U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5098

Prepared in cooperation with the Central Texas Groundwater Conservation District

Streamflow Gains and Losses in the Colorado River in 

Northwestern Burnet and Southeastern San Saba Counties, 

Texas, 2012–14
Front cover:

Backgound, Seeps along limestone outcrop downstream from where Jim John Creek flows into the

Colorado River, October 31, 2012 (photograph by Jennifer Wilson, U.S. Geological Survey).

Bottom right, Faulting in limestone outcrop downstream from where Greenwood Creek flows into the

Colorado River, October 31, 2012 (photograph by Jennifer Wilson, U.S. Geological Survey).

Back cover:

Backgound, Travertine deposits near site 4 (Post Oak Falls near Tow, Texas, October 31, 2012) 

(photograph by Jennifer Wilson, U.S. Geological Survey).

Top right, Wading discharge measurement made using the U.S. Geological Survey midsection method 

at site 1 (Colorado River downstream from Yancey Creek near Tow, Texas, December 3, 2012) (photograph 

by Christopher Braun, U.S. Geological Survey).

Top left, Concurrent discharge measurements made with extended wading rods using the U.S.

Geological Survey midsection method at site 5 (Colorado River at confluence of Jennings Creek near

Tow, Texas), December 4, 2012 (photograph by Christopher Braun, U.S. Geological Survey).
Streamflow Gains and Losses in the 

Colorado River in Northwestern Burnet and 

Southeastern San Saba Counties, Texas, 

2012–14

By Christopher L. Braun and Scott D. Grzyb

Prepared in cooperation with the Central Texas Groundwater Conservation 

District

Scientific Investigations Report 2015–5098

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

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

Suggested citation:

Braun, C.L., and Grzyb, S.D., 2015, Streamflow gains and losses in the Colorado River in northwestern Burnet and 

southeastern San Saba Counties, Texas, 2012–14: U.S. Geological Survey Scientific Investigations Report 2015–5098, 

32 p., http://dx.doi.org/10.3133/sir20155098.

ISSN 2328-0328 (online)
iii

Contents

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

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

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

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

Methods ..........................................................................................................................................................4

Discharge Measurements ..................................................................................................................4

Gain-Loss Surveys ...............................................................................................................................9

Streamflow Gains and Losses ..................................................................................................................18

Summary .......................................................................................................................................................26

References ...................................................................................................................................................26

Appendixes

1. Calculation of estimated evaporative losses within reaches on the Colorado 

River in northwestern Burnet County, Texas, December 3–6, 2012 ...................................31

2. Calculation of estimated evaporative losses within reaches on the Colorado 

River in northwestern Burnet County, Texas, May 31–June 1, 2014 .................................32

Figures

1. Map showing location of study area, northwestern Burnet and southeastern 

San Saba Counties, Texas ..........................................................................................................3

2. Diagram showing geologic and hydrogeologic units in northwestern Burnet and 

southeastern San Saba Counties, Texas .................................................................................4

3. Map showing surficial geology in northwestern Burnet and southeastern San 

Saba Counties, Texas ..................................................................................................................5

4. Map showing hydrogeologic units and discharge measurement sites in 

northwestern Burnet and southeastern San Saba Counties, Texas ...................................6

5. Photograph showing a tethered Acoustic Doppler current profiler (ADCP) boat ............9

6. Acoustic doppler current profiles made at the same location on A, May 31, 

2014, at 5:35 p.m. and on B, June 1, 2014, at 10:41 a.m. at U.S. Geological Survey 

station 310022098273300 Colorado River at Post Oak Falls near Tow, Texas ...................10

7. Photographs of faults and hydrogeologic unit contacts along the Colorado River 

in northwestern Burnet and southeastern San Saba Counties, Texas, and a map 

depicting photograph locations. A, faulting within confining units (Point Peak 

Member and Morgan Creek Limestone); B, fault at contact between the MidCambrian aquifer and Ellenburger-San Saba aquifer; and C, fault in the 

Ellenburger-San Saba aquifer .................................................................................................11

8. Photographs of seeps, springs, and travertine deposits along the Colorado River 

in northwestern Burnet and southeastern San Saba Counties, Texas, and a map 

depicting photograph locations. A and C, seeps; and B and D, springs and 

associated travertine deposits ................................................................................................12

9. Photographs of tributary streams, which act as discharge points to the Colorado 

River in northwestern Burnet and southeastern San Saba Counties, Texas, and 

a map depicting photograph locations. A, Jim John Creek; B, Greenwood Creek; 

and C, Deer Creek ......................................................................................................................13
iv

10. Graphs showing river stage, instantaneous discharge, and cumulative 

precipitation at Lower Colorado River Authority streamflow-gaging station 1925 

Colorado River at Bend, Texas, October 1, 2012–June 30, 2014 .........................................15

11. Graphs showing river stage and instantaneous discharge at Lower Colorado 

River Authority (LCRA) streamflow-gaging station 1925 Colorado River at Bend, 

Texas, November 30–December 9, 2012 ................................................................................16

12. Graphs showing river stage and instantaneous discharge at Lower Colorado 

River Authority (LCRA) streamflow-gaging station 1925 Colorado River at Bend, 

Texas, May 25–June 3, 2014 .....................................................................................................17

13. Schematic diagram of study area reaches showing streamflow-measurement 

sites and tributary inflows along the Colorado River in northwestern Burnet and 

southeastern San Saba Counties, Texas ...............................................................................20

14. Map showing reaches that were verifiably gaining or losing or unverifiably 

gaining or losing during the fall 2012 gain-loss survey in northwestern Burnet 

and southeastern San Saba Counties, Texas .......................................................................24

15. Map showing reaches that were verifiably gaining or losing or unverifiably 

gaining or losing during the spring 2014 gain-loss survey in northwestern Burnet 

and southeastern San Saba Counties, Texas .......................................................................25

Tables

1. Description of streamflow measurement sites on the Colorado River in 

northwestern Burnet and southeastern San Saba Counties, Texas, 2012–14 ...................7

2. Reaches evaluated for streamflow gains or losses on the Colorado River in 

northwestern Burnet and southeastern San Saba Counties, Texas, 2012–14 .................14

3. Description of tributary inflows to the Colorado River in northwestern Burnet 

and southeastern San Saba Counties, Texas, 2012–14 .......................................................18

4. Summary of gain-loss determinations for reaches on the Colorado River in 

northwestern Burnet and southeastern San Saba Counties, Texas, 2012–14 .................19

5. Summary of gain-loss determinations during the spring 2014 gain-loss survey 

for reaches on the Colorado River in northwestern Burnet and southeastern 

San Saba Counties, Texas, 2012–14 ........................................................................................23
v

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Flow Rate

cubic foot per second (ft3

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

Datum

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

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

(NAVD 88).

Abbreviations

ADCP Acoustic Doppler current profiler

CTGCD Central Texas Groundwater Conservation District

LCRA Lower Colorado River Authority

NWIS National Water Information System

QA Quality assurance

USGS U.S. Geological Survey

Streamflow Gains and Losses in the Colorado River 

in Northwestern Burnet and Southeastern San Saba 

Counties, Texas, 2012–14

By Christopher L. Braun and Scott D. Grzyb

Abstract 

In October 2012, the U.S. Geological Survey (USGS), in 

cooperation with the Central Texas Groundwater Conservation 

District, began an assessment to better understand if and 

where groundwater from the Ellenburger-San Saba aquifer is 

discharging to the Colorado River, and if and where Colorado 

River streamflow is recharging the Ellenburger-San Saba 

aquifer in the study area. Discharge measurements were 

made to determine if different reaches of the Colorado River 

in northwestern Burnet and southeastern San Saba Counties 

are gaining or losing streamflow, the locations and quantities 

of gains and losses, and whether the gains and losses can be 

attributed to interaction between the river and the EllenbugerSan Saba aquifer. To assess streamflow gains and losses, 

two sets of synoptic gain-loss discharge measurements 

representing different streamflow conditions were completed. 

In the first gain-loss streamflow survey during December 3–6, 

2012 (hereinafter the fall 2012 gain-loss survey), discharge 

measurements were made at low-flow conditions ranging from 

about 30 to 60 cubic feet per second (ft3

/s) at seven locations 

along the Colorado River. In the second gain-loss streamflow 

survey during May 31–June 1, 2014 (hereinafter the spring 

2014 gain-loss survey), discharge measurements were made 

at high-flow conditions ranging from about 660 to 900 ft3

/s at 

12 locations along the Colorado River. 

During the fall 2012 gain-loss survey, verifiable gains 

or losses of streamflow were identified in 4 of 6 reaches 

(the difference in measured discharge between the upstream 

and downstream boundaries of the reach was larger than the 

sum of potential errors associated with the two discharge 

measurements). The two reaches with a verifiable gain in 

streamflow cross areas where the Ellenburger-San Saba 

aquifer crops out. The more upstream of the two reaches with 

verifiable losses crosses a small part of the Ellenburger-San 

Saba aquifer outcrop and confining units (Point Peak Member 

and Morgan Creek Limestone); it is possible streamflow losses 

in this reach are in the form of recharge to the Ellenburger-San 

Saba aquifer; little streamflow is likely lost to the underlying 

formations in the downstream part of the reach, which consists 

of relatively impermeable aquifer confining units exposed at 

land surface. The more downstream of the two reaches where 

a verifiable loss of streamflow was measured also flows across 

relatively impermeable confining units before crossing the 

Mid-Cambrian aquifer outcrop in the lower part of the reach; 

most of the streamflow losses in this reach were likely a result 

of water infiltrating into the subsurface from the streambed 

and providing recharge to the relatively permeable MidCambrian aquifer.

During the spring 2014 gain-loss survey, 11 reaches 

were combined into 3 in an attempt to consolidate gains and 

losses as well as group reaches within the same hydrogeologic 

units. An unverifiable loss was measured in the reach farthest 

upstream, which crosses a combination of alluvium and 

Ellenburger-San Saba aquifer outcrop, whereas an unverifiable 

gain was measured in the middle reach, which crosses each of 

the different hydrogeologic units represented in the study area. 

The reach farthest downstream crosses an area where only the 

Ellenburger-San Saba aquifer crops out; a streamflow gain of 

123 ft3

/s was measured in this reach, exceeding the potential 

error of 93.9 ft3/s. The verifiable streamflow gain in this 

downstream reach implies the Ellenburger-San Saba aquifer 

was discharging groundwater to the Colorado River in this 

part of the study area under the hydrologic conditions of the 

spring 2014 gain-loss survey.

Introduction

Assessments of whether a given reach gains or 

loses streamflow can provide insights into the nature of 

groundwater/surface-water interactions and can help to 

determine the quantity and quality of groundwater and surface 

water (Pinder and Celia, 2006). In the absence of appreciable 

tributary inflows or diversions of flow out of the channel, the 

question of whether a given reach gains or loses streamflow 

depends largely on groundwater/surface-water interactions. 

