U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5181

Prepared in cooperation with the U.S. Army Corps of Engineers, The Nature Conservancy,

the Real Edwards Conservation and Reclamation District, and the Texas Parks and

Wildlife Department

Streamflow Gain and Loss and Water Quality in the Upper 

Nueces River Basin, South-Central, Texas, 2008–10
Front cover, Frio River at Garner State Park approximately 8 miles upstream from Concan, Texas 

(June, 2012).

Back cover, Frio River at Garner State Park approximately 8 miles upstream from Concan, Texas 

(June, 2012).
Streamflow Gain and Loss and Water 

Quality in the Upper Nueces River Basin, 

South-Central Texas, 2008–10

By J. Ryan Banta, Rebecca B. Lambert, Richard N. Slattery, and 

Darwin J. Ockerman

Prepared in cooperation with the U.S. Army Corps of Engineers, 

The Nature Conservancy, the Real Edwards Conservation and Reclamation 

District, and the Texas Parks and Wildlife Department

Scientific Investigations Report 2012–5181

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

This and other USGS information products are available at http://store.usgs.gov/

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Banta, J.R., Lambert, R.B., Slattery, R.N., and Ockerman, D.J., 2012, Streamflow gain and loss and water quality in 

the upper Nueces River Basin, south-central Texas, 2008–10: U.S. Geological Survey Scientific Investigations Report 

2012–5181, 40 p. 
iii

Contents

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

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

Purpose and Scope .............................................................................................................................3

Description of Study Area ..................................................................................................................3

Data-Collection Methods .............................................................................................................................3

Hydrologic Data Collection ................................................................................................................3

Quality Assurance of Hydrologic Measurements ........................................................................11

Computation of Streamflow Gain and Loss ...................................................................................11

Water-Quality Data Collection .........................................................................................................14

Quality Assurance of Water-Quality Samples ...............................................................................15

Streamflow Gain and Loss .........................................................................................................................15

Water-Quality Data .....................................................................................................................................20

Summary .......................................................................................................................................................27

References ...................................................................................................................................................28

Appendixes 1–3 

1. Quality-assurance hydrologic measurements during the July 2008, August 2009, 

and March 2010 surveys in the upper Nueces River Basin, south-central Texas ..........33

2. Water-quality data collected during the August 2009 and March 2010 surveys in 

the upper Nueces River Basin, south-central Texas ...........................................................34

3. Quality-assurance water-quality data during the August 2009 and March 2010 

surveys in the upper Nueces River Basin, south-central Texas ........................................39

Figures

1. Map showing location of data-collection sites in the upper Nueces River Basin 

study area, south-central Texas, 2008–10 ...............................................................................2

2. Map showing Edwards–Trinity (Plateau), Trinity, and Edwards aquifer outcrops 

and data-collection sites in the upper Nueces River Basin, south-central Texas ...........9

3. Map showing surficial geologic units and data-collection sites in the upper 

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

4. Graphs showing daily mean streamflow at U.S. Geological Survey streamflowgaging stations in south-central Texas during 1950–2010 ..................................................12

5. Map showing streamflow measurements in the upper Nueces River Basin, 

south-central Texas, during July 2008 ....................................................................................16

6. Map showing streamflow and springflow measurements in the upper Nueces 

River Basin, south-central Texas, during August 2009 ........................................................17

7. Map showing streamflow and springflow measurements in the upper Nueces 

River Basin, south-central Texas, during March 2010 .........................................................18

8. Graphs showing comparisons of measured rainfall, streamflow, and groundwater 

levels in the Nueces River watershed of the upper Nueces River Basin study 

area, south-central Texas, 2009–10 ........................................................................................21

9. Trilinear diagrams of chemical composition for streamflow, springflow, and 

groundwater samples collected in the upper Nueces River Basin, south-central 

Texas, August 2009 ....................................................................................................................22
iv

10. Trilinear diagrams of chemical composition for streamflow, springflow, and 

groundwater samples collected in the upper Nueces River Basin, south-central 

Texas, March 2010 .....................................................................................................................23

11. Graphs showing relations of molar ratios to calcium concentrations for 

streamflow, springflow, and groundwater samples collected in the upper 

Nueces River Basin, south-central Texas, August 2009 and March 2010 ........................24

12. Graph showing relation of inverse strontium concentration to strontium-87/

strontium-86 isotopic ratio for streamflow, springflow, and groundwater 

samples collected in the upper Nueces River Basin, south-central Texas, 

August 2009 and March 2010 ...................................................................................................25

13. Graphs showing relations between molar ratios and strontium-87/strontium-86 

isotopic ratios for streamflow, springflow, and groundwater samples collected 

in the upper Nueces River Basin, south-central Texas, August 2009 and 

March 2010 .................................................................................................................................26

Tables

1. Hydrologic and water-quality data-collection sites and streamflow, springflow, 

and groundwater measurements in the upper Nueces River Basin, south-central 

Texas ..............................................................................................................................................4

2. Daily mean streamflow at U.S. Geological Survey streamflow-gaging stations in 

the upper Nueces River Basin, south-central Texas, during 2008–10 surveys and 

percentiles of daily mean streamflow from long-term (1950–2010) streamflow 

records ........................................................................................................................................13
v

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

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

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

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

Volume

liter (L) 61.02 cubic inch (in3) 

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

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

°F=(1.8×°C)+32

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

°C=(°F-32)/1.8

Datums

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).

Water-Quality Units

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

25°C).

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

in micrograms per liter (μg/L).
vi

Isotope Units

Per mil: A unit expressing the ratio of stable-isotope abundances of an element in a sample to 

those of a standard material. Per mil units are equivalent to parts per thousand. Stable-isotope 

ratios, also known as delta values, are computed as follows (Kehew, 2001):

δX = [(Rsample - Rstandard)/ Rstandard] x 1,000

where

	 δ = delta,

X = heavier stable isotope, and

R = ratio of rare (heavier) isotope to common (lighter) isotope in sample or 

standard.

The δ values for stable-isotope ratios discussed in this report are referenced to the following 

standard materials:

Element R Standard identity and reference

Hydrogen Hydrogen-2/hydrogen-1 Vienna Standard Mean Ocean Water (Coplen, 1994)

Oxygen Oxygen-18/oxygen-16 Vienna Standard Mean Ocean Water (Coplen, 1994)
Streamflow Gain and Loss and Water Quality in the Upper 

Nueces River Basin, South-Central Texas, 2008–10

By J. Ryan Banta, Rebecca B. Lambert, Richard N. Slattery, and Darwin J. Ockerman

Abstract 

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

U.S. Army Corps of Engineers, The Nature Conservancy, 

the Real Edwards Conservation and Reclamation District, 

and the Texas Parks and Wildlife Department—investigated 

streamflow gain and loss and water quality in the upper 

Nueces River Basin, south-central Texas, specifically in the 

watersheds of the West Nueces, Nueces, Dry Frio, Frio, and 

Sabinal Rivers upstream from the Edwards aquifer outcrop. 

Streamflow in these rivers is sustained by groundwater 

contributions (for example, from springs) and storm 

runoff from rainfall events. To date (2012), there are few 

data available that describe streamflow and water-quality 

conditions of the rivers within the upper Nueces River Basin. 

This report describes streamflow gain-loss characteristics 

from three reconnaissance-level synoptic measurement 

surveys (hereinafter referred to as “surveys”) during 2008–10 

in the upper Nueces River Basin. To help characterize the 

hydrology, groundwater-level measurements were made, and 

water-quality samples were collected from both surface-water 

and groundwater sites in the study area from two surveys 

during 2009–10. The hydrologic (streamflow, springflow, 

and groundwater) measurements were made during three 

reconnaissance-level synoptic measurement surveys occurring 

in July 21–23, 2008; August 8–18, 2009; and March 22–24, 

2010. These survey periods were selected to represent 

different hydrologic conditions. Streamflow gains and losses 

were based on streamflow and springflow measurements 

made at 74 sites in the study area, although not all sites were 

measured during each survey. Possible water chemistry 

relations among sample types (streamflow, springflow, or 

groundwater), between surveys, and among watersheds were 

examined using water-quality samples collected from as many 

as 20 sites in the study area.

During the three surveys, reaches of gaining, losing, 

or no verifiable change in streamflow were observed in the 

watersheds in the study area. Reaches of generally consistent 

gaining or losing streamflow were identified in the Nueces, 

Frio, and Sabinal River watersheds. The water-quality data 

indicate that the streamflow, springflow, and groundwater 

have similar major ion chemical characteristics and generally 

can be categorized as a calcium-carbonate water type. Those 

data also indicate that the major ion chemistry was similar 

during the 2009 and 2010 surveys. Graphical comparisons 

among ratios of major ions, trace elements, and isotopes (for 

example, magnesium/calcium ratios to strontium isotopic 

ratios) indicate that samples collected from each watershed 

generally clustered together. Determining the source areas and 

other possible contributors on the basis of these data is not 

possible because of the small sample size of the water-quality 

dataset (both in number of samples and spatial distribution of 

samples). The different relations among the water-quality data 

indicate that the surface water in the different watersheds is 

likely influenced by differences in source areas, geochemical 

evolution, groundwater flow paths and residence time, local 

stratigraphy, or some combination thereof.

Introduction

The U.S. Geological Survey (USGS)—in cooperation 

with the U.S. Army Corps of Engineers, The Nature 

Conservancy, the Real Edwards Conservation and 

Reclamation District, and the Texas Parks and Wildlife 

Department—investigated streamflow gain and loss and 

water quality in the upper Nueces River Basin, south-central 

Texas, from 2008–10 (fig. 1). The upper Nueces River Basin, 

defined here as the part of the Nueces River Basin north 

of the Edwards aquifer outcrop, includes the West Nueces, 

Nueces, Dry Frio, Frio, and Sabinal Rivers. Streamflow in 

these rivers is sustained by groundwater contributions (for 

example, from springs) and storm runoff from rainfall events. 

The upper Nueces River Basin is an area of particular interest 

to water managers in south-central Texas because appreciable 

streamflow gains and losses are observed along various 

reaches in the area. Gains and losses in the study area have 

been documented in previous studies (Slade and others, 2002), 

and anecdotal observations indicate that streamflow might 

be present at the headwaters of a river, then the river channel 

may be dry a few miles downstream, and then streamflow 

reemerges farther downstream. Additionally, rivers originating 

in the upper Nueces River Basin lose streamflow as they cross 

the Edwards aquifer outcrop, thus providing recharge to the 
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EXPLANATION

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East Frio River

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Nueces River

Sabinal River

West Sabinal River

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East Frio River

Bullhead Creek

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Figure 1. Location of data-collection sites in the upper Nueces River Basin study area, south-central Texas, 2008–10. 
Data-Collection Methods 3

Edwards aquifer (Maclay, 1995). The Edwards aquifer is the 

primary source of drinking water for the greater San Antonio, 

Tex., area. 

Currently (2012) for the upper Nueces River Basin, few 

data are available that describe streamflow and water-quality 

conditions of the West Nueces, Nueces, Dry Frio, Frio, and 

Sabinal Rivers. Slade and others (2002) identified previous 

studies of streamflow gains and losses in the upper Nueces 

River Basin. The earliest streamflow gain-loss synoptic 

measurement survey was done in 1924 by the Texas Board 

of Water Engineers (TWBE) (the name and function of 

TWBE were changed several times by the Texas Legislature, 

and most functions related to hydrology were transferred 

to a new agency, the Texas Water Development Board in 

1965). Synoptic measurements are defined as “those done 

concurrently over a broad area at a set time to give a ‘snap 

shot’ of hydrologic conditions” (Beck and Wilson, 2006, p. 1). 

Several streamflow synoptic measurement surveys were done 

by the Texas Board of Water Engineers in the 1950s, during a 

period of pronounced drought in central Texas. These 1950s 

streamflow measurement surveys demonstrated that the upper 

Nueces River Basin is an area with both streamflow gains 

and losses (Slade and others, 2002). Since the 1950s, there 

has been little additional work to measure streamflow gains 

and losses, and only a few water-quality samples in the study 

area have been collected for chemical analysis (for example, 

Fahlquist and Ardis, 2004). 

Purpose and Scope

The purpose of this report is to describe streamflow gainloss characteristics from three reconnaissance-level synoptic 

measurement surveys in 2008, 2009, and 2010 in the upper 

Nueces River Basin, south-central Texas. Information obtained 

from groundwater levels that were measured and water-quality 

samples that were collected as part of the 2009 and 2010 

surveys was used to better understand hydrologic conditions 

in the study area. Streamflow gains and losses were based on 

streamflow and springflow measurements made at 74 sites in 

the study area, although not all sites were measured during 

each survey. Possible water chemistry relations among sample 

types (streamflow, springflow, or groundwater), between 

surveys, and among watersheds were examined using waterquality samples collected from as many as 20 sites in the study 

area. 

Description of Study Area

The upper Nueces River Basin covers 2,152 square miles 

in south-central Texas and is composed of the contributing 

areas for five USGS streamflow-gaging stations (sites 7, 33, 

38, 61, and 74; fig. 1, table 1). These contributing areas are 

hereinafter referred to as the West Nueces, Nueces, Dry Frio, 

Frio, and Sabinal River watersheds, respectively. The study 

area is predominantly rural and hilly, with an approximate 

1,000-foot (ft) range from the highest to lowest land-surface 

elevations in the study area (North American Vertical Datum 

of 1988 [NAVD 88]). The climate of the study area transitions 

from subtropical steppe in the western part of the study area to 

subtropical subhumid in the eastern part (Larkin and Bomar, 

1983). The rainfall pattern increases from west to east with the 

average annual rainfall (1951–80) ranging from approximately 

22 inches (in.) per year in the western part of the study area to 

28 in. per year in the eastern part (Larkin and Bomar, 1983). 

Daily rainfall amounts greater than 1 in. can occur anytime 

during the year (Larkin and Bomar, 1983). 

The Edwards–Trinity (Plateau) and Trinity aquifers are 

the primary aquifers in the upper Nueces River Basin area 

(Ashworth and Hopkins, 1995) (fig. 2). Information regarding 

surficial geologic formations in the study area was obtained 

from the “Geologic Atlas of Texas” by the University of Texas, 

Bureau of Economic Geology: San Antonio Sheet and Del Rio 

Sheet (Brown, 1963; Brown, 1965; Rose, 1972). The main 

geologic units outcropping in the study area include the upper 

member of the Glen Rose Limestone of the Trinity Group, 

the Devils River Limestone, and the Fort Terrett and Segovia 

Formations of the Edwards Group (fig. 3). The river channels 

generally consist of the Fort Terrett Formation of the Edwards 

Group and the upper member of the Glen Rose Limestone of 

the Trinity Group in the upper reaches of the study area, and 

of Quaternary-age deposits (for example, alluvium deposits) in 

the middle and lower reaches. 

Data-Collection Methods

Hydrologic (streamflow, springflow, and groundwater) 

measurements were made during three reconnaissance-level 

synoptic measurement surveys occurring in July 21–23, 2008; 

August 8–18, 2009; and March 22–24, 2010. Additionally, 

continuous groundwater levels were measured at site 76 

(fig. 1, table 1) during 2009–10. Water-quality samples were 

collected during the August 2009 and March 2010 surveys.

