A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas During 1951–56 and 2011

Prepared in cooperation with the Texas Water Development Board A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

Scientific Investigations Report 2013–5113

U.S. Department of the Interior U.S. Geological Survey Front and Back Covers: Photograph of the dry lake bed at O.C. Fisher Lake at San Angelo, Texas, July 15, 2011. The lake is downstream from U.S. Geological Survey streamflow-gaging station 08134000 North Concho River near Carlsbad, Texas.

Back Cover: Inset photographs looking upstream from U.S. Geological Survey streamflow-gaging station 08148500 North Llano River near Junction, Texas (left) October 30, 2006, and (right) July 28, 2011. A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

By Karl E. Winters

Prepared in cooperation with the Texas Water Development Board

Scientific Investigations Report 2013–5113

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director

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

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Suggested citation: Winters, K.E., 2013, A historical perspective on precipitation, drought severity, and streamflow in Texas during 1951–56 and 2011: U.S. Geological Survey Scientific Investigations Report 2013–5113, 24 p., http://pubs.usgs.gov/ sir/2013/5113/. iii

Contents

Abstract...... 1 Introduction...... 1 Purpose and Scope...... 2 Previous Studies...... 2 Description of the Study Area...... 2 Methods...... 5 Precipitation...... 5 Drought Severity...... 5 Streamflow...... 6 Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011...... 7 Precipitation...... 7 Drought Severity...... 7 Streamflow...... 9 Summary...... 23 References...... 24

Figures

1. Map showing locations of unregulated U.S. Geological Survey streamflow-gaging stations in Texas with complete records during the droughts of 1951–56 and 2011...... 3 2. Maps showing average annual precipitation in Texas; total precipitation during the 1956 calendar year; and the 2011 water year...... 4 3. Graph showing magnitude and extent of the drought in Texas during October 1, 2010, to September 20, 2012...... 8 4. Graphs showing monthly Palmer Drought Severity Index for Texas during 1900–2012 and annual runoff for Texas during 1901–2011...... 9 5. Graph showing relation between Palmer Drought Severity Index and annual runoff for all U.S. Geological Survey streamflow-gaging stations in Texas during 1901–2011...... 10 6. Graphs showing annual mean streamflow at selected unregulated U.S. Geological Survey streamflow-gaging stations in Texas during 1951–56 and 2011...... 11 7. Graphs showing streamflow duration for selected unregulated U.S. Geological Survey streamflow-gaging stations in Texas for 1956, 2011, and the period of record...... 12 8. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 07233500 Palo Duro Creek near Spearman, Texas...... 14 9. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 07343000 North Sulphur River near Cooper, Texas...... 14 10. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 07346070 Little Cypress Creek near Jefferson, Texas...... 15 iv

Figures—Continued

11. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08041500 Village Creek near Kountze, Texas...... 15 12. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08068500 Spring Creek near Spring, Texas...... 16 13. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08070000 East Fork San Jacinto River near Cleveland, Texas...... 16 14. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08070500 Caney Creek near Splendora, Texas...... 17 15. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08071000 Peach Creek at Splendora, Texas...... 17 16. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08134000 North Concho River near Carlsbad, Texas...... 18 17. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08148500 North Llano River near Junction, Texas...... 18 18. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08150000 Llano River near Junction, Texas...... 19 19. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08164000 Lavaca River near Edna, Texas...... 19 20. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08166000 Johnson Creek near Ingram, Texas...... 20 21. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08167500 Guadalupe River near Spring Branch, Texas...... 20 22. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08171000 Blanco River at Wimberley, Texas...... 21 23. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08189500 Mission River at Refugio, Texas...... 21 24. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08195000 Frio River at Concan, Texas...... 22 25. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08198000 Sabinal River near Sabinal, Texas...... 22 26. Hydrograph showing streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08205500 Frio River near Derby, Texas...... 23 v

Tables

1. Classification of drought severity by the Palmer Drought Severity Index and by the Drought Monitor...... 5 2. Unregulated U.S. Geological Survey streamflow-gaging stations in Texas with complete record during the droughts of 1951–56 and 2011...... 6 3. Twelve-month statewide average precipitation for selected water years in Texas...... 7 4. Monthly statewide Palmer Drought Severity Index (PDSI) during the 1951–56 and 2011 droughts in Texas...... 8

Conversion Factors

Inch/Pound to SI

Multiply By To obtain Length inch (in) 2.54 centimeter (cm) foot (ft) 0.3048 meter (m) 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)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88). Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). A water year is the 12-month period October 1 through September 30 designated by the calendar year in which it ends.

A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

By Karl E. Winters

low streamflows during 1951–56 occurred in 1956. During Abstract March to September 2011, record daily lows were measured at USGS streamflow-gaging station 08041500 Village Creek near The intense drought throughout Texas during 2011 Kountze, Tex., which has more than 70 years of record. Many resulted in substantial declines in streamflow. By April 2011, other USGS streamflow-gaging stations in Texas started the nearly all of the State was experiencing severe to extreme 2011 water year with normal streamflow but by the end of the drought according to data from the University of Nebraska– water year were flowing at near-record lows. Lincoln Drought Monitor. By the end of July 2011, more than 75 percent of the State was experiencing exceptional drought. The worst of the drought occurred around October 4, 2011, when 97 percent of Texas was suffering from extreme to Introduction exceptional drought. The historical drought of 1951–56 has long been used by water-resource managers, engineers, and In 2011, there was a severe drought in Texas, and scant scientists as a point of reference for water-supply planning. precipitation fell throughout most of the State. Record high A comparison of drought conditions during the 2011 water temperatures during June through August 2011 (Dallas year (October 1, 2010, through September 30, 2011) to the Morning News, 2011) combined with the scant precipitation historical drought of 1951–56 from a hydrologic perspective to help produce record low streamflows throughout the State. serves as an additional reference for water-supply planning. By August 4, 2011, the precipitation deficit was so severe that A record low statewide average annual precipitation of State Climatologist John Nielsen-Gammon declared 2011 to 11.27 inches for the period 1895–2011 was recorded during be the worst 1-year drought on record in Texas (Texas A&M the 2011 water year; the prior record low statewide average University, 2011). A record low statewide average annual precipitation was 13.91 inches during the 1956 water year. precipitation of 11.27 inches for the period 1895–2011 was The statewide monthly Palmer Drought Severity Index (PDSI) recorded during the 2011 water year; the prior record low declined to -7.93 during September 2011, which was larger statewide average precipitation was 13.91 inches during the in magnitude than the statewide PDSI during any drought- 1956 water year. (A water year is the 12-month period from affected month in the 1950s. October 1 through September 30 designated by the calendar Annual mean streamflow and streamflow-duration curves year in which it ends.) for the 1951–56 and 2011 water years were assessed for Drought conditions prevailed in Texas from 1947 to 19 unregulated U.S. Geological Survey (USGS) streamflow- 1957, with the most severe years of drought occurring in the gaging stations. At eight of these streamflow-gaging 1950s, providing historical perspective for the 2011 drought. stations, the annual mean streamflow was lower in 2011 The years of 1951 through 1956 in particular have long been than for any year during 1951–56; many of these stations used by water-resource managers, engineers, and scientists are located in eastern Texas. Annual mean streamflows for as a point of reference for water-supply planning (Texas streamflow-gaging stations in the Guadalupe, Blanco, and Water Development Board, 2013). A comparison of the upper Frio River Basins were lower in 1956 than in 2011. 2011 drought to the drought of 1951–56 from a hydrologic The streamflow-duration curves for many streamflow-gaging perspective serves as an additional reference for water-supply stations indicate a lack of (or diminished) storm runoff during planning. Accordingly, in 2012, the U.S. Geological Survey 2011. Low streamflows (those exceeded 90 to 95 percent of (USGS), in cooperation with the Texas Water Development days) were lower for 1956 than for 2011 at seven streamflow- Board (TWDB), assessed the effects of the 1951–56 and 2011 gaging stations. For most of these stations, the lowest of the droughts from a hydrologic perspective. 2 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