The relation between the altitude of the water table and the 

water-surface elevation of the stream referenced to an arbitrary 

datum (referred to as the river stage or stream stage) ultimately 
2

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

determines whether a stream gains water from or loses water 

to the underlying aquifer, as described by Maurer and others 

(2006, p. 33):

If the streambed is sufficiently permeable to allow 

flow, streams lose flow and the infiltrating surface 

water recharges the underlying aquifer when the 

altitude of the water table adjacent to the stream is 

lower than the stream’s stage. Conversely, when the 

altitude of the water table is higher than the stream’s 

stage, ground-water discharge from the aquifer 

to the stream takes place and streams gain flow. 

Locations of streamflow gain and loss, and estimates 

of their rates, are useful for evaluating the effects of 

changes in land use and developing updated water 

budgets. 

Groundwater recharge and groundwater withdrawals 

are important factors in determining whether a stream is 

gaining or losing in a given reach (Barlow and Leake, 2012). 

Groundwater recharge is dependent on factors such as climate, 

geology, soils, land-use practices (including irrigation effects), 

and depth to the water table (Healy and others, 2007); the 

distribution and extent of faults can also have an appreciable 

effect on groundwater recharge. 

The interaction between the Ellenburger-San Saba 

aquifer and the Colorado River in northwestern Burnet and 

southeastern San Saba Counties in central Texas and the 

conditions under which the river gains or loses streamflow 

to the aquifer are not well understood. Accordingly, the 

U.S. Geological Survey (USGS), in cooperation with the 

Central Texas Groundwater Conservation District (CTGCD), 

completed a preliminary assessment to determine if the 

Ellenburger-San Saba aquifer is losing water to or gaining 

water from the Colorado River in northwestern Burnet and 

southeastern San Saba Counties under two different flow 

conditions, to gain a better understanding of the quantities 

of water entering or exiting the river if gaining or losing 

conditions are identified, and to identify reaches where 

groundwater enters or exits the river. 

Purpose and Scope

This report provides a preliminary assessment of 

streamflow gains and losses along the Colorado River in 

northwestern Burnet and southeastern San Saba Counties 

in central Texas. Reaches were identified where streamflow 

gains and losses likely were occurring, along with the 

quantities of the gains and losses, and assessments were 

made as to whether the gains and losses were a result of 

the interaction of groundwater and surface water between 

the Ellenburger-San Saba aquifer and the Colorado River. 

In order to estimate streamflow gains and losses, two sets 

of synoptic streamflow discharge measurements were 

made representing different flow conditions. From these 

measurements, locations where discharge from and recharge to 

the Ellenburger-San Saba aquifer in northwestern Burnet and 

southeastern San Saba Counties were tentatively identified. 

Discharge measurements were made at seven locations 

along the Colorado River during the first gain-loss survey 

in December 3–6, 2012 (hereinafter the fall 2012 gain-loss 

survey). Discharge measurements were made at 12 locations 

along the Colorado River during the second gain-loss survey 

in May 31–June 1, 2014 (hereinafter the spring 2014 gainloss survey). The streamflow gains and losses documented 

in this report are specific to hydrologic regimes represented 

by the flow conditions measured during the fall 2012 and 

spring 2014 gain-loss surveys and are not suitable for broad 

characterization of streamflow gains and losses over all 

hydrologic regimes in the study area and should not be 

extrapolated over time.

Description of Study Area 

The study area consists of a 10-mile (mi) segment of the 

Colorado River and selected tributaries (Spicewood Creek, 

Jennings Creek, Greenwood Creek, Jim John Creek, and Deer 

Creek) from Colorado Bend State Park (near the county line 

between Lampasas and Burnet Counties) to the upstream 

extent of Lake Buchanan (near the county line between 

San Saba and Llano Counties) in central Texas (fig. 1). The 

Colorado River forms the border between Burnet and San 

Saba Counties in the study area.

The Ellenburger-San Saba aquifer, which underlies 

much of the Colorado River in the study area, is composed 

of dolomite and marine limestone deposits of the San Saba 

Member of the Wilberns Formation (Cambrian) and the 

Ellenburger Group (Ordovician) (fig. 2). The Ellenburger 

Group includes the Honeycut, Gorman, and Tanyard 

Formations (from youngest to oldest), and the San Saba 

Member is the upper member of the Wilberns Formation; the 

surficial geology of the study area is shown in figure 3. The 

Ellenburger Group and the San-Saba Member are classified 

as a single aquifer (the Ellenburger-San Saba aquifer) because 

of their hydrologic interconnection and the difficulty in 

distinguishing the two stratigraphic units in the subsurface 

(fig. 2) (Berehe, 2005). The aquifer is highly faulted in the 

subsurface and at the surface and was partially eroded prior 

to being covered by Cretaceous sediments, causing large 

variations in aquifer thickness (Berehe, 2005).
Introduction

Base modified from U.S. Geological Survey

digital data, 1:24,000

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

EXPLANATION

Lower Colorado River Authority 

 streamflow-gaging station

 and number 

1925

0 1.25 2.5 3.75 5 MILES

0 1.25 2.5 3.75 5 KILOMETERS

LAMPASAS COUNTY

BURNET COUNTY

LLANO COUNTY

SAN SABA COUNTY

Colorado River

Colorado River

Bend

T E X A S

Study area

Tow

1925

Post Oak Falls

Spicewood

Creek

Creek

Creek

98°20 98°30 98°25

31°05'

31°00'

30°55' Area shown on figures 3, 4, 7, 8, 9, 14, and 15

COLORADO BEND

STATE PARK

Lake Buchanan

Jennings Cre ek

Jim John Creek

Deer Creek

Greenwood Creek

Figure 1. Location of study area, northwestern Burnet and southeastern San Saba Counties, Texas.
4

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Methods

Two streamflow gain-loss surveys were done in different 

seasons representing different hydrologic conditions—fall 

2012 (December 3–6) at low-flow conditions and spring 2014 

(May 31–June 1) at high-flow conditions—to accurately 

determine the seasonal variation, locations, and magnitude of 

groundwater/surface-water interactions. Synoptic discharge 

measurements on the Colorado River were made at 7 sites 

during the fall 2012 gain-loss survey (ranging from about 

30 to 60 cubic feet per second [ft3/s]) and at 12 sites during 

the spring 2014 gain-loss survey (ranging from about 660 to 

900 ft3/s; fig. 4, table 1). Synoptic discharge measurements 

were also made on selected tributaries to gain a better 

understanding of streamflow gains and losses on the main 

stem of the Colorado River. 

Discharge Measurements

Different methods of measuring discharge were used 

depending on flow conditions. For wading measurements, 

width and depth were physically measured by using a 

graduated tape and wading rod while the water velocity 

was measured with a hand-held acoustic Doppler velocimeter 

(SonTek, 2013) (hereinafter referred to as a “FlowTracker”) 

attached to the wading rod. Wading discharge measurements 

were made by using the USGS midsection method (Young, 

1950) where the depth and mean velocity are measured 

at vertical sounding stations; each vertical sounding 

station represents a subsection of the overall channel cross 

section. Abbreviated discharge measurements, consisting 

of fewer than 25 vertical soundings, were made at some 

wading sites on tributaries to the Colorado River because 

the channel cross section was too narrow to collect more 

than 24 vertical soundings. Full discharge measurements 

consisting of 25 to 30 vertical soundings were made at 

most wading sites. For both abbreviated and full discharge 

measurements, the summation of the discharges for all the 

subsections equaled the total discharge of the stream (Rantz 

and others, 1982).

System

Group Formation

Hydrogeologic units

Ellenburger

Alluvium

Honeycut

Tanyard

localized alluvial aquifer

Wilberns

Oakville

Sandstone

Moore Hollow

Quaternary

Geologic units

Ordovician

Cambrian

Gorman

Member

undivided

undivided

Staendebach

Threadgill

Lion Mountain Sandstone

of Riley Formation

and Cap Mountain Limestone

Member of Riley Formation,

undivided

Morgan Creek

Limestone and Welge

Sandstone Members,

undivided

San Saba

Point Peak

Hickory Sandstone

Pleistocene to recent flood plain

Ellenburger-San Saba aquifer

confining units (Point Peak Member

and Morgan Creek Limestone)

confining unit (Cap

Mountain Limestone)

Mid-Cambrian aquifer (Welge

Sandstone and Lion Mountain

Sandstone)

Hickory aquifer

Modified from Preston and others, 1996.

Figure 2. Geologic and hydrogeologic units in northwestern Burnet and southeastern San Saba Counties, Texas (modified from 

Preston and others, 1996).
Methods

LAMPASAS COUNTY

BURNET COUNTY

SAN SABA COUNTY

LLANO COUNTY

Post Oak Creek

Creek

Spicewood

Jennings Creek

Greenwood Creek

Jim John Creek

Sycamore Branch

Colorado River

Deer Creek

Devils Hollow Creek

EXPLANATION

Alluvium 

Honeycut Formation

Gorman Formation

Tanyard Formation

Wilberns Formation

 San Saba Member

 Point Peak Member

 Morgan Creek Limestone 

 and Welge Sandstone

 Members, undivided

Riley Formation

 Lion Mountain Sandstone and

 Cap Mountain Limestone

 Members, undivided

Water

Fault—Ball and bar on downthrown block

Surficial geology modified from

Barnes and others (1981)

 and Kier and others (1976)

Base modified from U.S. Geological Survey digital data, 1:24,000

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

0 0.5 1.0 MILES

0 0.5 1.0 KILOMETERS

Figure 3. Surficial geology in northwestern Burnet and southeastern San Saba Counties, Texas.
6

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Streamflow-measurement site and number

 Measurements made during the fall 2012 (December 3–6, 2012)

 and spring 2014 (May 31–June 1, 2014) gain-loss surveys

 Measurements made only during the spring 2014

 gain-loss survey (May 31–June 1, 2014) 

Hydrogeologic units

 Alluvium

 Ellenburger-San Saba

 Confining units (Point Peak Member

 and Morgan Creek Limestone)

 Mid-Cambrian aquifer (Welge

 Sandstone and Lion Mountain

 Sandstone)

Fault—Ball and bar on

 downthrown block

7

9

C

C

EXPLANATION

LAMPASAS COUNTY

BURNET COUNTY

SAN SABA COUNTY

LLANO COUNTY

Post Oak Creek

Creek

Spicewood

Jennings Creek

Greenwood Creek

Jim John Creek

Sycamore Branch

Colorado River

Deer Creek

Devils Hollow Creek

1

2

5

6

7

8

4

3

9

10

11

12

C

C

C

C

C

C

C

C

C

C

C

C

Aquifers modified from surficial geology

of Barnes and others (1981)

 and Kier and others (1976)

Base modified from U.S. Geological Survey digital data, 1:24,000 

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

0 0.5 1.0 MILES

0 0.5 1.0 KILOMETERS

Figure 4. Hydrogeologic units and discharge measurement sites in northwestern Burnet and southeastern San Saba Counties, Texas.
Table 1. Description of streamflow measurement sites on the Colorado River in northwestern Burnet and southeastern San Saba Counties, Texas, 20[USGS, U.S. Geological Survey; ft3/s, cubic feet per second; FlowTracker, hand-held acoustic Doppler velocimeter (SonTek, 2013); G, good, measured discharge within 5 perce(5 percent used for calculations in this report); F, fair, measured discharge between 5 and 8 percent (8 percent used for calculations in this report); P, poor, measured discharge 8 actual discharge (10 percent used for calculations in this report); ADCP, acoustic Doppler current profiler; --, not measured]

Site 

identifier 

(fig. 4) 

USGS station 

number USGS station name

December 3–6, 2012 (fall 2012 gain-loss survey)

Individual 

discharge 

measurements 

(ft3/s)

Average 

measured 

discharge 

(ft3/s)

Instrument 

used to 

measure 

discharge

Date 

measured

Survey 

measurem

error 

ratings

1 310134098262100 Colorado River downstream from Yancey 

Creek near Tow, Tex.

