PreparedPrepared inin cooperationcooperation withwith thethe TexasTexas WaterWater DevelopmentDevelopment BoardBoard

TrendsTrends inin SelectedSelected StreamflowStreamflow StatisticsStatistics atat 1919 Long-TermLong-Term Streamflow-GagingStreamflow-Gaging StationsStations IndicativeIndicative ofof OutflowsOutflows fromfrom TexasTexas toto Arkansas,Arkansas, Louisiana,Louisiana, GalvestonGalveston Bay,Bay, andand thethe GulfGulf ofof Mexico,Mexico, 1922–20091922–2009

Scientific Investigations Report 2012–5182 Revised September 2012

U.S. Department of the Interior U.S. Geological Survey Background, Looking towards the right bank of the Sabine River during a flood measurement at stream- flow-gaging station 08030500 - Sabine River near Ruliff, , on October 23, 2006. Photograph by Doug McGhee, U.S. Geological Survey. Front cover: Left, Discharge measurement at streamflow-gaging station 08117500 - San Bernard River near Boling, Texas. Photograph by Mac Cherry, U.S. Geological Survey on April 1, 2007. Right, Gage shelter raised above 200-year flood-plain level at 08114000 - at Richmond, Texas, January 15, 2007. Photograph by Joe Stuart, U.S. Geological Survey. Back cover: Left, U.S. Geological Survey streamflow-gaging station 08475000 - near Brownsville, Texas, August 18, 2010. Photograph by Jaimie Ingold, U.S. Geological Survey. Right, Gage shelter and wire-weight gage at 08041000 - near Evadale, Texas. Photograph by Joe Stuart, November 17, 2006. Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows from Texas to Arkansas, Louisiana, , and the , 1922–2009

By Dana L. Barbie and Loren L. Wehmeyer

Prepared in cooperation with the Texas Water Development Board

Scientific Investigations Report 2012–5182 Revised September 2012

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director

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

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Suggested citation: Barbie, D.L., and Wehmeyer, L.L., 2012, Trends in selected streamflow statistics at 19 long-term streamflow-gaging stations indicative of outflows from Texas to Arkansas, Louisiana, Galveston Bay, and the Gulf of Mexico, 1922–2009: U.S. Geological Survey Scientific Investigations Report 2012–5182, 20 p. (Revised September 2012) iii

Contents

Abstract ...... 1 Introduction ...... 1 Purpose and Scope ...... 1 Description of Study Area ...... 3 Previous Studies ...... 3 Methods ...... 3 Trends in Selected Streamflow Statistics ...... 6 Outflows to Arkansas (Red and Basins) ...... 6 Outflows to Louisiana (Little Cypress Creek Basin) ...... 8 Outflows to Upper Coast Gulf of Mexico (Sabine and Neches River Basins) ...... 8 Outflows to Gulf of Mexico through Galveston Bay (Trinity and San Jacinto Rivers and Associated Creeks and Bayous) ...... 9 Outflows to Middle Coast Gulf of Mexico (Brazos, San Bernard, and Basins) ...... 13 Outflows to Lower Coast Gulf of Mexico (Guadalupe and Basins and Rio Grande Basin) ...... 16 Summary ...... 19 References ...... 20

Figures

1. Map showing basin boundaries for major rivers in Texas that outflow to Arkansas, Louisiana, Galveston Bay, and the Gulf of Mexico ...... 2 2. Map showing statistically-significant trends in the annual mean daily discharge for the period of record through 2009 for streamflow-gaging stations with more than 50 years of record indicative of outflows from Texas ...... 4 3. Graph showing annual mean daily discharge for the period of record through 2009 for U.S. Geological Survey streamflow-gaging station 07337000 Red River at Index, Arkansas ...... 7 4. Graph showing annual mean daily discharge for the period of record through 2009 for U.S. Geological Survey streamflow-gaging station 08041000 Neches River at Evadale, Texas ...... 10 5. Graph showing annual mean daily discharge for the period of record through 2009 for U.S. Geological Survey streamflow-gaging station 08066500 at Romayor, Texas ...... 12 6. Graph showing annual mean daily discharge for the period of record through 2009 for U.S. Geological Survey streamflow-gaging station 08073500 near Addicks, Texas ...... 14 7. Graph showing annual mean daily discharge for the period of record through 2009 for U.S. Geological Survey streamflow-gaging station 08076000 Greens Bayou near Houston, Texas ...... 15 8. Graph showing annual mean daily discharge for the period of record through 2009 for U.S. Geological Survey streamflow-gaging station 08475000 Rio Grande at Brownsville, Texas ...... 18 iv

Tables

1. Selected U.S. Geological Survey or International Boundary and Water Commission streamflow-gaging stations with more than 50 years of record that were used to assess trends in outflows from Texas to Arkansas, Louisiana, and the Gulf of Mexico ...... 5 2. Monotonic trends in outflows from the Red and Sulphur River Basins in Texas, 1937–2009 ...... 6 3. Monotonic trends in outflows from the Little Cypress Creek Basin in Texas, 1947–2009 ...... 8 4. Monotonic trends in outflows from the Sabine and Neches River Basins in Texas, 1925–2009 ...... 9 5. Monotonic trends in outflows from the Trinity and San Jacinto River Basins and associated creeks and bayous to Galveston Bay in Texas, 1925–2009 ...... 11 6. Monotonic trends in outflows from the Brazos, San Bernard, and Colorado River Basins in Texas, 1923–2009 ...... 16 7. Monotonic trends in outflows from the Guadalupe and Nueces River Basins, and the Rio Grande Basin in Texas, 1926–2009 ...... 17

Conversion Factors

Inch/Pound to SI

Multiply By To obtain Length mile (mi) 1.609 kilometer (km) Area square mile (mi2) 2.590 square kilometer (km2) Flow rate cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). A water year is the 12-month period October 1 through September 30 designated by the calendar year in which it ends. Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows from Texas to Arkansas, Louisiana, Galveston Bay, and the Gulf of Mexico, 1922–2009

By Dana L. Barbie and Loren L. Wehmeyer

Abstract Introduction

Trends in selected streamflow statistics during The major river basins in Texas include the Red River, 1922–2009 were evaluated at 19 long-term streamflow- Sabine River, Neches River, Trinity River, San Jacinto River, gaging stations considered indicative of outflows from Brazos River, Colorado River, , Texas to Arkansas, Louisiana, Galveston Bay, and the Gulf River, Nueces River, and the Rio Grande (fig. 1). The Red of Mexico. The U.S. Geological Survey, in cooperation River flows into Arkansas and then into Louisiana; one of with the Texas Water Development Board, evaluated its tributaries (Big Cypress Creek) flows directly from Texas streamflow data from streamflow-gaging stations with more into Louisiana. The Sabine, Neches, Brazos, San Bernard, than 50 years of record that were active as of 2009. The Colorado, Guadalupe, and Nueces Rivers and the Rio Grande outflows into Arkansas and Louisiana were represented by flow directly into the Gulf of Mexico. The Trinity and San 3 streamflow-gaging stations, and outflows into the Gulf Jacinto Rivers flow into Galveston Bay, which is part of the of Mexico, including Galveston Bay, were represented by Gulf of Mexico. Fresh surface-water usage in Texas is about 16 streamflow-gaging stations. Monotonic trend analyses two-thirds of the total freshwater usage in Texas (Kenny were done using the following three streamflow statistics and others, 2009, p. 6). As a result, studies of streamflow generated from daily mean values of streamflow: (1) annual statistics for outflows from Texas are useful in resource mean daily discharge, (2) annual maximum daily discharge, assessments, such as water-supply studies, as well as useful to and (3) annual minimum daily discharge. The trend analyses hydrologists, biologists, and ecologists. Accordingly, the U.S. were based on the nonparametric Kendall’s Tau test, which is Geological Survey (USGS), in cooperation with the Texas useful for the detection of monotonic upward or downward Water Development Board, evaluated streamflow data from trends with time. A total of 69 trend analyses by Kendall’s streamflow-gaging stations with more than 50 years of record Tau were computed—19 periods of streamflow multiplied by that were active as of 2009. the 3 streamflow statistics plus 12 additional trend analyses because the periods of record for 2 streamflow-gaging stations Purpose and Scope were divided into periods representing pre- and post-reservoir impoundment. Unless otherwise described, each trend analysis The purpose of this report is to assess monotonic trends used the entire period of record for each streamflow-gaging in streamflow to determine whether statistically significant station. The monotonic trend analysis detected 11 statistically monotonic changes in selected streamflow statistics have significant downward trends, 37 instances of no trend, and occurred over time for streamflow records likely indicative 21 statistically significant upward trends. One general region of outflows from Texas. Streamflow data were evaluated studied, which seemingly has relatively more upward trends and annual streamflow statistics were computed for 18 for many of the streamflow statistics analyzed, includes the selected USGS stations and one International Boundary rivers and associated creeks and bayous to Galveston Bay Water Commission (IBWC) station with more than 50 in the Houston metropolitan area. Lastly, the most western years of record and active as of 2009. Examination of river basins considered (the Nueces and Rio Grande) had historical patterns, cycles, and possible reasons for the statistically significant downward trends for many of the trends in streamflow such as trends in precipitation, changes streamflow statistics analyzed. in quantified water use, reservoir operation, or other 2 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows 90° Watershed boundary Watershed