Hydrologic Data Collection

In the five watersheds composing the study area (the 

West Nueces, Nueces, Dry Frio, Frio, and Sabinal Rivers) 

streamflow or springflow measurements were made at 74 

sites, although not all sites were measured during each survey 

(48 measurement sites during July 2008, 52 measurement 

sites during August 2009, and 33 measurement sites during 

March 2010) (fig. 1, table 1). The 74 sites included five USGS 

streamflow-gaging stations (sites 7, 33, 38, 61, and 74) where 

streamflow was monitored continuously during the study and 

which represented the downstream boundary of each of the 

five watershed drainage areas and at one additional USGS 

continuous streamflow-gaging station in the Nueces River 

watershed at site 22 (fig. 1, table 1). The survey measurement 

locations were selected where access was readily available; for 

example, considerations of physical constraints and landowner 

permissions often prevented access to the streams. 
Table 1. Hydrologic and water-quality data-collection sites and streamflow, springflow, and groundwater measurements in the upper Nueces River Texas.—Continued [dd, degrees; mm, minutes; ss, seconds; ft3/s, cubic foot per second; SW, surface-water streamflow; E, excellent; --, not measured; P, poor; NR, information not released per landspringflow; QW, water quality; shaded, water-quality sample collected; F, fair; Well, groundwater depth to water; G, good; RF, rainfall] Site identi- fier (fig. 1) Watershed U.S. Geological Survey station number U.S. Geological Survey station name Latitude (dd mm ss) Longitude (dd mm ss) Type of data July 21–23, 2008 August 8–18, 2

Measure- ment (ft3/s) Measure- ment rating Measure- ment (ft3/s) Mea

m

ra

1 West Nueces River 08190100 West Nueces River near Rock- springs, Tex. 29°53′17′′ 100°25′08′′ SW no flow E -- 2 West Nueces River 08190150 West Nueces River at Farm Road 674 near Rocksprings, Tex. 29°49′50′′ 100°24′08′′ SW no flow E -- 3 West Nueces River 08190195 West Nueces River downstream from Kickapoo Spring near Rocksprings, Tex. 29°45′24′′ 100°23′55′′ SW -- -- 4.46 4 West Nueces River 294529100234701 Spring 1 on West Nueces River1 NR NR Spring, QW -- -- 1.84 5 West Nueces River 294443100213701 Spring 2 on West Nueces River1 NR NR Spring, QW -- -- 0.06 6 West Nueces River 293913100230301 Spring 3 on West Nueces River1 NR NR Spring, QW -- -- 20.01 7 West Nueces River 08190500 West Nueces River near Brackett- ville, Tex. 29°28′52′′ 100°14′21′′ SW no flow3 F no flow3 8 Nueces River 08189979 Hackberry Creek at Farm Road 335 near Vance, Tex. 30°01′25′′ 100°04′04′′ SW, QW 0.73 P 1.96 9 Nueces River 0818998070 East Prong Nueces River up- stream of Eagle Ranch near Rocksprings, Tex. 29°58′59′′ 99°57′24′′ SW, QW -- -- 5.48 

10 Nueces River 295702099571801 Spring on East Prong Nueces River near Vance, Tex.1 NR NR Spring, QW -- -- -- 

11 Nueces River 0818998008 Unnamed spring run of East Prong Nueces River near Rock- springs, Tex. 29°57′03′′ 99°57′27′′ SW -- -- 1.44 

12 Nueces River 08189981 East Prong Nueces River down- stream from East Rose Draw near Vance, Tex. 29°56′46′′ 99°58′16′′ SW 11.6 P 7.12 13 Nueces River 08189983 Nueces River downstream from Hackberry Creek near Vance, 

Tex.

29°55′43′′ 100°00′30′′ SW 13.3 F 29.63 

14 Nueces River 08189984 Nueces River upstream of Vance, 

Tex.

29°53′12′′ 100°01′14′′ SW 12.4 F -- 

Table 1. Hydrologic and water-quality data-collection sites and streamflow, springflow, and groundwater measurements in the upper Nueces River Texas.[dd, degrees; mm, minutes; ss, seconds; ft3/s, cubic foot per second; SW, surface-water streamflow; E, excellent; --, not measured; P, poor; NR, information not released per landspringflow; QW, water quality; shaded, water-quality sample collected; F, fair; Well, groundwater depth to water; G, good; RF, rainfall]
Table 1. Hydrologic and water-quality data-collection sites and streamflow, springflow, and groundwater measurements in the upper Nueces River Texas.—Continued[dd, degrees; mm, minutes; ss, seconds; ft3/s, cubic foot per second; SW, surface-water streamflow; E, excellent; --, not measured; P, poor; NR, information not released per landspringflow; QW, water quality; shaded, water-quality sample collected; F, fair; Well, groundwater depth to water; G, good; RF, rainfall]

Site 

identifier 

(fig. 1)

Watershed

U.S. Geological 

Survey station 

number

U.S. Geological 

Survey station name

Latitude

(dd mm ss)

Longitude

(dd mm ss)

Type 

of data

July 21–23, 2008 August 8–18, 2

Measurement

(ft3/s)

Measurement

rating

Measurement

(ft3/s)

Mea

m

ra

15 Nueces River 08189987 Bullhead Creek downstream from 

Cord Spring Draw near Vance, Tex.

29°50′07′′ 99°55′48′′ SW -- -- 0.42 

16 Nueces River 0818998770 Bullhead Creek at Ranch Road 

2631 near Vance, Tex.

29°49′51′′ 99°57′15′′ SW -- -- 0.68 

17 Nueces River 08189988 Bullhead Creek upstream of 

Brushy Draw near Vance, Tex.

29°49′59′′ 99°58′31′′ SW 1.89 P 1.70 

18 Nueces River 08189989 Bullhead Creek at Vance, Tex. 29°48′43′′ 100°00′57′′ SW no flow E 3.79 19 Nueces River 08189985 Nueces River at Vance, Tex. 29°48′37′′ 100°01′01′′ SW 9.12 F 42.19 20 Nueces River 0818998970 Dry Creek near Barksdale, Tex. 29°45′08′′ 100°00′31′′ SW -- -- 0.57 21 Nueces River 08189990 Nueces River at Barksdale, Tex. 29°43′49′′ 100°01′36′′ SW 14.8 F 2.64 22 Nueces River 0818999010 Nueces River near Barksdale, Tex. 29°43′08′′ 100°02′22′′ SW, QW -- -- 316 23 Nueces River 08189992 Little Hackberry Creek at State 

Highway 55 near Barksdale, Tex.

29°50′27′′ 100°06′17′′ SW no flow P no flow 

24 Nueces River 08189991 Pulliam Creek upstream of Little 

Hackberry Creek near Barksdale, Tex.

29°50′06′′ 100°07′07′′ SW 4.56 F 1.17 

25 Nueces River 08189993 Pulliam Creek upstream of Cedar 

Creek near Barksdale, Tex.

29°45′47′′ 100°05′15′′ SW -- -- no flow 

26 Nueces River 08189994 Cedar Creek near Barksdale, Tex. 29°45′33′′ 100°06′08′′ SW 0.67 P no flow 27 Nueces River 08189995 Pulliam Creek downstream from 

Cedar Creek near Barksdale, Tex.

29°44′36′′ 100°05′52′′ SW 2.85 P -- 

28 Nueces River 08189996 Camp Wood Creek at State Highway 55 near Camp Wood, Tex. 29°41′01′′ 100°01′06′′ SW no flow E -- 29 Nueces River 0818999640 Old Faithful Spring near Camp 

Wood, Tex.

29°40′46′′ 100°00′48′′ Spring, 

QW

-- -- -- 

30 Nueces River 08189997 Nueces River at Camp Wood, Tex. 29°40′09′′ 100°01′20′′ SW 34.7 F -- 31 Nueces River 0818999850 Montell Creek near Montell, Tex. 29°31′41′′ 100°01′15′′ SW no flow E -- 32 Nueces River 08189998 Nueces River at County Road 414 

at Montell, Tex.

29°31′35′′ 100°01′06′′ SW 12.4 P 20.71 

33 Nueces River 08190000 Nueces River at Laguna, Tex. 29°25′42′′ 99°59′49′′ SW 331 G 320 
Table 1. Hydrologic and water-quality data-collection sites and streamflow, springflow, and groundwater measurements in the upper Nueces River Texas.—Continued [dd, degrees; mm, minutes; ss, seconds; ft3/s, cubic foot per second; SW, surface-water streamflow; E, excellent; --, not measured; P, poor; NR, information not released per landspringflow; QW, water quality; shaded, water-quality sample collected; F, fair; Well, groundwater depth to water; G, good; RF, rainfall] Site identi- fier (fig. 1) Watershed U.S. Geological Survey station number U.S. Geological Survey station name Latitude (dd mm ss) Longitude (dd mm ss) Type of data July 21–23, 2008 August 8–18, 2

Measure- ment (ft3/s) Measure- ment rating Measure- ment (ft3/s) Mea

m

ra

34 Dry Frio River 08195850 Dry Frio River upstream of Lee Creek near Reagan Wells, Tex. 29°39′16′′ 99°52′09′′ SW -- -- no flow 35 Dry Frio River 08195900 Dry Frio River downstream from Lick Creek near Reagan Wells, Tex. 29°34′22′′ 99°50′45′′ SW -- -- 0.22 36 Dry Frio River 08195935 Dry Frio River upstream of Brushy Creek at Reagan Wells, Tex. 29°32′19′′ 99°49′60′′ SW 0.40 P -- 37 Dry Frio River 08195970 Dry Frio River upstream of Fush Creek near Reagan Wells, Tex. 29°30′27′′ 99°47′17′′ SW no flow E -- 38 Dry Frio River 08196000 Dry Frio River near Reagan Wells, Tex. 29°30′16′′ 99°46′52′′ SW 31.3 G 30.24 39 Frio River 295454099473101 Spring 1 on West Frio River, Tex.1 NR NR Spring, QW -- -- 0.15 40 Frio River 295144099480201 Spring 2 on West Frio River, Tex.1 NR NR Spring, QW -- -- -- 41 Frio River 08194695 Kent Creek downstream from Ev- ans Springs near Leakey, Tex. 29°51′43′′ 99°48′02′′ SW -- -- 0.68 42 Frio River 08194690 West Frio River upstream of Kent Creek near Leakey, Tex. 29°51′15′′ 99°46′13′′ SW, QW 10.4 F 6.00 43 Frio River 08194700 Kent Creek at Farm Road 336 near Leakey, Tex. 29°50′10′′ 99°46′57′′ SW 1.34 P 0.45 44 Frio River 08194830 West Frio River at U.S. Highway 83 near Leakey, Tex. 29°44′41′′ 99°45′09′′ SW no flow E -- 45 Frio River 08194750 East Frio River upstream of Circle Bluff near Leakey, Tex. 29°52′03′′ 99°39′59′′ SW -- -- 0.58 46 Frio River 295100099403001 Spring on East Frio River, Tex.1 NR NR Spring, QW -- -- 0.24 47 Frio River 08194760 Bee Creek at U.S. Highway 83 near Leaky, Tex. 29°49′48′′ 99°40′21′′ SW no flow E -- 48 Frio River 08194770 East Frio River upstream of Cypress Creek near Leakey, Tex. 29°48′33′′ 99°40′45′′ SW 15.2 F 8.35 49 Frio River 08194780 Cypress Creek at Cypress Creek 

Road near Leakey, Tex.

29°40′29′′ 99°40′06′′ SW -- -- 1.50 
Table 1. Hydrologic and water-quality data-collection sites and streamflow, springflow, and groundwater measurements in the upper Nueces River Texas.—Continued[dd, degrees; mm, minutes; ss, seconds; ft3/s, cubic foot per second; SW, surface-water streamflow; E, excellent; --, not measured; P, poor; NR, information not released per landspringflow; QW, water quality; shaded, water-quality sample collected; F, fair; Well, groundwater depth to water; G, good; RF, rainfall]

Site 

identifier 

(fig. 1)

Watershed

U.S. Geological 

Survey station 

number

U.S. Geological 

Survey station name

Latitude

(dd mm ss)

Longitude

(dd mm ss)

Type 

of data

July 21–23, 2008 August 8–18, 2

Measurement

(ft3/s)

Measurement

rating

Measurement

(ft3/s)

Mea

m

ra

50 Frio River 08194800 East Frio River upstream of Indian Creek near Leakey, Tex. 29°46′52′′ 99°42′13′′ SW 413.3 G 7.26 51 Frio River 08194840 Frio River at Leakey, Tex. 29°43′23′′ 99°45′12′′ SW 4.61 P 41.03 52 Frio River 08194845 Leakey Spring at Leakey, Tex. 29°43′36′′ 99°45′13′′ Spring -- -- 2.86 53 Frio River 08194850 Leakey Spring Run at Leakey, 

Tex.

29°43′23′′ 99°45′24′′ SW, QW 6.96 G 3.61 

54 Frio River 08194860 Brooks Spring at Leakey, Tex. 29°42′54′′ 99°45′30′′ Spring -- -- 0.58 55 Frio River 08194900 Patterson Creek at U.S. Highway 

83 near Leakey, Tex.

29°42′01′′ 99°45′49′′ SW no flow E -- 

56 Frio River 08194880 Frio River at Farm Road 1120 

downstream from Leakey, Tex.

29°41′39′′ 99°45′15′′ SW 20.1 G -- 

57 Frio River 08194920 Little Dry Frio Creek at Rio Frio, 

Tex.

29°38′55′′ 99°44′15′′ SW no flow E -- 

58 Frio River 08194930 Frio River at Rio Frio, Tex. 29°37′49′′ 99°44′44′′ SW 10.3 F -- 59 Frio River 08194970 Frio River upstream of Concan, 

Tex.

29°32′11′′ 99°42′48′′ SW 19.8 F -- 

60 Frio River 08194980 Bear Creek near Concan, Tex. 29°32′06′′ 99°42′08′′ SW no flow E -- 61 Frio River 08195000 Frio River at Concan, Tex. 29°29′18′′ 99°42′16′′ SW, QW 324 G 37.2 62 Sabinal River 294950099353801 AS–69–12–401 29°49′50′′ 99°35′38′′ Spring, 

QW

-- -- 0.01 

63 Sabinal River 08197905 Wedgeworth Creek at Farm Road 

187 near Vanderpool, Tex.

29°48′26′′ 99°34′02′′ SW 3.12 P 1.40 

64 Sabinal River 08197907 Sabinal River downstream from 

Wedgeworth Creek near Vanderpool, Tex.

29°48′10′′ 99°34′30′′ SW, QW 1.33 P 1.48 

65 Sabinal River 08197910 Sabinal River downstream from 

Marler Creek near Vanderpool, Tex.

29°47′31′′ 99°34′28′′ SW 22.48 F 1.25 

66 Sabinal River 08197915 Brushy Creek near Vanderpool, 

Tex.

29°45′58′′ 99°33′48′′ SW 0.51 P -- 

67 Sabinal River 08197925 Sabinal River at Vanderpool, Tex. 29°44′40′′ 99°33′14′′ SW 2.65 F 1.07 68 Sabinal River 08197930 Mill Creek at Farm Road 337 near 

Vanderpool, Tex.