51.4, 46.0 48.7 FlowTracker December 3 F 

2 310104098264900 Colorado River near Lemons Springs 

Camp near Tow, Tex.

47.9, 45.8 46.8 FlowTracker December 3 F 

3 310049098272300 Colorado River at confluence of 

Spicewood Creek near Tow, Tex.

-- -- -- -- -- 

4 310022098273300 Colorado River at Post Oak Falls near 

Tow, Tex.

-- -- -- -- -- 

5 305958098271000 Colorado River at confluence of Jennings 

Creek near Tow, Tex.

52.9, 59.4 56.2 FlowTracker December 4 P 

6 305931098264400 Colorado River downstream from 

Greenwood Creek near Tow, Tex.

-- -- -- -- -- 

7 305914098263600 Colorado River near Tanyard Crossing 

near Tow, Tex.

47.0, 43.7 45.4 FlowTracker December 4 P 

8 305850098263300 Colorado River downstream from Tanyard 

Crossing near Tow, Tex.

-- -- -- -- -- 

9 305818098270300 Colorado River upstream from Jim John 

Creek near Tow, Tex.

-- -- -- -- -- 

10 305807098271100 Colorado River at confluence of Jim John 

Creek near Tow, Tex.

31.9, 27.4 29.6 FlowTracker December 5 P 

11 305658098263900 Colorado River downstream from Jim John 

Creek near Tow, Tex.

43.1, 32.9 38.0 FlowTracker December 5 P 

12 305533098250900 Colorado River downstream from 

Sycamore Creek near Tow, Tex.

40.2, 50.1 45.2 FlowTracker December 6 P 
Table 1. Description of streamflow measurement sites on the Colorado River in northwestern Burnet and southeastern San Saba Counties, Texas, 20[USGS, U.S. Geological Survey; ft3/s, cubic feet per second; FlowTracker, hand-held acoustic Doppler velocimeter (SonTek, 2013); G, good, measured discharge within 5 perce(5 percent used for calculations in this report); F, fair, measured discharge between 5 and 8 percent (8 percent used for calculations in this report); P, poor, measured discharge 8 actual discharge (10 percent used for calculations in this report); ADCP, acoustic Doppler current profiler; --, not measured] Site identifier (fig. 4) May 31–June 1, 2014 (spring 2014 gain-loss survey) Discharge determined from two or more transects (pass from one side of stream to other by using an ADCP) (ft3/s) Average measured discharge (ft3/s) Instrument used to measure discharge Date measured Survey measurement error rating Potential e

associat

with disch

measurem

(ft3/s)1 

1 2864, 2890 877 FlowTracker May 31 P 87.7 

2 838, 833, 839, 838 837 ADCP May 31 G 41.8 3 832, 848, 813, 854 837 ADCP May 31 G 41.8 4 3823, 3835; 4666, 4692 3829, 4679 ADCP May 31, June 1 3G, 4G 341.4, 434

5 676, 660 668 ADCP June 1 G 33.4 6 706, 709 708 ADCP June 1 G 35.4 7 707, 696 702 ADCP June 1 G 35.1 8 694, 719 706 ADCP June 1 G 35.3 

9 710, 730 720 ADCP June 1 G 36.0 

10 722, 787, 707, 786 750 ADCP June 1 G 37.5 

11 790, 761 776 ADCP June 1 G 38.8 

12 707, 704 706 ADCP June 1 F 56.5 

1The discharge measurement was multiplied by the percent difference assigned to the measurement rating to determine the potential error. 2Wading discharge measurements made by different hydrographers using a FlowTracker. 3Based on streamflow measurement made on May 31, 2014. 4Based on streamflow measurement made on June 1, 201
Methods

During the fall 2012 gain-loss survey, all discharge 

measurements were made by using the midsection method 

of measuring discharge with the FlowTracker. At sites 1 and 

2, discharge was measured by wading in the stream with the 

FlowTracker attached to a wading rod; the stream was too 

deep to safely wade in fall 2012 at the remaining sites. At the 

sites where the stream was too deep to wade, an extended 

wading rod was lowered from an inflatable raft tethered to the 

banks at the predetermined discharge measurement locations. 

The inflatable raft was attached to a rope that extended across 

the channel, and two hydrographers ferried themselves across 

the channel while measuring discharge concurrently, one 

hydrographer on either side of the raft.

During the spring 2014 gain-loss survey, discharge at site 

1 was again measured by using the midsection method with a 

FlowTracker while wading the stream. Because of high flows 

and unsuitable depths for wading measurements, a movingboat Acoustic Doppler current profiler (ADCP) method 

(Mueller and others, 2013) was used to collect discharge data 

at the remaining sites during the spring 2014 gain-loss survey. 

In the moving-boat ADCP method that was used, the discharge 

was measured by using an ADCP housed in a small (less than 

4 ft) boat (fig. 5). The boat housing the ADCP was tethered 

to a rod extending from the bow of a larger manned boat 

powered by an outboard motor. In order to accurately measure 

discharge, the operator of the motorized boat made either two 

or four passes across the stream. The small boat moved freely 

in the water and orientated itself to the direction of the current 

as it collected acoustic data throughout the water column, 

which minimized directional bias in the measured discharge 

(Oberg and others, 2005). Additional details of the standard 

USGS protocols that were used for measuring discharge are 

described in Rantz and others (1982) and Turnipseed and 

Sauer (2010). 

All discharge data collected using the ADCP were 

processed using WinRiver II software (Teledyne RD 

Instruments, 2007) and were recorded and calculated as data 

points with a two-dimensional XY planar position (channel 

width and depth) and a mean velocity magnitude and direction 

(fig. 6). In accordance with USGS standard methods, all 

moving-boat ADCP measurements consisted of an even 

number of transects (pass from one side of stream to other) 

made over a duration of at least 12 minutes (Mueller and 

others, 2013). In many instances, two passes were sufficient to 

meet the 12-minute duration limit; however, at sites 2, 3, and 

10, two additional passes (total of four) were made to meet 

the requirements to ensure that enough data were collected to 

adequately characterize streamflow conditions.

Quality assurance (QA) practices were followed to ensure 

the quality, precision, accuracy, and completeness of the 

discharge measurements and of the associated data pertaining 

to the discharge measurements. All digital data were reviewed 

by USGS Texas Water Science Center personnel to ensure 

proper documentation. Measurement field sheets were used 

to document proper operation and maintenance of equipment 

and collection of representative data. At least one duplicate 

discharge measurement was made at each site. All measured 

data were entered into the National Water Information 

System (NWIS) database (U.S. Geological Survey, 2015) 

and reviewed by USGS personnel following standard USGS 

procedures (Turnipseed and Sauer, 2010; Mueller and others, 

2013).

Gain-Loss Surveys 

Discharge measurement locations were selected for 

the gain-loss surveys (table 1) based on the locations of 

(1) hydrogeologic unit contacts (fig. 4); (2) faults (fig. 7); 

(3) seeps, springs, and travertine deposits (fig. 8); and 

(4) tributary inflows (fig. 9). Figures 4 and 7 illustrate the 

spatial location and extent of the hydrogeologic unit contacts 

and faults, respectively, that were used to select measurement 

locations in the study area. Measurement locations on the 

Colorado River were selected to bracket hydrogeologic 

units, where possible, in order to quantify gains and losses 

associated with the hydrogeologic units. Site 2 was selected 

downstream from a major fault (fig. 4) and just downstream 

from an area with known seeps (fig. 8). All of the reaches 

evaluated for streamflow gains or losses on the Colorado River 

in northwestern Burnet and southeastern San Saba Counties 

are depicted in table 2.

Figure 5. A tethered Acoustic Doppler current profiler (ADCP) 

boat (photograph by Geoffrey D. Cartano, U.S. Geological Survey, 

from Oberg and others, 2005).
AB 0.00 55.25 110.50 165.75 2

0.00 2.00 4.00 6.00 Channel width, in feet 8.

Depth, in feet

0.00 56.75 113.50 170.25 2

0.002.755.508.25

11.00

Depth, in feet

Left bank Right ba

Mean velocity, in feet per second

0.00 0.50 1.00 1.50 2.00

0.00 0.50 1.00 1.50 2.00

Mean velocity, in feet per second

Figure 6. Acoustic doppler current profiles made at the same location on A, May 31, 2014, at 5:35 p.m. and on B, June 1, 2014, at 10:41 a.m. at U.S. Ge

310022098273300 Colorado River at Post Oak Falls near Tow, Texas.
Methods

COLORADO

BEND

 STATE PARK

Colorado River Devils Hollow Creek

LAMPASAS COUNTY

BURNET COUNTY

LLANO COUNTY

SAN SABA COUNTY

C

DSB

Fault—Ball and bar on

 downthrown block

Location where photograph 

 was taken—Arrow indicates 

 approximate orientation of

 photograph

Most upstream streamflow or

 downstream measurement

 site—USB, upstream; DSB,

 downstream

Hydrogeologic units

 Alluvium

 Ellenburger-San Saba

 Confining units (Point Peak 

 Member and Morgan Creek

 Limestone)

 Mid-Cambrian aquifer (Welge

 Sandstone and Lion Mountain

 Sandstone)

EXPLANATION

A 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

A 

B

C

C

C

USB

DSB

Base modified from U.S. Geological Survey digital data, 1:24,000 

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

0 0.5 1 1.5 2 MILES

0 1 1.50.5 2 KILOMETERS

A. October 30, 2012

C. October 30, 2012

B. October 30, 2012

NOTE: Photograph labels correspond to map locations.