EXPLANATION

LOUISIANA ARKANSAS

94° Galveston Bay Galveston

Sabine

Neches San Bernard

San Jacinto GULF OF MEXICO OF GULF

Trinity

Guadalupe

98° OKLAHOMA

Red San Antonio

Nueces 28°

Brazos 102°

TEXAS Colorado

NEW MEXICO 150 106° 100 200 MILES 15050

COLORADO Rio Grande 50 0 0 100 200 KILOMETERS 40° 36° Base from U.S. Geological Survey 1:2,000,000-scale digital data Albers equal-area projection North American Datum of 1983 32° asin boundaries for major rivers in Texas that outflow to Arkansas, Louisiana, Galveston Bay, and the Gulf of Mexico. that outflow to Arkansas, Louisiana, Galveston Bay, B asin boundaries for major rivers in Texas

Figure 1. Methods 3 human-related changes, or the effects of direct groundwater identification number consistent with USGS station numbers contributions (gains or losses) to streamflow was beyond the but is operated by the IBWC. Streamflow data collected at the scope of this study. Rio Grande station are published by the IBWC (International Boundary and Water Commission, 2012). The daily mean discharges for each station (365 to Description of Study Area 366 values per year) were used in the analyses. These data Streamflow outflow from Texas occurs in the eastern were subsequently converted to the annual streamflow part of the State. The locations of streamflow-gaging stations statistics of (1) annual mean daily discharge, (2) annual and selected reservoirs discussed in this report are shown in maximum daily discharge, and (3) annual minimum figure 2. daily discharge. The stations used for this study, along with ancillary The Kendall’s Tau statistical test was used to detect information pertaining to each station including the period monotonic trends in annual mean daily, annual maximum of record, are listed in table 1. Collectively, the stations daily, and annual minimum daily streamflow over time (Helsel discussed in this report monitor streamflow from Texas into and Hirsch, 2002). Specifically, the test uses the relation Arkansas, Louisiana, Galveston Bay (and subsequently the (trend) between time and ranked discharges as opposed to Gulf of Mexico), and the Gulf of Mexico directly. Outflow discharge magnitude. The trend analyses reported in this report trends to Arkansas were evaluated using two stations (table 1, thus refer to the direction and not the magnitude of streamflow Outflows to Arkansas). Outflow trends to Louisiana were change. A statistically significant positive Kendall’s Tau value evaluated using one station (table 1, Outflows to Louisiana). indicates an upward monotonic streamflow trend; conversely, Outflow trends to the Gulf of Mexico on the upper coast a statistically significant negative Tau indicates a downward (near Louisiana) were computed at two stations (table 1, monotonic streamflow trend. The probability value or p-value Outflows to upper coast Gulf of Mexico). Outflow trends to of Kendall’s Tau is a measure of the statistical significance of the Gulf of Mexico through Galveston Bay were computed the trend. For this study, a p-value of less than 0.05 indicates using eight stations (table 1, Outflows to Gulf of Mexico a statistically significant trend, whereas, a p-value of 0.05 or through Galveston Bay). Outflow trends to the Gulf of greater indicates no significant trend. Mexico on the middle coast were computed at three stations Annual mean daily discharge is computed as the average (table 1, Outflows to middle-coast Gulf of Mexico). Lastly, of all the 365 or 366 daily discharges during a water year (a outflow trends to the Gulf of Mexico on the lower coast were water year is defined as the 12-month period from October 1 computed at three stations (table 1, Outflows to lower-coast to September 30). The annual minimum daily discharge is Gulf of Mexico). the discharge on the day of lowest daily mean discharge in a given water year. The annual maximum daily discharge is the discharge on the day of largest daily mean discharge in a given Previous Studies water year. The software package Statistica (StatSoft, 2009) was used to calculate the Kendall’s Tau test statistic. For each Several statistical and historical summaries of streamflow station, Kendall’s Tau statistics were computed using the three data in Texas have previously been done by the USGS streamflow statistics calculated for each station (annual mean, (Asquith and others, 2007a, 2007b; Asquith and Heitmuller, maximum, and minimum daily streamflow). The period of 2008). Lanning-Rush (2000) also provided regional regression records evaluated for each station is listed in table 1. equations to estimate mean annual discharge (the arithmetic A total of 69 trend analyses by Kendall’s Tau were mean of the annual mean discharges) as well as mean seasonal computed—19 periods of streamflow from USGS or discharge for unmonitored stream sites throughout Texas. IBWC stations multiplied by 3 streamflow statistics plus 12 Lastly, Asquith (2001) did a statewide study on the effects additional trend analyses because the periods of record for of flood-control regulation on statistics of annual peak 2 USGS stations were analyzed for trends pre- and post- streamflow time series for hundreds of streamflow-gaging reservoir impoundment, resulting in 4 periods of streamflow stations in Texas. multiplied by 3 streamflow statistics. The period of post- reservoir impoundment was defined as when at least 10 percent of contributing drainage area was regulated. Unless Methods otherwise indicated, each trend analysis used the entire period of record for each station. Some additional remarks concerning Streamflow data were evaluated and annual streamflow methods and decisions made for the presentation of the trend statistics were computed for 19 streamflow-gaging stations analysis results are required. There are many stations with consisting of 18 USGS stations and 1 IBWC station with more one or more upstream reservoirs. However, for circumstances than 50 years of record and active since 2009. Streamflow data in which there were no changes in streamflow trends pre- or used in this study are published in the USGS National Water post-reservoir impoundment, the entire period of record was Information System (U.S. Geological Survey, 2012a) with used for the trend analysis. Also, there are circumstances in the exception of the streamflow data for the Rio Grande near which a reservoir was impounded near the beginning of the Brownsville, Tex., station that is assigned an eight-digit station streamflow record—leaving perhaps only a few years prior to 4 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows

98° OKLAHOMA Lake Texoma 96° d River 34° Re TEXAS Index 07337000 #" 07343200 S # ulph " ur River Talco Jim Ellison Creek Reservoir Chapman ARKANSAS T Cypre r ig ss Possum in Lake B Lake O’ i Cre t ek LOUISIANA Kindgom y the Pines Little Lake Lake River Cypress #" Worth Lake Creek Jefferson Tawakoni Sab 07346070 ine R iver

Lake Lake 94° Halbert Palestine Atto Red River Lake N ya c 32° e Whitney c B Toledo Bend Richland-Chambers h a e y s o Reservoir Reservoir R u iv er B Sam Rayburn Waco ra Reservoir Colo z ra o do Lake s

