,

TEXAS WATER DEVELOPMENT BOARD

REPORT 22

WATER-DELIVERY AND LOW-FLOW STUDIES

PECOS RIVER, TEXAS

Quantity and Quality, 1964 and 1965

By

Richard U. Grozier, Harold W. Albert,James F. Blakey, and Charles H. Hembree

United States Geological Survey

Prepared by the U.S. Geological Surveyin cooperation with the

Texas Water Development Boardand the

Red Bluff Water Power Control District

May 1966

,

TEXAS WATER DEVELOPMENT BOARD

REPORT 22

WATER-DELIVERY AND LOW-FLOW SnrnlES

PECOS RIVER, TEXAS

Quantity and Quality, 1964 and 1965

By

Richard U. Grazier, Harold W. Albert,James F. Blakey, and Charles H. Hembree

United States Geological Survey

Prepared by the U.S. GeologicaL Surveyin cooperation with the

Texas Water Development Boardand the

Red 81uff Water Power ControL District

May 1966

TABLE OF CONTENTS

Page

INTRODUCTION. . ..•• .. ••••••••.•. •. .. .•.•. .. ..•. . . .. . .••. .. ..•.. .. .•.. . . .. 1

Purpose and Scope.................................................. 1

Method of Analysis................................................. 2

GENERAL GEOLOGY......................................................... 5

HYDROLOGY. . . • . • . • . . . . • . . . • . • . • • • • • • • . • • • • . • . • • • . • . . • . • . • . . . . . . • . . . . . . • . • 5

Reach From Red Bluff Reservoir (Mile 0) to Pecos (Mile 71.8)....... 5

Wa ter-Del ivery S tucly. • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Low-Flow Study................................................ 7

Reach From Pecos (Mile 71.8) to State Highway 18 Near Grandfalls(Mile 127.4).... ...•...... 7

Water-Delivery Study.................. •••....................• 7

Low-Flow Study................................................ 8

Reach From State Highway 18 Near Grandfalls (Mile 127.4) to Girvin(Mile 188.4)..................................................... 8

Water-Delivery Study.......................................... 8

Low-Flow Study.................. ••..............•......•...... 10

WATER QUALIlY AND USE................................................... 11

General........................................................ .. .. 11

Domestic.............................. .•.......•..... .•............ 11

Industrial............. .•..............................•......•.... 12

Irrigation......................................................... 12

SUMMARY AND CONCLUSIONS................................................. 12

REFERENCES. .. ..•.••.•....••.•.. ..•••........ .. .. . . .. ..•.•. 14

Iii

TABLE OF CONTENTS

Page

INTRODUCTION. . .••. .. •• •. ..• .. •. .• •. ..•.. .. ..•. . .. . . .•.. .. .. •. . . .. 1

Purpose and Scope.................................................. L

Method of Analysis................................................. 2

GENERAL GEOLOGY......................................................... 5

HYDROLOGY. . . . . . . . . . . . . . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . 5

Reach From Red Bluff Reservoir (Mile 0) to Pecos (Mile 71.8)... .•.• 5

Wa ter-Del ivery Study.......................................... 5

LO\o1-Flo\o1 Study................................................ 7

Reach From Pecos (Mile 71.8) to State Highway 18 Near Grandfalls(Mile 127.4)..................................................... 7

Water·Delivery Study.................. .•••....•...•.........•• 7

Low-Flow Study................................................ 8

Reach From State Highway L8 Near Grandfalls (Mile L27.4) to Girvin(Mile 188.4)..................................................... 8

WBter·De1ivery Study... ••••••.•••..•.. •.•......•.... ..••...... 8

Low-Flow Study................................................ 10

WATER QUALIlY AND USE................................................... 11

General................................................. .....•..... 11

Domestic........................................................... 11

Indus tr ia L. . . . . . . • . . . . . . • . . . . . . . . . . . . . . . • . . . . . . • . . . . . . . • . . . . . • . . . . . L2

Irrigation.............. .•......................•......•........... 12

SUMMARY AND CONCLUSIONS............................. . .. .. . ..•. . . .. . .•. . . 12

REFEREOCES. . . . . . . • . • . • . . . . . . . . • • • . . . . . • • • . . . . . • . • . . . . • • . . . . . • • . . . . . . • • • . 14

iii

TABLE OF CONTENTS (Cont 'd.)

Page

TABLES

1. Summary of water discharge measurements and chloride concen-trations, Pecos River water-delivery study, March 1964............ 15

2. Summary of water discharge measurements and chloride concen-trations, Pecos River low·flow study, May 1965.................... 16

3. Summary of chemical analyses of water from selected sites, PecosRiver watershed below Red Bluff Reservoir, March 3-5, 1964, andMay 10-12, 1965................................................... 17

ILLUSTRATIONS

Figures

1. Photographs of Several Sites Along the Pecos River, March 1964...... 3

2. Pho togra phs of Seve ra1 Sites Along the Pecos River, May 1965........ 4

3. Graph of Chloride Concentration and Water Discharge, Pecos River,March 3-5, 1964................................................... 18

4. Graph of Chloride Concentration and Water Discharge, Pecos River,May 10.12, 1965................................................... 19