Figure 7. Faults and hydrogeologic unit contacts along the Colorado River in northwestern Burnet and southeastern San Saba 

Counties, Texas, and a map depicting photograph locations. A, faulting within confining units (Point Peak Member and Morgan Creek 

Limestone); B, fault at contact between the Mid-Cambrian aquifer and Ellenburger-San Saba aquifer; and C, fault in the Ellenburger-San 

Saba aquifer.
12

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

COLORADO

BEND

 STATE PARK

Colorado River Devils Hollow Creek

LAMPASAS COUNTY

BURNET COUNTY

LLANO COUNTY

SAN SABA COUNTY C

DSB

Fault—Ball and bar on

 downthrown block

Location where photograph 

 was taken—Arrow indicates 

 approximate orientation of

 photograph

Most upstream streamflow or

 downstream measurement

 site—USB, upstream; DSB,

 downstream

Hydrogeologic units

 Alluvium

 Ellenburger-San Saba

 Confining units (Point Peak 

 Member and Morgan Creek

 Limestone)

 Mid-Cambrian aquifer (Welge

 Sandstone and Lion Mountain

 Sandstone)

Approximate location of a

 combination of seeps or

 travertine deposits 

EXPLANATION

A 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

A 

B

C

D

C

C

USB

DSB

Base modified from U.S. Geological Survey digital data, 1:24,000 

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

0 0.5 1 1.5 2 MILES

0 1 1.50.5 2 KILOMETERS

NOTE: Photograph labels correspond to map locations.

A. December 21, 2012 B. October 30, 2012

C. October 30, 2012

D. October 30, 2012

Figure 8. Seeps, springs, and travertine deposits along the Colorado River in northwestern Burnet and southeastern San Saba 

Counties, Texas, and a map depicting photograph locations. A and C, seeps; and B and D, springs and associated travertine deposits.
Methods

COLORADO

BEND

 STATE PARK

Colorado River Devils Hollow Creek

LAMPASAS COUNTY

BURNET COUNTY

LLANO COUNTY

SAN SABA COUNTY

C

DSB

Fault—Ball and bar on

 downthrown block

Location where photograph 

 was taken—Arrow indicates 

 approximate orientation of

 photograph

Most upstream streamflow or

 downstream measurement

 site—USB, upstream; DSB,

 downstream

Hydrogeologic units

 Alluvium

 Ellenburger-San Saba

 Confining units (Point Peak 

 Member and Morgan Creek

 Limestone)

 Mid-Cambrian aquifer (Welge

 Sandstone and Lion Mountain

 Sandstone)

EXPLANATION

A 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

A 

B

C

NOTES: Photograph labels correspond to map locations. Photographs at top of page

 (October 30, 2012 and June 2, 2014) were taken at the same location, approximately 50 feet apart. 

C

C

USB

DSB

Base modified from U.S. Geological Survey digital data, 1:24,000 

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

0 0.5 1 1.5 2 MILES

0 1 1.50.5 2 KILOMETERS

C. June 2, 2014

A. October 30, 2012

B. October 30, 2012

A. June 2, 2014

Figure 9. Tributary streams, which act as discharge points to the Colorado River in northwestern Burnet and southeastern San Saba 

Counties, Texas, and a map depicting photograph locations. A, Jim John Creek; B, Greenwood Creek; and C, Deer Creek.
14

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Table 2. Reaches evaluated for streamflow gains or losses on the Colorado River in northwestern Burnet and southeastern San Saba 

Counties, Texas, 2012–14.

December 3–6, 2012 (fall 2012 gain-loss survey)

Reach

(fig. 13)

Length 

(miles)

U.S. Geological Survey station name of upstream 

streamflow measurement site and site number 

(table 1, fig. 4)

U.S. Geological Survey station name of downstream 

streamflow measurement site and site number 

(table 1, fig. 4)

A 0.76 Colorado River downstream from Yancey Creek near 

Tow, Tex. (1)

Colorado River near Lemons Springs Camp near Tow, 

Tex. (2)

B 1.83 Colorado River near Lemons Springs Camp near Tow, 

Tex. (2)

Colorado River at confluence of Jennings Creek near 

Tow, Tex. (5)

C 1.03 Colorado River at confluence of Jennings Creek near 

Tow, Tex. (5)

Colorado River near Tanyard Crossing near Tow, Tex. (7)

D 1.51 Colorado River near Tanyard Crossing near Tow, Tex. (7) Colorado River at confluence of Jim John Creek near 

Tow, Tex. (10)

E 1.47 Colorado River at confluence of Jim John Creek near 

Tow, Tex. (10)

Colorado River downstream from Jim John Creek near 

Tow, Tex. (11)

F 3.13 Colorado River downstream from Jim John Creek near 

Tow, Tex. (11)

Colorado River downstream from Sycamore Creek near 

Tow, Tex. (12)

May 31–June 1, 2014 (spring 2014 gain-loss survey)

Reach

(fig. 13)

Length 

(miles)

U.S. Geological Survey station name of upstream 

streamflow measurement site and site number 

(table 1, fig. 4)

U.S. Geological Survey station name of downstream 

streamflow measurement site and site number 

(table 1, fig. 4)

A 0.76 Colorado River downstream from Yancey Creek near 

Tow, Tex. (1)

Colorado River near Lemons Springs Camp near Tow, 

Tex. (2)

B.1 0.63 Colorado River near Lemons Springs Camp near Tow, 

Tex. (2)

Colorado River at confluence of Spicewood Creek near 

Tow, Tex. (3)

B.2 0.61 Colorado River at confluence of Spicewood Creek near 

Tow, Tex. (3)

Colorado River at Post Oak Falls near Tow, Tex. (4)

B.3 0.59 Colorado River at Post Oak Falls near Tow, Tex. (4) Colorado River at confluence of Jennings Creek near 

Tow, Tex. (5)

C.1 0.68 Colorado River at confluence of Jennings Creek near 

Tow, Tex. (5)

Colorado River downstream from Greenwood Creek near 

Tow, Tex. (6)

C.2 0.35 Colorado River downstream from Greenwood Creek near 

Tow, Tex. (6)

Colorado River near Tanyard Crossing near Tow, Tex. (7)

D.1 0.48 Colorado River near Tanyard Crossing near Tow, Tex. (7) Colorado River downstream from Tanyard Crossing near 

Tow, Tex. (8)

D.2 0.78 Colorado River downstream from Tanyard Crossing near 

Tow, Tex. (8)

Colorado River upstream from Jim John Creek near Tow, 

Tex. (9)

D.3 0.25 Colorado River upstream from Jim John Creek near Tow, 

Tex. (9)

Colorado River at confluence of Jim John Creek near 

Tow, Tex. (10)

E 1.47 Colorado River at confluence of Jim John Creek near 

Tow, Tex. (10)

Colorado River downstream from Jim John Creek near 

Tow, Tex. (11)

F 3.13 Colorado River downstream from Jim John Creek near 

Tow, Tex. (11)

Colorado River downstream from Sycamore Creek near 

Tow, Tex. (12)
Methods

Discharge data from a Lower Colorado River Authority 

(LCRA) streamflow-gaging station (1925 Colorado River at 

Bend, Tex.; fig. 1) (Lower Colorado River Authority, 2015) 

and a USGS streamflow-gaging station (08147000 Colorado 

River near San Saba, Tex. [hereinafter Colorado River near 

San Saba]) were used to determine the optimal sampling 

times for the two gain-loss surveys. Based on long-term 

streamflow records (81 years) from Colorado River near San 

Saba, approximately 15.7 mi upstream from the LCRA gage, 

the median streamflow in the Colorado River in that area 

during the October–December timeframe is slightly less than 

200 ft3/s (U.S. Geological Survey, 2015). Uncharacteristically 

low streamflow (about 40 ft3/s) from October through 

December 2012 at Colorado River near San Saba provided an 

opportunity to quantify gains and losses during uncommon 

conditions (fig. 10). The intent was to return the following 

spring in May or June 2013 when it was anticipated that 

streamflow would likely range from about 300 to 500 ft3/s 

(median streamflow based on 81 years of record is about 

400 ft3/s during May and June at the Colorado River near San 

Saba), providing an opportunity to target flow conditions for 

characterizations that were markedly different from those 

5

6

7

8

9

10

11

1

1,000

Instantaneous discharge, in cubic feet per second River stage, in feet

10

100

0

5

10

15

20

25

30

Cumulative precipitation, in inches

Oct. JulyJuneMayApr.Mar.Feb.Jan.Dec.Nov.

35

40

Aug. Sept. Oct. JuneMayApr.Mar.Feb.Jan.Dec.Nov.

2012 2013

Date

2014

12

13

10,000

Figure 10. River stage, instantaneous discharge, and cumulative precipitation at Lower Colorado River Authority streamflow-gaging 

station 1925 Colorado River at Bend, Texas, October 1, 2012–June 30, 2014.
16

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

measured during the fall 2012 gain-loss survey. A lack of 

appreciable winter rains, followed by severe drought during 

spring 2013, resulted in low streamflows unsuitable for the 

second set of synoptic discharge measurements. As a result 

of the unsuitable streamflow conditions in spring 2013, the 

second set of synoptic measurements was delayed until spring 

2014.

The fall 2012 gain-loss survey represented a period 

of relatively stable base flow when appreciable rainfall and 

storm runoff were not occurring and had not occurred for 

at least the previous 2 weeks (figs. 10–11). The completion 

of gain-loss surveys during periods of relatively stable base 

flow helps minimize variations in streamflow conditions that 

might introduce errors into the estimation of gains and losses. 

Because unwadeable streamflow conditions were anticipated 

based on preliminary reconnaissance measurements made in 

October and November 2012, FlowTrackers attached to 8-foot 

(ft) wading rods were used to make discharge measurements 

from an inflatable raft as described in the “Methods” section. 

During the fall 2012 gain-loss survey, stream velocities 

were so low in some parts of the Colorado River that the 

FlowTrackers were not able to accurately measure the 

velocities. As a result, four of the predetermined measurement 

sites were moved downstream (sites 5, 7, and 11) or upstream 

(site 10) to more suitable locations. Measurement locations 

were presumed to be more suitable for accurate discharge 

measurements at locations where the Colorado River 

narrowed, typically (sites 5, 7, and 10) in conjunction with 

small tributaries to the Colorado River. Deltaic deposits from 

the tributaries created small peninsulas that extended into 

the Colorado River, resulting in narrowing of the Colorado 

River in these locations and relatively higher stream velocities 

compared to wider parts of the river. Because depths in the 

Colorado River remained relatively consistent throughout 

the lower part of the study area (downstream from Colorado 

Bend State Park), narrowing of the channel at these tributaries 

resulted in a slight increase in velocities at these locations as a 

consequence of the reduction in stream width.

