2019 Discharge Report

HYDROLOGIC DATA FACT SHEETS

GROUNDWATER DISCHARGE AND USAGE 2019

2019 GROUNDWATER DISCHARGE AND USAGE Groundwater discharges from the Edwards Aquifer either as springflow or as pumping from wells. Comal and San Marcos springs, the largest and second-largest springs in Texas, respectively, are fed by the Edwards Aquifer. This springflow greatly benefits the recreational economies in New Braunfels and San Marcos, and both springs provide habitat for threatened and endangered species. Figure 1 shows locations of the major springs in the Edwards Aquifer region. Wells drilled into the Edwards Aquifer throughout the region provide water for many diverse uses, including irrigation, municipal water supplies, industrial applications, and domestic/livestock consumption. Estimates of total annual groundwater discharge from combined springflow and pumping for the Edwards Aquifer are provided in Table 1 for the period of record (1934–2019). Annual total groundwater discharge estimates range from a low of 388,800 acre-feet in 1955 to a high of 1,130,000 acre-feet in 1992. In 2019, the total groundwater discharged from the Edwards Aquifer from both wells and springs is estimated at 884,588 acre-feet: 526,000 acre- feet as springflow and 358,588 acre-feet as pumping from wells. The portion of discharge as springflow is estimated by measuring streamflow downstream of the springs and converting the streamflow measurements to spring discharge by subtracting any estimated contributions from surface runoff. Total annual spring discharge has varied from a low of 69,800 acre-feet in 1956 to a high of 802,800 acre-feet in 1992. Monthly springflow estimates for 2019 at each of the six major Edwards Aquifer springs are provided in Table 2. In Figures 2 and 3, flows at Comal and San Marcos springs are shown as mean annual flows compared with the long-term historical mean annual flow rate for the available period of record. The 2019 mean annual flow rate was greater than the historical mean discharge at both Comal Springs and San Marcos Springs. Discharge as well pumping can be classified as either reported or unreported discharge. Reported discharge refers to water pumped from the aquifer by a person or entity holding a groundwater withdrawal permit. These users, who are typically larger quantity users, meter their withdrawals and report the totals to the EAA. Unreported discharge refers to use that does not require a groundwater withdrawal permit from the EAA, such as domestic, livestock, or federal facility use. Unreported discharge is estimated based on numbers of wells and statistical estimates of per-well usage. In 2019, unreported discharge for domestic and livestock wells was estimated at 14,174 acre-feet, and non-reporting federal facility discharge was estimated at 5,394 acre-feet, for a total of 19,568 acre-feet of unreported discharge. Reported discharge totaled 339,020 acre-feet. The total of all reported and unreported pumping discharge is 358,588 acre-feet. Table 3 provides a summary of well and spring discharge for 2019 based on type of use and county. The distribution of discharge from springflows and the different types of pumping for 2019 is shown graphically in Figure 4. Total annual discharge from pumping and springflow are compared in Figure 5 for the period of record from 1934–2019. The years

when springflow exceeds pumping tend to be wet years when pumping demand is lowered by more frequent rainfall and higher aquifer levels produce increased springflows. Conversely, during dry years pumping tends to exceed springflow due to increased municipal and agricultural demand and lower aquifer levels. Since 1997, however, the increase in pumping demand during dry years has been limited by the withdrawal permit system and critical period pumping reductions implemented under the Edwards Aquifer Authority Act. Table 4 provides a historical list of total annual discharge by type of use for the period 1955– 2019.

Figure 1. Major Springs in the Southern Segment of the Balcones Fault Zone Edwards Aquifer

Table 1. Annual Estimated Groundwater Discharge Data by County for the Edwards Aquifer, 1934–2019 (measured in thousands of acre-feet) Year Uvalde a Medina Bexar b Comal c Hays Total Total Wells Total Springs

1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988

12.6 12.2 26.6 28.3 25.2 18.2 16.1 17.9 22.5 19.2 11.6 12.4 13.2 17.8 16.9 22.7 27.5 26.6 28.3 59.6 29.0 23.7 43.0 53.7 56.5 64.6 51.4 49.3 46.8 48.5 81.1 58.0 88.5 6.2 13.8 9.2

1.3 1.5 1.5 1.5 1.6 1.6 1.6 1.6 1.7 1.7 1.7 1.7 1.7 2.0 1.9 2.0 2.2 2.2 3.1 4.0 6.3 6.6 8.3 7.6 6.4 8.1 9.7 8.6