5. Hydrograph of Flow, Pecos River Near Or1a and Pecos River NearGirvin, February 15 to March 31, 1964............................. 20

6. Graph of Daily Chloride Concentration, Pecos River Below Red BluffDam Near Or1a and Pecos River Near Girvin, February 15 toMarch 31, 1964.................................................... 21

Plates

Follows

1. Map of Pecos River Watershed, Showing Water Discharge andChemical Character of Water, March 3-5, 1964 .

2. Map of Pecos River Watershed, Showing Water Discharge andChemical Character of Water, May 10-12, 1965 .•...••.....•.....

iv

Page 21

PIa te I

WATER-DELIVERY AND LOW FLO W STUDIES

Quantity

P E COS

and

R I V E R

Quality

INTRODUCTION

T E X A S

1 964 and 1 9 6 5

Purpose and Scope

The water-delivery study was made February 15 to March 31, 1964, and thelow-flow study was made May 10-12, 1965, by the U.S. Geological Survey under anagreement with the Red Bluff Water Power Control District, Pecos, through thethen Texas Water Commission.

The purpose of these studies was to determine changes in the quantity andthe quality of a uniform flow of water from Red Bluff Reservoir in a l88.4-milereach of the Pecos River between the dam and Girvin, Texas, and to determinethe quantity and the quality of the low flow in this same reach of the PecosRiver when no water was being released from Red Bluff Reservoir. The capacityof Red Bluff Reservoir at the top of the Tainter gates is 310,000 acre-feet.Water in storage in the reservoir was about 33,000 acre-feet at the beginningof the water-delivery study and 19,750 acre-feet during the low-flow study.

Water is released from Red Bluff Reservoir during the spring and summermonths for irrigation of land on both sides of the Pecos River in an areaextending from about mile 43.3, the first diversion at Reeves County W.I.D.(Water Improvement District) No.2 dam, to mile 111.5, the last diversion atWard County W.I.D. No.2 dam. Some 28,000 acres of land in this area can beirrigated from the river (Pecos River Commission, 1961, p. 128); however, theactual number of acres irrigated varies from year to year, depending on thequantity and quality of water in Red Bluff Reservoir.

Before releases of water were made for the water-delivery study of Febru­ary 15 to March 31, 1964, the flow in the Pecos River at the stream-gaging sta­tion near Or1a (mile 14.3) was only 7.0 cfs (cubic feet per second) and con­sisted of seepage and leakage through gates from Red Bluff Reservoir and someinflow from Salt (Screwbean) Draw near Orla. There was no flow at the site ofthe inactive stream-gaging station, Pecos River at Pecos (mile 71.8). The flowat the stream-gaging station, Pecos River near Girvin (mile 188.4) was 24 cfs.In comparison, the flow at Orla during the low-flow study of May 10-12, 1965,was only 0.39 cfs. There was no flow at the Pecos station and 11.5 cfs at theGirvin station.

During February 15 to March 31, 1964, conditions were favorable for deter­mining channel losses of water released from Red Bluff Reservoir. A prolonged

dry period preceded the investigation; there was no surface runoff and the onlyinflow was from small springs in Salt (Screwbean) Draw. No great water losscould be attributed to evapotranspiration because the salt cedars were dormant.Other than seepage through three headgates, no diversions were being made. Someof the checkgates in the diversion dams on the Pecos River had been opened todecrease storage behind the dams.

The Red Bluff Water Power Control District, which operates Red Bluff Reser­voir, released a constant flow from the reservoir during the water-deliverystudy. The measured release from Red Bluff Reservoir was 129 cfs and this dis­charge was maintained from February 21 to March 9, 1964. During the periodMarch 3-5, 1964, a series of measurements was made and samples for chemicalanalyses were collected at sites along the Pecos River (Plate 1).

During the investigation of May 10-12, 1965, conditions were favorable fordetermining gains and losses in the river when there was no surface runoff andno releases were being made from Red Bluff Reservoir. In May the· salt cedarsare in full leaf and some water loss can be attributed to evapotranspiration.None of the irrigation districts were taking water from the Pecos River duringthis period. During the low-flow study a series of measurements was made andsamples for chemical analyses were collected at sites along the Pecos River(PIa te 2).

Between Red Bluff Reservoir and Girvin the Pecos River is a meanderingstream with a channel about 60 feet wide. The banks are low, are generallycovered with salt cedars and other brushy vegetation, and have not been over­topped since the floods of September and October 1941. The river channel ischaracterized by long pools formed by gravel bars, rock outcrops, and low diver­sion dams. Photographs of the river at several sites in the study area duringthe investigations are shown in Figures 1 and 2.

Method of Analysis

For both the water-delivery and low-flow studies, water losses or gainsbetween sites usually were determined by differences in measured discharge. Theflow released from Red Bluff Reservoir during the study in February and March1964 was constant; and during the low-flow study in May 1965, no tributarieswere flowing and no water was released from the reservoir. Therefore, differ­ences in the measured discharges represent the net gains or losses throughoutthe study reach.