The spring 2014 gain-loss survey was done following 

a large rain event on May 25 (2.46 inches), which was 

followed by additional rain on May 26 (0.54 inches) and 

May 27 (0.92 inches) (fig. 10). Because there were few 

opportunities with stable base flow in the desired flow range 

in the 18 months following the fall 2012 gain-loss survey 

(that is, appreciably larger flow compared to the low-flow 

conditions in the fall 2012 survey accompanied by an absence 

6.00

6.05

6.10

6.15

6.20

6.25

6.30

0

5

10

15

20

25

30

50

Instantaneous discharge,

 in cubic feet per second

November 30 December 9

River stage, in feet

December 1 December 2 December 3 December 4 December 5 December 6 December 7 December 8

35

40

45

Date

Figure 11. River stage and instantaneous discharge at Lower Colorado River Authority (LCRA) streamflow-gaging station 1925 

Colorado River at Bend, Texas, November 30–December 9, 2012.
Methods

of rain for at least 2 weeks) (fig. 10), the decision was made to 

complete the spring 2014 gain-loss survey during May 31–June 

1 after streamflow began to recede and stabilize following the 

May 25–27 rainfall (figs. 10 and 12). Discharge measurement 

locations from the fall 2012 gain-loss survey were used again 

in the spring 2014 gain-loss survey for comparison purposes 

between the two gain-loss surveys, and additional sites were 

included in the spring 2014 gain-loss survey to provide 

supplementary data in support of gain-loss survey results. On 

the basis of previous measurement experience, the decision 

was made to use FlowTrackers attached to 4-ft wading rods to 

measure discharge at all wadeable sites, which turned out to 

be only the most upstream site on the Colorado River (USGS 

station 310134098262100 Colorado River downstream from 

Yancey Creek near Tow, Tex.; site 1 in table 1) and three 

tributary sites on streams that flow into the Colorado River 

(Jennings Creek, Jim John Creek, and Deer Creek) (table 3). All 

other discharge measurements were made by using an ADCP.

During the spring 2014 gain-loss survey, the accuracy of 

gain-loss determinations may have been affected by receding 

streamflow conditions. To eliminate or reduce the effects of 

receding streamflow conditions on gain-loss calculations, a 

discharge measurement at the upstream reach boundary should 

ideally be followed during receding streamflow conditions by 

a discharge measurement at the downstream boundary after a 

time interval that corresponds to the streamflow traveltime in 

the reach. Because the time interval between measurements 

at upstream and downstream reach boundaries did not 

correspond to the reach traveltime, measured streamflows 

were normalized to account for the difference between actual 

measurement times and estimated streamflow traveltime 

during the spring 2014 gain-loss survey. To normalize 

streamflows, the average velocity between sites as determined 

by the discharge measurements was used in conjunction with 

the distance between sites to define a traveltime for the water 

in a given reach. Once a traveltime was established for a 

reach, the average decrease in discharge per unit time between 

the two measurements at site 4 (Colorado River at Post Oak 

Falls near Tow, Tex.; hereinafter the Post Oak Falls site) was 

applied to the time allowed for streamflow in the Colorado 

River to travel downstream in order to compute a normalized 

discharge at each discharge measurement location downstream 

from the Post Oak Falls site. Because the discharge was 

known at the Post Oak Falls site (site 4; fig. 4, table 1) on 

both days that discharge measurements were made (last site 

measured on May 31, 2014, and first site measured on June 1, 

2014), it was used as a starting point for the extrapolation of 

streamflows both upstream and downstream from that site. 

5

6

7

8

9

10

11

12

13

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

Instantaneous discharge,

 in cubic feet per second

May 25 May 26 May 27 May 28 May 29 May 30 May 31 June 1 June 2 June 3

River stage, in feet

Figure 12. River stage and instantaneous discharge at Lower Colorado River Authority (LCRA) streamflow-gaging station 1925 

Colorado River at Bend, Texas, May 25–June 3, 2014.
18

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Streamflow Gains and Losses

Streamflow gains and losses are often in large part 

attributable to groundwater/surface-water interactions 

in the form of groundwater discharged to streams and 

groundwater recharged from streams (Winter and others, 

1998). Groundwater/surface-water interactions are processes 

that typically cannot be measured directly because they 

usually cannot be observed. For this report, streamflow gains 

or losses within the study area were estimated by measuring 

the difference in streamflow at the upstream and downstream 

extent of each reach (table 4) while accounting for other 

sources of gains and losses. In addition to groundwater 

inflows, other sources of gains include tributary inflows, 

inflows from springs or seeps, and return flows. In addition to 

groundwater outflows, other sources of losses include stream 

diversions and evaporative losses. The difference between 

inflows and outflows, referred to as the streamflow gain or 

loss, G, is estimated as

G = QD – QU – I + D – R – S + E (1)

where

QD is measured streamflow at the downstream 

boundary of the reach, 

QU is measured streamflow at the upstream 

boundary of the reach, 

I is measured or estimated inflows from 

tributaries,

D is diversions from the reach,

R is return flows to the reach,

S is inflows from springs or seeps, and

E is estimated evaporation losses. 

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

A positive value for G indicates a gaining stream reach, 

whereas a negative value for G indicates a losing stream reach. 

No diversions (D) or return flows (R) were identified in the 

study area, so these contributions were not included in the 

streamflow gain or loss calculations. Schematic diagrams of 

the study area reaches, including discharge measurement sites 

and tributary inflows for the fall 2012 and spring 2014 gainloss surveys, are shown in figure 13.

Spring-flow contributions to streamflow often cannot 

be measured (Hem, 1985); even visible inflow from springs 

cannot always be accurately measured (Ockerman, 2002). 

Spring and seep contributions (S) to streamflow were not 

measured directly at any of the known springs in the study 

area. Contributions associated with springs that provide 

flow near site 4 (Post Oak Falls site) (photograph B in fig. 8) 

and springs associated with other travertine deposits near 

the southern end of the study area (photograph D in fig. 8) 

could not be measured because the flow was divided between 

multiple release locations. Contributions associated with seeps 

(fig. 8A, C) also could not be measured and were considered 

negligible. As a result, spring contributions could not be 

included as a separate source in the streamflow gain or loss 

calculations. 

By eliminating the terms D, R, and S from equation 1, 

equation 2 for G reduces to

G = QD – QU – I + E (2)

Table 3. Description of tributary inflows to the Colorado River in northwestern Burnet and southeastern San Saba Counties, Texas, 

2012–14.

[USGS, U.S. Geological Survey; ft3/s, cubic feet per second; AM, abbreviated streamflow measurement with a hand-held acoustic Doppler velocimeter 

(FlowTracker); VE, visual estimate; FM, full streamflow measurement with a FlowTracker; SVE, surface velocity estimate; --, not measured]

USGS station 

number

USGS station 

name

Short 

name

Gain-loss survey

December 3–6, 2012 

(fall 2012 gain-loss survey)

May 31–June 1, 2014 

(spring 2014 gain-loss survey)

Streamflow 

determination 

method

Approximate 

streamflow 

(ft3

/s)

Streamflow 

determination 

method

Approximate 

streamflow 

(ft3/s)

310050098272600 Spicewood Creek near Tow, Tex. Spicewood Creek AM 0.35 -- --

305957098271200 Jennings Creek near Tow, Tex. Jennings Creek VE1 0.1 AM 0.67

305942098265100 Greenwood Creek near Tow, Tex. Greenwood Creek VE1 0.2 VE1 2

305808098271300 Jim John Creek near Tow, Tex. Jim John Creek VE1 0.02 FM 0.98

305654098245800 Deer Creek near Tow, Tex. Deer Creek SVE 1.0 AM 3.9

1

Visual estimates were noncontact estimations of the upper limit of streamflow based on the hydrographer’s experience measuring similar flows and were only 

made when (1) the flow could not be physically measured with the Flowtracker, and (2) it was readily apparent the flow in the tributary was trivial compared to 

the flow in the Colorado River and would not tangibly affect streamflow gain-loss calculations.
Streamflow Gains and Losses

Table 4. Summary of gain-loss determinations for reaches on the Colorado River in northwestern Burnet and southeastern San Saba 

Counties, Texas, 2012–14.

[ft3/s, cubic feet per second; positive value indicates gain or inflow entering the reach; negative value indicates loss or outflow leaving the reach. Green font 

indicates a verifiable streamflow gain that was larger than the measurement uncertainty associated with the discharge measurements made in this reach, and red

font indicates a verifiable streamflow loss that was larger than the measurement uncertainty associated with the discharge measurements made in this reach; --, 

not measured]

December 3–6, 2012 (fall 2012 gain-loss survey)

Reach 

(table 2; 

fig. 13)

Discharge 

measured 

at the 

upstream site

(ft3

/s)

Discharge 

measured 

at the 

downstream 

site

(ft3

/s)

Mean 

streamflow 

in reach

(ft3

/s)

Measured 

difference in 

streamflow 

within reach

(ft3

/s)

Estimated 

evaporation 

loss within 

reach

Tributary 

inflow from 

creeks 

within reach 

(ft3

/s)

Estimated 

streamflow 

gain or loss 

within reach 

(ft3

/s)

Potential error 

associated 

with discharge 

measurements 

at the sites 

defining 

upstream and 

downstream 

extent of the 

reach 

(ft3

/s)

A 48.7 46.8 47.8 -1.9 0.08 0.00 -1.98 7.64

B 46.8 56.2 51.5 9.4 0.23 0.35 9.52 9.36

C 56.2 45.4 50.8 -10.8 0.16 0.30 -10.7 10.2

D 45.4 29.6 37.5 -15.8 0.30 0.02 -16.1 7.5

E 29.6 38.0 33.8 8.4 0.35 0.00 8.05 6.76

F 38.0 45.2 41.6 7.2 0.87 1.0 7.33 8.32

May 31–June 1, 2014 (spring 2014 gain-loss survey)

Reach 

(table 2; 

fig. 13)

Discharge 

measured 

at the 

upstream site

(ft3

/s)

Discharge 

measured 

at the 

downstream 

site

(ft3

/s)

Mean 

streamflow 

in reach

(ft3

/s)

Measured 

difference in 

streamflow 

within reach 

(ft3

/s)

Estimated 

evaporation 

loss within 

reach

Tributary 

inflow from 

creeks 

within reach 

(ft3

/s)

Estimated 

streamflow 

gain or loss 

within reach 

(ft3

/s)

Potential error 

associated 

with discharge 

measurements 

at the sites 

defining 

upstream and 

downstream 

extent of the 

reach 

(ft3

/s)

A 892 853 872 -39 0.29 0 -39.3 130

B.1 853 835 844 -18 0.22 0 -18.2 83.6

B.2 835 829 832 -6 0.22 0 -6.22 83.2

B.3 679 687 683 8 0.23 0 7.77 67.4

C.1 687 695 691 8 0.28 2.67 10.4 68.8

C.2 695 701 698 6 0.15 0 5.85 70.5

D.1 701 702 702 1 0.23 0 0.77 70.4

D.2 702 721 712 19 0.38 0 18.6 71.3

D.3 721 716 718 -5 0.12 0.98 -4.14 73.5

E 716 754 735 38 0.75 0 37.2 76.3

F 754 838 796 84 2.06 3.9 85.8 95.3
20

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Tributary inflow where streamflow was 

 measured or estimated

Streamflow-measurement site and number 7 C

EXPLANATION

Creek

Spicewood

Jennings Creek

Greenwood Creek

Jim John Creek

Colorado River

Deer Creek

Jennings Creek

Greenwood Creek

Jim John Creek

Colorado River

Deer Creek

1

2

5

7

10

11

12

C

C

C

C

C

C

C

1

2

5

6

7

8

4

3

9

10

11

12

C

C

C

C

C

C

C

C

C

C

C

Base modified from U.S. Geological Survey digital data, 1:24,000 C

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

98°26'