Purpose and Scope Thomas and others (1963) reported on the effects of drought in central and south Texas during 1942–56 and The purpose of this report is to document precipitation, noted that many streams in central Texas formerly regarded drought severity, and streamflow in Texas during the droughts as perennial had ceased flowing during drought years. of 1951–56 and 2011. Isohyetal maps are presented for the Nace and Pluhowski (1965) reported on the drought of the purpose of comparing normal annual precipitation in Texas 1950s in Colorado, Iowa, Kansas, Missouri, New Mexico, and total precipitation during the 1956 and 2011 water years. Oklahoma, and Texas. Those authors noted that Texas had the The magnitude and extent of the 2011 drought in Texas are greatest precipitation deficiency in the United States during described by using the Palmer Drought Severity Index (PDSI) the 1951–56 drought, and that discharge on many unregulated (Palmer, 1965) and by using the Drought Monitor’s drought streams in Texas diminished to record-breaking lows, severity classification (University of Nebraska–Lincoln, 2012). including no-flow conditions. Those authors also noted that, For historical perspective on the 1951–56 and 2011 droughts, as early as 1953, streamflow in the Texas Panhandle region precipitation, drought severity, and statewide runoff data returned to normal. were analyzed from 1895–2011, 1900–2011, and 1901–2011, Asquith and others (2007) reported the occurrence of respectively. Annual mean streamflows for 19 unregulated zero flows at USGS streamflow-gaging stations in Texas. streamflow-gaging stations in Texas are presented for the Graphs of the annual percentage of zero flow through 2003 1951–56 and 2011 water years, and streamflow-duration are presented for each station. Asquith and Heitmuller (2008) curves are presented for these stations for 1956 and 2011. reported trends in mean and harmonic mean streamflows for Comparisons are made between the 1951–56 and 2011 620 streamflow-gaging stations in Texas. Although accounting droughts. Drought severity is discussed using (aggregate) for changes in streamflow over time was beyond the scope statewide data and not with respect to climatic divisions within of this report, the reports by Asquith and others (2007) and the State. This report does not discuss the effects of drought Asquith and Heitmuller (2008) may help to inform the reader on lakes or groundwater levels or the effects of drought on as to whether streamflows at a particular streamflow-gaging agriculture, water quality, or habitat. station may have changed over time.

Previous Studies Description of the Study Area

The Texas State Climatologist reported on precipitation The study area is Texas (fig. 1). Average annual deficits during the 2011 drought (Nielsen-Gammon, 2011). precipitation in Texas ranges from about 9 inches in the That report details the use of a Standardized Precipitation western part of the State to more than 50 inches in the Index (SPI) (U.S. Department of Commerce, National southeastern part of the State (fig. 2A). Statewide average Climatic Data Center, 2012) and provides maps showing annual precipitation is 27.95 inches. Figure 1 depicts the the SPI for each county in Texas during October 2010 to location of the long-term unregulated streamflow-gaging October 2011. The SPI relates precipitation recorded during a stations with complete record for the 1951–56 and 2011 water specific period to the historical precipitation record at a given years. These streamflow-gaging stations are generally in location. Texas has 10 climatic divisions (U.S. Department south-central and eastern Texas, with one station in the Texas of Agriculture, National Agriculture Statistics Service, 2013) Panhandle (fig. 1). Relatively few perennial streams exist in recognized by climatologists for purposes of data aggregation western Texas, and no USGS streamflow‑gaging stations in and scientific investigations. The report by Nielsen-Gammon that part of the State have complete streamflow record for the (2011) also presents PDSI values throughout Texas for periods 1951–56 and 2011. Streamflows at stations on the 13 drought periods during 1900–2011. Colorado, Brazos, and Trinity Rivers are regulated and not discussed in this report. Introduction 3

ARKANSAS OKLAHOMA NEW 102˚ 100˚ MEXICO

Spearman Palo LOUISIANA 36˚ 07233500 TEXAS Duro Creek r ve Canadian Ri Amarillo P ra iri F e D or og Town k R ed River Red River 98˚ 34˚ 96˚ 07343000 h Nort Sulphur R Cooper iver Little Cypress Cypres Creek s S Creek Dallas abi ne R Fort T iver ri 07346070 Worth n Jefferson ity

106˚ R 94˚ 32˚ 104˚ N iv or Colorado e N th TEXAS r El Paso C ec on h c River Brazos e h s Carlsbad o River R 08134000 iv Village e O C Fisher Lake r Creek River 08150000 Area enlarged North Llano iver River Llano R 08041500 Johnson Ingram 08148500 Creek Kountze Junction Blanco 30˚ Wimberley 08166000 08171000 Spring River S L 08198000 R a 08167500 av Houston i b Branch a v G c Concan i a e n u r a R 08195000 San Antonio a l S d i an v Sabinal a e A l r nt u on p Edna io e 08164000 08205500 Derby Mission R R F iver i r River ve Gulf of Mexico Base modified from U.S. Geological Survey 1:250,000-scale digital data Nueces io River r River Texas Centric Mapping System, Albers Equal Area projection Refugio North American Datum of 1983 S 08189500 S a E a n as 28˚ n J t a F J c o a in r c to k i Peach n Creek R t Caney Creek i o v e EXPLANATION R r iv e Cleveland r U.S. Geological Survey R 08070000 i o 08195000 Splendora streamflow-gaging 0 50 100 MILES G ra 08070500 station and number nd reek 08071000 e g C 0 50 100 KILOMETERS Sprin 08068500 26˚ Spring

Figure 1. Locations of unregulated U.S. Geological Survey streamflow-gaging stations in Texas with complete records during the droughts of 1951–56 and 2011.

Figure 1. Locations of unregulated U.S. Geological Survey streamflow-gaging stations in Texas with complete records during the droughts of 1951–56 and 2011. 4 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

A. Average annual precipitation

B. Total precipitation during 1956 calendar year

C. Total precipitation during 2011 water year (October 1, 2010–September 30, 2011)

EXPLANATION Precipitation, in inches— Interval varies 0 to 5 Greater than 5 to 10 Greater than 10 to 20 Greater than 20 to 30 N Greater than 30 to 40 Greater than 40 to 50 Greater than 50

Figure 2. A, Average annual precipitation in Texas (National Weather Service, 2012); Figure 2. totalA, Average precipitation annual during precipitation B, the 1956 in Texascalendar (National year (modified Weather from Service, U.S. Department 2012); total of precipitationCommerce, during B Weather, the 1956 Bureau, calendar 1957) year; and (modified C, the 2011 from water U.S. yearDepartment (National of Weather Commerce, Service, Weather Bureau,2012). 1957); and C, the 2011 water year (modified from National Weather Service, 2012). Methods 5