Total water losses, in acre-feet, between the gaging station on the PecosRiver near Orla (mile 14.3) and Pecos River near Girvin (mile 188.4) were deter­mined from streamflow records for February and March 1964. Also, the water lostbetween Red Bluff Dam near Drla (mile 0) and the Girvin station (mile 188.4)was determined by the salt-dilution method of measuring water discharge. Fromthe composition of the mixture of water at Girvin and the known rate of flow,and the known composition of the salt inflow, the water loss and the rate ofsalt inflow was computed by using simultaneous algebraic equations.

During the low-flow study of May 10-12, 1965, the continuous records offlow at the gaging stations, Pecos River near OrIa (mile 14.3) and Pecos Rivernear Girvin (mile 188.4), indicated that the flow was constant.

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A. View upstream toward stream-gaging station,Pecos River near Oria (mile 14.3)

B. Pecos River downstream fr~ Grandfalls-Big Valleydiversion dam (mile 93.6)

C. Pecos River at stream-gaging station near Girvin(mile 188.4)

Figure

Sites Along the Pecos River, March 1964

us Geologlcol Surveyand the

In cooperaTion wllh the Tuas Waler Development Boord

Red Bluff Waler Power ConlTol Dlslrlct

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A. View upstream toward stream-gaging station,Pecos River near Orla (mile 14.3)

B. View upstream toward Reeves County W.I.D. No.2dam near Mentone (mile 43.4)

C. View downstream from bridge on State Highway 18near Grandfalls (mile 127.4)

Figure 2

Sites Along the Pecos River I May 1965

u.s Geologicol Survey in

and the Red

cooperation with the Teltos Woler Development

Bluff Woler Power Control District

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Boord

GENERAL GEOLOGY

The study area is a part of the Pecos Plains and Toyah Basin. Alluvium ofCenozoic age is at the surface in most of the study area and unconformably over­lies rocks ranging from the Rustler Formation of the Ochoa Series of Late Per­mian age to rocks of the Gulf Series of Late Cretaceous age. Rocks ranging inage from Permian to Recent crop out in small areas on both sides of the PecosRiver. The Cenozoic alluvium consists of unconsolidated to partially consoli­dated sand, silt, gravel, boulders, clay, gypsum, and caliche. This alluviumis the principal aquifer in Reeves and northern Pecos Counties and is heavilypumped for irrigation in the vicinity of Pecos and Coyanosa.

HYDROLOGY

Discharge was measured and samples f9r chemical analyses were collectedMarch 3-5, 1964, at 22 sites in the study reach. The results of water dis­charge measurements and chloride concentrations are given in Table 1, and chem­ical analyses of samples from 10 of these sites are shown in Table 3. Thesedata, which are also shown graphically on Figure 3, show changes in chemicalquality and gains and losses of flow throughout the reach during the periodMarch 3-5, 1964. The flood wave, but not the actual water (as determined bychemical analysis) released from Red Bluff Reservoir, had reached the lower endof the reach (below site 18) at the time samples were collected on March 4-5,1964. Because the chemical analyses of water samples obtained below site 18(mile 105.8) were not representative of the released water they are not includedin Table 3.

Discharge was measured and samples for chemical analyses were collectedMay 10-12, 1965, at 26 sites in the study reach. The results of water dischargemeasurements and chloride concentrations are given in Table 2, and chemicalanalyses are shown in Table 3. These data, which are also shown graphicallyon Figure 4, show changes in chemical quality and gains and losses of flowthroughout the reach during the study period.

The study reach has been subdivided where significant changes in water dis­charge and chemical quality occurred.

Reach From Red Bluff Reservoir ~iile 0)To Pecos (Mile 71.8)

Water-Delivery Study

The river channel from Red Bluff Reservoir to Pecos is about 60 feet wide,and the channel bed is sand and gravel. Throughout this reach of the river,salt-cedar growth is very heavy along the low banks and in the flood plain.These water-loving plants have a potential ability to consume as much as 5 acre­feet of water per acre per year (Pecos River Commission, 1955, p. 8). Duringthe period March 3-5, 1964, the plants were dormant and probably consumed nostreamflow. During the period May 10-12, 1965, the plants were in full leafand the quantity of water consumed was probably large.

Before the development of irrigation wells in Reeves County, whose north­eastern boundary is the Pecos River, ground water moved toward the Pecos River

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along most of the reach between Red Bluff Reservoir and the eastern corner ofReeves County. Hydrologic studies conducted in 1918 (Grover, Gray, and Ells­worth, 1922, p. 103) indicated that during periods of little or no rainfall theflow of the Pecos River increased about 30 cfs between Red Bluff Reservoir andthe eastern corner of Reeves County. Ground-water studies in 1958-59 (Ogilbee,Wesselman, and Irelan, 1962, v. 1, p. 33) indicated that little or no groundwater was discharged from the Reeves County side of the Pecos River from a pointabout 15 miles north-northwest of Pecos to a point 7 miles east of Pecos. In1918, part of this reach was also a losing reach. Along this reach in the cen­tral part of the county the water table has been lowered by the withdrawals ofground water for irrigation, and the water table slopes away from, rather thantoward, the river.