29°45′59′′ 99°30′13′′ SW 0.72 P 0.30 
Table 1. Hydrologic and water-quality data-collection sites and streamflow, springflow, and groundwater measurements in the upper Nueces River Texas.—Continued [dd, degrees; mm, minutes; ss, seconds; ft3/s, cubic foot per second; SW, surface-water streamflow; E, excellent; --, not measured; P, poor; NR, information not released per landspringflow; QW, water quality; shaded, water-quality sample collected; F, fair; Well, groundwater depth to water; G, good; RF, rainfall] Site identi- fier (fig. 1) Watershed U.S. Geological Survey station number U.S. Geological Survey station name Latitude (dd mm ss) Longitude (dd mm ss) Type of data July 21–23, 2008 August 8–18, 2

Measure- ment (ft3/s) Measure- ment rating Measure- ment (ft3/s) Mea

m

ra

69 Sabinal River 08197933 Evans Creek at Farm Road 337 near Vanderpool, Tex. 29°45′22′′ 99°31′54′′ SW -- -- no flow 70 Sabinal River 08197945 Sabinal River upstream of Utopia, Tex. 29°38′59′′ 99°32′01′′ SW 0.81 F -- 71 Sabinal River 08197955 West Sabinal River at Farm Road 337 near Vanderpool, Tex. 29°44′11′′ 99°37′14′′ SW -- -- no flow 72 Sabinal River 08197970 Sabinal River at Utopia, Tex. 29°36′44′′ 99°31′46′′ SW, QW no flow E no flow 73 Sabinal River 08197995 Sabinal River upstream of Onion Creek near Utopia, Tex. 29°31′01′′ 99°30′31′′ SW 1.17 P 0.12 74 Sabinal River 08198000 Sabinal River near Sabinal, Tex. 29°29′27′′ 99°29′33′′ SW 31.4 F no flow3 

Site identi- fier (fig. 1) Watershed U.S. Geological Survey station number State well number Latitude (dd mm ss) Longitude (dd mm ss) Type of data July 21–23, 2008 August 8–18, 2009 

Measure- ment, depth to water (feet) Measure- ment rating Measure- ment, depth to water (feet) Measur

ment rating 

75 West Nueces River 293551100281701 RP–70–29–101 29°35′51′′ 100°28′17′′ Well, QW -- -- 237.37 -- 76 Nueces River 300259100030801 JJ–55–64–503 30°02′59′′ 100°03′08′′ Well, QW -- -- 330.35 -- 77 Sabinal River 294815099343801 AS–69–12–501 29°48′41′′ 99°34′29′′ Well, QW -- -- -- -- 

Site identi- fier (fig. 1) Watershed National Weather Service station number National Weather Service station name Latitude (dd mm ss) Longitude (dd mm ss) Type of data 78 Nueces River 417706 Rocksprings 1S 30°00′11′′ 100°15′36′′ RF 79 Frio River 415113 Leakey 29°44′20′′ 99°45′40′′ RF

1Official U.S. Geological Survey station name not used here per landowner privacy request.2Average of replicate measurements.3Average of daily mean discharge from continuous measurements during synpotic measurement survey period.4Better rated measurement reported.5Average of daily depth to water (in feet) from continuous measurements during synpotic measurement survey period.
EDWARDS COUNTY KERR COUNTY

KINNEY COUNTY

REAL COUNTY

30°00'

29°50'

29°40'

29°30'

99°30'

99°40'

99°50'

100°00'

100°20' 100°10'

100°30'

EXPLANATION

Aquifer system (Ashworth and Hopkins, 1995) Edwards–Trinity (Plateau)  aquifer outcrop Trinity aquifer outcrop Edwards aquifer outcropEdwards aquifer boundaryWatershed boundaryPerennial streamEphemeral stream

Sites wher or samp identifie Streamflo U.S. Geol gaging  Springflow of flow Groundw National W

55

5

74

7778

f

E

C

!

7

Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey

Base from U.S. Geological Survey 1:24,000-scale digital dataUniversal Transverse Mercator Projection, zone 14North American Datum of 1983

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

9

8

7

6

5 4

3

2

1

77

76

78

79

75

74

73

72

71

70

69 68

67

66

65

64

62

61

60 59

58

57

56 55

54

52

50

48 49

47

46

45

43

42

41

40

39

38

37

36

35

34

33

32

31

30

28

27

26 25

24

23

22 21

20

19

18

17

16

15

14

13 12

11 10

29

53

51

44

63

9

8

7

6

5 4

3

2

1

77

76

78

79

75

74

73

72

71

70

69 68

67

66

65

64

62

61

60 59

58

57

56 55

54

52

50

48 49

47

46

45

43

42

41

40

39

38

37

36

35

34

33

32

31

30

28

27

26 25

24

23

22 21

20

19

18

17

16

15

14

13 12

11 10

29

53

51

44

63

7

7

7

7

7

7

7

7

7

7

7

##

#

#

#

# #

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#

# #

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#

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#

# #

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#

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#

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#

#

# #

# #

#

#

#

#

#

#

#

## #

#

#

# # #

#

#

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E

E

E

E

E

E

E

E

E

E

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E

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E

E

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E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

#

EE

E

E

E

E

E

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f

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0 5 10 15 20 MILES0 5 10 15 20 KILOMETERS

Figure 2. Edwards–Trinity (Plateau), Trinity, and Edwards aquifer outcrops and data-collection sites in the upper Nueces River Basin, south-central 
EDWARDS COUNTY KERR COUNTY

KINNEY COUNTY

REAL COUNTY

30°00'

29°50'

29°40'

29°30'

99°30'

99°40'

99°50'

100°00'

100°20' 100°10'

100°30'

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey

Base from U.S. Geological Survey 1:24,000-scale digital dataUniversal Transverse Mercator Projection, zone 14North American Datum of 1983

Surficial geology 

1:250,000 (Brow

Geologic names mo

0 5 10 15 20 MILES0 5 10 15 20 KILOMETERS

EXPLANATION

Sites w or sa ident Stream U.S. G gag Spring of f Groun Nation

Surface geology Alluvium Fluviatile terrace deposits

Undifferentiated

 Buda Limestone of the Washita Group Del Rio Clay of the  Washita Group Segovia Formation of the Edwards Group Fort Terrett Formation of the Edwards Group

15

7

77

78

Kbu

SYSTEM

 UPPER

CRETACEOUS

 UPPER

CRETACEOUS QUATERNARY LOWER

CRETACEOUS

 Devils River Limestone Salmon Peak Limestone McKnight Formation West Nueces Formation Upper member of the 

Glen Rose Limestone

 of the Trinity Group Watershed boundaryPerennial streamEphemeral stream

Qal

Kdr

Kbu

Kft

Ks

Qd

Qt

Kgru

Kwn

Kmk

Ksa

Kdvr

f

E

C

!

7

7

7

7

7

7

7

7

7

7

7

7

##

#

#

#

# #

#

#

#

#

#

# #

#

#

##

#

#

# #

#

#

#

#

# #

#

#

#

#

#

#

# #

# #

#

#

#

#

#

#

#

## #

#

#

# # #

#

#

EE

E

E

E

E

E

E

E

E

E

E

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E

E#E

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E

E

EE

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E#E

E

E

E

E

E

E

E

E

E

E

E

E

E

C

C

C

C

C

C

9

8

7

6

5

4

3

2

1

77

78

79

76

75

74

73

72

71

70

69

68

67

66

65

64

62

61

60

59

58

57

56 55

54

52

50

48 49

47

46

45

43

42 41

40

39

38

37

36

35

34

33

32 31

30

28

27

26 25

24

23

22

21

20

19

18

17

16

15

14

13

12

11 10

29

53

51

44

63

Kdvr

Ks

Kft

Kdvr

Kgru

Ksa

Kmk

Kwn

Qal

Qt

Qt

Qt

Qd

Kbu

Kdr

Kgru

Kgru

Kgru

Qd

Ksa

Kmk

Kwn

Kft

Qd

Qd

Qd

Qd

Qd

Ks

Kft

Kft

Qal

Qt

Kgru

Qt

Qal

!

!

!

!

!

!

Figure 3. Surficial geologic units and data-collection sites in the upper Nueces River Basin, south-central Texas. 
Data-Collection Methods 11

Streamflow and springflow measurements were made 

by using USGS methods described by Rantz and others 

(1982a, b) and Turnipseed and Sauer (2010). The streamflow 

and springflow measurements were made by wading 

through the stream and using either a rod-mounted acoustic 

velocity meter or a pygmy current meter. Some low flows 

(for example, less than 1 cubic feet per second, ft3/s) were 

measured by using a portable Parshall flume. Continuous 

streamflow was measured at the six USGS streamflow-gaging 

stations in the study area by following methods described by 

Turnipseed and Sauer (2010) and Rantz and others (1982a, b). 

Flow conditions in each of the five watersheds 

composing the study area were evaluated by using the longterm (1950–2010) streamflow records from the farthest 

downstream USGS streamflow-gaging station in each of the 

watersheds (U.S. Geological Survey, 2012a). The surveys 

were done during conditions chosen to represent three 

different streamflow conditions: “low-flow,” “very low flow,” 

and “medium-flow” conditions during July 2008, August 

2009, and March 2010, respectively. Specifically, in July 

2008, when streamflow at the farthest downstream station in 

each of the five contributing watersheds was generally less 

than the 25th percentile of long-term streamflow measured at 

these stations, the streamflow conditions were referred to as 

“low flow”; “very low flow” refers to conditions that existed 

in August 2009 when streamflow of the five rivers generally 

was less than the 10th percentile of the respective long-term 

streamflows; and “medium flow” refers to conditions that 

existed in March 2010 when streamflow was generally around 

the 50th percentile of long-term streamflow. For example, 

during the 1950–2010 period of record at site 33 (fig. 1), the 

farthest downstream gage in the Nueces River watershed 

within the study area, the daily mean streamflow was 31 ft3/s 

(low flow), 20 ft3/s (very low flow), and 98 ft3/s (medium 

flow) during the 2008, 2009, and 2010 surveys, respectively 

(fig. 4, table 2). While the three surveys do not capture the full 

range of historical streamflows, they do represent a range of 

different hydrologic conditions. 

To better understand the gain-loss characteristics of 

stream reaches in the study area, each survey was done during 

periods of stable flow, selected to minimize the possible 

influence of storm runoff on streamflow. For example, in 

the 7 days prior to the 2008 and 2009 surveys, no rainfall 

was measured at Rocksprings, Tex., near the headwaters of 

Nueces River, and in the 7 days prior to the 2010 survey, 

a total of only 0.5 in. of rainfall was measured (National 

Weather Service [NWS] cooperative station number 417706, 

Rocksprings 1S; National Climatic Data Center, 2011). 

Rainfall amounts were similar at Leakey, Tex., in the central 

region of the study area (NWS cooperative station number 

415113; National Climatic Data Center, 2011). Because scant 

rainfall occurred prior to each survey, the effect of potential 

storm runoff on streamflow conditions was considered 

minimal.

Groundwater-level measurements were collected at two 

sites (75–76) by using a graduated electric tape and following 

methods described by Cunningham and Schalk (2011). 

Groundwater-level measurements were reported as depth to 

water (in feet) below the land surface at the well. Continuous 

groundwater-level measurements were made at site 76 every 

15 minutes with a pressure transducer and transmitted every 

4 hours by a Geostationary Operational Environmental 

Satellite (GOES) to the USGS National Water Information 

System (NWIS) database (U.S. Geological Survey, 2012a). 

The groundwater-level data were verified and corrected as 

necessary by periodic measurements using a graduated electric 

tape, as described by Freeman and others (2004). 

Quality Assurance of Hydrologic Measurements

Quality-assurance measurements (replicate 

measurements) were made for selected streamflow and 

springflow measurements. Quality-assurance measurements 

were compared to the associated primary measurements by 

calculating the relative percent difference (RPD) (app. 1). The 

RPD was computed by using the equation 

RPD = [|X1 – X2|]/[(X1 + X2)/2] x 100, (1) 

where

X1 = primary measurement for the variable of 

interest, and 

X2 = replicate measurement for the variable of 

interest. 

Generally, the RPDs for streamflow and springflow 

measurements were within 5 percent. Larger RPDs were 

measured during low-flow conditions in tributary streams and 

when springflow amounts were relatively small. For instance, 

the largest RPD (51 percent) was calculated for two replicate 

streamflow measurements (1.03 and 0.61 ft3/s) made at site 51 

(app. 1). The percent difference in this example might be in 

part because the streamflow measurement was rated fair and 

the quality assurance measurement was rated poor. Where 

replicate measurements were made, the measurement with 

the better quality rating assigned by the hydrographer was 

used in the analyses and reported in table 1. For example, if 

measurements were rated good and fair, the good measurement 

was used for the analyses, or if the measurements were rated 

the same, the average of the two measurements was reported 

(table 1) and used in subsequent analyses. At streamflowgaging stations where continuous daily mean streamflows 

were available, the average of the daily mean streamflows 

during the survey period was reported. 

Computation of Streamflow Gain and Loss 

Stream reaches can be characterized as having a gain, 

a loss, or no change in streamflow. Possible sources of 

gains or losses can be attributed to groundwater inflow or 

outflow, inflow from tributaries and return flows, outflow 

from diversions, and evaporation (Slade and others, 2002; 
12 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

Year

1950 1960 1970 1980 1990 2000 2010

0.1

1

10

100

1,000

10,000

100,000

0.1

1

10

100

1,000

10,000

100,000

0.1

1

10

100

1,000

10,000

100,000

0.1

1

10

100

1,000

10,000

100,000

0.1

1

10

100

1,000

10,000

100,000

Daily mean streamflow, in cubic feet per second 

A. Site 7

B. Site 33

C. Site 38

D. Site 61

E. Site 74

Daily mean streamflow during survey

Daily mean streamflow less than 0.1 cubic

 foot per second

EXPLANATION

Figure 4. Daily mean streamflow at U.S. Geological Survey streamflow-gaging stations in south-central Texas during 1950–2010. 

A, 08190500 West Nueces River near Brackettville, Tex. (site 7). B, 08190000 Nueces River at Laguna, Tex. (site 33). C, 08196000 Dry Frio 

River near Reagan Wells, Tex. (site 38). D, 08195000 Frio River at Concan, Tex. (site 61). E, 08198000 Sabinal River near Sabinal, Tex. 

(site 74). 
Data-Collection Methods 13

Ockerman, 2002; Turco, 2007; Braun, 2011). The methods 

used for computation of streamflow gain and loss followed 

those described in Ockerman (2002, p. 7): 

Groundwater inflow to the streams or outflow to

groundwater are not directly measurable because 

the inflow and outflow processes usually cannot

be observed. Even visible inflow from springs

and seeps cannot always be measured accurately. 

Therefore, inflow from or outflow to groundwater in

subreaches of the streams was measured indirectly 

by measuring the difference in streamflow at the

upstream and downstream ends of the subreaches. 

Groundwater inflow and outflow are not the only

sources of gain or loss along the streams. Other 

sources are tributary inflow, diversions, return flows,

and evaporation. By accounting for these factors, 

groundwater inflow or outflow can be estimated.

Groundwater inflow, G, is estimated as

G = QD – QU – I + D – R + E, (1)

where

QD = measured streamflow at the downstream 

boundary of the subreach,

QU = measured streamflow at the upstream 

boundary of the subreach,

I = measured or estimated inflows from creeks 

or tributaries,

D = diversions in the subreach,

R = return flows in the subreach, and

E = estimated evaporation losses.