Methods Advanced Hydrologic Prediction Service (National Weather Service, 2012). The isohyetal map for the 1956 calendar year Precipitation, drought severity, and streamflow were was obtained from the Weather Bureau (now the National summarized for the droughts of 1951–56 and 2011 by using Weather Service) climatological data summary for 1956 (U.S. previously published data obtained from various sources. Department of Commerce, 1957). The U.S. Department of Commerce, the Drought Monitor, and the U.S. Geological Survey were the primary sources of Drought Severity these data. All of the sources of data are described in detail in the following discussions pertaining to precipitation, drought Two drought severity classifications table( 1) were used severity and streamflow. to assess the intensity of drought in Texas during 1951–56 and 2011. The PDSI is a quantitative assessment of soil moisture Precipitation based on precipitation and temperature data (Palmer, 1965). PDSI values greater than 0.49 corresponding to wetter than Statewide average annual precipitation data for Texas normal conditions are not shown in table 1. The NCDC were obtained from the National Climatic Data Center calculates monthly and annual PDSI values for each State and (NCDC) (U.S. Department of Commerce, National Climatic for each climatic division. Texas has 10 climatic divisions Data Center, 2012) for the years 1895–2011. The 12-month (U.S. Department of Agriculture, National Agriculture statewide averages were ranked by water year from lowest Statistics Service, 2013) recognized by climatologists for to highest to assess the 1951–56 and 2011 precipitation purposes of data aggregation and scientific assessment; amounts and to compare those amounts to the average annual assessment of drought severity by climatic division is beyond precipitation. Additionally, isohyetal maps showing lines the scope of this report. The Drought Monitor, a public of equal precipitation (Jain and Singh, 2005) are presented service operated by the University of Nebraska–Lincoln, in figure 2 showing average annual precipitation in Texas classifies drought into five qualitative categoriestable ( 1; and total precipitation during calendar year 1956 and University of Nebraska–Lincoln, 2012). Areal percentages water year 2011. Isohyetal maps showing average annual of Texas corresponding to the various drought categories precipitation and total precipitation during the 2011 water at weekly intervals during 2011 were obtained from the year were obtained from the National Weather Service’s Drought Monitor.

Table 1. Classification of drought severity by the Palmer Drought Severity Index and by the Drought Monitor.

[Each classification system is different, and the classification indexes and categories are not equivalent. Palmer Drought Severity Index from Palmer, 1965; Drought Monitor from University of Nebraska-Lincoln, 2012]

Palmer Drought Severity Index classifications Drought Monitor classifications

Palmer Drought Drought Class Description Severity Index category 0.49 to -0.49 Near normal -0.50 to -0.99 Incipient drought D0 Abnormally dry -1.00 to -1.99 Mild drought D1 Moderate drought -2.00 to -2.99 Moderate drought D2 Severe drought -3.00 to -3.99 Severe drought D3 Extreme drought Less than -3.99 Extreme drought D4 Exceptional drought 6 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

Streamflow and 2011. In this report, USGS streamflow-gaging stations are frequently referred to by their station number followed by Streamflow data for 19 unregulated USGS their station name (table 2). streamflow‑gaging stations (fig. 1; table 2) were used to assess Annual runoff, in inches (computed as the average flow the effects of drought during 1951–56 and 2011. These data per unit area for streamflow-gaging stations in Texas), for the include annual and daily mean streamflow obtained from State of Texas for the period 1901–2011 was obtained from the USGS National Water Information System (NWIS; U.S. the USGS WaterWatch Web page (U.S. Geological Survey, Geological Survey, 2012a). Only stations with complete 2012b). This runoff is based on the entire network of USGS record during 1951–56 and 2011 were used in this study. streamflow-gaging stations in Texas, including streams Additionally, stations flagged as “regulated” in the NWIS that are affected by regulation. Compared to annual runoff peak-flow file (http://nwis.waterdata.usgs.gov/tx/nwis/ values computed since about 1925, annual runoff values peak) were not included in the analyses. As described by computed from about 1901 to about 1924 are likely to be Asquith (2001), two commonly used simple classification much less accurate because few stations were in operation schemes consider regulated stations as (1) those where at before 1924. An assessment of the effect of the number of least 10 percent of the drainage area of the basin is affected streamflow-gaging stations on the accuracy of statewide runoff or controlled by reservoirs, or (2) regulated to the degree computations is beyond the scope of this report. that annual peak streamflows are likely to be affected. USGS Streamflow-duration curves (Searcy, 1959) describe hydrologists assign a numeric code of “6” in the peak-flow file the percentage of time that a given streamflow was equaled to designate peak streamflows affected by regulation. or exceeded at a site. The median streamflow is exceeded USGS station 07233500 Palo Duro Creek near Spearman, 50 percent of the time. Streamflow values exceeded only Tex. (hereinafter the Palo Duro gage), has a small diversion 5 or 10 percent of the time usually represent storm runoff, upstream for irrigation. Data for this station are included in and a steeply-sloped curve indicates a greater magnitude and this report because no other unregulated station is available frequency of storm flows. On the drier end of the spectrum, in the Texas Panhandle with complete record during 1951–56 streamflows exceeded 95 percent of the time typically are

Table 2. Unregulated U.S. Geological Survey streamflow-gaging stations in Texas with complete record during the droughts of 1951–56 and 2011.