R East Fork i R v i e v San Jacinto River r e Lake r

Livingston r

West Fork B A Steinhagen e v i San Jacinto River Lake R

e n i See inset b a S Lake #" Evadale #" #08030500 " #" " Travis # # " 08041000 Ruliff Town Lake #" " Sabine 30° Guadal Canyon # upe San Lake M Lake Be R r " ed n # in i a R v a e rd Houston i r v #" e r R West Fork San Jacinto River i v S E e r a a #" # n s t Wharton " 08117500 Sa Lake J F Romayor n Caney a A 08162000 Boling c o " r # n Conroe i 08066500 t n k o t ni o Cleveland o R #" i Conroe 08070500 R v " i e Creek v 08070000 r # e F Victoria 08068000# r #" "r Splendora i 08068500 o Coleto Creek Sp T R Choke Canyon 08176500 r k r in e i i Reservoir g re # n ve C C Westfield Reservoir y Spring i r p " t r # y e 08069000 " Nuec s Greens Lake R e s reek i s C v Lake Corpus Bayou R # Houston e i r v Christi e Addicks Reservoir r 08076000 " Addicks Buffalo Bay # Mathis "# o u 28° Barker Reservoir 08211000 08073500 Braz Houston Galveston os R # iv Bay " er 08114000 Richmond GULF OF MEXICO

R

i o

R G i EXPLANATION ARKANSAS o r

B a

r n a d # U.S. Geological Survey OKLAHOMA v e NEW MEXICO o 08162000 streamflow-gaging station Falcon Reservoir and station number UNITED LOUISIANA STATES TEXAS Upward trend MEXICO UN ITE Downward trend D MEXICOSTA TE GULF OF S MEXICO 26° #" Brownsville 0 25 50 75 100 MILES Area enlarged Base from U.S. Geological Survey 08475000 1:100,000-scale digital data Albers equal-area projection 025 50 75 100 KILOMETERS North American Datum of 1983

Figure 2. Statistically-significant trends in the annual mean daily discharge for the period of record through 2009 for streamflow- gaging stations with more than 50 years of record indicative of outflows from Texas. Methods 5

Table 1. Selected U.S. Geological Survey or International Boundary and Water Commission streamflow-gaging stations with more than 50 years of record that were used to assess trends in outflows from Texas to Arkansas, Louisiana, and the Gulf of Mexico.

[mi; square miles; --, not applicable]

Year of first Contributing Latitude Longitude Drainage Station Period of substantial drainage Station name (decimal (decimal area number record1 reservoir area degrees) degrees) (mi2) impoundment2 (mi2) Outflows to Arkansas (Red and Sulphur River Basins—table 2) 07337000 Red River at Index, Ark. 1937–2009 1943 33.55207 94.04130 48,030 42,094 07343200 Sulphur River near Talco, Tex. 1957–2009 1991 33.39067 95.06244 1,405 1,405 Outflows to Louisiana (Little Cypress Creek Basin—table 3) 07346070 Little Cypress Creek near 1947–2009 -- 32.71292 94.34603 675 675 Jefferson, Tex. Outflows to the upper coast of the Gulf of Mexico (Sabine and Neches River Basins—table 4) 08030500 Sabine River near Ruliff, Tex. 1925–2009 1961 30.30382 93.74378 9,329 9,329 08041000 Neches River at Evadale, Tex. 1922–2009 1951 30.35576 94.09324 7,951 7,951 Outflows to the Gulf of Mexico through Galveston Bay (Trinity and San Jacinto River Basins, and Associated Creeks and Bayous—table 5) 08066500 Trinity River at Romayor, Tex. 1925–2009 before 1925 30.42521 94.85076 17,186 17,186 08068000 West Fork San Jacinto River near 1940–2009 1973 30.24466 95.45716 828 828 Conroe, Tex. 08068500 Spring Creek near Spring, Tex. 1940–2009 -- 30.11050 95.43633 409 409 08069000 Cypress Creek near Westfield, Tex. 1945–2009 -- 30.03578 95.42883 285 285 08070000 East Fork San Jacinto River near 1940–2009 -- 30.33660 95.10410 325 325 Cleveland, Tex. 08070500 Caney Creek near Splendora, Tex. 1945–2009 -- 30.25966 95.30244 105 105 08073500 Buffalo Bayou near Addicks, Tex. 1946–2009 before 1946 29.76190 95.60578 277 277 08076000 Greens Bayou near Houston, Tex. 1953–2009 -- 29.91828 95.30688 69 69 Outflows to the middle coast of the Gulf of Mexico (Brazos, Sen Bernard, and Colorado River Basins—table 6) 08114000 Brazos River at Richmond, Tex. 1923–2009 1941 29.58246 95.75773 45,107 35,541 08117500 San Bernard River near Boling, Tex. 1955–2009 -- 29.31358 95.89384 727 727 08162000 Colorado River at Wharton, Tex. 1939–2009 before 1939 29.30914 96.10385 42,003 30,600 Outflows to the lower coast of the Gulf of Mexico (Guadalupe and Nueces River Basins, and Rio Grande Basin—table 7) 08176500 Guadalupe River at Victoria, Tex. 1936–2009 before 1936 28.79305 97.01304 5,198 5,198 08211000 Nueces River near Mathis, Tex. 1940–2009 before 1940 28.03835 97.86028 16,503 16,503 08475000 Rio Grande near Brownsville, Tex.3 1935–2009 1953 25.87675 97.45443 176,333 176,333

1Period of record is shown in water years; a water year is defined as the 12-month period October 1 through September 30 designated by the calendar year in which it ends. 2Year reservoir impoundment first appreciably affected streamflow (Dowell, 1964). 3Station operated by the International Boundary and Water Commission. All other stations are operated by the U.S. Geological Survey. impoundment—for this study, the entire period of record was this year predates the activation of the station, for example used for the trend analysis. Lastly, time series plots of annual USGS streamflow-gaging station 082111000 Nueces River mean daily discharge for six selected stations are provided near Mathis, Tex. However, for two stations, where the period to illustrate this streamflow statistic. Similar plots to the of record was sufficient and the effect of impoundment on time series figures introduced later can be readily generated streamflow characteristics was evident (USGS streamflow- through the USGS National Water Information System Web gaging station 08041000 Neches River at Evadale, Tex., and (NWISWeb) Internet portal (http://waterdata.usgs.gov). IBWC streamflow-gaging station 08475000 Rio Grande Table 1 lists the year of the first large reservoir near Brownsville, Tex.), the streamflow record was divided impoundment upstream from the station. For several stations, into pre- and post-impoundment periods. Trend analysis 6 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows subsequently was performed for the entire period of record, outflow volumes from the two most westerly stations on the including the years before reservoir impoundment. Nueces River and Rio Grande show downward trends.

Trends in Selected Streamflow Outflows to Arkansas (Red and Sulphur River Basins) Statistics Streamflows at USGS streamflow-gaging stations This section is divided into six subsections that 07337000 Red River at Index, Ark. (Red River at Index correspond to logical and convenient groupings of stations. station), and 07343200 Sulphur River near Talco, Tex. Each section provides salient but limited background, (Sulphur River near Talco station), are indicative of outflow summarizes the stations involved, and concludes with from Texas to Arkansas. After exiting Texas and flowing reporting of the analysis to detect monotonic trends for each of through the southwest corner of Arkansas, the Sulphur River the three streamflow statistics. flows into the Red River in Louisiana. For the overall assessment in trends in selected The Red River at Index station is located at the Texas- streamflow statistics during 1922–2009 at 19 long-term Arkansas State boundary in far northeast Texas and is more streamflow-gaging stations considered indicative of outflows than 500 miles downstream from the Red River’s headwaters from Texas to Arkansas, Louisiana, Galveston Bay, and in New Mexico. The Red River Basin upstream from the Red the Gulf of Mexico, monotonic trend analysis detected River at Index station includes parts of New Mexico, Texas, 11 statistically significant downward trends, 37 instances of and Oklahoma. A particularly important reservoir in terms of no trend, and 21 statistically significant upward trends. Annual its effect on regulating flow in the Red River is Lake Texoma mean daily discharge is especially diagnostic because this on the Texas–Oklahoma border. Since 1944, Lake Texoma, statistic can be used to compute mean annual discharge over which is about 241 miles upstream from Index, Ark., has long periods of time and represents the expectation of the potentially affected general streamflow characteristics at the annual volume of water measured by a station and, therefore, Red River at Index station (Dowell, 1964; U.S. Geological water yields from a basin. Trends in annual mean daily Survey, 2012b). The time period analyzed for this study is discharge can be summarized as follows; (1) annual outflow 1937–2009 (table 2), which includes a few years prior to volumes from Texas into Arkansas and Louisiana as well completion of Lake Texoma. A downward trend for annual as the Gulf of Mexico (upper Texas coast) lack statistically maximum daily discharge was detected at this station. A significant trends; (2) annual inflows into Galveston Bay time series of the annual mean daily discharge is shown in (Houston metropolitan area) show upward trends for four of figure 3. eight stations; (3) annual outflow volumes from the Brazos The Sulphur River near the Talco station is 2.8 miles River (east of Houston metropolitan area) to the Guadalupe northeast of Talco, Tex. Jim Chapman Lake (fig. 2) was River lack statistically significant trends; and (4) annual impounded in 1991 and has potentially affected streamflow