Positive groundwater inflow indicates the reach is 

gaining streamflow, whereas negative groundwater inflow 

indicates the reach is losing streamflow. During this study, 

some tributary inflows were measured when field staff 

had access to the tributary site, however, there might have 

been unmeasured contributing inflows in some reaches. For 

this report, unquantified inflows from tributaries were not 

estimated. For example, a downstream reach might indicate 

a gain in streamflow, but this gain could also be a function 

of an unquantified tributary contributing to the streamflow. 

These unknown contributions might affect the interpretation of 

reaches gaining or losing streamflow, but a reach identified as 

losing streamflow that has a potential unmeasured contributing 

tributary is still a losing reach, regardless of the magnitude 

of contribution from the tributary. Streamflow gain-loss was 

not calculated for tributary reaches where the tributary was 

not measured at the confluence with the main stem. Although 

there are several permitted withdrawals in the study area, 

during the study there was only one reported diversion of 

streamflow (averaging 1.1 ft3/s), and this diversion occurred 

during the 2009 survey, about 4 miles upstream from site 32. 

Table 2. Daily mean streamflow at U.S. Geological Survey streamflow-gaging stations in the upper Nueces River Basin, south-central 

Texas, during 2008–10 surveys and percentiles of daily mean streamflow from long-term (1950–2010) streamflow records.

[Data are from U.S. Geological Survey, 2012a]

Survey

Daily mean streamflow during 2008–10 surveys

U.S. Geological 

Survey station 

08190500 

West Nueces River 

near Brackettville, Tex.

(site 7)

U.S. Geological 

Survey station 

08190000 

Nueces River at 

Laguna, Tex.

(site 33)

U.S. Geological 

Survey station 

08196000 

Dry Frio River near 

Reagan Wells, Tex.

(site 38)

U.S. Geological 

Survey station 

08195000 

Frio River at 

Concan, Tex.

(site 61)

U.S. Geological 

Survey station 

08198000 

Sabinal River 

near Sabinal, Tex.

(site 74)

July 21–23, 2008 no flow 31 1.3 24 1.4

August 8–18, 2009 no flow 20 0.24 7.2 no flow

March 22–24, 2010 0.31 98 16 64 37

Percentile Daily mean streamflow from long-term streamflow records1

Site 7 Site 33 Site 38 Site 61 Site 74

10th percentile no flow 26 2.3 18 no flow

25th percentile no flow 50 6.3 44 8.8

Median 0.22 87 14 74 28

75th percentile 1.9 156 31 125 63

Maximum 42,500 70,300 12,200 24,700 17,100

1

Long-term streamflow record for site 38 is 1952–2010.
14 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

Accounting for this diversion in the calculation of streamflow 

gain-loss (eq. 2) did not change the resulting classification 

of “losing” in this reach. No other known diversions 

occurred during the 2008–10 surveys (Angela Sander, Texas 

Commission of Environmental Quality, written commun., 

2012). There are no known return flows in the study area 

(for example, effluent from wastewater treatment plants). 

Evaporation was not measured. As explained by Turco (2007, 

p. 7), “the magnitude of error associated with [excluding 

evaporation] from equation 1 is assumed to be minor when 

compared to the potential errors associated with the flow 

measurements.” 

The streamflow gain or loss was then classified as 

“verifiable” as described in Braun and Lambert (2011, 

p. 14–15): 

A stream reach is classified as verifiably gaining

or losing only if the difference in streamflow

between the upstream and downstream measuring 

sites exceeds the potential error associated with 

the flow measurements made at those locations.

Measurement error is a function of the streamflow

measurement rating (excellent, good, fair, or poor) 

as determined by the hydrographer (streamgager) 

(Sauer and Meyer, 1992). The rating is based on 

streambed conditions, velocity homogeneity, crosssection uniformity, and any additional factors that 

affect the measurement accuracy. Measurements 

rated as excellent are believed to be within 2 percent 

of the actual flow, good are believed to be within

5 percent of flow, fair are believed to be within

8 percent of flow, and poor are believed to differ

from actual flow by greater than 8 percent (set at

10 percent for the purposes of error calculations in 

this report).

Water-Quality Data Collection

Water-quality and associated quality-control samples 

were collected from streamflow, springflow, and groundwater 

sites in the West Nueces, Nueces, Frio, and Sabinal River 

watersheds during two surveys in August 2009 and March 

2010 (app. 2). Water-quality samples were collected by 

following standard USGS methods (U.S. Geological Survey, 

variously dated). Depth-integrated streamflow samples were 

collected during base-flow conditions either by multiple 

verticals using a hand-held sampler when stream velocities 

were less than about 1.5 feet per second (ft/s) or by the 

flow-weighted, equal-width increment method (Edwards and 

Glysson, 1999) when stream velocities were greater than about 

1.5 ft/s. Depending on springflow rates, springflow samples 

were collected by using a hand-held sampler or a grab sample 

from the spring orifice (U.S. Geological Survey, variously 

dated). Groundwater samples were collected from a spigot on 

top of the well if a submersible pump was already installed 

in the well. If the well did not have an installed pump, the 

well was purged and the groundwater sample was collected 

by using a submersible piston pump (U.S. Geological Survey, 

variously dated). 

Physical properties including water temperature, 

dissolved oxygen, specific conductance, pH, turbidity, and 

alkalinity were measured in the field at the time of sample 

collection during both surveys in August 2009 and March 

2010. Samples collected in August 2009 were analyzed for 

major ions and strontium isotopes (strontium-87/strontium-86 

[87Sr/86Sr]). Samples collected in March 2010 were analyzed 

for major ions, trace elements, and environmental isotopes 

including hydrogen (hydrogen-2/hydrogen-1 [2H/1H]), oxygen 

(oxygen-18/oxygen-16 [18O/16O]), and strontium (87Sr/86Sr). 

Samples collected for major ion and trace element 

analyses were filtered in the field by using a 0.45-micron filter, 

preserved with nitric acid to a pH of less than 2, and shipped 

at 4 degrees Celsius to the USGS National Water Quality 

Laboratory (NWQL) in Denver, Colorado, for analysis. Major 

ions, silica, dissolved solids, and trace elements were analyzed 

by following the methods described in Fishman and Friedman 

(1989), Fishman (1993), American Public Health Association 

(1998), Garbarino (1999), and Garbarino and others (2006). 

The ratio of the naturally occurring, stable isotopes of 

strontium (87Sr/86Sr) was measured in the August 2009 and 

March 2010 samples by the USGS National Research Program 

Laboratory in Menlo Park, California, by following the 

methods described in Bullen and others (1996) and is reported 

as a dimensionless ratio. The laboratory reported 87Sr/86Sr ratio 

for standard reference material (SRM) 987 from the National 

Institute of Standards and Technology as 0.71024 (0.00002 

2-sigma, 95 percent confidence level). Samples collected in 

March 2010 also were analyzed for oxygen and hydrogen 

isotopes (18O/16O, 2H/1H) by the USGS Stable Isotope 

Laboratory in Reston, Virginia, by following the methods 

described in Révész and Coplen (2008a, b) and are reported 

in per mil relative to Vienna Standard Mean Ocean Water 

(VSMOW). 

The reporting of results for major ion and trace elements 

is described by Oden and others (2011, p. 9): 

The analytical quantification procedure used by

the NWQL for reporting results is based on the 

long-term method detection level (LT–MDL) and 

laboratory reporting level (LRL). The LT–MDL 

concentrations are defined as a censoring limit

for most analytical methods at the NWQL, and 

its purpose is to limit the false positive rate to 

less than or equal to 1 percent. An LT–MDL is a 

modification of the USEPA 40 Code of Federal

Regulations Part 136 definition of the method

detection limit (MDL). The LRL is defined as

twice the LT–MDL and is established to limit the 

occurrence of false negative detections to less than 

or equal to 1 percent (Childress and others, 1999). 

A constituent concentration is considered estimated 

by the laboratory when results are greater than the 

LT–MDL and less than the LRL; that is, a detection 
Streamflow Gain and Loss 15

is considered likely, but quantification is considered

questionable. The remark code of “E” (estimated) is 

assigned by the laboratory for these results.

Quality Assurance of Water-Quality Samples

Quality-control samples were collected at streamflow 

and springflow sites during August 2009 and March 2010 by 

following USGS procedures for the collection and processing 

of water-quality samples (U.S. Geological Survey, variously 

dated). The purpose of collecting quality-control samples is to 

evaluate results from the water-quality samples with respect 

to quality, precision, accuracy, and completeness. The types 

of quality-control samples collected for this study included 

an equipment blank, field blanks, and sequential replicates 

(app. 3). 

An equipment blank sample was collected on August 

10, 2009, prior to the start of sampling. The equipment blank 

was identified with U.S. Geological Survey station number 

294424099454101 (app. 3), though an environmental sample 

was not collected from this site. Analytical results from the 

equipment blank on August 10, 2009, indicate that only 

manganese was detected, with an estimated concentration of 

0.2 milligrams liter (mg/L). All other analyzed constituent 

concentrations were less than the LRL. 

Two field blank samples were collected during the 

sampling period (August 14, 2009, and March 22, 2010). 

For the August 14, 2009 sample, the estimated concentration 

of 0.07 mg/L for chloride was approximately two orders of 

magnitude less than the chloride concentrations measured 

in the August 14, 2009, environmental samples (apps. 2 

and 3). All other analyzed constituent concentrations were 

less than the LRL in the August 14, 2009, sample. Calcium, 

chloride, silica, cobalt, manganese, nickel, zinc, and antimony 

were detected in the field blank sample collected on March 

22, 2010 (app. 3). The concentrations of calcium, chloride, 

silica, nickel, and antimony were less than concentrations 

measured in the environmental samples, indicating that 

possible contamination likely did not affect the concentrations 

of these constituents in the environmental samples. Cobalt, 

manganese, and zinc were detected in the field blank sample 

at concentrations that exceeded the concentrations measured 

in some of the environmental samples (app. 3). For these 

constituents, the laboratory reported concentrations for 

the environmental samples are included in appendix 2 for 

completeness; however, the concentrations might be affected 

by possible contamination.

Sequential replicate samples were collected from site 

64 in August 2009 and site 62 in March 2010 (app. 3). 

Sequential replicate samples were compared to the associated 

environmental samples by calculating the RPD for each pair 

of detected constituents, where the variable of interest was 

concentration (eq. 1; app. 3). The RPD was not computed for a 

constituent pair if either of the values was reported as less than 

the LRL or if either of the values was reported as estimated 

values. RPDs of 10 percent or less were used to indicate good 

agreement between analytical results if the concentrations 

were sufficiently large compared to the LRL. RPDs were 

calculated for 19 constituents by using environmental 

and sequential replicate samples collected from site 64 in 

August 2009 (app. 3). The calculated RPDs for August 2009 

were 10 percent or less for all constituents, indicating that 

there was good agreement and reproducibility between the 

environmental sample values and the sequential-replicate 

values. RPDs were calculated for 30 constituents by using 

environmental and sequential replicate samples collected from 

site 62 in March 2010. The calculated RPDs for March 2010 

that exceeded 10 percent were fluoride (17 percent), cobalt 

(21 percent), nickel (11 percent), and selenium (26 percent) 

(app. 3). 

Streamflow Gain and Loss

During the 2008, 2009, and 2010 surveys, reaches of 

gaining, losing, or no change in streamflow were identified 

on the West Nueces, Nueces, Frio, Dry Frio, and Sabinal 

Rivers (figs. 5–7, table 1). On the basis of the three surveys, 

reaches of generally consistent gaining or losing streamflow 

were identified in the Nueces, Frio, and Sabinal River 

watersheds; the streamflow measurement data collected in 

the West Nueces and Dry Frio watersheds were insufficient 

to identify consistently gaining or losing reaches. Identifying 

reaches with consistent gains and losses during the three 

surveys is related in part to the measurement site locations, 

and differences in some site locations among surveys 

were considered when identifying specific reaches where 

streamflow gains or losses occurred. Changes in hydrologic 

conditions also might contribute to differences in observed 

streamflow gains and loss patterns. For example, several 

alternating reaches of gains and losses were observed during 

the 2008 and 2009 surveys (low-flow and very low flow 

conditions, respectively). During the 2010 survey (mediumflow conditions), some reaches exhibited similar patterns 

compared to those observed in 2008 and 2009; however, there 

were fewer losing reaches and more gaining reaches in 2010 

compared to the previous two surveys (possibly because of 

increase in springflows during medium-flow conditions as 

compared to low-flow and very low flow conditions). Because 

of differences in streamflow during each survey and because 

different measurement sites were used in each survey, general 

patterns of streamflow gains and losses are emphasized rather 

than absolute magnitudes of streamflow gains and losses. 

The headwaters of the Nueces River include Hackberry 

Creek and East Prong Nueces River. From site 13, downstream 

from the confluence of Hackberry Creek and East Prong 

Nueces River, to site 14, Nueces River streamflow decreased 

during the 2008 survey (fig. 5), though the difference was 

smaller than the sum of the potential measurement errors and 

thus is not a verifiable loss. The reach from site 14 to site 19 
EDWARDS COUNTY KERR COUNTY

KINNEY COUNTY

REAL COUNTY

30°00'

29°50'

29°40'

29°30'

99°30'

99°40'

99°50'

100°00'

100°20' 100°10'

100°30'

EXPLANATION

Contributing area for the  farthest downstream point of each watershed West Nueces River Nueces River Dry Frio River Frio River Sabinal RiverWatershed boundaryPerennial streamEphemeral stream

River reach gRiver reach lRiver reach n verifiable Sites where  with site i cubic feet  Streamflow U.S. Geolog gaging s

74

1.4

59

19.8

C

E

Base from U.S. Geological Survey 1:24,000-scale digital dataUniversal Transverse Mercator Projection, zone 14North American Datum of 1983

Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

# #

#

#

#

C

C

C

C

C

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

##

#

#

# #

#

#

##

#

#

#

#

#

#

#

EE

E

E

E

E

E

E

E

E

E

E

E#E

EE

E

E

E

EE

E

E

E

E

E

E

E

E

E

E

#

EE

E

E

E

E

E

E

E

#EE

E

0

12.4

0.40

0

0

0

0

0

0

0

0

0

0

0

0

0

1.4

1.17

0.81

0.72

2.65

2.48 0.51

1.33 3.12

1.3

24

19.8

10.3

20.1

6.96

4.61

13.3

15.2

1.34

10.4

31

34.7

2.85

0.67

4.56

14.8

1.89

9.12

12.4

13.3

11.6

0.73

0

12.4

0.40

0

0

0

0

0

0

0

0

0

0

0

0

0

1.4

1.17

0.81

0.72

2.65

2.48 0.51

1.33 3.12

1.3

24

19.8

10.3

20.1

6.96

4.61

13.3

15.2

1.34

10.4

31

34.7

2.85

0.67

4.56

14.8

1.89

9.12

12.4

13.3

11.6

0.73

1

2

7

8

12

13

14

17

19

18

21

23

24

26

27

28

30

31

32

33

38

37

36

42

43

47

48

50

44

53

51

56 55

57

58

60

59

61 74

73

72

70

67

66

68

63 64

65

1

2

7

8

12

13

14

17

19

18

21

23

24

26

27

28

30

31

32

33

38

37

36

42

43

47

48

50

44

53

51

56 55

57

58

60

59

61 74

73

72

70

67

66

68

63 64

65

0 5 10 15 20 MILES0 5 10 15 20 KILOMETERS

Figure 5. Streamflow measurements in the upper Nueces River Basin, south-central Texas, during July 2008.
EDWARDS COUNTY KERR COUNTY