98°28'

31°00'

30°58'

30°56'

98°26'

98°28'

31°00'

30°58'

30°56'

0 0.5 1.0 MILES

0 0.5 1.0 KILOMETERS

A. Fall 2012 gain-loss survey

 (December 3–6, 2012)

B. Spring 2014 gain-loss survey

 (May 31–June 1, 2014)

Reach A

Reach B.2

Reach B.3

Reach B.1

Reach C.2

Reach C.1

Reach E

Reach F

Reach D.1

Reach D.3

Reach D.2

Reach A

Reach B

Reach C

Reach E

Reach F

Reach D

Figure 13. Study area reaches showing streamflow-measurement sites and tributary inflows along the Colorado River in northwestern 

Burnet and southeastern San Saba Counties, Texas.
Streamflow Gains and Losses

Discharge estimates and measurements for tributary 

inflows (I) were also made on tributaries to the Colorado River 

within the study area. In some cases (Spicewood Creek during 

the fall 2012 gain-loss survey and Jennings and Deer Creeks 

during the spring 2014 gain-loss survey; table 3), abbreviated 

discharge measurements were made by wading with a 

FlowTracker. Abbreviated discharge measurements were made 

in place of full discharge measurements because of narrow 

widths in these streams at the time of measurement. Although 

the use of abbreviated midsection discharge measurements 

in place of full midsection discharge measurements may 

result in a reduction in measurement accuracy, the magnitude 

of these tributary discharge measurement results relative to 

estimated streamflow gains or losses would make the loss 

of accuracy negligible. A full discharge measurement was 

made at the Jim John Creek near Tow, Tex., site during the 

spring 2014 gain-loss survey (table 3). In most other cases of 

tributary inflows to the Colorado River from small streams, 

a visual estimate of streamflow was made by an experienced 

hydrographer in lieu of measuring discharge, typically 

because depths or velocities were insufficient for making 

accurate velocity measurements with the FlowTracker. Visual 

estimates were noncontact estimations of the upper limit of 

streamflow based on the hydrographer’s experience measuring 

similar flows and were only made when (1) the flow could 

not be physically measured with the FlowTracker, and (2) it 

was readily apparent the flow in the tributary was trivial 

compared to the flow in the Colorado River and would not 

tangibly affect streamflow gain-loss calculations. For example, 

Greenwood Creek was estimated as flowing at 0.2 and 2 

ft3/s during December 3–6, 2012, and May 31–June 1, 2014, 

respectively; the mean discharge in the Colorado River 

downstream from the confluence with Greenwood Creek 

during December 3–6, 2012, was 56.2 and 668 ft3/s during 

December 3–6, 2012, and May 31–June 1, 2014, respectively. 

A surface velocity estimate of streamflow was made at one 

site (discharge measurement at the Deer Creek near Tow, 

Tex., site during the fall 2012 gain-loss survey) using equation 

3 because it was determined to be the most appropriate 

streamflow estimation method:

Q = 0.8 (D × W × Vs) (3)

where

Q is estimated streamflow, in cubic feet per 

second;

D is average depth, in feet;

W is average width, in feet; and

Vs is surface velocity, in feet per second.

Evaporation (E) within each reach was estimated by 

using mean lake evaporation data from two quadrangles 

(609 and 709) provided by the Texas Water Development 

Board (2014) because the study area extends across both 

quadrangles. The following equation was used to calculate the 

amount of streamflow lost to evaporation in each reach:

Ereach = Lf (W × L)×Elake (4)

where

Ereach is the evaporation within each stream reach, in 

cubic feet per second;

Lf is a dimensionless daylight factor (2.34 and 

1.72 for the fall and spring gain-loss 

surveys, respectively);

W is average of the stream widths measured at 

the upstream and downstream boundaries 

of the reach, in feet;

L is reach length, in feet; and

Elake is estimated lake evaporation, in feet per 

second.

Monthly lake evaporation rates for December 2012 were used 

for the fall 2012 gain-loss survey. Because 2014 evaporation 

data were not yet available, average monthly evaporation 

rates for the entire period of record (1955–2013) from both 

quadrangles during May and June were used to calculate 

evaporation losses from each stream reach during the spring 

2014 gain-loss survey. The lake evaporation rate was applied 

to the surface area of each reach to compute an evaporation 

loss for the reach in cubic feet per second (apps. 1–2). 

Evaporative losses were assumed to occur only during the 

daytime hours, so the lake evaporation value applied to the 

reach was multiplied by a daylight factor (ratio of 24 hours to 

the hours of daylight) as described in Ockerman (2002, p. 7) 

to determine the evaporative rate during daytime hours. Data 

used in the calculation of evaporative loss estimates are listed 

in appendixes 1 and 2 for the fall 2012 and spring 2014 gainloss surveys, respectively. 

For this report, a stream reach was classified as verifiably 

gaining or losing if the difference in streamflow between 

the upstream and downstream measuring sites exceeded the 

sum of the potential errors of the discharge measurements at 

the upstream and downstream measurement sites. Sauer and 

Meyer (1992, p. 2) describe how a measurement error rating 

(excellent, good, fair, or poor) is assigned to each discharge 

measurement by using a “quasi-quantitative method * * * 

based on a qualitative evaluation of several factors, such as 

cross section uniformity, velocity uniformity, stream bed 

conditions, and other factors that might, in the opinion of 

the streamgager, affect the accuracy of the measurement.” 

Additional factors that affect the accuracy of the measurement 

include the number of observations of width and depth, 

magnitude and homogeneity of streamflow velocity, and 

measurement statistics generated by the FlowTracker or ADCP 

data processing software. Discharge measurements were rated 

following the rating system developed by Sauer and Meyer 

(1992) to estimate measurement error of individual discharge 

measurements with excellent, good, and fair discharge 

measurements believed to be within 2, 5, and 8 percent of 

the actual streamflow, respectively. Discharge measurements 

rated as poor are believed to differ from actual flow by more 

than 8 percent; a value of 10 percent was used for the purpose 
22

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

of error calculations in this report. None of the discharge 

measurements made in either the fall 2012 or spring 2014 

gain-loss surveys were rated as excellent. By multiplying 

the discharge measurement by the percent difference 

assigned to the measurement rating, a potential error for each 

measurement was determined. The potential errors associated 

with the upstream and downstream discharge measurements 

used to calculate gain-loss measurements for each reach 

were summed to obtain the potential composite error for 

comparison with the computed gain or loss (tables 4–5). 

All of the streamflow discharges determined by 

wading the stream were an average of two measurements 

(table 1), with each measurement typically made by a 

different hydrographer using a FlowTracker. In all cases, the 

measurement rating was unchanged between consecutive 

discharge measurements at a site. A summary of gain-loss 

determinations for reaches along the Colorado River during 

both of the streamflow-measurement surveys is provided in 

table 4. 

Of the 6 reaches assessed during the fall 2012 gainloss survey, 3 were gaining (reaches B, E, and F) and 3 

(reaches A, C, and D) were losing, although only 4 of these 

6 (reaches B through E) could be classified as verifiably 

gaining or losing streamflow because the potential error 

associated with the discharge measurements made at reaches 

A and F exceeded the difference in streamflow between the 

upstream and downstream measuring sites (fig. 14; table 4). 

The two reaches that were verifiably gaining streamflow 

were B and E. The Colorado River in reach B crosses a 

combination of alluvium and Ellenburger-San Saba aquifer 

outcrop, whereas the Colorado River in reach E crosses the 

Ellenburger-San Saba aquifer outcrop exclusively (fig. 14; 

table 4). Streamflow gains in reaches B and E were likely a 

result of groundwater discharge flowing into the Colorado 

River from the Ellenburger-San Saba aquifer either directly 

or indirectly through the faults that cross each reach. Reaches 

C and D were verifiably losing streamflow in fall 2012. The 

Colorado River in reach C crosses several hydrogeologic 

features, including the Ellenburger-San Saba aquifer outcrop 

in the upper two-thirds of the reach, a fault, and aquifer 

confining units (Point Peak Member and Morgan Creek 

Limestone) in the lower third of the reach (fig. 14; table 4). 

Because the lower part of reach C crosses a confining unit, it 

is likely that most of the streamflow losses in this reach are 

either direct recharge to the Ellenburger-San Saba aquifer 

as water infiltrates into the subsurface from the streambed 

and provides recharge to the aquifer in the upper two-thirds 

of the reach, or indirect recharge as water moves downward 

through the fault that crosses the reach (fig. 14; table 4). 

Little is known about the precise nature of how the faults and 

groundwater system interact in the study area. Faults that 

cross stream channels can act either as barriers or pathways 

for groundwater flow (Grover and Bailey, 1919; Fenelon and 

others, 2012). The Colorado River in reach D crosses the same 

confining units as reach C in the upper 40 percent of the reach 

before transitioning to the Mid-Cambrian aquifer in the lower 

60 percent of the reach (fig. 14; table 4). Because the upper 

part of reach D flows across a confining unit, it is more likely 

that most of the streamflow losses in this reach are associated 

with water infiltration into the subsurface from the streambed 

and recharge provided to the Mid-Cambrian aquifer.