Table 2. Monotonic trends in outflows from the Red and Sulphur River Basins in Texas, 1937–2009.

[USGS, U.S. Geological Survey; p-value, probability value; <, less than; --, no statistically significant trend was detected (p-value <0.05)]

USGS Time USGS station Streamflow statistic Kendall’s Trend station period p-value name (discharge) tau direction number analyzed

07337000 Red River at Index, Ark. 1937–2009 Annual mean daily 0.04 0.65 --

07337000 Red River at Index, Ark. 1937–2009 Annual maximum daily -0.25 <0.05 downward

07337000 Red River at Index, Ark. 1937–2009 Annual minimum daily 0.10 0.20 --

07343200 Sulphur River near Talco, Tex. 1957–2009 Annual mean daily -0.13 0.17 --

07343200 Sulphur River near Talco, Tex. 1957–2009 Annual maximum daily -0.18 0.054 --

07343200 Sulphur River near Talco, Tex. 1957–2009 Annual minimum daily 0.33 <0.05 upward

Trends in Selected Streamflow Statistics 7

2009

2007

2005

2003

2001 1999

EXPLANATION 1997

Annual mean daily discharge

1995

1993

1991

1989

1987

1985

1983

1981

1979

1977

1975

1973 1971

Water year

1969

1967

1965

1963

1961

1959

1957

1955

1953

1951

1949

1947

1945

Lake Texoma Texoma Lake Impoundment 1943

1941

1939 1937 A nnual mean daily discharge for the period of record through 2009 U.S. Geological Survey streamflow-gaging station 07337000 Red River at Index, Arkansas.

0

5,000

35,000 30,000 25,000 20,000 15,000 10,000 Discharge, in cubic feet per second per feet cubic in Discharge, Figure 3. 8 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows characteristics of the Sulphur River since its impoundment humid, subtropical climate (Larkin and Bomar, 1983). Three (U.S. Geological Survey, 2012b). The station is about principle reservoirs are Toledo Bend Reservoir on the Sabine 35 miles downstream from Jim Chapman Lake and about River (impounded in 1966), Sam Rayburn Reservoir on a 70 miles upstream from Texas-Louisiana State boundary. The tributary to the Neches River (impounded in 1965), and B.A. time period analyzed for this study is 1957–2009 (table 2). Steinhagen Lake on the Neches River (impounded in 1951) An upward trend for annual minimum daily discharge was (fig. 2); other reservoirs depicted on figure 2 include Lake detected at this station. Tawakoni on the Sabine River (impounded in 1960) and Lake Palestine on the Neches River (impounded in 1962) (Dowell, 1964; U.S. Geological Survey, 2012b). Outflows to Louisiana (Little Cypress USGS streamflow-gaging station 08030500 Sabine River Creek Basin) near Ruliff, Tex. (Sabine River near Ruliff station), is about 2 miles north of Ruliff and about 45 miles upstream from the Streamflow at USGS streamflow-gaging station mouth with that in turn drains into the Gulf of 07346070 Little Cypress Creek near Jefferson, Tex. (Little Mexico. This station is about 300 miles downstream from Cypress Creek station), is indicative of the unregulated the headwaters of the Sabine River. Streamflow in the Sabine contribution to outflows from Texas to Louisiana through Big River has been potentially affected by regulated outflows Cypress Creek, the only stream in Texas that flows directly from (fig. 2) since 1961 (Dowell, 1964; U.S. into Louisiana. Little Cypress Creek flows into the Big Geological Survey, 2012b). More importantly, the station is Cypress Creek, which flows into the Red River in Louisiana about 50 miles downstream from the relatively large Toledo (fig. 2). Little Cypress Creek streamflows were analyzed for Bend Reservoir. The time period analyzed was 1925–2009 trends because Big Cypress Creek has been highly regulated (table 4). An upward trend for annual minimum daily by Lake O’ the Pines after it was impounded in 1958 (Dowell, discharge was detected at this station. 1964; U.S. Geological Survey, 2012b). The streamflow in USGS streamflow-gaging station 08041000 Neches Little Cypress Creek can be considered reasonably natural. River at Evadale, Tex. (Neches River at Evadale station), is Most streams in Texas are affected by regulation, but Little about 200 miles downstream from the headwaters of the river Cypress Creek represents one of the few opportunities to and about 40 miles upstream from the mouth of the river. The analyze for trends in a reasonably natural stream. mouth of the Neches River empties into Sabine Lake, which The Little Cypress Creek station is 3.5 miles south of drains into the Gulf of Mexico. Since 1951, streamflow in Jefferson, Tex. The station is about 65 miles downstream from the Neches River has been appreciably regulated by B.A. the headwaters of Little Cypress Creek and about 7 miles Steinhagen Lake, which is about 32 miles upstream from the upstream from Big Cypress Creek. The time period analyzed Neches River at Evadale station. The Sam Rayburn Reservoir for this study is 1947–2009 (table 3). No trends were detected on the Angelina River, a major tributary of the Neches River, in streamflow at this station. is about 15 miles upstream from B.A. Steinhagen Lake (fig. 2), and has affected streamflow along the lower Neches River since 1965 (Dowell, 1964; U.S. Geological Survey, 2012b). Outflows to Upper Coast Gulf of Mexico (Sabine A time series of the annual mean daily discharge is shown and Neches River Basins) in figure 4 and includes the timing of impoundment by B.A. Steinhagen Lake and Sam Rayburn Reservoir. A distinction The Sabine and Neches Rivers flow directly into the Gulf of pre- and post-regulation at 1950 and 1951, respectively, of Mexico along the upper coastline of Texas. The two river is made for this analysis. The time periods analyzed for this basins drain the heavily forested east Texas region noted for its study were 1922–2009, 1922–50, and 1951–2009 (table 4).

Table 3. Monotonic trends in outflows from the Little Cypress Creek Basin in Texas, 1947–2009.

[USGS, U.S. Geological Survey; p-value, probability value; <, less than; --, no statistically significant trend was detected (p-value <0.05)]

USGS Time Streamflow USGS station Kendall’s Trend station period statistic p-value name tau direction number analyzed (discharge)

07346070 Little Cypress Creek near Jefferson, Tex. 1947–2009 Annual mean daily 0.02 0.82 --

07346070 Little Cypress Creek near Jefferson, Tex. 1947–2009 Annual maximum daily 0.01 0.88 --

07346070 Little Cypress Creek near Jefferson, Tex. 1947–2009 Annual minimum daily 0.12 0.18 -- Trends in Selected Streamflow Statistics 9

Table 4. Monotonic trends in outflows from the Sabine and Neches River Basins in Texas, 1925–2009.