During the water-delivery study, the released water was measured on March3, 1964, about 1,500 feet downstream from the dam (site 2, mile 0.35). Theamount measured (129 cfs) includes all of. the released water and seepage fromthe reservoir. The chloride concentration of the water at this site was 2,950ppm (parts per million). An inflow of 0.17 cfs was measured from Salt (Screw­bean) Draw (site 3, mile 2.9). This flow was saline and had a chloride concen­tration of 6,430 ppm. The measured flow at the recording stream-gaging station,Pecos River near Or1a at mile 14.3 (site 4), was 124 cfs. In the first 14.3miles of the river there was a loss in discharge of 5.2 cfs (0.36 cfs per mile),and an increase in chloride concentration from 2,950 ppm to 2,990 ppm. Flowhad been constant in this reach of the river since February 21, 1964, and thebanks should have been well saturated with water. Thus the loss must be attrib­uted to water entering the alluvium and not returning to the river.

The next measurement of flow was made at mile 43.4 (site 6) just downstreamfrom Reeves County W.I.D. No.2 brush dam. This brush dam is capped with con­crete and is almost water tight. Seepage through the headgates to the canal was0.15 cfs. The discharge of the river below the dam was 110 cfs, or a loss indischarge of 13.8 cfs in the 29.1-mile reach between sites 4 and 6 (0.47 cfs permile). The water quality changed very little between sites 4 and 6.

At mile 52.8 (site 8), a short distance downstream from Ward County W.I.D.No.3 dam (site 7, mile 52.6), the discharge was 102 cfs. No water was divertedat the dam and no other diversions or inflow were found between sites 6 and 8.The channel loss was 0.85 cfs per mile between these sites and the water qualityremained unchanged.

The discharge of the Pecos River at Pecos (site 11, mile 71.8) was 77.6cfs, a loss of 24.4 cfs between sites 8 and 11. Seepage into Ward County Irri­gation District No.1 canal (site 9, mile 61.0) was 0.3 cfs. The water lost inthe 19.0 miles of river channel between sites 8 and 11 was 1.27 cfs per mile,the highest loss rate measured. The chloride concentration increased from 2,990to 3,180 ppm between sites 8 and 11.

During the period March 3-5, 1964, in the 71.8-mile reach of river betweenRed Bluff Reservoir and the fonner gaging station on the Pecos River at Pecos,the total loss of flow was about 51 cfs, or 40 percent of the discharge (129cfs) measured 1,500 feet downstream from the reservoir.

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Low-Flow Study

During the investigation of May 10-12, 1965, the Pecos River had a flow of2.58 cfs and a chloride concentration of 5,970 ppm about 1,500 feet downstreamfrom the dam (site 2, mile 0.35). This flow was seepage from the reservoir andleakage through the gates. Salt (Screwbean) Draw (site 3, mile 2.9) was notflowing. The measured flow at the gaging station, Pecos River near Orla (site4, mile 14.3), was 0.39 cfs. The water lost between Red Bluff Dam (mile 0) andthe Orla station (mile 14.3) was 0.15 cfs per mile. Chloride concentrationincreased from 5,970 to 7,710 ppm.

The river was dry between Reeves County W.LD. No.2 brush dam (site 5,mile 43.3) and Pecos (site 11, mile 71.8).

Prior to the investigation in May 1965, there had been no releases from thereservoir or surface runoff for at least 30 days; therefore, the loss in flowis attributed to seepage into the alluvium and to evapotranspiration (the saltcedars, which consume large quantities of water, were in full leaf at thistime).

Reach From Pecos Q1i1e 71.8) to State Highway 18Near 'Grandfalls (Mile 127.4)

Water-Delivery Study

Ground-water studies in 1958 (Armstrong and McMillion, 1961) indicated thatthe ground-water table was sloping towards the Pecos River in the Coyanosa Drawarea of Pecos County. However, the gradient at that time was very low and heavypumping for irrigation in recent years has probably reversed the gradient insome areas so that water is now being lost from the Pecos River into the Ceno~

zoic alluvium along most of the reach between Pecos and Grandfalls.

During the period March 3-5, 1964, there was an apparent increase in flowof 2.6 cfs between the former gaging station, Pecos River at Pecos (site 11,mile 71.8), and Grandfalls~Big Valley Diversion Dam (site 16, mile 93.6). Novisible inflow from creeks or return flow from irrigated lands entered theriver. The apparent increase in flow is attributed to accretion of water fromthe river alluvium.

An abandoned oil well (site 14, mile 93.0), known locally as "The RiverWell," was discharging about 0.08 cfs of saline water (6,820 ppm chloride) onMarch 5, 1964. The flow follows a small draw about 1,000 feet to the river.On March 5, 1964, all of the flow from this well was going into the groundbefore it reached the river, but probably reached the river as ground-watereffluent.

On March 4, 1964, the flow decreased from 80.2 cfs at site 16 (mile 93.6)to 74.2 cfs, below the Pecos County W.I.D. No.2 (upper diversion) canal (site18, mile 105.8). Outflow from the river to the canal was 1.8 cfs. Thisdecrease in discharge was accompanied by a small increase in the chloride con­centration. The increase in chloride concentration from 3,180 ppm at site 11to 3,280 at site 18 probably resulted from the mixing of release water with themore saline water from pools in the reach and pickup of soluble salts from thechannel.