During the spring 2014 gain-loss survey, most of the 

reaches (7 of 11) were gaining, although none of the reaches 

could be classified as verifiably gaining or losing because 

the potential error (table 4) associated with the discharge 

measurements made in each of the 11 reaches exceeded 

the difference in streamflow between the upstream and 

downstream measuring sites (table 4). Therefore, reaches 

were combined in an attempt to consolidate streamflow gains 

or losses while keeping potential error relatively constant 

(fig. 15; table 5). In order to facilitate direct comparisons 

between the results of the fall 2012 and spring 2014 gainloss surveys, the 11 reaches established in the spring 2014 

gain-loss survey were initially combined to match the extents 

of the 6 reaches (A, B, C, D, E, and F) from the fall 2012 

gain-loss survey (for example, spring 2014 reaches B.1, B.2, 

B.3, were combined into a reach B) (table 2). After combining 

the reaches in this manner, the potential error associated with 

the upstream and downstream flow measurements within each 

reach still exceeded the estimated streamflow gains or losses 

within each reach, so none of the reaches could be classified 

as verifiably gaining or losing. Thus, reaches were combined 

a second time to reduce the number from 6 to 3 (referred to 

as reaches AB, BD, EF) in an attempt to consolidate gains 

and losses and group reaches together when they crossed 

the same hydrogeologic units (fig. 15; table 5). An estimated 

loss of 63.7 ft3

/s was measured in reach AB (a combination 

of reaches A, B.1, and B.2) that flows across a combination 

of alluvium and the Ellenburger-San Saba aquifer outcrop, 

which was much smaller than the potential measurement 

error of 129 ft3/s, resulting in an unverifiable loss. Reach 

BD flows across each of the different hydrogeologic units 

represented in the study area (fig. 15) and is a combination 

of 6 of the 11 reaches (B.3, C.1, C.2, D.1, D.2, and D.3) that 

were examined initially in the spring 2014 gain-loss survey 

(fig. 15; table 5). Of the 6 reaches that combined to make up 

reach BD, 5 were unverifiably gaining, whereas the sixth (D.3) 

was unverifiably losing. An estimated gain of 39.3 ft3/s was 

measured for reach BD, which was unverifiable because it 

was smaller than the potential error of 71.5 ft3/s. A verifiable 

streamflow gain of 123 ft3/s was measured in reach EF, which 

flows exclusively across the Ellenburger-San Saba aquifer; 

the estimated gain in streamflow exceeded the potential error 

of 93.9 ft3

/s for this reach. This means that the EllenburgerSan Saba aquifer is losing in this part of the study area at flow 

conditions observed during the spring 2014 gain-loss survey.
Table 5. Summary of gain-loss determinations during the spring 2014 gain-loss survey for reaches on the Colorado River in northwestern Burnet and Counties, Texas, 2012–14.[ft3/s, cubic feet per second; positive value indicates gain or inflow entering the reach; negative value indicates loss or outflow leaving the reach. Green font indicates a streamflo

measurement uncertainty for this reach; --, not measured]

Reach 

(table 2; 

fig. 13)

Discharge 

measured at the 

upstream site 

(ft3/s)

Discharge 

measured at 

the 

downstream 

site 

(ft3/s)

Mean 

adjusted 

streamflow 

in reach

Measured 

difference in 

adjusted 

streamflow 

within reach

Estimated 

evaporation 

loss 

within 

reach

Tributary 

inflow from 

creeks 

within 

reach

Estimated 

streamflow 

gain or loss 

within 

reach

Potential error 

from streamflow 

measurement at 

upstream site 

(ft3/s)

Potential er

from streamf

measuremen

downstream 

(ft3/s)

A 892 853 872 -39 0.29 0 -39.3 87.7 41.8 

B.1 853 835 844 -18 0.22 0 -18.2 41.8 41.8 

B.2 835 829 832 -6 0.22 0 -6.2 41.8 141.4 

B.3 679 687 683 8 0.23 0 7.8 234.0 33.4 

C.1 687 695 691 8 0.28 2.67 10.4 33.4 35.4 

C.2 695 701 698 6 0.15 0 5.8 35.4 35.1 

D.1 701 702 702 1 0.23 0 0.8 35.1 35.3 

D.2 702 721 712 19 0.38 0 18.6 35.3 36.0 

D.3 721 716 718 -5 0.12 0.98 -4.1 36.0 37.5 

E 716 754 735 38 0.75 0 37.3 37.5 38.8 

F 754 838 796 84 2.06 3.9 85.8 38.8 56.5 

Selected reaches combined by 

using the most upstream and 

downstream measurement sites 

from the first gain-loss survey 

(see table 2 for description 

and fig. 14 for location) 

Estimated streamflow 

gain or loss within 

a reach defined by 

streamflow-measurement sites from the first 

gain-loss survey

Potential error 

from streamflow measurement at 

upstream site 

(ft3/s)

Potential 

error from 

streamflow 

measurement 

at downstream 

site 

(ft3/s)

Sum of potential error 

from streamflow 

measurements at 

upstream and downstream sites of reaches 

A, B, C, D, E, and F 

(ft3/s)

Reaches further 

grouped to minimize potential 

measurement 

errors 

(see fig. 14 for 

location)3

Estimated 

streamflow gain 

or loss within 

reach grouped 

to minimize potential measurment errors

A -39.3 87.7 41.8 130 AB -63.7 

B4 -16.7 41.8 33.4 75.2

BD 39.3 

C5 16.2 33.4 35.1 68.5

D6 15.2 35.1 37.5 72.6

E 37.3 37.5 38.8 76.3

EF 123 

F 85.8 38.8 56.5 95.3

1Based on streamflow measurement made on May 31, 2014.2Based on streamflow measurement made on June 1, 2014.3Reaches A–F were combined into upstream, middle, and downstream reaches (reach AB, reach BD, and reach EF) in an attempt to consolidate gains and losses as well as gro

hydrogeologic units.

4Reaches B.1, B.2, and B.3 combined.5Reaches C.1 and C.2 combined.6Reaches D.1, D.2, and D.3 combined.
24

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

River reach gains verifiable streamflow

River reach loses verifiable streamflow

River reach neither gains nor loses verifiable

 streamflow

Streamflow-measurement site and number

Hydrogeologic units

 Alluvium

 Ellenburger-San Saba

 Confining units (Point Peak Member

 and Morgan Creek Limestone)

 Mid-Cambrian aquifer (Welge

 Sandstone and Lion Mountain

 Sandstone)

Fault—Ball and bar on

 downthrown block 7 C

EXPLANATION

LAMPASAS COUNTY

BURNET COUNTY

SAN SABA COUNTY

LLANO COUNTY

Post Oak Creek

Creek

Spicewood

Jennings Creek

Greenwood Creek

Jim John Creek

Sycamore Branch

Colorado River

Deer Creek

Devils Hollow Creek

Reach A

Reach B

Reach C

Reach D

Reach E

Reach F

1

2

5

6

7

8

4

3

9

10

11

12

C

C

C

C

C

C

C

C

C

C

C

C

Aquifers modified from surficial geology

of Barnes and others (1981)

 and Kier and others (1976)

Base modified from U.S. Geological Survey digital data, 1:24,000 

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

0 0.5 1.0 MILES

0 0.5 1.0 KILOMETERS

Figure 14. Reaches that were verifiably gaining or losing or unverifiably gaining or losing during the fall 2012 gain-loss survey in 

northwestern Burnet and southeastern San Saba Counties, Texas.
Streamflow Gains and Losses

River reach gains verifiable streamflow

River reach neither gains nor loses verifiable

 streamflow

Streamflow-measurement site and number

Hydrogeologic units

 Alluvium

 Ellenburger-San Saba

 Confining units (Point Peak Member

 and Morgan Creek Limestone)

 Mid-Cambrian aquifer (Welge

 Sandstone and Lion Mountain

 Sandstone)

Fault—Ball and bar on

 downthrown block

7 C

EXPLANATION

LAMPASAS COUNTY

BURNET COUNTY

SAN SABA COUNTY

LLANO COUNTY

Post Oak Creek

Creek

Spicewood

Jennings Creek

Greenwood Creek

Jim John Creek

Sycamore Branch

Colorado River

Deer Creek

Devils Hollow Creek

Reach AB

(between sites 1 and 4)

Reach BD

(between sites 4 and 10)

Reach EF

(between sites 10 and 12)

1

2

5

6

7

8

4

3

9

10

11

12

C

C

C

C

C

C

C

C

C

C

C

C

Aquifers modified from surficial geology

of Barnes and others (1981)

 and Kier and others (1976)

Base modified from U.S. Geological Survey digital data, 1:24,000 

Texas Centric Mapping System

Albers Equal Area Conic

North American Datum of 1983 

98°28' 98°26' 98°24'

31°02'

31°00'

30°58'

30°56'

0 0.5 1.0 MILES

0 0.5 1.0 KILOMETERS

Figure 15. Reaches that were verifiably gaining or losing or unverifiably gaining or losing during the spring 2014 gain-loss survey in 

northwestern Burnet and southeastern San Saba Counties, Texas.
26

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Summary 

In October 2012, the U.S. Geological Survey (USGS), in 

cooperation with the Central Texas Groundwater Conservation 

District (CTGCD), began a gain-loss study of streamflow in 

the Colorado River in northwestern Burnet and southeastern 

San Saba Counties, Texas. This report presents the results of 

the study to determine if different reaches of the Colorado 

River in northwestern Burnet and southeastern San Saba 

Counties are gaining or losing streamflow, where the gains 

and losses have occurred and in what quantities, and whether 

the gains and losses can be attributed to interaction of 

groundwater and surface water between the Ellenburger-San 

Saba aquifer and the Colorado River.

Two sets of synoptic discharge measurements were made 

under different flow conditions. In the first gain-loss survey 

during December 3–December 6, 2012 (hereinafter the fall 

2012 gain-loss survey), discharge measurements were made 

at low-flow conditions ranging from about 30 to 60 cubic 

feet per second (ft3

/s) at seven locations along the Colorado 

River. In the second gain-loss survey during May 31–June 

1 (hereinafter the spring 2014 gain-loss survey), discharge 

measurements were made at high-flow conditions ranging 

from about 660 to 900 ft3/s at 12 locations along the Colorado 

River. Discharge measurement locations were selected for 

the gain-loss surveys based on several criteria including the 

locations of hydrogeologic unit contacts, faults, seeps, springs, 

travertine deposits, and tributary inflows.

During the fall 2012 gain-loss survey, verifiable gains 

or losses of streamflow were identified in 4 of 6 reaches 

(the difference in measured discharge between the upstream 

and downstream boundaries of the reach was larger than the 

sum of potential errors associated with the two discharge 

measurements). The two reaches with a verifiable gain in 

streamflow cross areas where the Ellenburger-San Saba 

aquifer crops out. The more upstream of the two reaches with 

verifiable losses crosses a small part of the Ellenburger-San 

Saba aquifer outcrop and confining units (Point Peak Member 

and Morgan Creek Limestone); it is possible streamflow losses 

in this reach are in the form of recharge to the Ellenburger-San 

Saba aquifer; little streamflow is likely lost to the underlying 

formations in the downstream part of the reach, which consists 

of relatively impermeable aquifer confining units exposed at 

land surface. The more downstream of the two reaches where 

a verifiable loss of streamflow was measured also flows across 

relatively impermeable confining units before crossing the 

Mid-Cambrian aquifer outcrop in the lower part of the reach; 

most of the streamflow losses in this reach were likely a result 

of water infiltration into the subsurface from the streambed 

and recharge provided to the relatively permeable MidCambrian aquifer.