Contributing Station Station name drainage area Period of record number (square miles) 07233500 Palo Duro Creek near Spearman, Tex. 556 1945–79, 1999–2011 07343000 North Sulphur River near Cooper, Tex. 276 1950–2011 07346070 Little Cypress Creek near Jefferson, Tex. 675 1946–2011 08041500 Village Creek near Kountze, Tex. 860 1939–2011 08068500 Spring Creek near Spring, Tex. 409 1939–2011 08070000 East Fork San Jacinto River near Cleveland, Tex. 325 1939–2011 08070500 Caney Creek near Splendora, Tex. 105 1944–2011 08071000 Peach Creek at Splendora, Tex. 117 1944–77, 1999–2011 08134000 North Concho River near Carlsbad, Tex. 1,191 1924–2011 08148500 North Llano River near Junction, Tex. 914 1916–77, 2001–2011 08150000 Llano River near Junction, Tex. 1,849 1916–93, 1998–2011 08164000 Lavaca River near Edna, Tex. 817 1938–2011 08166000 Johnson Creek near Ingram, Tex. 114 1941–59, 1962–93, 1999–2011 08167500 Guadalupe River near Spring Branch, Tex. 1,315 1922–2011 08171000 Blanco River at Wimberley, Tex. 355 1924–26, 1928–2011 08189500 Mission River at Refugio, Tex. 690 1939–2011 08195000 Frio River at Concan, Tex. 389 1931–2011 08198000 Sabinal River near Sabinal, Tex. 206 1943–2011 08205500 Frio River near Derby, Tex. 3,429 1915–2011 Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 7 indicative of low flows that occur in Texas during August and Table 3. Twelve-month statewide average precipitation for September. Streamflow-duration curves were computed for the selected water years in Texas. 19 unregulated USGS streamflow-gaging stations table( 2), for water years 1956 and 2011, and (for comparison) for the [Data source: U.S. Department of Commerce, National Climatic Data Center, 2012] period of record (1956 was selected to represent the 1951–56 drought for the streamflow-duration assessment). Streamflow- Precipitation Rank duration curves were based on daily mean streamflow data Period (inches) (1895–2011) obtained from NWIS and computed by using the USGS Automated Data Processing System (U.S. Geological Survey, October 1950–September 1951 18.98 6 2008). Computations included daily mean streamflows that October 1951–September 1952 19.88 9 were equaled or exceeded 5, 10, 25, 50, 75, 90, and 95 percent October 1952–September 1953 22.67 20 of the time. October 1953–September 1954 19.59 8 Additionally, daily streamflow-duration data for the October 1954–September 1955 24.89 37 period of record for each of the 19 unregulated USGS October 1955–September 1956 13.91 2 streamflow-gaging stations intable 2 were obtained from October 2010–September 2011 11.27 1 USGS WaterWatch (U.S. Geological Survey, 2012b). These data indicate the percentage of time that a given streamflow was not exceeded for a specific date (for example, during all precipitation that infiltrates before any runoff is generated) of the August 15ths in the period of record). for 92 watersheds in Texas. The median initial abstraction for 41 undeveloped watersheds was 1.1 inches, which indicates storms producing 1.1 inches or less rainfall likely do not generate runoff. Because the analysis by Asquith and Roussel Historical Perspective on Precipitation, (2007) was performed only for storms that generated runoff, Drought Severity, and Streamflow in larger amounts of initial abstraction may have occurred but not detected during periods of extreme soil moisture deficits Texas during 1951–56 and 2011 such as the 2011 drought (William Asquith, U.S. Geological Survey, written commun., 2012). The magnitude of the 2011 drought in Texas is best understood by comparing selected metrics of drought from 1951–56 with those measured in 2011. Precipitation, drought Drought Severity severity, and streamflow are the metrics used to gain a Figure 3 depicts the magnitude and extent of drought in historical perspective on the 2011 severe drought compared to Texas during the 2011 water year by using data obtained from drought conditions during 1951–56. the Drought Monitor (University of Nebraska–Lincoln, 2012) from October 1, 2010, to September 20, 2012. On October 1, Precipitation 2010, parts of Texas were abnormally dry, but none of Texas was classified as being in a drought. By April 2011, nearly Statewide average annual precipitation is 27.95 inches. all of Texas was in a severe to extreme drought, and by the Statewide average precipitation for the 1951–56 and 2011 end of July 2011, more than 75 percent was in an exceptional water years is shown in table 3. Also shown is the ranking drought. Figure 3 depicts the widespread extent of drought in (lowest to highest) for each of those years relative to the Texas during the 2011 water year in contrast to water years of period 1895–2011. Prior to 2011, the driest 1-year period 2010 and 2012 when drought conditions were less prevalent. was the 1956 water year, when Texas received only about The greatest areal extent of the drought occurred a few days 50 percent of its normal annual precipitation. During the 2011 after the end of the 2011 water year, around October 4, 2011, water year, Texas received only about 40 percent of its normal when 97 percent of Texas was characterized as in an extreme annual precipitation. to exceptional drought. Isohyetal maps of total precipitation in Texas during Statewide monthly values of the PDSI during the 1956 and 2011 are shown in figures 2B and 2C, respectively. droughts of 1951–56 and 2011 are listed in table 4 (U.S. Figure 2C highlights the extent of the 2011 drought Department of Commerce, National Climatic Data Center, when large parts of Texas received less than 10 inches of 2012). Between August 1951 and November 1952, 14 of precipitation during the year. During 2011, few storms in 16 monthly statewide PDSI values indicated extreme drought Texas generated more than about an inch of precipitation (PDSI less than -3.99; table 1), and extreme drought also (National Weather Service, 2012); thus, a larger fraction occurred during the entire 1955 and 1956 water years. The of the precipitation evaporated or entered the ground as lowest statewide PDSI indicating the most severe drought infiltration rather than contributing to streamflow. Asquith and conditions during the period 1951–56 was -7.8, which Roussel (2007) reported the initial abstraction (the amount of occurred September 1956. 8 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

100

80 EXPLANATION Drought severity classification 60 D0—Abnormally dry D1—Moderate drought 40 D2—Severe drought D3—Extreme drought affected by drought 20 D4—Exceptional drought Percentage of State Texas

0 10/1/2010 10/1/2011 9/30/2012 Date

Figure 3. Magnitude andFigure extent 3. of theMagnitude drought and in Texas extent during of the droughtOctober in 1, Texas 2010, duringto September October 30, 1, 2012. Data courtesy of the Drought Monitor2010, to (UniversitySeptember 20,of Nebraska-Lincoln,2012. Data courtesy 2012). of the Drought Monitor (University of Nebraska–Lincoln, 2012).

Table 4. Monthly statewide Palmer Drought Severity Index (PDSI) during the 1951–56 and 2011 droughts in Texas.

[Data source: U.S. Department of Commerce, National Climatic Data Center, 2012]

Water year Month 1951 1952 1953 1954 1955 1956 2011 October -0.95 -4.24 -5.75 -2.98 -5.30 -4.31 -0.71 November -1.64 -4.28 -4.46 -2.95 -5.21 -4.55 -1.17 December -2.38 -4.60 -3.70 -2.69 -5.42 -4.82 -1.75 January -2.81 -5.14 -3.88 -2.87 -5.26 -4.90 -1.84 February -3.04 -5.25 -3.71 -3.66 -4.88 -4.76 -2.35 March -2.70 -4.87 -3.55 -4.02 -4.97 -5.01 -3.19 April -3.05 -3.93 -3.17 -3.88 -5.27 -5.19 -4.19 May -3.10 -3.62 -3.05 -3.44 -5.01 -5.72 -5.08 June -3.27 -4.53 -3.86 -4.09 -5.08 -6.54 -6.24 July -3.89 -4.69 -4.02 -4.89 -4.92 -7.05 -7.08 August -4.49 -5.55 -3.29 -5.23 -4.43 -7.30 -7.72 September -4.01 -5.42 -3.74 -5.91 -4.25 -7.80 -7.93

The statewide monthly PDSI declined to -7.93 during For a historical perspective, monthly statewide PDSI September 2011, which was larger in magnitude than the PDSI data for the period 1900–2012 are shown in figure 4A. The values recorded for any drought-affected month during the data show both the severity and duration of droughts in Texas. 1950s. Also noteworthy is that it only took 12 months from Prolonged periods of drought occurred during 1909–11, the onset of the 2011 drought for the statewide PDSI to drop 1917–18, 1951–56, and 1963–64. Cleaveland and others below -7; whereas, it took about 6 years from the onset of (2011) used dendrochronology and other methods to evaluate the 1950s drought until the statewide monthly PDSI values drought in several parts of Texas. According to Cleaveland and dropped below -7. others (2011, p. 54) “this and previous studies indicate that severe decadal-scale droughts have occurred in Texas at least once a century since the 1500s.” Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 9

Streamflow therefore, statewide runoff computed for those years may not be representative of the actual statewide runoff. Comparison The USGS WaterWatch Web page (U.S. Geological of figures 4A and 4B shows the effect of drought on runoff. Survey, 2012b) displays annual mean runoff, in inches, for Annual statewide values of PDSI were computed as the each State. Annual runoff for Texas during 1901–2011 is average of the monthly (October to September) PDSI values; shown in figure 4B. The lowest 4 years and the respective the relation between the annual PDSI and annual runoff for runoff depths are 1917 (0.61 inches), 1918 (0.66 inches), 1956 Texas is shown in figure 5. The annual PDSI values for water (0.71 inches), and 2011 (0.49 inches). These values represent years 1956 and 2011 were -5.66 and -4.10, respectively; annual runoff from gaged basins only. Prior to 1924, fewer however, statewide runoff in 2011 was less than during 1956. than 40 streamflow-gaging stations were operated in Texas;

10 8 A 6 4 2 0 -2 -4

Palmer Drought Severity Index -6 -8 -10

10 9 B 8 7 6 5 4 3 Annual runoff, in inches 2 1 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year

FigureFigure 4. A, 4.Monthly A, Monthly Palmer Palmer Drought Drought Severity Severity Index Index for Texas for Texas during during 1900–2012 1900–2012 (U.S. (U.S. Department of Commerce,Department National of Commerce, Climatic NationalData Center, Climatic 2012) Data and Center, B, annual 2012) runoff and B for, annual all U.S. runoff Geological for Texas Survey streamﬂow-gagingduring 1901–2011 stations (U.S. Geologicalin Texas during Survey, 1901–2011 2012b). (U.S. Geological Survey, 2012b). 10 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