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On March 4, 1964, between site 18 (mile 105.8) and the bridge on StateHighway 18 near Grandfalls (site 21, mile 127.4), there was a loss in dischargeof 13.6 cfs. Because of the possibility that the maximum flow of water releasedfrom Red Bluff Reservoir had not reached site 21 at the time of measurement the,actual loss in the reach is uncertain. A discharge of 60.6 cfs at State Highway18 near Grandfalls was the lowest discharge measured on the Pecos River duringthe water-delivery study.

At State Highway 18, which is below all diversions for irrigation from thePecos River in this area, the total measured loss between Red Bluff Reservoirand this site was 68.4 cfs, or 53 percent of the amount released. There wassome ground-water inflow to the river between Pecos and State Highway 18 asshown by the investigation in May 1965; therefore, the loss of water releasedfrom Red Bluff Reservoir may have been greater than indicated by measurementsmade in March 1964.

Low-Flow Study

During the investigation of May 10-12, 1965, the flow increased from zeroat Pecos River at Pecos (site II, mile 71.8) to 3.18 cfs 0.1 mile downstreamfrom Toyah Creek (site 13, mile 86.4), which was not flowing, and then decreasedto 1.99 cfs below Grandfalls-Big Valley Diversion Dam (site 16, mile 93.6). Thechloride concentration was 7,020 ppm at site 13 and increased to 7,910 ppm atsite 16.

The flow decreased from 1.99 cfs to zero in the reach of river from site16 to site 18 (mile 93.6 to mile 105.8) on May 11, 1965, with no diversion toPecos County W.I.D. No.2 (upper diversion) canal (site 17, mile 105.6). Therewas some seepage (0.1 gallon per minute) between pools in the river below theupper diversion dam.

On May II, 1965, the flow increased from zero just below Pecos CountyW.I.D. No.2 (upper diversion) dam (site 18, mile 105.8) to 0.99 cfs at thebridge on Farm Road 1776 near Grandfalls (site 20, mile 114.3), and increasedto 1.59 cfs at the bridge on State Highway 18 near Grandfalls (site 21, mile127.4). The inflow between these latter two sites was highly saline, as evi­denced by the chloride concentration of 7,910 ppm at site 20 and 16,300 ppm atsite 21. The inflow of 0.6 cfs between these two sites had to have an averagechloride concentration of 30,150 ppm to account for this increase. The sourceof the very saline inflow in this reach is unknown but may be associated withoil production in the area (see oil well in channel, Figure 2).

Reach From State Highway 18 Near Grandfalls (Mile 127.4)To Girvin (Mile 188.4)

Water-Delivery Study

During March 1964 the flow of the Pecos River was 66.2 cfs at the formergaging station, Pecos River below Grandfalls (site 22, mile 141.4), and 68.5cfs at the Farm Road 1053 bridge near Imperial (site 23, mile 150.2), and appar­ent gain of 2.3 cfs. No major ground-water irrigation occurs along this reachof the river, and the ground-water table slopes toward and intersects thechannel. Ground-water studies by Armstrong and McMillion (1961) in 1958 showed

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that the ground-water gradient was toward the river between State Highway 18 andFarm Road 1053. The elevation of the ground-water table where it intersects theriver is higher than the elevation of the river channel, and water would flowfrom the aquifer into the river.

The discharge at the stream-gaging station, Pecos River near Girvin (site26, mile 188.4) was measured on March 5, 1964. This discharge measurement andthose made at all sites below site 18 (mile 105.8) were made after the floodwave created by water released from Red Bluff Reservoir reached these sites,but before the actual water released from the reservoir arrived. The water mea­sured in this reach of the channel was in reality water displaced from channelpools. Chemical analyses indicate that water released from Red Bluff Reservoirdid not reach Girvin until March 9, 1964, and the mixture of releases and seep­age flows did not reach equilibrium until about March 13, 1964 (Figures 5 and6). The flow of the Pecos River near Girvin reached a maximum of 75 cfs onMarch 11, 1964, and continued at this rate until March 15, 1964.

The amount of water lost between Red Bluff Reservoir and Girvin was com­puted for the water-delivery study by using the salt-dilution method. The waterdischarges and chloride concentrations are related as follows:

(I) ql + q2 • q3

(2) qlcl + q2c2 : Q3c3

(3) qScl + q4c4 + Q2c2 - LCI - Oc l : Q3c3

Where: Ql - discharge in cfs of water from Red Bluff Reservoir that reachedGirvin station

ci : concentration of chloride in water released from Red Bluff Reser­voir (2,950 ppm)

Q2 = discharge in cfs of inflow between Red Bluff and Girvin

c2 = concentration of chloride in inflow water as determined at Girvinstation before water from Red Bluff Reservoir reached that station(7, sao ppm)

Q3 = maximum water discharge at Girvin (75 cfs)

c3 '" concentration of chloride in water at Girvin after released waterand seepage inflow reached equilibrium about March 13 (4,L20 ppm)

Q4 = discharge of Salt (Screwbean) Draw (0.17 cfs)

c4 - concentration of chloride in Q4 (6,430 ppm)

qs =discharge from Red Bluff Reservoir, including seepage (129 cfs)

L = reduction in peak rate of flow due to Losses, cis

o "" measured outflow (diversions) of released water (2.3 cis)

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Solving equations (1) and (2) simultaneously we get:

(2) ql (2,950 ppm) + q2 (7,500 ppm) = 75 cfs (4,120 ppm)

(1) ql (2,950 ppm) + q2 (2,950 ppm) = 75 cfs (2,950 ppm)

q2 (4,550 ppm) = 75 cfs (1,170 ppm)

q2 = 19.3 cfs inflow.