[USGS, U.S. Geological Survey; p-value, probability value; <, less than; --, no statistically significant trend was detected (p-value <0.05)]

USGS Time period Streamflow statistic Kendall’s Trend station USGS station name p-value analyzed (discharge) tau direction number

08030500 Sabine River near Ruliff, Tex. 1925–2009 Annual mean daily -0.02 0.79 --

08030500 Sabine River near Ruliff, Tex. 1925–2009 Annual maximum daily -0.05 0.49 --

08030500 Sabine River near Ruliff, Tex. 1925–2009 Annual minimum daily 0.29 <0.05 upward

08041000 Neches River at Evadale, Tex. 1922–2009 Annual mean daily 0.0005 1.0 --

08041000 Neches River at Evadale, Tex. 1922–2009 Annual maximum daily -0.16 <0.05 downward

08041000 Neches River at Evadale, Tex. 1922–2009 Annual minimum daily 0.4 <0.05 upward

08041000 Neches River at Evadale, Tex. 1922–1950 Annual mean daily 0.06 0.65 --

08041000 Neches River at Evadale, Tex. 1922–1950 Annual maximum daily 0.02 0.85 --

08041000 Neches River at Evadale, Tex. 1922–1950 Annual minimum daily 0.14 0.27 --

08041000 Neches River at Evadale, Tex. 1951–2009 Annual mean daily 0.23 <0.05 upward

08041000 Neches River at Evadale, Tex. 1951–2009 Annual maximum daily 0.04 0.67 --

08041000 Neches River at Evadale, Tex. 1951–2009 Annual minimum daily 0.46 <0.05 upward

A downward trend for annual maximum daily discharge nearest the station (fig. 2) and was impounded in 1969 (U.S. and conversely an upward trend for annual minimum daily Geological Survey, 2012b). The time period analyzed for discharge were detected for Neches River at Evadale station the Trinity River at Romayor station is 1925–2009 (table 5). for the period 1922–2009 (period of record). No trends were In addition to Lake Livingston, there are other reservoirs detected for the Neches River at Evadale, Tex., station for the regulating flow on the Trinity River upstream from the period 1922–50; however, upward trends for annual mean Trinity River at Romayor station, including some that were daily and annual minimum daily discharge were detected for impounded as early as 1916 (Lake Worth) and 1921 (Lake the period 1951–2009. Halbert) (Texas Historical Association, 2012a, b; Dowell, 1964). An upward trend for annual minimum daily discharge Outflows to Gulf of Mexico through Galveston was detected at the Trinity River at Romayor station. A time Bay (Trinity and San Jacinto Rivers and series of the annual mean daily discharge is shown in figure 5. Associated Creeks and Bayous) San Jacinto River flows from Lake Houston into Galveston Bay. Major inflows into Lake Houston are West Galveston Bay is a large estuary on the Texas coast Fork San Jacinto River, Spring Creek, Cypress Creek, East and has substantial and varied sources of inflow. The Trinity Fork San Jacinto River, and Caney Creek. USGS streamflow- River, with its headwaters in north Texas adjacent to the Red gaging station 08068000 West Fork San Jacinto River near River Basin (fig. 1), is the largest tributary to the bay. The Conroe, Tex. (West Fork San Jacinto River near Conroe Trinity River is followed in size by the San Jacinto River and station), is about 4 miles south of Conroe. The station is about its associated tributaries in the Houston metropolitan area, 40 miles downstream from the headwaters of the river and including West Fork San Jacinto River, Spring Creek, Cypress about 10 miles downstream from Lake Conroe. Since 1973, Creek, East Fork San Jacinto River, Caney Creek, Buffalo Lake Conroe has potentially affected streamflow in the West Bayou, and Greens Bayou. Fork San Jacinto River (U.S. Geological Survey, 2012b). The USGS streamflow-gaging station 08066500 Trinity time period analyzed for this study is 1940–2009 (table 5). River at Romayor, Tex. (Trinity River at Romayor station), An upward trend for annual minimum daily discharge was is about 45 miles upstream from Galveston Bay and about detected at this station. 300 miles downstream from the headwaters of this river. USGS streamflow-gaging station 08068500 Spring Lake Livingston, about 20 miles upstream, is the reservoir Creek near Spring, Tex. (Spring Creek near Spring station),

10 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows

2010

2008

2006

2004

2002

2000

1998

1996

1994

1992

1990

1988

1986

1984

1982

1980

1978

1976

1974

1972

1970

1968 1966

Sam Rayburn Reservoir Impoundment

1964 1962

Water year 1960

1958

1956

1954 1952

B.A. Steinhagen Lake Impoundment

1950

1948

1946

1944

1942

1940

1938

1936

1934

1932

1930 1928

EXPLANATION

Annual mean daily discharge 1926

1924 1922 A nnual mean daily discharge for the period of record through 2009 U.S. Geological Survey streamflow-gaging station 08041000 Neches River at Evadale, Texas. 0

8,000 6,000 4,000 2,000

14,000 12,000 10,000 Discharge, in cubic feet per second per feet cubic in Discharge, Figure 4. Trends in Selected Streamflow Statistics 11

Table 5. Monotonic trends in outflows from the Trinity and San Jacinto River Basins and associated creeks and bayous to Galveston Bay in Texas, 1925–2009.

[USGS, U.S. Geological Survey; p-value, probability value; <, less than; --, no statistically significant trend was detected (p-value <0.05)]

USGS Time Streamflow statistic Kendall’s Trend station USGS station name period p-value (discharge) tau direction number analyzed 08066500 Trinity River at Romayor, Tex. 1925–2009 Annual mean daily 0.09 0.25 -- 08066500 Trinity River at Romayor, Tex. 1925–2009 Annual maximum daily 0.12 0.10 -- 08066500 Trinity River at Romayor, Tex. 1925–2009 Annual minimum daily 0.51 <0.05 upward 08068000 West Fork San Jacinto River near Conroe, Tex. 1940–2009 Annual mean daily 0.04 0.60 -- 08068000 West Fork San Jacinto River near Conroe, Tex. 1940–2009 Annual maximum daily -0.06 0.43 -- 08068000 West Fork San Jacinto River near Conroe, Tex. 1940–2009 Annual minimum daily 0.20 <0.05 upward 08068500 Spring Creek near Spring, Tex. 1940–2009 Annual mean daily 0.23 <0.05 upward 08068500 Spring Creek near Spring, Tex. 1940–2009 Annual maximum daily 0.10 0.23 -- 08068500 Spring Creek near Spring, Tex. 1940–2009 Annual minimum daily 0.25 <0.05 upward 08069000 Cypress Creek near Westfield, Tex. 1945–2009 Annual mean daily 0.29 <0.05 upward 08069000 Cypress Creek near Westfield, Tex. 1945–2009 Annual maximum daily 0.20 <0.05 upward 08069000 Cypress Creek near Westfield, Tex. 1945–2009 Annual minimum daily 0.74 <0.05 upward 08070000 East Fork San Jacinto River near Cleveland, Tex. 1940–2009 Annual mean daily 0.09 0.25 -- 08070000 East Fork San Jacinto River near Cleveland, Tex. 1940–2009 Annual maximum daily -0.01 0.88 -- 08070000 East Fork San Jacinto River near Cleveland, Tex. 1940–2009 Annual minimum daily 0.18 <0.05 upward 08070500 Caney Creek near Splendora, Tex. 1945–2009 Annual mean daily 0.16 0.053 -- 08070500 Caney Creek near Splendora, Tex. 1945–2009 Annual maximum daily 0.09 0.27 -- 08070500 Caney Creek near Splendora, Tex. 1945–2009 Annual minimum daily 0.18 <0.05 upward 08073500 Buffalo Bayou near Addicks, Tex. 1946–2009 Annual mean daily 0.34 <0.05 upward 08073500 Buffalo Bayou near Addicks, Tex. 1946–2009 Annual maximum daily -0.19 <0.05 downward 08073500 Buffalo Bayou near Addicks, Tex. 1946–2009 Annual minimum daily 0.69 <0.05 upward 08076000 Greens Bayou near Houston, Tex. 1953–2009 Annual mean daily 0.59 <0.05 upward 08076000 Greens Bayou near Houston, Tex. 1953–2009 Annual maximum daily 0.29 <0.05 upward 08076000 Greens Bayou near Houston, Tex. 1953–2009 Annual minimum daily 0.83 <0.05 upward