KINNEY COUNTY

REAL COUNTY

30°00'

29°50'

29°40'

29°30'

99°30'

99°40'

99°50'

100°00'

100°20' 100°10'

100°30'

EXPLANATION

Contributing area for the most

downstream point of each

 watershed West Nueces River Nueces River Dry Frio River Frio River Sabinal RiverWatershed boundaryPerennial streamEphemeral stream

River reach gRiver reach lRiver reach n verifiable Sites where  or sample identifier  per secon Streamflow U.S. Geolog gaging s Springflow— of flow

E

61 C

7.2

50

7.26

4

1.84

7

Base from U.S. Geological Survey 1:24,000-scale digital dataUniversal Transverse Mercator Projection, zone 14North American Datum of 1983

7

7

7

7

7

7

7

7

C

C

C

C

C

C

#

#

#

# #

#

# # #

# #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

#

#

# #

#

#

E

E

E

E

E

#EE

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E#E

E

E

E

EE

E

E

E

E

E

E

0.68

0.58

0

0

0

0

0

6.00

0

0

0

0

0.30

1.70 1.40

0.15

0.24 0.01

1.84

0.12

1.07

1.25

1.48

0.24

0.22

7.2

3.61

1.03

7.26

8.35

0.58

0.45

20

1.17

16

0.57

3.79

0.68

0.42

2.19

7.12

5.48

1.44

1.96

0.06

0.01

9.63

4.46

0.71

2.64

1.50

2.86

3

4

7

8

12

13

15

16

17

19

18

21

23

24

26

25

22

20

32

33

38

35

42

43

41

39

46

49

50

48

45

54

53

51

34

61 74

73

72

71 67

69 68

63

62

64

65

5

6

9

11

52

0.68

0.58

0

0

0

0

0

6.00

0

0

0

0

0.30

1.70 1.40

0.15

0.24 0.01

1.84

0.12

1.07

1.25

1.48

0.24

0.22

7.2

3.61

1.03

7.26

8.35

0.58

0.45

20

1.17

16

0.57

3.79

0.68

0.42

2.19

7.12

5.48

1.44

1.96

0.06

0.01

9.63

4.46

0.71

2.64

1.50

2.86

3

4

7

8

12

13

15

16

17

19

18

21

23

24

26

25

22

20

32

33

38

35

42

43

41

39

46

49

50

48

45

54

53

51

34

61 74

73

72

71 67

69 68

63

62

64

65

5

6

9

11

52

Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

0 5 10 15 20 MILES0 5 10 15 20 KILOMETERS

Figure 6. Streamflow and springflow measurements in the upper Nueces River Basin, south-central Texas, during August 2009.
EDWARDS COUNTY KERR COUNTY

KINNEY COUNTY

REAL COUNTY

30°00'

29°50'

29°40'

29°30'

99°30'

99°40'

99°50'

100°00'

100°20' 100°10'

100°30'

EXPLANATION

Contributing area for the farthest downstream  point of each watershed West Nueces River Nueces River Dry Frio River Frio River Sabinal RiverWatershed boundaryPerennial streamEphemeral stream

River reach gRiver reach lRiver reach n verifiable Sites where  with site i cubic feet  Streamflow U.S. Geolog gaging s Springflow— of flow

616455

0.40

41.91

E

C

7

Base from U.S. Geological Survey 1:24,000-scale digital dataUniversal Transverse Mercator Projection, zone 14North American Datum of 1983

Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey Barksdale

Utopia

Camp Wood

Rocksprings

Vanderpool

Vance

MontellLaguna

Concan

ReaganWells

Rio Frio

Leakey

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

Hackberry

Creek

Spring

Creek

Creek Mill Creek

Cedar Creek

West Nueces River

Nueces River

Sabinal River

West Sabinal River

Frio River West Frio River

Kent Creek

Little Hackberry Creek

Little Creek

Pulliam

East Prong Nueces River

Dry Frio River

East Frio River

Bullhead Creek

Evans Creek

#

# #

# #

#

#

#

#

#

#

#

#

#

#

#

#

# ##

#

#

#

#

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E#E

E

E

EE

E

E

E

E

C

C

C

C

C

C

7

7

64

50

0.40

1.50

0.50

2.70

4.90

7.20

23.3

1.72

2.11

3.37

21.7 9.56

18.7

1.94

7.67

2.23

16

98

79.7

2.49

6.69

5.48

36.9

0.91

15.4

6.81

0.19

1.91

0.31

37

1.75

4

7

8

14

13

17 16

21

26

27

25

22

30

29

33

38

42

43

41

50

49

44

53

55

51

61

72

71

68

63

64

9

64

50

0.40

1.50

0.50

2.70

4.90

7.20

23.3

1.72

2.11

3.37

21.7 9.56

18.7

1.94

7.67

2.23

16

98

79.7

2.49

6.69

5.48

36.9

0.91

15.4

6.81

0.19

1.91

0.31

37

1.75

4

7

8

14

13

17 16

21

26

27

25

22

30

29

33

38

42

43

41

50

49

44

53

55

51

61 74

72

71

68

63

64

9

0 5 10 15 20 MILES0 5 10 15 20 KILOMETERS

Figure 7. Streamflow and springflow measurements in the upper Nueces River Basin, south-central Texas, during March 2010.
Streamflow Gain and Loss 19

during the 2008 survey did exhibit a verifiable loss. During the 

2009 survey (fig. 6), a verifiable loss was identified between 

sites 13 and 19, though measurements were not made at 

site 14. During the 2010 survey (fig. 7), measurements were 

not made at sites 18 or 19, so it is not possible to confirm this 

pattern. A verifiable loss was identified, however, between 

sites 13 and 14 during the 2010 survey (similar to the 2008 

survey), so it is possible that a consistent loss in streamflow 

occurs from site 13 to 19. 

From site 19 to site 21, the Nueces River was gaining 

streamflow during the 2008 survey and losing during the 

2009 survey. Differences in measurement locations between 

surveys prevent direct comparisons with the 2010 survey, 

but measurements made at site 14 (upstream from site 19) to 

site 21 indicate that this was a gaining reach during the 2010 

survey. Additionally, the 2009 and 2010 surveys indicate a 

substantial gain in streamflow occurring between sites 21 

and 22. 

From site 22 to site 30, streamflow might be affected 

by potential inflows from Pulliam Creek. Pulliam Creek is 

identified as a perennial stream in the National Hydrography 

Dataset (U.S. Geological Survey, 2012b), and some 

measurements were made in the upper reaches but not at the 

confluence with the Nueces River during the surveys.

From site 30 downstream to site 32, the Nueces River 

was losing streamflow during the 2008 survey. Of the 

calculated streamflow losses, the largest streamflow loss 

between any two sites occurred in this reach during the 2008 

survey (22.3 ft3/s), when 34.7 ft3/s was measured at site 30 and 

12.4 ft3/s was measured at site 32. Site 30 was not measured 

during the 2009 survey, so it is not possible to assess the 

consistency of loss under different hydrologic conditions; 

however, the reach from site 22 to 32 did exhibit a loss during 

this survey. The farthest downstream reach of the Nueces 

River in the study area, from site 32 to site 33, exhibited gains 

in streamflow during the 2008 and 2009 surveys. During the 

2010 survey, a gain in streamflow was identified between sites 

30 and 33, though it is not known where in that reach the gains 

occurred because a measurement was not made at site 32. 

Similar to the Nueces River, the Frio River exhibited 

patterns of reaches alternating between gaining and losing 

streamflow. The West Frio River and East Frio River 

originate from springs in the headwaters and then exhibit 

gaining and losing reaches downstream. Notably, the West 

Frio River was a losing stream from site 42 to site 44 during 

the 2008 and 2010 surveys. During the 2009 survey (very 

low flow conditions), site 44 was not measured. Because 

no flow was observed at site 44 during the 2008 survey 

(low-flow conditions), and because the reach from site 42 

to site 44 during the 2010 survey (medium-flow conditions) 

exhibited a loss, it is likely that a loss was also present in 

2009 (very low flow conditions). The East Frio River was 

a losing stream from site 50 to site 51 during the 2008 and 

2009 surveys and neither gaining nor losing during the 2010 

survey. In the reaches near Leakey (approximately site 51 to 

site 56), springs contribute to the Frio River streamflow (for 

example, Leakey Springs). During each of the surveys, the 

Frio River was a gaining stream from site 51 to the farthest 

downstream measurement site in the Frio River watershed 

study area (site 61). Along this reach, between the upstream 

and downstream sites used to characterize a gain or loss in 

streamflow in 2009 and 2010, there were additional sites 

where streamflow was measured during the 2008 survey, one 

of which was identified as a losing reach (site 56 to site 58). 

Because these additional sites were not measured during the 

2009 and 2010 surveys, it is not possible to confirm these 

additional gaining or losing reaches identified in 2008.

Compared to the streamflow measured at the USGS 

streamflow-gaging stations on the Nueces and Frio Rivers 

(sites 33 and 61, respectively), measured streamflow was 

lower at the USGS streamflow-gaging station on the Sabinal 

River (site 74) during the three surveys. Upstream from site 

72 on the Sabinal River, the reaches were generally losing or 

were neither gaining nor losing streamflow during the 2008 

and 2009 surveys. No flow was observed at site 72, and the 

Sabinal River was gaining in the reach between site 72 and 

site 73 during the 2008 and 2009 surveys. The increase in flow 

between these sites might be caused by inflows from Little 

Creek, by groundwater inflows, or by both. Little Creek is 

identified as a perennial stream in the National Hydrography 

Dataset (U.S. Geological Survey, 2012b), but it is not known 

if Little Creek was flowing at the confluence with the Sabinal 

River during the surveys. During the 2010 survey, the reach 

between site 72 and site 74 was gaining, though again, not all 

of the same sites were measured as in previous surveys, and 

potential contributions from Little Creek are not known. 

To help understand streamflow gains and losses, 

groundwater levels (which might be indicative of groundwater 

contributions to streamflow) near the headwaters of the 

Nueces River (site 76) and streamflow in the Nueces River 

watershed (site 22) were examined for possible relations. A 

continuous groundwater-level monitor was installed at site 76, 

north of the northernmost measured streamflow and spring 

locations, in July 2009. Although a hydrologic connection 

between site 76 (a 398 ft deep well) and the surface water 

has not been identified, some springs in the study area likely 

originate from the Edwards–Trinity (Plateau) aquifer (Long, 

1962, Broad, 2011)—the same aquifer in which site 76 is 

completed. Hence, groundwater levels measured at site 

76 might provide information pertaining to groundwater 

input to the springs in the area. In February 2009, a USGS 

continuous streamflow-gaging station was installed on 

the Nueces River near Barksdale, Tex. (site 22; fig. 1, 

table 1). This streamflow-gaging station is approximately 

halfway between the headwaters of the Nueces River and 

the downstream extent of the Nueces River watershed. A 

coefficient of determination (R2) of 0.15 was calculated 

between the daily mean streamflow measured at site 22 and 

the daily mean groundwater levels at site 76 for the period 

of record. Though it is statistically significant (p-value was 

less than 0.01), the small R2 value indicates a relatively weak 

relation, and other processes might be contributing to the 
20 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

streamflow and groundwater measurements (the p-value is 

the probability of obtaining the computed R2 value if the null 

hypothesis of no relation between the streamflow at site 22 

and groundwater levels measured at site 76 were true [Helsel 

and Hirsch, 2002]). It is important to note that there likely are 

several springs and tributaries contributing to the streamflow 

measured at site 22. Additionally, the R2 does not take into 

account other factors, such as different lag times between 

surface water and groundwater in response to rainfall events 

and recession curves. Graphical comparisons of streamflow 

measured at site 22 and groundwater levels measured at site 76 

indicate that, at times, streamflow at site 22 and groundwater 

levels at site 76 respond similarly to rainfall events measured 

at Rocksprings (site 78, National Climate Data Center, 2011), 

but more gradual responses and longer recession curves were 

observed for groundwater levels compared to streamflow 

(fig. 8). Although the results indicate a possible relation 

between groundwater levels and streamflow, additional data 

representing a larger range of hydrologic conditions are 

needed to confirm this relation. 

Water-Quality Data

Water-quality samples were collected during the August 

2009 and March 2010 surveys at selected sites in each 

watershed, except from the Dry Frio watershed (table 1, 

app. 2). The water-quality data were examined for possible 

relations among sample type (streamflow, springflow, or 

groundwater), between synoptic measurement surveys (to see 

if temporal differences were observed), and among watersheds 

in which the samples were collected. 

The median specific conductance measured in the 

laboratory for all samples collected in the study area during 

2008–10 was 410 microsiemens per centimeter (μS/cm), and

the specific conductance ranged from 311 to 509 μS/cm for all

but one sample (the exception was the specific conductance of 

1,180 μS/cm measured in the groundwater sample collected

from site 77). These results are consistent with previous USGS 

water-quality studies in south-central Texas (for example, 

Mahler, 2008; Musgrove and others, 2010). 

Trilinear (Piper) diagrams were constructed for the waterquality samples collected during the 2009 and 2010 surveys 

(figs. 9 and 10) (Piper, 1944). These diagrams indicate that the 

streamflow, springflow, and groundwater have similar major 

ion chemical characteristics and generally can be categorized 

as a calcium-carbonate water type. The trilinear diagrams 

also indicate that the major ion chemistry was similar during 

the 2009 and 2010 surveys. The sampling events occurred 

during relatively stable hydrologic conditions (for example, 

no rain for 7 days prior to sampling) to reduce the potential 

influence of storm runoff on the water chemistry. During 

periods of base-flow conditions, the chemical characteristics 

of the streamflow, springflow, and groundwater samples 

are likely similar because streamflow in the study area is 

composed primarily from springs throughout the upper 

Nueces River Basin, some of which likely originate from 

the Edwards–Trinity (Plateau) aquifer (Long, 1962; Broad, 

2011). Similarities in water quality might indicate possible 

connectivity between groundwater and springs that originate 

in the study area, though the wells at sites 75 and 76 are deep 

(502 and 398 ft deep, respectively) and known mechanisms 

of hydrologic connection between the groundwater at sites 75 

and 76 with the springs in the study area are unknown.

Site 75 is just outside the study area (approximately 

3 miles to the west). Site 75 is completed in the Edwards–

Trinity (Plateau) aquifer, which might be contributing to 

springflow in the study area (Long, 1962; Broad, 2011). The 

trilinear diagrams (and subsequent isotopic ratio figs. 11–13) 

indicate that the water chemistry in the groundwater sample 

collected from site 75 is similar to the water chemistry from 

nearby springflow samples collected in the West Nueces River 

watershed. Hence, site 75 is included with samples from the 

West Nueces River watershed in subsequent discussions for 

this report. 

The trilinear diagram depicting the chemical 

concentrations for the groundwater sample collected from 

site 77 in August 2009 indicates different water-quality 

characteristics compared to those for the remaining waterquality samples (fig. 9). This difference might be in part 

because the well is completed in the Trinity aquifer, which is 

a different aquifer from the Edwards–Trinity (Plateau) aquifer 

in which the other wells were completed. Hence, water-quality 

data collected from site 77 are not included in the subsequent 

analyses but are included in appendix 2 and figure 9 for 

completeness. 