Then using the above value of q2 in equation (3):

129 (2,950) + 0.17 (6,430) + 19.3 (7,500) - L (2,950) - 2.3 (2,950)

• 75 (4,120)

L '" 71.4 cfs

Therefore, the constant discharge of 129 cfs released from Red Bluff Reservoirin February and March 1964 was reduced to 57.6 cfs at the Girvin Station, or areduction of 55 percent.

After the gates were closed on Red Bluff Reservoir on March 9, 1964, andbefore the released water passed the lower end of the study reach near Girvin,some surface runoff occurred at the lower end of the reach as a result of rainshowers on March 18-19, 1964. There was no effect on the flow hydrograph forPecos River near Orla, but surface runoff had to be el imina ted from the flow atPecos River near Girvin to obtain the total released flow passing the Girvingaging station. (See Figure 5.) The released water continued to drain out ofthe river until about March 29, 1964, when the flow at Girvin was back to 24cfs, which was the base flow at this station before the study began. The reduc­tion of the base flow from 24 cfs to the computed inflow of 19.3 cfs during thestudy is attributed to a damming or backwater effect on the effluent groundwa ter.

Low-Flow Study

The gain in flow in the reach between State Highway 18 (site 21, mile127.4) and Farm Road 1053 (site 23, mile 150.2) that was indicated by measure­ments made during the water-delivery study in March 1964 was verified by themeasurements made in May 1965. The flow increased from 1.59 cfs at the bridgeon State Highway 18 near Grandfalls to 4.90 cfs at the former gaging station,Pecos River below Grandfalls (site 22, mile 141.4), with a further increase to5.44 cfs at the bridge on Farm Road 1053 near Imperial.

Between State Highway 18 (site 21) and Pecos River below Grandfalls (site22), the chloride concentration of the water decreased from 16,300 to 7,220 ppm,indicating that about 3.31 cfs of better quality water (about 2,860 ppm chlo­ride) entered the river. The chloride concentration of the water increased to8,680 ppm at Farm Road 1053 near Imperial (site 23), indicating that the inflowbetween sites 22 and 23 contained a higher concentration of chloride than theinflow between sites 21 and 22.

- 10 -

During the investigation in May 1965 the flow increased from 5.44 cfs atthe bridge on Farm Road 1053 near Imperial (site 23, mile 150.2) to 5.75 cfs atthe former stream-gaging station, Pecos River near Buenavista (site 24, mile158.2). The largest increase in flow occured between this point and the PecosRiver at Horsehead Crossing near Girvin (site 25, mile 173.2) where the flowwas 11.2 cfs. The flow was apparently stable (11.2 to 11.5 cfs) from HorseheadCrossing to the lower end of the reach at Pecos River near Girvin (site 26,mile 188.4). No surface runoff occurred in the area during May 10-12, 1965, andthe increase in flow in the reach is attributed to effluent ground water.

Between Farm Road 1053 (site 23) and Horsehead Crossing (site 25) the flowincreased from 5.44 to 11.2 cfs, a gain in 5.76 cfs. In the same reach thechloride concentration decreased from 8,680 ppm to 8,290 ppm. The inflow of5.76 cfs thus had an average chloride concentration of 7,920 ppm. BetweenHorsehead Crossing and the station at Girvin the concentration remained con­stant.

WATER QUALITY AND USE

General

Extreme drouth conditions have prevailed in the Pecos valley since 1960.Inflow to Red Bluff Reservoir through 1965 consisted mainly of low flows withhigh salt concentrations. Therefore, the salt concentrations recorded duringthese investigations were not representative of average runoff conditions thatwould include flood inflow with a diluting effect causing the reservoir waterto be usable for irrigation. Salinity alleviation projects proposed by theBureau of Reclamation are estimated to reduce the average annual concentrationof dissolved solids in diverted water by 10 percent or more. The character ofthe water is predominantly calcium-sulfate and has been proven satisfactory forirrigation of free-draining soils.

Domestic

Drinking water used on common carriers in interstate traffic should notexceed limits of concentrations of dissolved constituents listed by the U.S.Public Health Service (1962). These standards are usually accepted as thebasis for determining the suitability of waters for municipal and domestic use.The recommended limits for chloride and sulfate concentrations are 250 ppm, andthe total dissolved solids should not exceed 500 ppm.

The saline water in Red Bluff Reservoir at the time of these investigationsgreatly exceeded these limits and was unsatisfactory for domestic use. The con­centrations of Red Bluff water in February 1964 and May 1965 were as follows:

February 1964 May 1965

Chloride 2,950 ppm 6,050 ppmSulfate 2,020 ppm 2,860 ppmDissolved sol ids 7,640 ppm 13,900 ppm

- 11 -

Waterha~.

3,270

with more than 180 ppm hardness (as calcium carbonate) is considered veryThe hardness of the Red Bluff water was 2,260 ppm in February 1964 and

ppm in May 1965.