8 streamflows on Palo Duro Creek are caused by local diversion for agriculture or by declining water levels in the High Plains 7 aquifer. McGuire (2011) indicates that between about 1950 and 2007, water levels in the High Plains aquifer declined by 6 50 to 100 feet in the northern part of the Texas Panhandle near Palo Duro Creek. 5 Other USGS streamflow-gaging stations for which the annual mean streamflow was lower in 2011 than for any year 4 during 1951–56 include 07343000 North Sulphur River near Cooper, Tex., 07346070 Little Cypress Creek near Jefferson, 3 Tex., 08041500 Village Creek near Kountze, Tex., 08070000

Annual runoff, in inches East Fork San Jacinto River near Cleveland, Tex., 08070500 2 Caney Creek near Splendora, Tex., 08134000 North Concho 1956 River near Carlsbad, Tex., and 08205500 Frio River near 1 Derby, Tex.; many of these stations are located in eastern 2011 Texas. Upstream from Derby, Tex., in the upper Frio River 0 -8 -4-6 -2 0 2 4 6 8 Basin, annual mean streamflows for USGS streamflow-gaging Palmer Drought Severity Index stations 08195000 Frio River at Concan, Tex., and 08198000 Sabinal River near Sabinal, Tex., were lower in 1956 than in FigureFigure 5. 5. R Relationelation between between Palmer Palmer Drought Drought Severity Severity Index 2011. Annual mean streamflows for stations in the Guadalupe Index(U.S. (U.S.Department Department of Commerce, of Commerce, National National Climatic Climatic Data River Basin (08167500 Guadalupe River near Spring Branch, DataCenter, Center, 2012) 2012) and and annual annual runoff runoff for for all allU.S. U.S. Geological Survey Tex.) and Blanco River Basin (08171000 Blanco River at Geologicalstreamﬂow-gaging Survey streamflow-gaging stations in Texas stations during in1901–2011 Texas Wimberley, Tex.) also were lower in 1956 than in 2011. during(U.S. Geological1901–2011 (U.S. Survey, Geological 2012b). Survey, 2012). Streamflow-duration curves showing the percentage of time that a given streamflow was equaled or exceeded during Annual mean streamflow during 1951–56 and 2011 is 1956 and 2011 at 19 unregulated USGS streamflow-gaging shown in figure 6 for 19 unregulated USGS streamflow‑gaging stations are shown in figure 7. Additionally, streamflow stations (fig. 1, table 2). Also, the mean streamflow for the duration for the period of record is shown in figure 7 for period of record is shown for each station for reference. For reference. For sites that occasionally go to zero flow, curves most of these stations, annual mean streamflow during these were extended to approximate the location of 0.1 ft3/s, the drought years was well below the mean for the period of minimum flow plotted for the logarithmic scale. At stations record. One exception is the Palo Duro gage in the northern 07346070 Little Cypress Creek near Jefferson, Tex., 08041500 part of the Texas Panhandle (fig. 1). The annual mean Village Creek near Kountze, Tex., 08070000 East Fork San streamflow depicted for the Palo Duro gage (07233500, Jacinto River near Cleveland, Tex., and 08070500 Caney fig. 6) is consistent with the finding reported by Nace and Creek near Splendora, Tex., streamflows during 2011 were Pluhowski (1965) that as early as 1953, streamflow in the lower than for any year during 1951–56 for all computed Texas Panhandle region returned to normal. The annual mean exceedance percentages. For many of the streamflow-gaging streamflow for the Palo Duro gage was 0.0 cubic feet per stations, the 2011 streamflow-duration curves lack the second (ft3/s) (zero flow) during 2011, and the daily mean typical upward bend near the 5- and 10-percent exceedance streamflow for each day in 2011 also was zero flow. Asquith percentages found in years with near-normal amounts of and others (2007) showed an increasing occurrence of zero precipitation; the patterns of the streamflow-duration curves flow for the Palo Duro gage (07233500) for parts of each in figure 7 are consistent with a lack of storm runoff during year during 1945–2003, but prior to 2011, an entire year of 2011. The right-hand side of the curves represents lower zero flow had never previously been recorded. The mean streamflows typically maintained by inflows of local near- annual streamflow for the Palo Duro gage during 2000–10 surface groundwater. was 3.05 ft3/s. It is not known to what extent the diminishing Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 11

50 500 1,200 2,500 40 07233500 400 07343000 1,000 07346070 2,000 08041500 800 30 300 1,500 600 20 200 1,000 400 10 100 200 500 0 No flow 0 0 0

19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011

500 500 160 250 08068500 08070000 08070500 08071000 400 400 120 200 300 300 150 80 200 200 100 100 100 40 50 0 0 0 0

19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011

50 80 250 400 08134000 40 60 200 300 30 08148500 150 08150000 08164000 40 200 20 100 10 20 50 100 0 0 0 0

19511952 1953 1954 1955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011

30 400 160 140 25 120 300 120 20 08166000 08167500 08171000 100 08189500 80 15 200 80 60 10 100 40 40 5 20 Annual mean streamflow, in cubic feet per second Annual mean streamflow, 0 0 0 0

19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 Water year 150 80 160 125 60 120 EXPLANATION 100 08195000 08198000 08205500 75 40 80 Annual mean streamflow— 50 Value, too small to see as 20 40 25 a bar, shown in parenthesis (0.67) 0 0 0 Mean streamflow for period 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 19511952 1953 19541955 1956 2011 of record Water year 08205500 U.S. Geological Survey streamflow-gaging station number—Table 2

FigureFigure 6. Annual 6. A nnualmean meanstreamﬂow streamflow at selected at selected unregulated unregulated U.S. U.S. Geological Geological Survey Survey streamﬂow-gaging streamflow-gaging stations in Texasstations during in 1951–56Texas during and 2011.1951–56 and 2011. 12 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

100 10,000 10,000

07233500 1,000 07343000 1,000 07346070 10 No flow at streamflow-gaging 100 100 station during 2011 10 10 1 water year 1 1

0.1 0.1 0.1 10,000 10,000 10,000 08041500 08068500 08070000 1,000 1,000 1,000 100 100 100 10 10

10 1 1 1,000 1,000 1,000 08070500 08071000 08134000 100 100 100 10 /s) 3

ft 10 10 1

1 1 0.1 1,000 1,000 10,000

08148500 08150000 1,000 08164000 100 100 100 10 10 10 1 1

0.1 1 0.1 100 10,000 1,000

08166000 1,000 08167500 08171000 100 100

Daily mean streamflow, in cubic feet per second ( Daily mean streamflow, 10 10 10 1

1 0.1 1 0 10 20 30 40 50 60 70 80 90 100 1,000 1,000 Percentage of time the indicated 08189500 08195000 value was equaled or exceeded 100 100 EXPLANATION 10 10 Daily mean streamflow—Point 1 1 represents value equaled or exceeded 5, 10, 25, 50, 75, 90, or 95 percent of the time. 0.1 0.1 Dash indicates approximate 1,000 1,000 extension to zero-ﬂow value based on an interpolated 08198000 08205500 100 100 location of 0.1 ft3/s, the minimum flow plotted for 10 10 the logarithmic scale 1956 water year 1 1 2011 water year Period of record 0.1 0.1 08205500 U.S. Geological Survey 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 streamflow-gaging Percentage of time the indicated value was equaled or exceeded station number—Table 2

Figure 7. Streamflow duration for selected unregulated U.S. Geological Survey streamflow-gaging Figure 7. stationsStreamflow in Texas duration for 1956, for selected2011, and unregulatedthe period of U.S.record Geological. Survey streamﬂow-gaging stations in Texas for water years 1956, 2011, and the period of record. Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 13