During the spring 2014 gain-loss survey, most of the 

reaches (7 of 11) were gaining although none of the reaches 

could be classified as verifiably gaining or losing because 

the potential error associated with the flow measurements 

made at each of the 11 reaches exceeded the difference in 

streamflow between the upstream and downstream measuring 

sites. The 11 reaches were combined into upstream, middle, 

and downstream reaches (reach AB, reach BD, and reach EF) 

in an attempt to consolidate gains and losses as well as group 

reaches within the same hydrogeologic units. An unverifiable 

loss in streamflow of 63.7 ft3

/s was measured in the upstream 

reach AB, which flows across a combination of alluvium 

and the Ellenburger-San Saba aquifer outcrop. The loss in 

reach AB was considered unverifiable because it was smaller 

than the potential measurement error of 129 ft3/s determined 

from discharge measurements used to estimate the loss. An 

estimated gain of 39.3 ft3/s was measured in middle reach BD 

that flows across each of the different hydrogeologic units 

represented in the study area; this estimated gain was smaller 

than the potential error of 71.5 ft3/s, so it was also considered 

unverifiable. The reach farthest downstream in the study area 

(reach EF) flows exclusively across the Ellenburger-San Saba 

aquifer. A streamflow gain of 123 ft3/s was measured in reach 

EF, which was larger than the potential error of 93.9 ft3/s for 

this reach. This means that groundwater from the EllenburgerSan Saba aquifer is likely contributing to streamflow in this 

part of the study area at the flow conditions observed during 

the spring 2014 gain-loss survey.

References

Barlow, P.M., and Leake, S.A., 2012, Streamflow depletion 

by wells—Understanding and managing the effects of 

groundwater pumping on streamflow: U.S. Geological 

Survey Circular 1376, 84 p. [Also available at http://pubs.

usgs.gov/circ/1376/.]

Barnes, V.E., Shell Oil Co., Boyer, R.E., Clabaugh, S.E., and 

Baker, E.T., 1981, Geologic atlas of Texas, Llano sheet: 

The University of Texas at Austin, Bureau of Economic 

Geology, accessed April 22, 2015, at http://www.twdb.texas.

gov/groundwater/aquifer/GAT/llano.htm.

Berehe, A.K., 2005, Updated evaluation for the Williamson, 

Burnet and northern Travis Counties priority groundwater 

management study area: Texas Commission on 

Environmental Quality, Priority Groundwater Management 

Area File Report, 134 p.

Fenelon, J.M., Sweetkind, D.S., Elliott, P.E., and Laczniak, 

R.J., 2012, Conceptualization of the predevelopment 

groundwater flow system and transient water-level 

responses in Yucca Flat, Nevada National Security Site, 

Nevada: U.S. Geological Survey Scientific Investigations 

Report 2012–5196, 61 p. 

Grover, N.C., and Bailey, C.T., 1919, Surface water supply of 

Hawaii—July 1, 1917 to June 30, 1918: U.S. Geological 

Survey Water Supply Paper 485, 169 p., accessed April 23, 

2015, at http://pubs.usgs.gov/wsp/0485/report.pdf.
References

Healy, R.W., Winter, T.C., LaBaugh, J.W., and Franke, O.L., 

2007, Water budgets—Foundations for effective waterresources and environmental management: U.S. Geological 

Survey Circular 1308, 90 p.

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water (3d ed.): U.S. Geological 

Survey Water-Supply Paper 2254, 263 p. (Reprinted 1992.) 

Kier, R.S., Brown, L.F., Harwood, P., Jr., and Goodson, 

J.L., 1976, Geologic atlas of Texas, Brownwood sheet: 

The University of Texas at Austin, Bureau of Economic 

Geology, accessed April 22, 2015, at http://www.twdb.texas.

gov/groundwater/aquifer/GAT/brownwood.htm.

Lower Colorado River Authority, 2015, LCRA hydrologic 

data: Accessed on April 23, 2015, at http://hydromet.lcra.

org/full.aspx.

Maurer, D.K., Berger, D.L., Tumbusch, M.L., and Johnson, 

M.J., 2006, Rates of evapotranspiration, recharge from 

precipitation beneath selected areas of native vegetation, 

and streamflow gain and loss in Carson Valley, Douglas 

County, Nevada, and Alpine County, California: U.S. 

Geological Survey Scientific Investigations Report 2005–

5288, 70 p. [Also available at http://pubs.water.usgs.gov/

sir2005-5288.]

Mueller, D.S., Wagner, C.R., Rehmel, M.S., Oberg, K.A., 

and Rainville, Francois, 2013, Measuring discharge with 

acoustic Doppler current profilers from a moving boat (ver. 

2.0, December 2013): U.S. Geological Survey Techniques 

and Methods, book 3, chap. A22, 95 p., accessed June 15, 

2015, at http://dx.doi.org/10.3133/tm3A22.

Oberg, K.A., Morlock, S.E., and Caldwell, W.S., 2005, 

Quality-assurance plan for discharge measurements using 

acoustic Doppler current profilers: U.S. Geological Survey 

Scientific Investigations Report 2005–5183, 35 p.

Ockerman, D.J., 2002, Gain-loss study of lower San Pedro 

Creek and the San Antonio River, San Antonio, Texas, 

May–October 1999: U.S. Geological Survey Open-File 

Report 2002–023, 15 p.

Pinder, G.F., and Celia, M.A., 2006, Groundwater–surfacewater interaction, in Subsurface Hydrology: Hoboken, 

N.J., John Wiley and Sons, Inc., p. 343–365, doi: 

10.1002/0470044209.ch9.

Preston, R.D., Pavilcek, D.J., Bluntzer, R.L., and Derton, 

John, 1996, The Paleozoic and related aquifers of central 

Texas: Texas Water Development Board Report 346, 95 p., 

accessed June 17, 2015, at https://www.twdb.texas.gov/

publications/reports/numbered_reports/doc/R346/R346.pdf.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow—Volumes 1 and 2: U.S. Geological Survey 

Water-Supply Paper 2175, 631 p.

Sauer, V.B., and Meyer, R.W., 1992, Determination of error in 

individual discharge measurements: U.S. Geological Survey 

Open-File Report 92–144, 21 p. [Also available online at 

http://pubs.usgs.gov/of/1992/ofr92-144/.]

SonTek, 2013, FlowTracker handheld acoustic Doppler 

velocimeter: Accessed February 6, 2013, at http://www.

sontek.com/flowtracker.php.

Teledyne RD Instruments, 2007, WinRiver II user’s guide: San 

Diego, Calif., Teledyne RD Instruments, P/N 957–6231–00, 

166 p.

Texas Water Development Board, 2014, Precipitation and lake 

evaporation: Accessed on December 19, 2014, at http://

www.twdb.texas.gov/surfacewater/conditions/evaporation/

index.asp.

Turnipseed, D.P., and Sauer, V.B., 2010, Discharge 

measurements at gaging stations: U.S. Geological Survey 

Techniques and Methods, book 3, chap. A8, 87 p. 

U.S. Geological Survey, 2015, National Water Information 

System: Accessed April 13, 2015, at http://waterdata.usgs.

gov/tx/nwis/.

Winter, T.C., Harvey, J.W., Franke, O.L., and Alley, W.M., 

1998, Ground water and surface water—A single resource: 

U.S. Geological Survey Circular 1139, 79 p., accessed 

March 31, 2015, at http://pubs.water.usgs.gov/circ1139.

Young, K.B., 1950, A comparative study of mean-section 

and mid-section methods for computation of discharge 

measurements: U.S. Geological Survey Open-File Report 

53–277, 52 p., accessed April 24, 2015, at http://pubs.usgs.

gov/of/1953/0277/report.pdf.

Appendixes

Appendix 1

Appendix 1. Calculation of estimated evaporative losses within reaches on the Colorado River in northwestern Burnet County, Texas, 

December 3–6, 2012.

[ft, feet; in/d, inch per day; ft/s, feet per second; ft3/s, cubic feet per second]

Reach

Reach 

length 

(ft)

Stream width 

at upstream 

boundary 

of reach 

(ft)

Stream width 

at downstream 

boundary 

of reach 

(ft)

Average 

stream 

width for 

entire reach 

(ft)

Lake 

evaporation1

(in/d)

Lake 

evaporation 

applied to 

the reach 

(ft/s)

Estimated 

evaporation 

loss within 

reach 

(ft3

/s)2

A 4,013 99 152 125.5 0.07419 0.0000000716 0.08

B 9,662 152 137 144.5 0.07419 0.0000000716 0.23

C 5,438 137 219 178 0.07419 0.0000000716 0.16

D 7,973 219 235 227 0.07419 0.0000000716 0.30

E 7,762 235 301 268 0.07419 0.0000000716 0.35

F 16,526 301 330 315.5 0.07419 0.0000000716 0.87

1

Texas Water Development Board, 2014, Precipitation and lake evaporation, accessed on December 19, 2014, at http://www.twdb.texas.gov/surfacewater/

conditions/evaporation/index.asp.

2

A dimensionless daylight factor of 2.34 was used to calculate the estimated evaporation loss within each reach for measurements made during the fall 2012 

(December 3–6, 2012) gain-loss survey. The dimensionless daylight factor is the ratio of 24 hours to the hours of daylight as described in Ockerman (2002, p. 7). 

Appendix 1
32

Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Tex

Appendix 2. Calculation of estimated evaporative losses within reaches on the Colorado River in northwestern Burnet County, Texas, 

May 31–June 1, 2014.

[ft, feet; in/d, inch per day; ft/s, feet per second; ft3/s, cubic feet per second]

Reach

Reach 

length 

(ft)

Stream width 

at upstream 

boundary of 

reach 

(ft)

Stream width 

at downstream 

boundary 

of reach 

(ft)

Average 

stream width 

for entire reach 

(ft)

Lake 

evaporation1

(in/d)

Lake evaporation 

applied to 

the reach 

(ft/s)

Estimated 

evaporation loss 

within reach 

(ft3

/s)2

A 4,013 265.5 202 233.75 0.1899 0.000000183 0.29

B.1 3,326 202 216 209 0.1899 0.000000183 0.22

B.2 3,221 216 225.5 220.75 0.1899 0.000000183 0.22

B.3 3,115 225.5 249 237.25 0.1899 0.000000183 0.23

C.1 3,590 249 247 248 0.1899 0.000000183 0.28

C.2 1,848 247 279 263 0.1899 0.000000183 0.15

D.1 2,534 279 288 283.5 0.1899 0.000000183 0.23

D.2 4,118 288 306 297 0.1899 0.000000183 0.38

D.3 1,320 306 288 297 0.1899 0.000000183 0.12

E 7,762 288 324 306 0.1899 0.000000183 0.75

F 16,526 324 469 396.5 0.1899 0.000000183 2.06

1

Texas Water Development Board, 2014, Precipitation and lake evaporation, accessed on December 19, 2014, at http://www.twdb.texas.gov/surfacewater/

conditions/evaporation/index.asp.

2

A dimensionless daylight factor of 1.72 was used to calculate the estimated evaporation loss within each reach for measurements made during the spring 

2014 (May 31–June 1, 2014) gain-loss survey. The dimensionless daylight factor is the ratio of 24 hours to the hours of daylight as described in Ockerman 

(2002, p. 7). 

Publishing support provided by

Lafayette Publishing Service Center

Information regarding water resources in Texas is available at 

http://tx.usgs.gov/
Braun and Grzyb—Streamflow Gains and Losses in the Colorado River in Northwestern Burnet and Southeastern San Saba Counties, Texas—SIR 2015–5098

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155098