The concentration of dissolved constituents of base flow of the PecosRiver at Girvin in February 1964 was about double the concentration of the RedBluff water.

Industrial

Saline waters, similar to the Red Bluff Reservoir water at the time of thisinvestigation, are highly corrosive, and when these waters are heated or evapo­rated, scale will form rapidly in pipes or other containers. Because of thesetwo characteristics, saline water is unsatisfactory for most industrial uses.

Irrigation

The U.S. Salinity Laboratory Staff (1954, p. 69) lists the total concen­tration of soluble salts and the relative proportion of sodium to the othercations as the two most important characteristics in determining water qualityfor irrigation. Based on standards of the Salinity Laboratory Staff, the RedBluff Reservoir water would be classified as having a very high sodium hazard.The salinity hazard of the water would be classified as very high; therefore,the Red Bluff Reservoir water at the time of this investigation was undesirablefor irrigation. However, the reservoir content has been held at low levelsfor the last few years so that any probable flood inflow could be retained.During years of above-average runoff the quality of water is better than whenthese studies were made.

SUMMARY AND CONCLUSIONS

During the period February 21 to March 9, 1964, the rate of release fromRed Bluff Reservoir, including the seepage, was 129 cfs as measured about 1,500feet downstream from the dam. The chloride concentration of the water at thissite was 2,950 ppm. In the 188.4 miles of river studied, there was only 2.27cfs of surface outflow (leakage into diversion canals). No other diversionsfrom the river are known. During this period 4,370 acre-feet of water passedthe stream-gaging station, Pecos River near Orla (mile 14.3), which is near theupper end of the reach. This included 0.17 cfs of saline water (6,430 ppm chlo­ride) from Salt (Screwbean) Draw near Orla (mile 2.9) and seepage flow (0.15cfs) from Red Bluff Reservoir measured at mile 0.05.

The released water, minus losses and plus base flow and surface runoff,passed the stream-gaging station, Pecos River near Girvin (mile 188.4), at thelower end of the reach during the period March 2-29, 1964. A total of 3,000acre-feet of water passed the gaging station during this period. This includedthe base flow (chloride concentration 7,500 ppm) and surface runoff of March17-21, 1964. Subtracting the base flow (1,165 acre-feet), which was computedfrom streamflow and quality-of-water records for Pecos River near Girvin, andthe surface runoff (75 acre-feet) between Pecos and Girvin, from the watermeasured at the Girvin gaging station leaves 1,760 acre-feet. This remainderis the quantity of released water that passed the lower end of the reach.

- 12 -

The total diversions during this investigation were 2.27 cfs. The diver­sion rate was constant during the period March 2-29, 1964, and a total of 130acre-feet was diverted from the river.

In summation, of the 4,370 acre-feet of water passing the stream-gagingstation Pecos River near Orla (mile 14.3), 130 acre-feet was diverted from theriver, and 1,760 acre-feet passed the stream-gaging station Pecos River nearGirvin (mile 188.4), The difference, 2,480 acre-feet, is 57 percent of thewater measured at Pecos River near Orla. The water was lost to ground-wateraquifers, evaporated, or transpired in the 174.1 miles between the stationsnear Orla and near Girvin. Because the weather was cool and phreatophytes wererelatively dormant in February and March, most of the loss was to ground-wateraquifers.

During the low-flow study of May 10-12, 1965, the flow in the Pecos River1,500 feet downstream from Red Bluff Reservoir was 2.58 cfs, which was seepagefrom the reservoir and leakage through the central gates at the dam. The chlo­ride concentration was 5,970 ppm. There was no inflow from Salt (Screwbean)Draw (mile 2.9). The flow in the river decreased to 0.39 cfs and the chlorideconcentration increased to 7,710 ppm at the gaging station Pecos River nearDrla (mile 14.3). The river was completely dry at the Reeves County W.I.D. No.2 dam (mile 43.3) and at the former gaging station Pecos River at Pecos (mile71.8). Between the Pecos station and Toyah Creek (mile 86.3) the river beganto flow again and had a flow of 3.18 cfs with a chloride concentration of 7,020ppm 0.1 mile downstream from Toyah Creek, which was not flowing. At PecosCounty W.I.D. No.2 (upper diversion) dam (mile 105.8) the river was dry. Belowthis site the flow began again and increased to 11.5 cfs at the gaging stationPecos River near Girvin (mile 188.4). In this same reach the chloride concen­tration decreased from 16,300 ppm (concentration at site 21, probably due toupstream oil-field pollution) to 8,290 ppm.

The water in Red Bluff Reservoir in March 1964 was of poor quality (2,950ppm chloride), and most of the ground-water inflow to the river was of poorerquality (7,500 ppm chloride). The reservoir water at this time was unsatisfac­tory for domestic use, unsatisfactory for most industrial uses, and undesirablefor irrigation. In May 1965 the water in Red Bluff Reservoir was even poorerin quality (6,050 ppm chloride). However, because of the prolonged dry periodpreceding these investigations, the quality of the water in Red Bluff Reservoirin March 1964 and May 1965 is not indicative of the quality to be expected dur­ing years of average or above-average runoff.