Comparing the low flows of the 1951–56 and 2011 near Kountze, Tex., which has more than 70 years of record droughts from a historical perspective by considering data (fig. 11), and station 08070000 East Fork San Jacinto River from the periods of record at individual streamflow-gaging near Cleveland, Tex., was at or near record daily lows during stations is informative. For example, streamflows at station March to September 2011 (fig. 13). 07233500 Palo Duro Creek near Spearman, Tex., were Many USGS streamflow-gaging stations in Texas frequently higher during 1951–55 than for the period of record started the 2011 water year with normal streamflow but by (fig. 6). Low flows at station 07346070 Little Cypress Creek the end of the 2011 water year were flowing at near-record near Jefferson, Tex., during 1953 were higher than for the lows. Streamflows at USGS streamflow-gaging station period of record. At station 08166000 Johnson Creek near 08068500 Spring Creek near Spring, Tex., were below normal Ingram, Tex., a lack of storm runoff during 2011 is apparent, during February through June 2011, but normal during July but for median and lower streamflows, streamflows in 2011 through September 2011 (fig. 12). Stations 08070500 Caney were greater than those for the period of record (fig. 7). Creek near Splendora, Tex., and 08071000 Peach Creek Streamflows exceeded 90 or 95 percent of the time were near Splendora, Tex., (figs. 14 and 15, respectively) were at lower for water year 1956 than for water year 2011 at stations or near record daily lows during May to September 2011. 08068500 Spring Creek near Spring, Tex., 08071000 Peach Station 08134000 North Concho River near Carlsbad, Tex., Creek at Splendora, Tex., 8150000 Llano River near Junction, frequently goes dry during summer months; streamflows Tex., 08164000 Lavaca River near Edna, Tex., 08166000 on the North Concho River were at or below normal during Johnson Creek near Ingram, Tex., 08167500 Guadalupe all of 2011, except for a brief period of storm runoff in River near Spring Branch, Tex., and 08171000 Blanco River August 2011 (fig. 16). Streamflows at stations 08148500 at Wimberley, Tex. (fig. 7). For most of these stations, the North Llano River near Junction, Tex., and 08150000 Llano minimum of the low streamflows during 1951–56 occurred in River near Junction, Tex., (figs. 17 and 18, respectively) 1956 (fig. 6). were near normal during October 2010 to February 2011, but The USGS WaterWatch Web page (U.S. Geological below normal during March to September 2011. Streamflows Survey, 2012b) displays current and recent streamflow at station 08166000 Johnson Creek near Ingram, Tex., were conditions with respect to daily streamflow duration. The near normal during the 2011 water year (fig. 20). Stations effects of the 2011 drought on streamflow for 19 unregulated 08164000 Lavaca River near Edna, Tex., (fig. 19) and USGS streamflow-gaging stations (table 2) are shown in 08189500 Mission River at Refugio, Tex. (fig. 23), recorded figures 8–26. Parts of the 2010 and 2012 water years are storm runoff during January 2011 but by September 2011 included for comparison to 2011. Station 07233500 Palo were flowing at near‑record lows. Streamflows at stations Duro Creek near Spearman, Tex., was dry throughout 2011, 08167500 Guadalupe River near Spring Branch, Tex., and but recorded storm runoff during 2010 and 2012 (fig. 8). 08171000 Blanco River near Wimberley, Tex., (figs. 21 and Streamflow at station 07343000 North Sulphur River near 22, respectively) were at or near normal from October 2010 Cooper, Tex., was below normal (for this section of this through February 2011, but then remained below normal report, normal indicates daily streamflow between the through September 2011. Streamflows at stations 08195000 25th and 75th percentile of recorded streamflows) during Frio River at Concan, Tex., and 08198000 Sabinal River near parts of March and April 2011, and during July through Sabinal, Tex., (figs. 24 and 25, respectively) fell below normal September 2011 (fig. 9). Streamflow at station 07346070 Little in October 2010, and remained there through September 2011. Cypress Creek near Jefferson, Tex., was well below normal Station 08205500 Frio River near Derby, Tex., which typically from February through September 2011 (fig. 10). During records zero flow about 30 percent of the time, recorded zero March to September 2011, record daily lows were measured flow for 9 months during the 2011 water year fig.( 26). at USGS streamflow‑gaging station 08041500 Village Creek 14 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

20,000 10,000

EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 10 25 to 75 10 to less than 25 1 0 to less than 10 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 8. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 8. S treamflowstreamflow-gaging duration and station daily 07233500 mean streamflow Palo Duro during Creek January near Spearman, 2010 to September Texas (modified 2012 from U.S. Geologicalfor U.S. Geological Survey, 2012b).Survey streamflow-gaging station 07233500 Palo Duro Creek near Spearman, Texas (modified from U.S. Geological Survey, 2012b).

50,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90

10 25 to 75 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Figure 9. StreamflowFigure 9. Sdurationtreamflow and duration daily mean and daily streamflow mean streamflow during January during 2010January to September 2010 to September 2012 for 2012 for U.S. U.S. GeologicalGeological Survey Survey streamflow-gaging streamflow-gaging station station 07343000 07343000 North North Sulphur Sulphur River River near near Cooper, Cooper, Texas Texas (modified (modified from U.S. Geologicalfrom U.S. GeologicalSurvey, 2012b). Survey, 2012b). Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 15

40,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 10 25 to 75 10 to less than 25

1 0 to less than 10 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 10. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 10. streamflow-gagingStreamflow duration station and daily 07346070 mean streamflow Little Cypress during Creek January near 2010 Jefferson, to September Texas (modified2012 for U.S. from U.S. GeologicalGeological Survey, Survey 2012b). streamflow-gaging station 07346070 Little Cypress Creek near Jefferson, Texas (modified from U.S. Geological Survey, 2012b).

70,000

10,000 EXPLANATION Percentile class, for period of record 1,000 Greater than 90 to 100 Greater than 75 to 90 25 to 75

100 10 to less than 25 0 to less than 10 Daily mean streamflow

10 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Figure 11. FigureStreamflow 11. S durationtreamflow and duration daily mean and daily streamflow mean streamflow during January during January2010 to September 2010 to September 2012 for 2012 for U.S. U.S. GeologicalGeological Survey Survey streamflow-gaging streamflow-gaging station station 08041500 08041500 Village Village Creek Creek near near Kountze, Kountze, Texas Texas (modified (modified from U.S. from U.S. GeologicalGeological Survey, Survey, 2012b). 2012b). 16 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

60,000

10,000 EXPLANATION Percentile class, for 1,000 period of record Greater than 90 to 100 Greater than 75 to 90 100 25 to 75 10 to less than 25 10 0 to less than 10 Daily mean streamflow

1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 12. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 12. Sstreamflow-gagingtreamflow duration stationand daily 08068500 mean streamflow Spring Creek during near January Spring, 2010 Texas to September (modified 2012 for U.S. from U.S. GeologicalGeological Survey, Survey 2012b).streamflow-gaging station 08068500 Spring Creek near Spring, Texas (modified from U.S. Geological Survey, 2012b).

