Guadalupe River near New Braunfels, Tex., lost 97.2 

ft3/s. Reach 10, the Blanco River near Kyle, lost 18.7 ft3/s, and 

reach 17, which includes the confluence of the Guadalupe and 

San Marcos Rivers, lost 155 ft3/s. 

During the August 19–25, 2011, base-flow period, three 

reaches had gains greater than the uncertainty in the computed 

streamflow. Reach 3 on the Comal River gained 168 ft3/s, 

nearly all of which represents inflow from Comal Springs. 

Reach 21 on Sandies Creek gained 0.092 ft3/s. Reach 27, 

including Coleto Creek, Perdido Creek, and Coleto Creek 

Reservoir, gained 1.98 ft3/s, likely as a result of groundwater 

inflows from the Gulf Coast aquifer, which are enhanced in 

the area near reach 27 by seepage losses to the groundwater 

system from Coleto Creek Reservoir. During this period of 

extreme drought, five reaches had losses greater in magnitude 

than the uncertainty in the computed streamflow. Reach 4, 

including the confluence of the Guadalupe and Comal Rivers, 

lost 82.8 ft3/s. Reach 5 on the Guadalupe River lost 53.5 

ft3/s, with part of that loss possibly occurring as infiltration to 

the alluvium of the streambed or as recharge to the CarrizoWilcox aquifer outcrop. Reaches 9 and 10 of the Blanco 

River lost 2.20 and 6.60 ft3/s, respectively, likely through the 

numerous faults that intersect the stream channel northwest of 

Kyle. Reach 15 on Plum Creek between Lockhart and Luling 

lost 2.11 ft3/s; this loss was also likely in the form of recharge 

to the Carrizo-Wilcox aquifer outcrop. 

Analysis of the September 22–28, 2012, base-flow 

period was limited to reaches 6, 7, 16, and 17 on the 

Guadalupe River between Seguin, Tex., and Gonzalez, Tex., 

including flows from San Marcos River and Plum Creek. 

The streamflow-gaging station San Marcos River at Ottine, 

Tex., was not active during 2012 so the streamflows for San 

Marcos River at Luling, Tex., and Plum Creek near Luling, 

Tex., were included in the assessment of the Guadalupe River 

reach between Seguin, Tex., and Gonzalez, Tex. During the 

September 22–28, 2012, base-flow period no computed gains 

or losses were greater in magnitude than the uncertainty in the 

computed streamflow.

References Cited

Aronow, Saul., Brown, T.E., Brewton, J.L., Eargle, D.H., 

and Barnes, V.E., 1987, Geologic atlas of Texas, GA0005 

Beeville-Bay City sheet: Austin, The University of Texas, 

Bureau of Economic Geology, 4 p., 1 sheet.

Brown, T.E., Waechter, N.B., Owens, Frith, Howeth, Ike, 

and Barnes, V.E., 1976, Geologic atlas of Texas, GA0011 

Crystal-City Eagle Pass sheet: Austin, The University of 

Texas, Bureau of Economic Geology, 6 p., 1 sheet.

Brown, T.E., Waechter, N.B., and Barnes, V.E., 1983, 

Geologic atlas of Texas, GA0029 San Antonio sheet: 

Austin, The University of Texas, Bureau of Economic 

Geology, 8 p., 1 sheet.

Brune, G.M., 1975, Major and historical springs of Texas: 

Texas Water Development Board Report 189, 91 p.

Environmental Systems Research Institute, Inc., 2008, 

ArcMap, GIS software, Version 9.2: Redlands, Calif. 
References Cited 29

Fulford, J.M., 1992, Characteristics of U.S. Geological 

Survey discharge measurements for water year 1990: U.S. 

Geological Survey Open-File Report 92–493, 79 p.

George, P.G., Mace, R.E., and Petrossian, Rima, 2011, 

Aquifers of Texas: Texas Water Development Board Report 

380, 172 p.

Granato, G.E., 2009, Computer programs for obtaining 

and analyzing daily mean streamflow data from the U.S. 

Geological Survey National Water Information System Web 

Site: U.S. Geological Survey Open-File Report 2008–1362, 

123 p.

Guadalupe-Blanco River Authority, 2007a, Canyon Lake fact 

sheet: accessed October 10, 2007, at http://www.gbra.org/

Public/CanyonReservoir.aspx.

Guadalupe-Blanco River Authority, 2007b, Coleto Creek 

Park and reservoir fact sheet: Guadalupe-Blanco River 

Authority, accessed October 10, 2007, at http://www.gbra.

org/Recreation/ColetoCreek/Default.aspx.

Hanson, J.A., and Small, T.A., 1995, Geologic framework 

and hydrogeologic characteristics of the Edwards aquifer 

outcrop, Hays County, Texas: U.S. Geological Survey 

Water-Resources Investigations Report: 95–4265, 10 p.

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources—Hydrologic analysis and interpretation: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 4, chap. A3, 510 p., accessed March 

2008, at http://pubs.usgs.gov/twri/twri4a3/.

Hirsch, R.M., 1982, A comparison of four streamflow record 

extension techniques: Water Resources Research, v. 18, 

no. 4, p. 1081–1088.

Larkin, T.J., and Bomar, G.W., 1983, Climatic atlas of Texas: 

Texas Department of Water Resources Limited Printing 

Report LP–192, 151 p.

Lizárraga, J.S., and Ockerman, D.J., 2010, Simulation of 

streamflow, evapotranspiration, and groundwater recharge 

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Wehmeyer and others—A Preliminary Assessment of Streamflow Gains and Losses for Selected Stream Reaches in the Lower Guadalupe River Basin—SIR 2013–5209

Printed on recycled paper

ISSN 2328-0328 (online)

ISSN 2328-031X (print)

http://dx.doi.org/10.3133/sir20135209

I SBN 978- 1- 4113-3725- 1

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