is about 2 miles northeast of Spring, Tex., and northwest of station), is about 2 miles northwest of Westfield. The station Houston. The station is about 50 miles downstream from the is about 55 miles downstream from the headwaters and about headwaters of this stream and about 15 miles upstream from 11 miles upstream from West Fork San Jacinto River. The Cypress Creek. Although development has been occurring in streamflow in Cypress Creek can be considered reasonably the Spring Creek watershed for several years, the streamflow natural (U.S. Geological Survey, 2012b). The time period in Spring Creek was considered reasonably natural for the analyzed for this study is 1945–2009 (table 5). Upward trends period of record analyzed because there are no documented in annual mean, maximum, and minimum daily discharges impoundments on Spring Creek (U.S. Geological Survey, were detected at this station. 2012b). The time period analyzed for this study is 1940–2009 USGS streamflow-gaging station 08070000 East Fork (table 5). Upward trends for annual mean daily and annual San Jacinto River near Cleveland, Tex. (East Fork San minimum daily discharges were detected at this station. Jacinto River near Cleveland station), is about 1 mile west USGS streamflow-gaging station 08069000 Cypress of Cleveland, Tex. The station is about 35 miles downstream Creek near Westfield, Tex. (Cypress Creek near Westfield from the headwaters of the river and 20 miles upstream from

12 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows

2009

2007

2005

2003

2001

1999 EXPLANATION 1997

Annual mean daily discharge

1995

1993

1991

1989

1987

1985

1983

1981

1979

1977

1975

1973

1971

1969

1967

1965 Water year

1963

1961

1959

1957

1955

1953

1951

1949

1947

1945

1943

1941

1939

1937

1935

1933

1931

1929 1927

Trinity River at Romayor, Texas. River at Romayor, A nnual mean daily discharge for the period of record through 2009 U.S. Geological Survey streamflow-gaging station 08066500 Trinity 1925

0

5,000

20,000 15,000 10,000 Discharge, in cubic feet per second per feet cubic in Discharge, Figure 5. Trends in Selected Streamflow Statistics 13

Lake Houston. The streamflow in the East Fork San Jacinto Survey, 2012b); channel rectification is typically done by the River can be considered reasonably natural (U.S. Geological U.S. Army Corps of Engineers (USACE) to improve channel Survey, 2012b). The time period analyzed for this study is conveyance and mitigate flood risks (U.S. Army Corps of 1940–2009 (table 5). An upward trend for annual minimum Engineers, 2012). daily discharge was detected at this station. USGS streamflow-gaging station 08070500 Caney Creek near Splendora, Tex. (Caney Creek near Splendora station), Outflows to Middle Coast Gulf of Mexico is about 8 miles west of Splendora, Tex. The station is about (Brazos, San Bernard, and Colorado 25 miles downstream from the headwaters of the stream and River Basins) about 20 miles upstream from East Fork San Jacinto River. The streamflow in Caney Creek can be considered reasonably The Brazos, San Bernard, and Colorado Rivers flow natural (U.S. Geological Survey, 2012b). The time period directly into the Gulf of Mexico along the middle coastline of analyzed for this study is 1945–2009 (table 5). An upward Texas. The Brazos and Colorado River Basins extend across trend for annual minimum daily discharge was detected at Texas into New Mexico (fig. 1). The lower parts of these this station. basins narrow as the rivers flow towards the Gulf of Mexico, USGS streamflow-gaging station 08073500 Buffalo particularly near about the 98th meridian. The San Bernard Bayou near Addicks, Tex. (Buffalo Bayou near Addicks River Basin is much smaller and is located between the Brazos station), is about 3 miles southeast of Addicks, Tex. The and Colorado River Basins. station is downstream from Barker and Addicks Reservoirs in USGS streamflow-gaging station 08114000 Brazos River the western part of Houston and is about 45 miles upstream at Richmond, Tex. (Brazos River at Richmond station), is from Galveston Bay. Barker Reservoir has regulated more than 500 miles downstream from the headwaters of the streamflow for the station over the entire period of record. Brazos River in New Mexico and about 70 miles upstream Barker Reservoir was impounded in 1945 and Addicks from the Gulf of Mexico. Although it is about 300 miles Reservoir was impounded in 1948. Both reservoirs generally upstream, Possum Kingdom Lake, which was impounded in are empty and function as large detention reservoirs for flood- 1941, is the main reservoir affecting streamflow at the Brazos peak attenuation for the large and densely populated greater River at Richmond station (Dowell, 1964; U.S. Geological Houston area. The time period analyzed for this study is Survey, 2012b). There are additional reservoirs on the main 1946–2009 (table 5). Upward trends in annual mean daily and stem and major tributaries of the Brazos River, including minimum discharges were detected at this station, whereas, a Lake Whitney and Waco Lake. The time period analyzed for downward trend for the annual maximum daily discharge was this study is 1923–2009 (table 6). No trends were detected at detected. A time series of the annual mean daily discharge is this station. shown in figure 6. USGS streamflow-gaging station 08117500 San Bernard USGS streamflow-gaging station 08076000 Greens River near Boling, Tex. (San Bernard River near Boling Bayou near Houston, Tex. (Greens Bayou near Houston station), is about 5 miles northeast of Boling, Tex. The station station), is about 1 mile northeast of Houston. The station is about 90 miles downstream from the headwaters and about is about 25 miles downstream from the bayou’s headwaters 45 miles upstream from the mouth with the Gulf of Mexico. and about 25 miles upstream from Buffalo Bayou. The The streamflow for the San Bernard River can be considered streamflow in Greens Bayou is unregulated (U.S. Geological reasonably natural (U.S. Geological Survey, 2012b). The time Survey, 2012b), but because the watershed of Greens Bayou period analyzed for this study is 1955–2009 (table 6). No has become increasingly developed since the station was trends were detected at this station. installed, streamflow might deviate from the characteristics USGS streamflow-gaging station 08162000 Colorado of reasonably natural flow. Konrad and Booth (2005, p. 157) River at Wharton, Tex. (Colorado River at Wharton station), reported that “urban development modifies the production and is more than 500 miles downstream from the headwaters delivery of runoff to streams and the resulting rate, volume, in north Texas and about 65 miles upstream from the Gulf and timing of streamflow” and identified “four hydrologic of Mexico. Although numerous reservoirs have been changes resulting from urban development: increased constructed along the Colorado River and many of its principle frequency of high flows, redistribution of water from base tributaries, the main reservoir for flood control and volume flow to stormflow, increased daily variation in streamflow, storage is , which is about 150 miles upstream and reduction in low flow.” The time period analyzed for this from the Wharton station. The streamflow recorded by this study is 1953–2009 (table 5). Upward trends for annual mean, station has been affected by reservoir operations (mostly maximum, and minimum daily discharges were detected for by Lake Travis) over the entire period of record. The time the Greens Bayou near Houston. Tex., station. A time series of period analyzed for this study is 1939–2009 (table 6). A the annual mean daily discharge is shown in figure 7. Channel downward trend in annual minimum daily discharge was rectification occurred during 1974–75 (U.S. Geological detected at this station.

14 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

1987

1986

1985

1984

1983

1982

1981

1980

1979

1978

1977

1976

1975

1974

1973

1972

1971

Water year

1970

1969

1968

1967

1966

1965

1964

1963

1962

1961

1960

1959

1958

1957

1956

1955

1954

1953

1952

1951

1950

1949

EXPLANATION

1948

Annual mean daily discharge mean Annual

1947 1946 A nnual mean daily discharge for the period of record through 2009 U.S. Geological Survey streamflow-gaging station 08073500 Buffalo Bayou near Addicks, Texas.

0

800 700 600 500 400 300 200 100 Discharge, in cubic feet per second per feet cubic in Discharge, Figure 6.