To further evaluate temporal (between surveys) and 

spatial (among watersheds) comparisons, the water chemistry 

can be examined in regard to elemental and isotopic ratios. 

Relations among ratios of major ions, trace elements, 

or isotopes have be used in previous studies to evaluate 

groundwater geochemical processes of water-rock interactions 

such as geochemical evolution (Trudgill, 1995; Oetting 

and others, 1996; Clark and Fritz, 1997; Sharp and Banner, 

1997; Musgrove and Banner, 2004; Musgrove and others, 

2010). Water-rock interactions are the geochemical processes 

between the fluid and host rock matrix. For example, 

Musgrove and others (2010) assessed geochemical evolution 

in carbonate groundwater systems and found that increased 

residence times or longer flow paths were often associated 

with increased magnesium to calcium (Mg/Ca) molar ratio 

and strontium to calcium (Sr/Ca) molar ratio, and decreased 

strontium isotopic ratios.

The relations of Mg/Ca molar ratios to Ca concentrations 

from all available samples (streamflow, springflow, and 

groundwater samples) collected from four of the watersheds 

in the study area during two surveys (August 2009 and March 

2010) are depicted in figure 11. The Mg/Ca molar ratio to 

calcium concentrations from the samples generally plotted in 

clusters according to the watershed from which the samples 

were collected. In general, lower Mg/Ca molar ratios were 

measured in samples from the West Nueces River watershed 
Water-Quality Data 21

Calendar year

2009 2010 2011

0

1

2

3

4

Rainfall, in inches per day Daily mean streamflow, in cubic feet per second

0

20

40

60

80

100

120

140

160

180

200

220 330.1

330.2

330.3

330.4

330.5

330.6

330.7

330.8

330.9

331.0

331.1

331.2

Depth to ground

water, in feet

Daily mean streamflow at site 22

Depth to groundwater at site 76

EXPLANATION

A

B

Figure 8. Comparisons of measured rainfall, streamflow, and groundwater levels in the Nueces River watershed of the upper Nueces 

River Basin study area, south-central Texas, 2009–10. A, Rainfall at site 78 (National Weather Service station 417706, Rocksprings 1S), 

in Rocksprings, January 2009–December 2010. B, Daily mean streamflow at site 22 (U.S. Geological Survey streamflow-gaging station 

0818999010) and groundwater levels, reported as depth to water, at site 76 (U.S. Geological Survey station 300259100030801), July 2009–

December 2010.
22 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

Magnesium

PERCENT

Sodium plus potassium

Carbonate plus bicarbonate

PERCENT

Calcium plus magnesium

PERCENT Calcium Chloride, fluoride, nitrite plus nitrate

Sulfate

Sulfate plus chloride

 0 80 

 60 

 40 

 20 

 0 

 20 

 40 

 60 

 80 

 100 0 

 20 

 40 

 60 

 80 

 100 

 0

 20 

 40 

 60 

 80 

 100

 100 

 80 

 60 

 40 

 20 

 0 

 100 

 80 

 60 

 40 

 20 

 0 

 0 

 20 

 40 

 60 

 80 

 100 

 0 

 20 

 40 

 60 

 80 

 100 100 

 80 

 60 

 40 

 20 

 0 

 100 

 80 

 60 

 40 

 20 

 0 

 100 

Site 77

Site 77

Site 77

Note: Site 77 represents U.S. Geological Survey station 294815099343801

EXPLANATION

Sample, by watershed and type—

 Samples collected August 2009

 West Nueces River watershed

 Springflow

 Groundwater

 Nueces River watershed

 Streamflow

 Springflow

 Groundwater

 Frio River watershed

 Streamflow

 Springflow

 Sabinal River watershed

 Streamflow

 Springflow

 Groundwater

Figure 9. Trilinear diagrams of chemical composition for streamflow, springflow, and groundwater samples collected in the upper 

Nueces River Basin, south-central Texas, August 2009. 
Water-Quality Data 23

Magnesium

PERCENT

Sodium plus potassium

Carbonate plus bicarbonate

PERCENT

Calcium plus magnesium

PERCENT Calcium Chloride, fluoride, nitrite plus nitrate

Sulfate

Sulfate plus chloride

 0 80 

 60 

 40 

 20 

 0 

 20 

 40 

 60 

 80 

 100 0 

 20 

 40 

 60 

 80 

 100 

 0

 20 

 40 

 60 

 80 

 100

 100 

 80 

 60 

 40 

 20 

 0 100 

 80 

 60 

 40 

 20 

 0 

 0 

 20 

 40 

 60 

 80 

 100 

 0 

 20 

 40 

 60 

 80 

 100 100 

 80 

 60 

 40 

 20 

 0 

 100 

 80 

 60 

 40 

 20 

 0 

 100 

EXPLANATION

Sample, by watershed and type—

 Samples collected March 2010

 West Nueces River watershed

 Springflow

 Groundwater

 Nueces River watershed

 Streamflow

 Springflow

 Frio River watershed

 Streamflow

 Springflow

 Sabinal River watershed

 Streamflow

 Springflow

Figure 10. Trilinear diagrams of chemical composition for streamflow, springflow, and groundwater samples collected in the upper 

Nueces River Basin, south-central Texas, March 2010.
24 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

Site 76

0 20 40 60 80 100

0 20 40 60 80 100

Calcium concentration, in milligrams per liter

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Strontium to calcium, molar ratio x 103

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Magnesium to calcium, molar ratio

A

B

Note: Site 76 represents U.S. Geological Survey station 300259100030801

EXPLANATION

Cluster

Sample, by watershed and type—

 Filled symbols represent

 samples collected August 2009.

 Open symbols represent samples

 collected March 2010

 West Nueces River watershed

 Springflow

 Groundwater

 Nueces River watershed

 Streamflow

 Springflow

 Groundwater

 Frio River watershed

 Streamflow

 Springflow

 Sabinal River watershed

 Streamflow

 Springflow

Figure 11. Relations of molar ratios to calcium concentrations for streamflow, springflow, and groundwater samples collected in the 

upper Nueces River Basin, south-central Texas, August 2009 and March 2010. A, Relation between magnesium to calcium molar ratio 

and calcium concentration. B, Relation between strontium to calcium molar ratio and calcium concentration.
Water-Quality Data 25

compared to those from the other watersheds. This indicates 

the water samples obtained from the West Nueces River 

watershed might be less geochemically evolved. Compared 

to the other watersheds, samples from the Sabinal River 

watershed generally exhibited higher Mg/Ca molar ratios. 

The Mg/Ca molar ratio to calcium concentration relation 

for samples did not always plot within the corresponding 

watershed from which the sample was collected. These 

differences might be in part related to the media type of 

the sample. For example, the Mg/Ca molar ratio of the 

groundwater sample collected in the Nueces River watershed 

(site 76) plotted close to the Mg/Ca molar ratios measured in 

samples collected from Sabinal River watershed (fig. 11A). 

Given the small sample size, it is difficult to identify the 

source of discrepancies in Mg/Ca molar ratio to calcium 

concentrations for samples collected from a given watershed. 

Additionally, while plots of molar ratios sometimes exhibited 

general clusters by watershed, a clear spatial pattern was 

not always observed. For example, the Sr/Ca molar ratio 

to calcium concentrations from samples did not cluster by 

watershed (fig. 11B). The different relations among the 

water-quality data indicate that the surface water in the 

different watersheds is likely influenced by a combination 

of differences in water-rock interactions and geochemical 

evolution (Trudgill, 1995; Oetting and others, 1996; Clark 

and Fritz, 1997; Musgrove and Banner, 2004; Musgrove and 

others, 2010). 

Strontium isotopes (87Sr/86Sr) can also be an indicator of 

water-rock interactions and geochemical evolution (Trudgill, 

1995; Clark and Fritz, 1997; Banner, 2004; Musgrove and 

others, 2010). Figure 12 depicts the relation of the inverse 

strontium concentration (1/Strontium) to the 87Sr/86Sr ratio for 

samples collected from different watersheds in the study area 

during the 2009 and 2010 surveys. Samples collected from the 

West Nueces River and Nueces River watersheds generally 

clustered separately. Samples collected from the Frio and 

Sabinal River watersheds plotted in a single cluster. Although 

the reasons for these differences are not fully understood, 

they might be caused in part by groundwater water-rock 

interactions which can vary with local lithology (Trudgill, 

1995; Clark and Fritz, 1997; Musgrove and Banner, 2004; 

Musgrove and others, 2010). The relations between Mg/Ca 

molar ratio and 87Sr/86Sr isotopic ratio (fig. 13A) and Sr/Ca 

molar ratio and 87Sr/86Sr isotopic ratio (fig. 13B) for samples 

collected from different watersheds in the study area during 

the August 2009 and March 2010 surveys are depicted in 

figure 13. Compared to samples from the other watersheds, 

higher 87Sr/86Sr isotopic ratios were measured in the samples 

collected in the West Nueces River watershed. The relation 

between the Mg/Ca molar ratio and 87Sr/86Sr isotopic ratio 

indicates that the samples collected from the West Nueces 

River watershed were chemically different from the others; 

however, samples from the other watersheds do not form 

distinct clusters (fig. 13A). Similar to the clusters of analytical 

0.7076 0.7078 0.7080 0.7082 0.7084 0.7086 0.7088 0.7090

Strontium-87/strontium-86 isotopic ratio

0

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

1/Strontium concentration, in micrograms per liter

EXPLANATION

Cluster

Sample, by watershed and type—

 Filled symbols represent

 samples collected August 2009.

 Open symbols represent samples

 collected March 2010

 West Nueces River watershed

 Springflow

 Groundwater

 Nueces River watershed

 Streamflow

 Springflow

 Groundwater

 Frio River watershed

 Streamflow

 Springflow

 Sabinal River watershed

 Streamflow

 Springflow

Figure 12. Relation of inverse strontium concentration to strontium-87/strontium-86 isotopic ratio for streamflow, springflow, and 

groundwater samples collected in the upper Nueces River Basin, south-central Texas, August 2009 and March 2010.
26 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

Site 76

0.7076 0.7078 0.7080 0.7082 0.7084 0.7086 0.7088 0.7090

0.7076 0.7078 0.7080 0.7082 0.7084 0.7086 0.7088 0.7090

Strontium-87/strontium-86 isotopic ratio

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Strontium to calcium, molar ratio x 103

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Magnesium to calcium, molar ratio

A

B

Note: Site 76 represents U.S. Geological Survey station 300259100030801

EXPLANATION

Cluster

Sample, by watershed and type—

 Filled symbols represent

 samples collected August 2009.

 Open symbols represent samples

 collected March 2010

 West Nueces River watershed

 Springflow

 Groundwater

 Nueces River watershed

 Streamflow

 Springflow

 Groundwater

 Frio River watershed

 Streamflow

 Springflow

 Sabinal River watershed

 Streamflow

 Springflow

Figure 13. Relations between molar ratios and strontium-87/strontium-86 isotopic ratios for streamflow, springflow, and groundwater 

samples collected in the upper Nueces River Basin, south-central Texas, August 2009 and March 2010. A, Magnesium to calcium molar 

ratio to strontium-87/strontium-86 isotopic ratio. B, Strontium to calcium molar ratio and strontium-87/strontium-86 isotopic ratio.
Summary 27

results depicted in figures 11 and 12, the Nueces, Frio, and 

Sabinal River watershed samples generally plotted in clusters 

in fig. 13B. The groundwater sample collected in August 

2009 from the Nueces River watershed (site 76) plots notably 

outside of the cluster for this watershed—likely because the 

groundwater was more geochemically evolved compared to 

the streamflow and springflow samples from the Nueces River 

watershed.

The different relations among the water-quality data (as 

shown in figs. 11–13) indicate that the water quality in the 

different watersheds is likely influenced by differences in 

water-rock interactions which can vary with local lithology, 

and geochemical evolution which is linked with groundwater 

flow paths and residence time, or some combination thereof. 

Determining the source areas and other possible contributors 

on the basis of these data is not possible because of the small 

sample size of the water-quality dataset (both in number of 

samples and spatial distribution of samples).

Summary 

The U.S. Geological Survey (USGS)—in cooperation 

with the U.S. Army Corps of Engineers, The Nature 

Conservancy, the Real Edwards Conservation and 

Reclamation District, and the Texas Parks and Wildlife 

Department—investigated streamflow gain and loss and 

water quality in the upper Nueces River Basin, south-central 

Texas. The study area (2,152 square miles) consists of the 

contributing areas (watersheds) of five streams (equipped 

with a total of six USGS streamflow-gaging stations) in the 

upper Nueces River Basin, north of the Edwards aquifer 

outcrop. These contributing areas are referred to as the West 

Nueces, Nueces, Dry Frio, Frio, and Sabinal River watersheds. 

Streamflow in these rivers is sustained by groundwater 

contributions (for example, from springs) and by storm 

runoff from rainfall events. To date (2012), there are few data 

available that describe streamflow conditions of these major 

rivers within the upper Nueces River Basin. 

This report describes the results of streamflow sampling 

during three reconnaissance-level synoptic measurement 

surveys (hereafter, surveys) in the upper Nueces River Basin 

in south-central Texas during July 2008, August 2009, and 

March 2010 and water-quality sampling during August 2009 

and March 2010. Streamflow and springflow measurements 

were collected at as many as 74 sites during each of the three 

survey periods, although not all sites were measured during 

each survey. These survey periods were selected to represent 

different hydrologic conditions—low flow, very low flow, 

and medium flow. In July 2008, when streamflow at the 

farthest downstream station in each of the five contributing 

watersheds was generally less than the 25th percentile 

of long-term streamflow measured at these stations, the 

streamflow conditions were referred to as “low flow”; “very 

low flow” refers to conditions that existed in August 2009 

when streamflow of the five rivers generally was less than the 

10th percentile of the respective long-term streamflows; and 

“medium flow” refers to conditions that existed in March 2010 

when streamflow was generally around the 50th percentile of 

long-term streamflow.

During the 2008, 2009, and 2010 surveys, reaches of 

gaining, losing, or no verifiable change in streamflow were 

identified on the West Nueces, Nueces, Frio, Dry Frio, and 

Sabinal Rivers. Reaches of generally consistent gaining or 

losing streamflow were identified in the Nueces, Frio, and 

Sabinal River watersheds. Identifying reaches with consistent 

gains and losses during the three surveys is related in part to 

the measurement site locations, some of which were different 

between the surveys, as well as to changes in hydrologic 

conditions. For example, several alternating reaches of gains 

and losses were observed during the 2008 and 2009 surveys 

(low-flow and very low flow conditions, respectively). During 

the 2010 survey (medium-flow conditions), some reaches 

exhibited similar patterns; however, there were fewer losing 

reaches and more gaining reaches. 

To help understand streamflow gains and losses, 

groundwater levels (which might be indicative of 

groundwater contributions to streamflow) near the 

headwaters of the Nueces River (site 76, U.S. Geological 

Survey station 300259100030801) and streamflow in the 

Nueces River watershed (site 22, U.S. Geological Survey 

station 0818999010) were examined for possible relations. 

Graphical comparisons of streamflow measured at site 22 and 

groundwater levels measured at site 76 indicate that, at times, 

streamflow at site 72 and groundwater levels at site 76 respond 

similarly to rainfall events measured at Rocksprings, Tex. 