50,000

10,000 EXPLANATION Percentile class, for 1,000 period of record Greater than 90 to 100 Greater than 75 to 90 100 25 to 75 10 to less than 25 10 0 to less than 10 Daily mean streamflow

1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 13. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 13. Sstreamflow-gagingtreamflow duration stationand daily 08070000 mean streamflow East Fork duringSan Jacinto January River 2010 near to September Cleveland, 2012 Texas for U.S. (modified fromGeological U.S. Geological Survey streamflow-gaging Survey, 2012b). station 08070000 East Fork San Jacinto River near Cleveland, Texas (modified from U.S. Geological Survey, 2012b). Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 17

20,000 10,000

EXPLANATION 1,000 Percentile class, for period of record Greater than 90 to 100 100 Greater than 75 to 90 25 to 75 10 to less than 25 10 0 to less than 10 Daily mean streamflow

1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 14. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for Figure 14. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. U.S. Geological Survey streamflow-gaging station 08070500 Caney Creek near Splendora, Texas (modified Geological Survey streamflow-gaging station 08070500 Caney Creek near Splendora, Texas (modified from from U.S. Geological Survey, 2012b). U.S. Geological Survey, 2012b).

20,000 10,000

EXPLANATION 1,000 Percentile class, for period of record Greater than 90 to 100 100 Greater than 75 to 90 25 to 75 10 to less than 25 10 0 to less than 10 Daily mean streamflow

1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 15. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for Figure 15. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. Geological Survey streamflow-gaging station 08071000 Peach Creek at Splendora, Texas (modified U.S. Geological Survey streamflow-gaging station 08071000 Peach Creek at Splendora, Texas (modified from U.S. Geological Survey, 2012b). from U.S. Geological Survey, 2012b). 18 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

70,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 25 to 75 10 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 16. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 16. Sstreamflow-gagingtreamflow duration stationand daily 08134000 mean streamflow North Concho during River January near 2010 Carlsbad, to September Texas (modified 2012 for U.S. from U.S. GeologicalGeological Survey, Survey 2012b).streamflow-gaging station 08134000 North Concho River near Carlsbad, Texas (modified from U.S. Geological Survey, 2012b).

50,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90

10 25 to 75 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 17. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 17. S treamflowstreamflow-gaging duration and station daily 08148500 mean streamflow North Llano during River January near Junction,2010 to September Texas (modified 2012 for U.S. from U.S. GeologicalGeological SurveySurvey, streamflow-gaging 2012b). station 08148500 North Llano River near Junction, Texas (modified from U.S. Geological Survey, 2012b). Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 19

200,000 100,000

EXPLANATION 10,000 Percentile class, for period of record 1,000 Greater than 90 to 100 Greater than 75 to 90 100 25 to 75 10 to less than 25 10 0 to less than 10 Daily mean streamflow

1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 18. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 18. Sstreamflow-gagingtreamflow duration stationand daily 08150000 mean streamflow Llano River during near January Junction, 2010 Texas to September (modified 2012 for U.S. from U.S. GeologicalGeological Survey, Survey 2012b).streamflow-gaging station 08150000 Llano River near Junction, Texas (modified from U.S. Geological Survey, 2012b).

200,000 100,000

10,000 EXPLANATION Percentile class, for 1,000 period of record Greater than 90 to 100 100 Greater than 75 to 90 25 to 75 10 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Figure 19. FigureStreamflow 19. S durationtreamflow and duration daily mean and daily streamflow mean streamflow during January during January2010 to September 2010 to September 2012 for 2012 for U.S. U.S. GeologicalGeological Survey Survey streamflow-gaging streamflow-gaging station station 08164000 08164000 Lavaca Lavaca River River near near Edna, Edna, Texas Texas (modified (modified from U.S. from U.S. GeologicalGeological Survey, Survey, 2012b). 2012b). 20 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

20,000 10,000

EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 10 25 to 75 10 to less than 25 1 0 to less than 10 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 20. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for Figure 20. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. U.S. Geological Survey streamflow-gaging station 08166000 Johnson Creek near Ingram, Texas (modified Geological Survey streamflow-gaging station 08166000 Johnson Creek near Ingram, Texas (modified from from U.S. Geological Survey, 2012b). U.S. Geological Survey, 2012b).

80,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 25 to 75 10 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 21. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 21. Sstreamflow-gagingtreamflow duration stationand daily 08167500 mean streamflow Guadalupe during River January near Spring 2010 toBranch, September Texas 2012 for U.S. (modified fromGeological U.S. Geological Survey streamflow-gaging Survey, 2012b). station 08167500 Guadalupe River near Spring Branch, Texas (modified from U.S. Geological Survey, 2012b). Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 21

40,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 10 25 to 75 10 to less than 25

1 0 to less than 10 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 22. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 22. Sstreamflow-gagingtreamflow duration stationand daily 08171000 mean streamflow Blanco River during at Wimberley,January 2010 Texas to September (modified 2012 for from U.S. GeologicalU.S. Geological Survey, Survey 2012b). streamflow-gaging station 08171000 Blanco River at Wimberley, Texas (modified from U.S. Geological Survey, 2012b).

70,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 25 to 75 10 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 23. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 23. Sstreamflow-gagingtreamflow duration stationand daily 08189500 mean streamflow Mission River during at JanuaryRefugio, 2010 Texas to September(modified from 2012 for U.S. U.S. GeologicalGeological Survey, Survey 2012b). streamflow-gaging station 08189500 Mission River at Refugio, Texas (modified from U.S. Geological Survey, 2012b). 22 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

60,000

10,000 EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90

10 25 to 75 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 24. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 24. Sstreamflow-gagingtreamflow duration andstation daily 08195000 mean streamflow Frio River during at Concan, January Texas 2010 (modified to September from 2012 for U.S. GeologicalU.S. GeologicalSurvey, 2012b). Survey streamflow-gaging station 08195000 Frio River at Concan, Texas (modified from U.S. Geological Survey, 2012b).

20,000 10,000

EXPLANATION 1,000 Percentile class, for period of record 100 Greater than 90 to 100 Greater than 75 to 90 10 25 to 75 10 to less than 25 1 0 to less than 10 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 25. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigure Survey 25. Sstreamflow-gagingtreamflow duration andstation daily 08198000 mean streamflow Sabinal River during near January Sabinal, 2010 Texas to September (modified 2012 for U.S. from U.S. GeologicalGeological Survey, Survey 2012b).streamflow-gaging station 08198000 Sabinal River near Sabinal, Texas (modified from U.S. Geological Survey, 2012b). Summary 23

200,000 100,000

10,000 EXPLANATION Percentile class, for 1,000 period of record Greater than 90 to 100 100 Greater than 75 to 90 25 to 75 10 10 to less than 25 0 to less than 10 1 Daily mean streamflow

0.1 Daily mean streamflow, in cubic feet per second Daily mean streamflow,

Apr. Apr. Oct. Apr. Jan. Feb. Oct. Jan. Feb. Nov. Jan. Feb. Mar. May July Aug. Nov. Dec. Mar. May July Aug. Dec. Mar. May July Aug. June Sept. June Sept. June Sept. 2010 2011 2012 2011 water year (October 1, 2010–September 30, 2011) Figure 26. Streamflow duration and daily mean streamflow during January 2010 to September 2012 for U.S. GeologicalFigue Survey 26. S streamflow-gagingtreamflow duration and station daily 08205500 mean streamflow Frio River during near Derby,January Texas 2010 to(modified September 2012 for U.S. from U.S. GeologicalGeological Survey, Survey 2012b).streamflow-gaging station 08205500 Frio River near Derby, Texas (modified from U.S. Geological Survey, 2012b).