Trends in Selected Streamflow Statistics 15

2009

2007

2005

2003

2001

1999

1997

1995

1993

1991

1989

1987

1985 1983

Water year

1981

1979 1977

channel rectified channel 1974-75 years water 1975

1973

1971

1969

1967

1965

1963

1961

1959 1957 EXPLANATION

Annual mean daily discharge mean Annual 1955 A nnual mean daily discharge for the period of record through 2009 U.S. Geological Survey streamflow-gaging station 08076000 Greens Bayou near Houston, Texas.

1953 0

50

250 200 150 100 Discharge, in cubic feet per second per feet cubic in Discharge, Figure 7. 16 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows

Table 6. Monotonic trends in outflows from the Brazos, San Bernard, and Colorado River Basins in Texas, 1923–2009.

[USGS, U.S. Geological Survey; p-value, probability value; <, less than; --, no statistically significant trend was detected (p-value <0.05)]

USGS USGS station Time period Streamflow statistic Kendall’s Trend station p-value name analyzed (discharge) tau direction number

08114000 Brazos River at Richmond, Tex. 1923–2009 Annual mean daily -0.01 0.88 --

08114000 Brazos River at Richmond, Tex. 1923–2009 Annual maximum daily -0.12 0.095 --

08114000 Brazos River at Richmond, Tex. 1923–2009 Annual minimum daily 0.07 0.35 --

08117500 San Bernard River near Boling, Tex. 1955–2009 Annual mean daily 0.14 0.12 --

08117500 San Bernard River near Boling, Tex. 1955–2009 Annual maximum daily 0.15 0.11 --

08117500 San Bernard River near Boling, Tex. 1955–2009 Annual minimum daily 0.14 0.12 --

08162000 Colorado River at Wharton, Tex. 1939–2009 Annual mean daily -0.02 0.78 --

08162000 Colorado River at Wharton, Tex. 1939–2009 Annual maximum daily 0.002 0.98 --

08162000 Colorado River at Wharton, Tex. 1939–2009 Annual minimum daily -0.22 <0.05 downward

Outflows to Lower Coast Gulf of Mexico which is upstream from this station on the near (Guadalupe and Nueces River Basins and Rio the confluence of the Frio and Nueces Rivers (fig. 2). The time period analyzed for this study is 1940–2009 (table 7). Grande Basin) Downward trends for annual mean and maximum daily discharges were detected at this station, whereas, an upward The Guadalupe River at Victoria streamflow-gaging trend for annual minimum daily discharge was detected. station 08176500 Guadalupe River at Victoria, Tex. Streamflow-gaging station 08475000 Rio Grande near (Guadalupe River at Victoria station), is about 250 miles Brownsville, Tex. (Rio Grande near Brownsville station), is downstream from the headwaters and about 30 miles upstream operated by IBWC and is more than 1,000 miles downstream from the Gulf of Mexico. The time period analyzed for this from the headwaters and about 25 miles upstream from the station is 1936-2009, and streamflow recorded by this station Gulf of Mexico. Discharge at the Rio Grande near Brownsville has been affected by reservoir operations over the entire period station has been substantially affected by Falcon Reservoir of record (table 1) (Dowell, 1964). No trends were detected at since 1953 (Dowell, 1964; U.S. Geological Survey, 2012b). this station. Falcon Reservoir is about 120 miles upstream from the station. USGS streamflow-saging station 08211000 Nueces River A time series of the annual mean daily discharge is shown near Mathis, Tex. (Nueces River near Mathis station), is about in figure 8 and includes the timing of the Falcon Reservoir 4 miles southwest of Mathis, Tex. The station is about 200 impoundment. The time periods analyzed were 1935–2009, miles downstream from the headwaters and about 30 miles 1935–54, and 1955–2009 (table 7). Downward trends for upstream from the Gulf of Mexico. Lake Corpus Christi is less annual mean and maximum daily discharges were detected at than 1 mile upstream and has maintained a pool in some form this station, whereas, an upward trend for annual minimum throughout the entire period of record of the station (Dowell, daily discharge was detected for 1935–2009. Additionally, 1964; U.S. Geological Survey, 2012b). downward trends for annual mean daily, maximum, and The Frio River is a major tributary to the Nueces River. minimum discharges were detected at this station for the Additional regulation of flow at the Nueces River near period 1935–54. No trends were detected at this station for the Mathis station is provided by Choke Canyon Reservoir, period 1955–2009. Trends in Selected Streamflow Statistics 17

Table 7. Monotonic trends in outflows from the Guadalupe and Nueces River Basins, and the Rio Grande Basin in Texas, 1926–2009.

[USGS, U.S. Geological Survey; IBWC, International Boundary and Water Commission; p-value, probability value; <, less than; --, no statistically significant trend was detected (p-value <0.05)]

Time Streamflow Station Kendall’s Trend Station name Agency period statistic p-value number tau direction analyzed (discharge)

08176500 Guadalupe River at Victoria, Tex. USGS 1936–2009 Annual mean daily 0.11 0.16 --

08176500 Guadalupe River at Victoria, Tex. USGS 1936–2009 Annual maximum daily -0.006 0.94 --

08176500 Guadalupe River at Victoria, Tex. USGS 1936–2009 Annual minimum daily 0.02 0.75 --

08211000 Nueces River near Mathis, Tex. USGS 1940–2009 Annual mean daily -0.20 <0.05 downward

08211000 Nueces River near Mathis, Tex. USGS 1940–2009 Annual maximum daily -0.25 <0.05 downward

08211000 Nueces River near Mathis, Tex. USGS 1940–2009 Annual minimum daily 0.26 <0.05 upward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1935–2009 Annual mean daily -0.38 <0.05 downward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1935–2009 Annual maximum daily -0.49 <0.05 downward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1935–2009 Annual minimum daily 0.15 <0.05 upward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1935–1954 Annual mean daily -0.62 <0.05 downward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1935–1954 Annual maximum daily -0.35 <0.05 downward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1935–1954 Annual minimum daily -0.43 <0.05 downward

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1955–2009 Annual mean daily -0.08 0.39 --

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1955–2009 Annual maximum daily -0.17 0.064 --

08475000 Rio Grande near Brownsville, Tex.1 IBWC 1955–2009 Annual minimum daily 0.05 0.61 --

1Streamflow data for Rio Grande near Brownsville, Tex., are currently (2012) operated and data published by the International Boundary and Water Commission (2012).

18 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows

2009

2007

2005

2003

2001 1999 EXPLANATION

Annual mean daily discharge mean Annual 1997

1995

1993

1991

1989

1987

1985

1983

1981

1979

1977

1975

1973 1971

Water year

1969

1967

1965

1963

1961

1959

1957 1955

Falcon Reservoir Regulation

1953

1951

1949

1947

1945

1943

1941

1939

1937 1935 A nnual mean daily discharge for the period of record through 2009 U.S. Geological Survey streamflow-gaging station 08475000 Rio Grande at Brownsville, Texas.