(site 78, National Weather Service cooperative station number 

417706), but more gradual responses and longer recession 

curves were observed for groundwater levels compared to 

streamflow.

The chemical data were examined for possible relations 

among sample types (streamflow, springflow, or groundwater), 

the timing of the synoptic measurement surveys (to see if 

temporal differences were observed), and the locations of the 

watersheds in which the samples were collected. Trilinear 

diagrams indicate that the streamflow, springflow, and 

groundwater have similar major ion chemical characteristics 

and can be categorized as a calcium-carbonate water type. 

The diagrams also indicate that the major ion chemistry was 

similar during the 2009 and 2010 surveys.

Relations between chemical concentrations and ratios 

can be used to evaluate groundwater geochemical processes 

of water-rock interaction. Graphical comparisons among 

ratios of major ions, trace elements, and isotopes (for 

example, magnesium/calcium ratios to strontium isotopic 

ratios) indicate that samples collected from each watershed 

generally clustered together. Determining the source areas and 

other possible contributors on the basis of these data is not 

possible because of the small sample size of the water-quality 

dataset (both in number of samples and spatial distribution of 

samples).The relations among the water-quality data indicate 

that the water quality in the different watersheds is likely 

influenced by differences in water-rock interactions, which 
28 Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central Texas, 2008–10

can vary with local lithology and geochemical evolution, or 

some combination thereof. 

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for the examination of water and wastewater (20th ed.): 

Washington, D.C., v. 2130, p. 2-8 to 2-11.

Ashworth, J.B., and Hopkins, Janie, 1995, Aquifers of Texas: 

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Banner, J.L., 2004, Radiogenic isotopes—Systematics and 

applications to earth surface processes and chemical 

stratigraphy: Earth Science Reviews, v. 65, p. 141–194.

Barker, R.A., and Ardis, A.F., 1996, Hydrogeologic framework 

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aquifer system: U.S. Geological Survey Professional Paper 

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Bayless, E.R., Bullen, T.D., and Fitzpatrick, J.A., 2004, Use 

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Braun, C.L., and Lambert, R.B., 2011, Streamflow,

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Geological Survey Scientific Investigations Report 2011–

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Appendixes 1–3

Appendix 1. Quality-assurance hydrologic measurements during the July 2008, August 2009, and March 2010 surveys in the upper Nueces River Bas[ft3/s, cubic feet per second; Spring, springflow; --, not collected or not applicable; P, poor; RPD, relative percent difference; %, percent; SW, surface-water streamflow; G, good

Site 

identifier 

(fig. 1)

Watershed

U.S. Geological 

Survey station 

number

U.S. Geological Survey 

station name

Type 

of data

July 21–23, 2008 August 8–18, 2009 

Measurement

(ft3/s)

Measurement

rating

Measurement

(ft3/s)

Measurement

rating

6 West Nueces 

River

293913100230301 Spring 3 on West Nueces River1 Spring -- -- 0.01 P 

Spring -- -- 0.01 P 

RPD 0%

13 Nueces River 08189983 Nueces River downstream from 

Hackberry Creek near Vance, Tex.

SW -- -- 9.49 P SW -- -- 9.76 P 

RPD 3%

19 Nueces River 08189985 Nueces River at Vance, Tex. SW -- -- 2.19 G 

SW -- -- 2.28 F 

RPD 4%

32 Nueces River 08189998 Nueces River at County Road 414 

at Montell, Tex.

SW -- -- 0.72 F SW -- -- 0.70 F 

RPD 3%

33 Nueces River 08190000 Nueces River at Laguna, Tex. SW -- -- 18.3 F 

SW -- -- 18.5 F 

RPD 1%

50 Frio River 08194800 East Frio River upstream of Indian 

Creek near Leakey, Tex.

SW 13.3 G -- -- SW 12.4 F -- -- 

RPD 7%

51 Frio River 08194840 Frio River at Leakey, Tex. SW -- -- 1.03 F 

SW -- -- 0.61 P 

RPD 51%

61 Frio River 08195000 Frio River at Concan, Tex. SW -- -- 6.94 F 

SW -- -- 6.95 F 

RPD 0%

65 Sabinal River 08197910 Sabinal River downstream from 

Marler Creek near Vanderpool, Tex.

SW 2.45 F -- -- SW 2.50 F -- -- 

RPD 2%

1Official U.S. Geological Survey station name not used here per landowner privacy request.
Appendix 2. Water-quality data collected during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central Texas.[°C, degrees Celsius; na, not applicable; ENV, environmental sample; --, not analyzed; mg/L, milligrams per liter; LED, light-emitting diode; nm, nanometers; E, estimated; <, lliter]

Site 

identifier Watershed

U.S. Geological 

Survey station 

number

State well 

number

U.S. Geological Survey 

station name Date Time Sample type

Barometric 

pressure, 

millimeters 

of mercury

Temperature, 

air

(°C)

4 West Nueces River 294529100234701 na Spring 1 on West Nueces River1 8/18/2009 1600 ENV -- -- 4 West Nueces River 294529100234701 na Spring 1 on West Nueces River1 3/23/2010 920 ENV 717 13.4 5 West Nueces River 294443100213701 na Spring 2 on West Nueces River1 8/18/2009 1330 ENV -- -- 6 West Nueces River 293913100230301 na Spring 3 on West Nueces River1 8/18/2009 1045 ENV -- -- 8 Nueces River 08189979 na Hackberry Creek at Ranch Road 335 

near Vance, Tex.

8/13/2009 1430 ENV 715 -- 

8 Nueces River 08189979 na Hackberry Creek at Ranch Road 335 

near Vance, Tex.

3/23/2010 1400 ENV 710 20.8 

9 Nueces River 0818998070 na East Prong Nueces River upstream of 

Eagle Ranch near Rocksprings, Tex.

8/12/2009 1730 ENV -- -- 

9 Nueces River 0818998070 na East Prong Nueces River upstream of 

Eagle Ranch near Rocksprings, Tex.

3/23/2010 1620 ENV 711 22.8 

10 Nueces River 295702099571801 na Spring on East Prong Nueces River 

near Vance, Tex.1

8/12/2009 1830 ENV -- -- 

22 Nueces River 0818999010 na Nueces River near Barksdale, Tex. 3/23/2010 1500 ENV 718 22.6 29 Nueces River 0818999640 na Old Faithful Spring near Camp Wood, 

Tex.

3/24/2010 0920 ENV 724 17.1 

39 Frio River 295454099473101 na Spring 1 on West Frio River, Tex.1 8/12/2009 1630 ENV 713 22.7 40 Frio River 295144099480201 na Spring 2 on West Frio River, Tex.1 8/12/2009 1400 ENV -- 28.0 40 Frio River 295144099480201 na Spring 2 on West Frio River, Tex.1 3/22/2010 1700 ENV 716 -- 42 Frio River 08194690 na West Frio River upstream of Kent 

Creek near Leakey, Tex.

3/22/2010 1800 ENV 719 -- 

46 Frio River 295100099403001 na Spring on East Frio River, Tex.1 8/13/2009 1100 ENV 715 22.5 53 Frio River 08194850 na Leakey Spring Run at Leakey, Tex. 8/12/2009 1430 ENV -- 36.0 53 Frio River 08194850 na Leakey Spring Run at Leakey, Tex. 3/22/2010 1430 ENV 727 21.2 61 Frio River 08195000 na Frio River at Concan, Tex. 3/22/2010 1230 ENV 737 15.4 62 Sabinal River 294950099353801 na AS-69-12-401 8/13/2009 1615 ENV -- -- 62 Sabinal River 294950099353801 na AS-69-12-401 3/24/2010 1400 ENV 711 -- 64 Sabinal River 08197907 na Sabinal River downstream from 

Wedgeworth Creek near Vanderpool, Tex.

8/14/2009 1000 ENV 718 25.0 

64 Sabinal River 08197907 na Sabinal River downstream from 

Wedgeworth Creek near Vanderpool, Tex.

3/24/2010 1300 ENV 717 -- 

72 Sabinal River 08197970 na Sabinal River at Utopia, Tex. 3/24/2010 1600 ENV 728 20.1 75 West Nueces River 293551100281701 RP–70–29–101 RP–70–29–101 (Kickapoo Caverns) 8/17/2009 1540 ENV 722 -- 75 West Nueces River 293551100281701 RP–70–29–101 RP–70–29–101 (Kickapoo Caverns) 3/23/2010 1100 ENV -- -- 76 Nueces River 300259100030801 JJ–55–64–503 JJ–55–64–503 (Lazy H Ranch) 8/13/2009 1200 ENV 705 -- 77 Sabinal River 294815099343801 AS–69–12–501 AS–69–12–501 8/13/2009 1530 ENV -- -- 
Appendix 2. Water-quality data collected during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central Texas.—C[°C, degrees Celsius; na, not applicable; ENV, environmental sample; --, not analyzed; mg/L, milligrams per liter; LED, light-emitting diode; nm, nanometers; E, estimated; <, lliter]

Site 

identifier Date

Dissolved 

oxygen, 

water, 

unfiltered

(mg/L)

Dissolved 

oxygen, 

water, 

unfiltered

(percent of saturation)

pH, 

water, 

unfiltered, 

field

(standard 

units)

pH, 

water, 

unfiltered, 

laboratory

(standard 

units)

Specific 

conductance, 

water, 

unfiltered, 

laboratory

(microsiemens per 

centimeter 

at 25°C)

Specific 

conductance, 

water, 

unfiltered

(microsiemens per 

centimeter 

at 25°C)

Temperature, 

water

(°C)

Turbidity, water, 

unfiltered, 

monochrome 

near infrared LED 

light, 780–900 nm, 

detection angle 

90 +/ -2.5 degrees, 

formazin nephelometric units

(FNU)

Dissolved 

solids 

dried at 

180°C, 

water, 

filtered

(mg/L)

Hardness, 

water

(mg/L as 

CaCO3)

Noncarbonate hardness, water, 

filtered, field

(milligrams 

per liter as 

calcium 

carbonate)

Calc

wa

filte

(m

4 8/18/2009 7.8 -- E7.0 7.8 373 366 23.2 1.5 214 178 4 54 3/23/2010 8.5 100 7.9 7.9 360 379 20.4 -- 213 178 -- 55 8/18/2009 7.2 -- 7.2 7.6 504 499 21.7 <1.0 282 264 21 746 8/18/2009 -- -- -- -- -- -- -- -- -- -- -- -8 8/13/2009 6.6 80 6.9 7.6 411 410 21.4 <1.0 236 209 -- 628 3/23/2010 7.6 90 7.4 7.7 394 405 20.4 -- 221 200 -- 59 8/12/2009 10.9 -- 7.8 8.0 398 400 25.0 -- 228 196 6 59 3/23/2010 11.3 138 8.4 8.2 372 383 21.8 -- 213 191 -- 5

10 8/12/2009 8.1 -- E7.4 7.7 428 420 20.5 -- 244 201 -- 522 3/23/2010 10.4 119 8.1 8.2 353 366 18.9 -- 206 178 -- 429 3/24/2010 8.2 91 7.5 7.9 375 375 18.1 -- 203 185 -- 5439 8/12/2009 8.1 96 E7.2 7.7 412 405 20.5 <1.0 231 189 -- 640 8/12/2009 8.2 -- E7.3 7.8 427 421 21.0 -- 242 208 1 6440 3/22/2010 7.9 93 7.8 7.9 401 424 20.0 -- 229 208 -- 642 3/22/2010 9.9 108 8.4 8.2 311 317 16.8 -- 182 156 6 446 8/13/2009 8.2 97 7.5 7.8 418 416 20.4 2.2 235 214 15 652 8/12/2009 7.3 -- 7.1 7.6 451 443 22.0 <1.0 245 212 -- 652 3/22/2010 7.7 85 7.9 7.9 396 415 18.1 -- 219 205 22 661 3/22/2010 10.2 104 7.9 8.2 439 446 14.6 -- 265 215 31 662 8/13/2009 7.7 -- 7.1 7.7 466 467 19.9 <1.0 267 228 -- 662 3/24/2010 9.0 99 7.5 7.7 462 480 16.7 -- 268 249 -- 764 8/14/2009 6.3 84 8.0 8.0 397 402 26.8 <1.0 226 204 6 5464 3/24/2010 9.2 99 7.9 8.2 421 437 16.4 -- 257 226 -- 572 3/24/2010 9.7 111 7.8 8.1 509 530 19.4 -- 283 273 -- 875 8/17/2009 6.7 84 7.3 7.6 384 383 23.8 5.3 226 187 -- 6475 3/23/2010 7.1 -- 7.9 7.7 373 383 23.5 -- 209 188 -- 676 8/13/2009 6.7 85 E7.3 7.8 410 413 23.2 2.0 231 199 -- 577 8/13/2009 0.2 -- E7.0 7.5 1,180 1,190 25.2 -- 808 515 242 9
Appendix 2. Water-quality data collected during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central Texas.—C[°C, degrees Celsius; na, not applicable; ENV, environmental sample; --, not analyzed; mg/L, milligrams per liter; LED, light-emitting diode; nm, nanometers; E, estimated; <, lliter] Site iden- tifier Date Sodium adsorp- tion ratio, water, number Sodium fraction of cations, water, percent in equiva- lents of major cations Sodium, water, filtered (mg/L) Alkalinity, water, filtered, fixed end- point (pH 4.5) titration, field (mg/L as CaCO3) Alkalinity, water, filtered, inflection-point titration method (incremental titration method), field (mg/L as CaCO3) Bicarbonate, water, filtered, inflection- point titration method (incremental titration method), field (mg/L) Bro- mide, water, filtered (mg/L) Carbon diox- ide, water, unfil- tered (mg/L) Carbonate, water, filtered, inflection-point titration method (incremental titration method), field (mg/L) Chlo- ride, water, filtered (mg/L) Fluo- ride, water, filtered (mg/L) H

io

u

ca

4 8/18/2009 0.17 6 5.26 -- 174 212 0.06 E34 <1 9.85 0.14 E4 3/23/2010 0.16 6 5.02 -- 210 255 0.06 5.7 <1 10.5 0.19 5 8/18/2009 0.15 4 5.52 -- 243 296 0.07 28 <1 10.5 E0.10 6 8/18/2009 -- -- -- -- -- -- -- -- -- -- -- 8 8/13/2009 0.15 5 4.91 -- -- -- 0.06 -- -- 9.15 0.15 8 3/23/2010 0.14 5 4.51 186 -- -- 0.05 14 -- 9.50 0.18 9 8/12/2009 0.17 6 5.57 -- 191 232 0.06 6.0 <1 10.2 0.16 9 3/23/2010 0.16 6 5.13 184 -- -- 0.06 1.5 -- 9.99 0.19 