Summary extreme drought during the entire 1955 and 1956 water years. The lowest statewide PDSI during the period 1951–56 was The intense drought that occurred throughout Texas -7.8, occurring September 1956. The statewide monthly PDSI during 2011 resulted in large precipitation deficits throughout declined to -7.93 during September 2011 and was larger in the State, large drought severity indexes (Drought Monitor magnitude (larger negative value) than the monthly PDSI for and Palmer Drought Severity Indexes), and substantial any drought-affected month during the 1950s. declines in streamflow. A record low statewide average annual Annual mean streamflow during 1951–56 and 2011 precipitation of 11.27 inches for the period 1895–2011 was was assessed for 19 unregulated USGS streamflow-gaging recorded during the 2011 water year; the prior record low stations. For most of these sites, annual mean streamflows statewide average precipitation was 13.91 inches during the were well below the mean for the period of record. At eight of 1956 water year. The statewide average annual precipitation these streamflow-gaging stations, the annual mean streamflow during each of the years 1951–56 was less than the normal was lower in 2011 than for any year during 1951–56; many statewide average annual precipitation of 27.95 inches. of these stations are located in eastern Texas. Annual mean The historical drought of 1951–56 has long been used by streamflow for streamflow-gaging stations in the Guadalupe, water-resource managers, engineers, and scientists as a Blanco, and upper Frio River Basins were lower in 1956 than point of reference for water‑supply planning. A comparison in 2011. of the 2011 drought to the drought of 1951–56 provides an Streamflow-duration curves for 1956, 2011, and the additional reference for water-supply planning. In 2012, the period of record for the 19 unregulated USGS streamflow- U.S. Geological Survey (USGS), in cooperation with the gaging stations show streamflows exceeded 90 to 95 percent Texas Water Development Board, assessed the effects of the of days were lower during 2011 than during 1956 at seven 1951–56 and 2011 droughts from a hydrologic perspective. of the streamflow-gaging stations. The streamflow-duration Between August 1951 and November 1952, 14 of 16 monthly curves for many streamflow-gaging stations indicate a lack of Palmer Drought Severity Index (PDSI) values indicated (or diminished) storm runoff during 2011. During March to extreme drought. The 2011 water year began October 1, September 2011, record daily lows were measured at USGS 2010, with parts of Texas being abnormally dry, but none of streamflow-gaging station 08041500 Village Creek near Texas was classified as in drought, according to data from the Kountze, Tex., which has more than 70 years of record. Many Drought Monitor. By April 2011, nearly all of the State was other USGS streamflow-gaging stations in Texas started the experiencing severe to extreme drought, and by the end of 2011 water year (October 1, 2010) with normal streamflow July 2011, more than 75 percent of the State was experiencing but by the end of the 2011 water year (September 2011) were exceptional drought. Statewide PDSI values also indicated flowing at near-record lows. 24 A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011

References Palmer, W.C., 1965, Meteorological drought: U.S. Department of Commerce Weather Bureau Research Paper No. 45, 58 p.

Asquith, W.H., 2001, Effects of regulation on L-moments of Searcy, J.K., 1959, Flow-duration curves: U.S. Geological annual peak streamflow in Texas: U.S. Geological Survey Survey Water-Supply Paper 1542–A, 33 p. Water-Resources Investigations Report 01–4243, 66 p. Texas A&M University, 2011, Texas drought officially the Asquith, W.H., and Heitmuller, F.T., 2008, Summary of annual worst ever: accessed August 2011, at http://tamunews.tamu. mean and annual harmonic mean statistics of daily mean edu/texas-drought-officially-the-worst-ever/. streamflow for 620 U.S. Geological Survey streamflow- gaging stations in Texas through water year 2007: U.S. Texas Water Development Board, 2013, Water for Texas Geological Survey Data Series 372, 1,259 p. 2012 State Water Plan: Texas Water Development Board, accessed March 25, 2013, at http://www.twdb.state.tx.us/ Asquith, W.H., and Roussel, M.C., 2007, An initial- publications/state_water_plan/2012/2012_SWP.pdf. abstraction, constant-loss model for unit-hydrograph modeling for applicable watersheds in Texas: U.S. Thomas, H.E., and others, 1963, Drought in the Southwest, Geological Survey Scientific Investigations Report 2007– 1942–56; Effects of drought in central and south Texas: 5243, 82 p. U.S. Geological Survey Professional Paper 372–C, 31 p. Asquith, W.H., Vrabel, Joseph, and Roussel, M.C., 2007, University of Nebraska–Lincoln, 2012, The Drought Monitor, Summary of percentages of zero daily mean streamflow for accessed July 2012, at http://droughtmonitor.unl.edu/. 712 U.S. Geological Survey streamflow-gaging stations in U.S. Department of Agriculture, National Agriculture Texas through 2003: U.S. Geological Survey Data Series Statistics Service, 2013, Texas climate divisions map: Texas 247, 721 p. Field Office, U.S. Department of Agriculture, accessed Cleaveland, M.K., Votteler, T.H., Stahle, D.K., Casteel, R.C., January 24, 2013, at http://www.nass.usda.gov/Statistics_ and Banner, J.L., 2011, Extended chronology of drought by_State/Texas/Charts_&_Maps/cwmap.htm. in south central, southeastern and west Texas: Texas Water U.S. Department of Commerce, National Climatic Journal, vol. 2, no. 1, accessed August 3, 2012, at https:// Data Center, 2012, Texas Precipitation, October– journals.tdl.org/twj/article/view/2049. September 1896–2012: Asheville, North Carolina, Dallas Morning News, 2011, Texas has hottest June–August National Climatic Data Center, accessed October 2012, on record in the U.S.: The Associated Press, September 8, at http://www.ncdc.noaa.gov/temp-and-precip/time- 2011, accessed March 25, 2013, at http://www.dallasnews. series/index.php?parameter=pcp&month=9&year= com/news/state/headlines/20110908-texas-has-hottest-june- 2011&filter=12&state=41&div=0. august-on-record-in-the-u.s..ece. U.S. Department of Commerce, Weather Bureau, 1957, Jain, S.K., and Singh, V.P., 2005, Isohyetal method: Water Climatological data: Texas, annual summary 1956: v. LXI, Encyclopedia, v. 4, p. 290–292. no. 13, 27 p. McGuire, V.L., 2011, Water-level changes in the High Plains U.S. Geological Survey, 2008, User’s manual for the National aquifer, predevelopment to 2009, 2007–08, and 2008–09, Water Information System of the U.S. Geological Survey and change in water in storage, predevelopment to 2009: Automated Data Processing System (ADAPS): U.S. U.S. Geological Survey Scientific Investigations Report Geological Survey database, accessed October 11, 2012, at 2011–5089, 13 p. (Also available at http://pubs.usgs.gov/ http://nwis.usgs.gov/nwisdocs4_8/adaps/adaps.book.html. sir/2011/5089/.) U.S. Geological Survey, 2012a, National Water Information Nace, R.L., and Pluhowski, E.J., 1965, Drought of the 1950’s System (NWISWeb): U.S. Geological Survey database, with special reference to the midcontinent: U.S. Geological accessed August 2012, at http://waterdata.usgs.gov/tx/nwis/. Survey Water-Supply Paper 1804, 88 p. U.S. Geological Survey, 2012b, WaterWatch: U.S. Geological National Weather Service, 2012, Advanced Hydrologic Survey Web site, accessed November 2012, at http:// Prediction Service: accessed August 2012, at http://water. waterwatch.usgs.gov/. weather.gov/precip/. Nielsen-Gammon, J.W., 2011, The 2011 Texas drought – A briefing packet for the Texas legislature: Office of the State Climatologist, College Station, Texas A&M University, accessed August 26, 2012, at http://climatexas.tamu.edu/ files/2011_drought.pdf. Publishing support provided by Lafayette and Tacoma Publishing Service Centers

Information regarding water resources in Texas is available at http://tx.usgs.gov/ Winters— A Historical Perspective on Precipitation, Drought Severity, and Streamflow in Texas during 1951–56 and 2011 —Scientific Investigations Report 2013–5113