0

9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 Discharge, in cubic feet per second per feet cubic in Discharge, Figure 8. Summary 19

Summary Outflows to Louisiana (Little Cypress Creek Basin)— No trends were detected for the Little Cypress Creek near Jefferson, Tex., station. The major river basins in Texas include the Red River, Outflows to the upper coast of the Gulf of Mexico Sabine River, Neches River, Trinity River, San Jacinto River, (Sabine and Neches River Basins)—An upward trend for Brazos River, Colorado River, Guadalupe River, San Antonio annual minimum daily discharge was detected for the Sabine River, Nueces River, and the Rio Grande. The Red River River near Ruliff, Tex., station. A downward trend for annual flows into Arkansas and then into Louisiana. The Sabine, maximum daily discharge and conversely an upward trend for Neches, Brazos, San Bernard, Colorado, Guadalupe, and annual minimum daily discharge were detected for Neches Nueces Rivers and Rio Grande all flow directly into the Gulf River at Evadale, Tex., station for the period 1922–2009 of Mexico. The Trinity River, San Jacinto River, and Buffalo (period of record). No trends were detected for the Neches Bayou flow into Galveston Bay, which subsequently flows River at Evadale, Tex., station for the period 1922–50; into the Gulf of Mexico. Fresh surface-water usage in Texas however, upward trends for annual mean and minimum daily is about two-thirds of the total freshwater usage in Texas. As discharges were detected for the period 1951–2009. a result, studies of streamflow statistics, likely indicative of Outflows to the Gulf of Mexico through Galveston Bay outflows from Texas, are useful in resource assessments, such (Trinity and San Jacinto River Basins, and associated Creeks as water-supply studies, as well as useful to hydrologists, and Bayous [Galveston Bay inflows])—An upward trend for biologists, and ecologists. Accordingly, the U.S. Geological annual minimum daily discharge was detected for the Trinity Survey, in cooperation with the Texas Water Development River at Romayor, Tex., station. An upward trend for annual Board, evaluated streamflow data from streamflow-gaging minimum daily discharge was detected for the West Fork San stations with more than 50 years of record that were active as Jacinto River near Conroe, Tex., station. Upward trends for of 2009. annual mean and minimum daily discharges were detected for The streamflow data for 18 selected U.S. Geological the Spring Creek near Spring, Tex., station. Upward trends in Survey and one International Boundary Water Commission annual mean, maximum, and minimum daily discharges were streamflow-gaging stations were used to compute selected detected for the Cypress Creek near Westfield, Tex., station. streamflow statistics for trend analysis. The outflows into An upward trend for annual minimum daily discharge was Arkansas and Louisiana were represented by streamflow detected for the East Fork San Jacinto River near Cleveland, records from 3 stations, and outflows into the Gulf of Mexico Tex., station. An upward trend for annual minimum daily were represented by streamflow records from 16 stations. discharge was detected for the Caney Creek near Splendora, Monotonic trend analyses were performed on the Tex., station. Upward trends in annual mean and minimum following three annual streamflow statistics: (1) annual mean daily discharges were detected for the Buffalo Bayou near daily discharge, (2) annual maximum daily discharge, and Addicks, Tex., station, whereas, a downward trend for the (3) annual minimum daily discharge. Trends were determined annual maximum daily discharge was detected. Upward using the nonparametric Kendall’s Tau test, which is useful for trends for annual mean, maximum, and minimum daily the detection of monotonic upward or downward trends with discharges were detected for the Greens Bayou near Houston, time. A positive Kendall Tau value indicates an upward trend Tex., station. and a negative Tau value indicates a downward trend. The Outflows to the middle coast of the Gulf of Mexico p-value for the test is a measure of the statistical significance (Brazos, San Bernard, and Colorado River Basins)—No of the trend. Small p-values (less than 0.05) indicate a trends in streamflow were detected for the Brazos River statistically significant trend for purposes of this study. at Richmond, Tex., or for San Bernard River near Boling, A total of 69 trend analyses by Kendall’s Tau were Tex., stations. A downward trend in annual minimum daily computed—19 periods of streamflow from USGS stations discharge was detected for the Colorado River at Wharton, multiplied by 3 streamflow statistics (annual mean, maximum, Tex., station. and minumum discharge) plus 12 additional trend analyses Outflows to the lower coast of the Gulf of Mexico because the periods of record for 2 stations were further (Guadalupe and Nueces River Basins, and Rio Grande analyzed for trends pre- and post-reservoir impoundment. Basin)—No trends were detected for the Guadalupe River Unless otherwise described, each trend analysis used the entire at Victoria, Tex., station. Downward trends for annual mean period of record for each station. The monotonic trend analysis and maximum daily discharges were detected for the Nueces detected 11 statistically significant downward trends, 37 River near Mathis, Tex., station, whereas, an upward trend for instances of no trend, and 21 statistically significant upward annual minimum daily discharge was detected. Downward trends. Statistically significant trends follow for each station trends for annual mean and maximum daily discharges were and organized by a logical grouping according to river system. detected for the Rio Grande near Brownsville, Tex., station, Outflows to Arkansas (Red and Sulphur River Basins)—A whereas, an upward trend for annual minimum daily discharge downward trend for annual maximum daily discharge was was detected for 1935–2009. Additionally, downward trends detected for the Red River at Index, Ark., station. An upward for annual mean, maximum, and minimum daily discharges trend for annual minimum daily discharge was detected for the were detected for the Rio Grande near Brownsville, Tex., Sulphur River near Talco, Tex., station. station for the period 1935–54. No trends were detected for 20 Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows the Rio Grande near Brownsville, Tex., station for the period International Boundary and Water Commission, 2012, Rio 1955–2009. Grande water flows: International Boundary and Water Annual mean daily discharge is especially diagnostic Commission, accessed June 7, 2012, at http://www.ibwc. because this statistic can be used to compute annual mean state.gov/Water_Data/rio_grande_WF.html#Stream. discharge over long periods of time and represents the expectation of the annual volume of water measured by Kenny, J.F., Barber, N.L., Hutson, S.S., Linsey, K.S., a station. Trends in annual mean daily discharge can be Lovelace, J.K., and Maupin, M.A., 2009, Estimated use of summarized as follows: (1) annual outflow volumes from water in the United States in 2005: U.S. Geological Survey Texas into Arkansas and Louisiana as well as the Gulf of Circular 1344, 52 p. (Also available at http://pubs.usgs.gov/ Mexico (upper Texas coast) lack statistically significant circ/1344/.) trends; (2) annual inflows into Galveston Bay (Houston metropolitan area) show upward trends for four of eight Konrad, C.P., and Booth, D.B., 2005, Hydrologic changes in stations; (3) annual outflow volumes from the Brazos River urban streams and their ecological significance,in Brown, (east of Houston metropolitan area) to the Guadalupe River L.R. Gray, R.H. Hughes, R.M. and Meador, M.R. eds., lack statistically significant trends; and (4) annual outflow American Fisheries Society Symposium, v. 47, p. 157–177, volumes from the two most westerly stations on the Nueces accessed June 25, 2012, at http://water.usgs.gov/nawqa/ River and Rio Grande show downward trends. urban/pdf/157-178_Konrad.pdf. Lanning-Rush, Jennifer, 2000, Regional equations for estimating mean annual and mean seasonal runoff for References natural basins in Texas, base period 1961–90: U.S. Geological Survey Water-Resources Investigations Report Asquith, W.H., 2001, Effects of regulation on L-moments of 00–4064, 27 p. (Also available at http://pubs.usgs.gov/ annual peak streamflow in Texas: U.S. Geological Survey wri/2000/4064/.) Water-Resources Investigations Report 01–4243, 66 p. Larkin, T.J., and Bomar, G.W., 1983, Climatic atlas of Texas: (Also available at http://pubs.usgs.gov/wri/wri014243/.) Texas Department of Water Resources, Limited Printing Asquith, W.H., Vrabel, Joseph, and Roussel, M.C., 2007a, Report LP–192, 151 p. Summary of percentages of zero daily mean streamflow for 712 U.S. Geological Survey streamflow-gaging StatSoft, 2009, STATISTICA 10, version 10.0.1011.4: StatSoft stations in Texas through 2003: U.S. Geological Survey Inc., Tulsa, Oklahoma. Data Series 247, 721 p. (Also available at http://pubs.usgs. gov/ds/2007/247/.) Texas State Historical Association, 2012a, The handbook of Texas online—Lake Worth: Texas State Historical Asquith, W.H., Vrabel, Joseph, and Roussel, M.C., 2007b, Association, accessed June 6, 2012, at http://www. Summary of annual mean, maximum, minimum, and tshaonline.org/handbook/online/articles/rol87. 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Information regarding water resources in Texas is available at http://tx.usgs.gov/ Barbie and Wehmeyer —Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows— SIR 2012–5182 Barbie and Wehmeyer —Trends in Selected Streamflow Statistics at 19 Long-Term Streamflow-Gaging Stations Indicative of Outflows— SIR 2012–5182

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