10 8/12/2009 0.15 5 4.79 -- 206 250 0.07 E16 <1 10.1 0.10 E22 3/23/2010 0.18 6 5.50 170 -- -- 0.05 2.6 -- 12.1 0.18 29 3/24/2010 0.18 6 5.47 177 -- -- 0.06 10 -- 11.8 0.11 39 8/12/2009 0.14 5 4.26 -- 192 233 0.07 E27 <1 9.34 E.07 E40 8/12/2009 0.15 5 4.89 -- 208 252 0.07 E18 <1 10.6 E.06 E40 3/22/2010 0.15 5 4.88 -- 210 255 0.06 7.3 E1 11.2 0.15 42 3/22/2010 0.18 7 5.05 -- 151 183 0.04 1.1 <1 10.6 0.18 46 8/13/2009 0.14 5 4.81 -- 201 244 0.07 13 <1 9.07 E0.09 52 8/12/2009 0.17 6 5.68 -- 213 259 0.07 33 <1 11.3 E0.09 52 3/22/2010 0.17 6 5.51 -- 184 224 0.05 5.0 <1 12.3 0.16 61 3/22/2010 0.19 6 6.49 -- 185 225 0.04 4.7 <1 13.5 0.18 62 8/13/2009 0.14 4 4.67 -- 261 318 0.06 38 <1 9.33 0.12 62 3/24/2010 0.14 4 4.92 226 -- -- 0.05 15 -- 10.7 0.16 64 8/14/2009 0.18 6 5.87 -- 198 239 0.08 4.3 1 10.5 E0.09 64 3/24/2010 0.17 5 5.83 215 -- -- 0.03 5.8 -- 12.1 0.15 72 3/24/2010 0.17 5 6.45 204 -- -- 0.05 6.9 -- 13.0 0.19 75 8/17/2009 0.15 5 4.55 -- 189 230 0.06 19 <1 8.82 E.08 75 3/23/2010 0.15 5 4.60 174 -- -- 0.06 4.1 -- 9.38 0.14 76 8/13/2009 0.17 6 5.63 -- 201 244 0.06 E20 <1 10.8 0.21 E77 8/13/2009 1.04 18 53.9 -- 273 332 0.25 E54 <1 33.3 2.85 E
Appendix 2. Water-quality data collected during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central Texas.—C[°C, degrees Celsius; na, not applicable; ENV, environmental sample; --, not analyzed; mg/L, milligrams per liter; LED, light-emitting diode; nm, nanometers; E, estimated; <, lliter]

Site 

identifier Date

Aluminum, 

water, 

filtered 

(μg/L)

Barium, 

water, 

filtered 

(μg/L)

Beryllium, 

water, 

filtered 

(μg/L)

Cadmium, 

water, 

filtered 

(μg/L)

Chromium, 

water, 

filtered 

(μg/L)

Cobalt, 

water, 

filtered 

(μg/L)

Copper, 

water, 

filtered 

(μg/L)

Iron, 

water, 

filtered 

(μg/L)

Lead, 

water, 

filtered 

(μg/L)

Lithium, 

water, 

filtered 

(μg/L)

Manganese

water, 

filtered 

(μg/L)

4 8/18/2009 -- -- -- -- -- -- -- <4 -- -- E0.16 4 3/23/2010 <3.4 54 <0.01 <0.02 <0.12 0.37 <1 E3 <0.03 1.3 0.9 5 8/18/2009 -- -- -- -- -- -- -- <4 -- -- E.13 6 8/18/2009 -- -- -- -- -- -- -- -- -- -- -- 8 8/13/2009 -- -- -- -- -- -- -- 5 -- -- 0.4 8 3/23/2010 <3.4 108 <0.01 <0.02 0.12 0.42 <1 <6 <0.03 1.9 0.8 9 8/12/2009 -- -- -- -- -- -- -- 4 2.0 9 3/23/2010 <3.4 75 <0.01 <0.02 0.12 0.43 <1 <6 <0.03 1.9 1.0 

10 8/12/2009 -- -- -- -- -- -- -- E3 -- -- 0.6 22 3/23/2010 -- -- -- -- -- -- -- <6 -- -- 1.4 29 3/24/2010 <3.4 33 <0.01 <0.02 <0.12 0.25 <1 <6 <0.03 1.3 0.5 39 8/12/2009 -- -- -- -- -- -- -- E2 -- -- 0.4 40 8/12/2009 -- -- -- -- -- -- -- E2 -- -- E0.19 40 3/22/2010 <3.4 27 <0.01 <0.02 <0.12 0.48 <1 <6 <0.03 1.3 0.8 42 3/22/2010 <3.4 27 <0.01 E0.01 <0.12 0.35 <1 E4 <0.03 1.5 1.2 46 8/13/2009 -- -- -- -- -- -- -- <4 -- -- 0.3 52 8/12/2009 -- -- -- -- -- -- -- E3 -- -- 0.8 52 3/22/2010 E2.2 29 <0.01 <0.02 <0.12 0.34 E0.59 <6 <0.03 1.6 0.7 61 3/22/2010 <3.4 33 <0.01 <0.02 <0.12 0.32 <1 <6 <0.03 2.2 0.8 62 8/13/2009 -- -- -- -- -- -- -- E2 -- -- 0.5 62 3/24/2010 E3.1 25 <0.01 <0.02 <0.12 0.16 <1 <6 <0.03 1.1 E0.23 64 8/14/2009 -- -- -- -- -- -- -- 13 -- -- 8.5 64 3/24/2010 -- -- -- -- -- -- -- <6 -- -- 0.8 72 3/24/2010 <3.4 38 <0.01 <0.02 <0.12 0.32 <1 <6 <0.03 2.3 1.8 75 8/17/2009 -- -- -- -- -- -- -- 4 -- -- 1.4 75 3/23/2010 E2.3 124 <0.01 0.07 0.13 1.2 0.95 10 0.06 1.5 3.8 76 8/13/2009 -- -- -- -- -- -- -- 5 -- -- 0.8 77 8/13/2009 -- -- -- -- -- -- -- 729 -- -- 31.1 
Appendix 2. Water-quality data collected during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central Texas.—C[°C, degrees Celsius; na, not applicable; ENV, environmental sample; --, not analyzed; mg/L, milligrams per liter; LED, light-emitting diode; nm, nanometers; E, estimated; <, lliter]Site identi- fier Date Silver, water, filtered (μg/L) Strontium, water, filtered (μg/L) Thallium, water, filtered (μg/L) Vanadium, water, filtered (μg/L) Zinc, water, filtered (μg/L) Antimony, water, filtered (μg/L) Arsenic, water, filtered (μg/L) Boron, water, filtered (μg/L) Selenium, water, filtered (μg/L) Uranium (natural), water, filtered (μg/L) Deuteri

protiu

ratio

wate

unfilter

(per m

4 8/18/2009 -- 83.0 -- -- -- -- -- -- -- -- -- 4 3/23/2010 <0.01 78.0 <0.02 3.9 <2.8 0.10 0.49 30 0.49 0.59 -29.15 8/18/2009 -- 66.0 -- -- -- -- -- -- -- -- -- 6 8/18/2009 -- 73.0 -- -- -- -- -- -- -- -- -- 8 8/13/2009 -- 159 -- -- -- -- -- -- -- -- -- 8 3/23/2010 <0.01 140 E0.01 4.5 <2.8 0.12 0.60 32 0.41 0.60 -30.79 8/12/2009 -- 224 -- -- -- -- -- -- -- -- -- 9 3/23/2010 <0.01 192 <0.02 4.6 <2.8 0.16 0.48 31 0.41 0.63 -29.7

10 8/12/2009 -- 188 -- -- -- -- -- -- -- -- -- 22 3/23/2010 -- -- -- -- -- -- -- -- -- -- -24.829 3/24/2010 <0.01 155 <0.02 2.5 <2.8 0.09 0.45 34 0.52 0.57 -26.539 8/12/2009 -- 103 -- -- -- -- -- -- -- -- -- 40 8/12/2009 -- 95.0 -- -- -- -- -- -- -- -- -- 40 3/22/2010 <0.01 88.0 <0.02 3.3 3.6 0.13 0.37 34 0.52 0.63 -29.142 3/22/2010 <0.01 165 <0.02 2.8 E2.0 0.12 0.48 31 0.41 0.70 -24.746 8/13/2009 -- 110 -- -- -- -- -- -- -- -- -- 52 8/12/2009 -- 236 -- -- -- -- -- -- -- -- -- 52 3/22/2010 <0.01 191 <0.02 2.2 E1.8 0.10 0.33 31 0.71 0.56 -25.061 3/22/2010 <0.01 296 <0.02 1.8 3.5 0.07 0.33 39 0.55 0.69 -23.662 8/13/2009 -- 113 -- -- -- -- -- -- -- -- -- 62 3/24/2010 <0.01 89.0 <0.02 2.5 <2.8 0.08 0.31 33 0.51 0.68 -27.964 8/14/2009 -- 158 -- -- -- -- -- -- -- -- -- 64 3/24/2010 -- -- -- -- -- -- -- -- -- -- -25.372 3/24/2010 <0.01 336 <0.02 1.6 E1.6 0.12 0.22 45 0.86 0.82 -22.175 8/17/2009 -- 82.0 -- -- -- -- -- -- -- -- -- 75 3/23/2010 <0.01 76.4 E0.01 3.5 116 0.10 0.42 35 0.46 0.64 -28.476 8/13/2009 -- 436 -- -- -- -- -- -- -- -- -- 77 8/13/2009 -- 7,290 -- -- -- -- -- -- -- -- -- 

1Official U.S. Geological Survey station name not used here per landowner privacy request.
Appendix 3. Quality-assurance water-quality data during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central T[°C, degrees Celsius; mg/L, milligrams per liter; na, not applicable; EB, equipment blank sample; <, less than; FB, field blank sample; E, estimated; ENV, environmental samplequality-assurance sample; RPD, relative percent difference in percent; %, percent; --, not analyzed; nc, not calculated; μg/L, micrograms per liter]

Site 

identifier Watershed

U.S. Geological 

Survey station 

number

U.S. Geological Survey 

station name Date Time

Sample 

type

Dissolved 

solids, dried 

at 180°C, 

water, filtered 

(mg/L)

Hardness, 

water 

(mg/L as 

CaCO3)

Calc

wa

filte

(mg

na Frio River 294424099454101 WA–69–18–303 8/10/2009 1400 EB <10 <0.10 <0

61 Frio River 08195000 Frio River at Concan, Tex. 3/22/2010 1231 FB <10 <0.12 E064 Sabinal River 08197907 Sabinal River downstream from Wedgeworth 

Creek near Vanderpool, Tex.

8/14/2009 1030 FB <10 <0.10 <0

62 Sabinal River 294950099353801 AS–69–12–401 3/24/2010 1400 ENV 268 248 7062 Sabinal River 294950099353801 AS–69–12–401 3/24/2010 1410 REP 265 248 70

RPD 1% 0% 0

64 Sabinal River 08197907 Sabinal River downstream from Wedgeworth 

Creek near Vanderpool, Tex.

8/14/2009 1000 ENV 226 204 54

64 Sabinal River 08197907 Sabinal River downstream from Wedgeworth 

Creek near Vanderpool, Tex.

8/14/2009 1010 REP 226 196 52

RPD 0% 4% 5

Site 

identifier

Sodium 

adsorption ratio, 

water, 

number

Sodium 

fraction of 

cations, 

water, 

percent in 

equivalents 

of major 

cations

Sodium, 

water, 

filtered 

(mg/L)

Alkalinity, 

water, filtered, 

fixed endpoint 

(pH 4.5) 

titration, field 

(mg/L as CaCO3)

Alkalinity, 

water, filtered, 

inflection-point 

titration method 

(incremental titration method), field 

(mg/L as CaCO3)

Bicarbonate, 

water, filtered, 

inflection-point 

titration method 

(incremental 

titration 

method), field 

(mg/L)

Bromide, 

water, 

filtered 

(mg/L)

Carbon 

dioxide, 

water, 

unfiltered 

(mg/L)

Carbonate, 

water, filtered, 

inflection-point 

titration method 

(incremental 

titration 

method), field

(mg/L)

Chloride, 

water, 

filtered 

(mg/L)

Fluoride, 

water, 

filtered 

(mg/L)

na -- -- <0.12 -- -- -- <0.02 -- -- <0.12 <0.08 

61 -- -- <0.10 -- -- -- <0.02 -- -- 0.26 <0.08 64 -- -- <0.12 -- -- -- -- -- -- E0.07 <0.08 62 0.14 4 4.92 226 -- -- 0.05 15.0 -- 10.7 0.16 62 0.14 4 4.90 214 -- -- 0.05 14.0 -- 10.9 0.19 

0% 0% 0% 5% nc nc 0% 7% nc 2% 17% 

64 0.18 6 5.87 -- 198 239 0.08 4.2 1.0 10.5 E0.09 64 0.17 6 5.59 -- 197 237 0.08 4.2 1.0 10.4 E0.08 

6% 0% 5% nc 1% 1% 0% 0% 0% 1% nc 
Appendix 3. Quality-assurance water-quality data during the August 2009 and March 2010 surveys in the upper Nueces River Basin, south-central T[°C, degrees Celsius; mg/L, milligrams per liter; na, not applicable; EB, equipment blank sample; <, less than; FB, field blank sample; E, estimated; ENV, environmental samplequality-assurance sample; RPD, relative percent difference in percent; %, percent; --, not analyzed; nc, not calculated; μg/L, micrograms per liter] Site identifier Barium, water (μg/L) Beryllium, water, filtered (μg/L) Cadmium, water, filtered (μg/L) Chromium, water, filtered (μg/L) Cobalt, water, filtered (μg/L) Copper, water, filtered (μg/L) Iron, water, filtered (μg/L) Lead, water, filtered (μg/L) Lithium, water, filtered (μg/L) Manganese, water, filtered (μg/L) Molybdenum

water, filtered (μg/L) 

na -- -- -- -- -- -- <4 -- -- E0.2 -- 

61 <0.14 <0.01 <0.02 <0.12 0.51 <1.0 <6 <0.03 <0.4 1.0 <0.03 64 -- -- -- -- -- -- <4 -- -- <0.2 -- 62 25 <0.01 <0.02 <0.12 0.16 <1.0 <6 <0.03 1.10 E0.2 0.43 62 25 <0.01 <0.02 <0.12 0.13 <1.0 <6 <0.03 1.10 E0.2 0.41 

0% nc nc nc 21% nc nc nc 0% nc 5% 

64 -- -- -- -- -- -- -- -- -- 8.5 -- 64 -- -- -- -- -- -- -- -- -- 8.0 -- 

nc nc nc nc nc nc nc nc nc 6% nc 

Site identi- fier Strontium, water, filtered (μg/L) Thallium, water, filtered (μg/L) Vanadium, water, filtered (μg/L) Zinc, water, filtered (μg/L) Antimony, water, filtered (μg/L) Arsenic, water, filtered (μg/L) Boron, water, filtered (μg/L) Selenium, water, filtered (μg/L) Uranium (natural), water, filtered (μg/L) Deuterium/ protium ratio, water, unfiltered (per mil) 

na -- -- -- -- -- -- -- -- -- -- 

61 <0.40 <0.02 <0.16 12.5 0.06 <0.04 <2.8 <0.04 <0.01 -- 64 -- -- -- -- -- -- -- -- -- -- 62 89.0 <0.02 2.5 <3 0.08 0.31 33 0.51 0.68 -27.90 62 88.2 <0.02 2.5 E1.4 0.08 0.31 32 0.66 0.68 -27.00 

1% nc 0% nc 0% 0% 3% 26% 0% 3% 

64 158 -- -- -- -- -- -- -- -- -- 64 159 -- -- -- -- -- -- -- -- -- 

1% nc nc nc nc nc nc nc nc nc 
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Banta and others—Streamflow Gain and Loss and Water Quality in the Upper Nueces River Basin, South-Central, Texas, 2008–10—SIR 2012–5181

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