- 13 -

REFERENCES

Armstrong, C. A., and McMillion, L. G., 1961, Geology and ground-water resourcesof Pecos County, Texas: Texas Board Water Engineers Bull. 6106, v. I, 250 p.,12 figs., 15 pIs.

Grover, N. C., Gray, G. A., and Ellsworth, C. E., 1922, Surface water supply ofthe United States and Hawaii, pt. 8, Western Gulf of Mexico basins, 1918:U.S. Geol. Survey Water-Supply Paper 478, 106 p.

Ogilbee, William, Wesselman, J. B., and Irelan, Burdge, 1962, Geology andground-water resources of Reeves County, Texas: Texas Water Comm. Bull. 6214,v. I, 213 p., 10 figs., 13 pIs.

Pecos River Commission, 1955, Initial development, water salvage and salinityalleviation programs, Pecos River basin: 69 p., 2 figs., 13 pIs.

------1961, The Pecos River Commission of New Mexico and Texas, A report of adecade of progress, 1950-1960: 284 p., 10 figs., 12 pIs.

U.S. Public Health Service, 1962, Public Health Service drinking water stan­dards: U.S. Public Health Service Pub. 956, 61 p.

U.S. Salinity Laboratory Staff, 1954, Diagnosis and improvement of saline andalkali soils: U.S. Dept. Agriculture Handb. 60, 160 p.

- 14 -

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2

I

Based on sample

)collected March 13\_

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RIVER MILES DOWNSTREAM FADM RED BLUFF RESERVOIR

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Figure 3

Chloride Concentration and Water Discharge, Pecos River, March 3-5, 1964

u.s. GeoloQieol Survey in cooperotion with the Telos Waler Development Boord and the Red Bluff Woler Power Control O"lricl

20,000,--,--,-----,---,-----,--,-----,---,-----,---_, 20

18,000 f----+----+-----j----f-----f----+----+-----j----f-------j "

l----+----+-----j----f-----f----+-i~'"--+-----j----f-------j16,000 r 16

"Site ~umb..

EXPLANATION

~_ L---+----+-----j----f-----f----++---\--+-----j----f-----:: 14,000 r••••<Il IZ,OOO I------jj~:•

cz

14 8••~

-"'26 ~

/ ~~ 10,000 f-----I----__j---+---+---+----++---+lI----__j--/1--+---- 10 a~ ~0: vori~K!"oool/V 7"" ~/" ii . 'I~ 6,000 ~,f----__j----I_---+_---+---+-----1L---I_---f_---+----6 ~is 1 ~ 4 ;1< 23

4,OOOI-----t---t----t---t----t---t---fj----t---__j--- •

~ /\ ''''~HZ,OOO I\--+--+---I---!'--*+--+--.:;I----I---f---+--- 2

\ / ",,,,0'o~--~"_fr-;=-"'~~,:",''--_'L~'''--""L'--!::------;'C'\"'-'--~---c!::---~;;---~L.:_--__:! 0o 20 ~ W 00 100 IW I~ IW ~ ~

RIVER MILES DOWNSTREAM FROM RED BLUFF RESERVOIR

Figure 4

Concentration andChloride

Pecos River,

Water Discharge,

Moy 10-12, 1965

us GeoloQicol Survey in cooperation wIth the Tues Weter Development Boord

and the Red Blull Woler Power Control District

- 19 -

--

,, -

, _Poc•• ~i.... , n•• , 0.1.

,,,-

_ht•• II ,or ."", 1i,..I., ;-~----~ ----- ------ -- ---------<''. r,,- - , ,,

, ~- '1----i,~_'L...-' '".0"~ h" ...... '''''.'0' ....... \, ; "01'.""" II..' _ \, -".0" ' ...,

~-, ,"

,....._--------------- ----,

"--....-._------- --------------- - --------' -

"-,

, - , , , . , ~, , , , •., • , ., " " .. ",.

" " " " .. , , • , , , , , ," .. , .. ., ., " ., .,

" " .. ",.

",.

" .. .. " "fE8RUARO, 196_ "'R'~, In.

Figure 5

Hydrograph of Flow, Pecos River Near Orlo ond Pecos River Near Girvin,

February 15 10 March 31,1964us Geological Survey in coop.rallon WIlli the T'lOI Wol" DeYtlopmlnl Boord

and the R,d Bluif Water Power Conl,ol Dtst,w;:1

••.."•·00••~~•~ .'~•a·,.wt,~~.,•"; .

~

o

N~

UOOI II~ /\~T."oo / ~

,-,,", \,,Z ",'00

~ \ I'OC" RI ••••t., GI.. I. r--~.,.oo "V

'.'00 1'«0. AI •• , b.'.~ AU 81uH Oom .t., 0" ....

,"Dol , II' ~ I~ '7 " ,. ~ ,. " ., ,. ,. •• ,. n.. 2'.".... © ~,' " '" .6 ,. IS It ID " I' ., 2' ,. 2. ,. U 2. ~ "

FEBRUARY, ".. MARO., '964

Figure 6

Daily Chloride Concentrations, Pecos River Below Red Bluff Dam Near Orla and

Pecos River Near Girvin, February 15 to March 31,1964

U S Geolo'ilicol Survey 'n cooperalion With the Texas Waler Development Boord

and Ihe Red Bluff WeIer Power Control District