109.3 171.8 215.2 201.8 187.6 122.5 116.7 197.4 203.2 172.0 166.3 199.8 180.1 193.3 159.2 165.3 177.3 186.9 187.1 193.7 208.9 215.2 229.6 189.4 199.5 217.5 215.4 230.3 220.0 217.3 201.0 201.1 198.0 239.7 207.1 216.3 230.6 262.8 247.7 273.0 272.1 259.0 253.2 317.5 269.5 294.5 300.3 280.7 305.1 277.6 309.7 295.5 294.0 326.6 317.4

229.1 237.2 261.7 252.5 250.0 219.4 203.8 250.0 255.1 249.2 252.5 263.1 261.9 256.8 203.0 209.5 191.1 150.5 133.2 141.7 101.0 113.2 231.8 231.7 235.2 249.5 197.5 155.7 141.8 194.7 198.9 139.1 238.2 218.2 229.2 168.2 234.3 289.3 286.1 296.0 279.7 295.0 245.7 300.0 220.3 241.8 213.2 186.6 108.9 200.0 229.3 286.2 236.5 70.1 33.6

85.6 96.9 93.2 87.1 93.4 71.1 78.4

437.9 519.6 598.2 571.2 557.8 432.8 416.6 601.2 594.7 539.3 567.4 614.8 583.9 593.5 450.6 479.8 466.7 425.6 424.9 468.3 424.3 388.8 390.9 456.5 617.5 619.0 655.4 683.5 589.0 516.0 474.0 578.9 571.2 557.4 660.0 658.7 727.1 679.5 747.1 838.0 861.2 868.2 853.4 960.9 807.3 914.5 819.4 794.4 786.4 720.1 708.1 856.5 817.3 922.0 909.7

101.9 103.7 112.7 120.2 120.1 118.9 120.1 136.8 144.6 149.1 147.3 153.3 155.0 167.0 168.7 179.4 193.8 209.7 215.4 229.8 246.2 261.0 321.1 237.3 219.3 234.5 227.1 228.2 267.9 276.4 260.2 256.1 255.9 341.3 251.7 307.5 329.4 406.8 371.3 310.4 377.4 327.8 349.5 380.6 431.8 391.5 491.1 387.1 453.1 418.5 529.8 522.5 429.3 364.1 540.0

336.0 415.9 485.5 451.0 437.7 313.9 296.5 464.4 450.1 390.2 420.1 461.5 428.9 426.5 281.9 300.4 272.9 215.9 209.5 238.5 178.1 127.8 219.2 398.2 384.5 428.3 455.3 321.1 239.6 213.8 322.8 315.3 216.1 408.3 351.2 397.7 272.7 375.8 527.6 483.8 540.4 503.9 580.3 375.5 523.0 328.3 407.3 333.3 301.6 178.3 334.0 388.0 557.9 369.7 69.8

134.3 112.2

97.2

135.3 137.8 134.0 127.6 77.3 89.8 78.3 69.1 78.8 81.5 64.1 50.4 101.4 113.0 155.9 118.5 143.5 140.8 146.8 122.1 149.9 123.7 164.3 141.1 178.6 164.7 172.0 157.0 107.9 141.6 105.5 118.5 144.9 160.4 198.4 116.9 99.1 99.1 85.7 98.8 81.9 73.3 126.3 115.4 82.3

11.1 17.7 11.9

10.0 10.4 15.2 13.6 16.5 32.4 28.8 14.9 28.6 22.6 19.4 19.9 38.7 32.9 39.9 26.1 33.4 29.7 46.9 59.2 41.9 15.9 82.2 9.9

100.9 117.0 112.6 133.3 112.0 136.4 156.5 154.3 130.1 151.0 104.2 129.2 107.7 156.9 156.9 96.5

91.7 94.9

156.7

(Table 1. continued)

Total Wells

Total Springs

Year

Medina

Bexar b

Comal c

Hays

Total 766.5 730.0 790.6 996.7 814.8 761.0 705.6 761.1 917.6 898.8 752.3 890.0 981.2 976.9 940.3 766.5 940.9 845.7 683.7 862.6 692.9 687.0 588.6 527.5 729.7 870.3 872.2 763.6 884.6 1130.0 1035.7

Uvalde a

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

156.9 118.1

70.5 69.7 25.6 17.8 41.1 35.2 66.3 31.4 51.3 49.2 45.1 33.9 40.6 34.8 22.5 37.3 64.9 18.4 48.8 47.3 36.4 57.4 44.3 42.8 43.1 27.6 31.9 43.6 42.0 40.9 9.3

305.6 276.8 315.5 370.5 371.0 297.7 272.1 286.8 260.2 312.4 307.1 283.6 291.6 311.9 331.7 331.9 366.1 289.5 330.2 320.4 265.2 298.5 277.2 267.5 251.0 230.5 256.3 262.6 305.3 277.1 290.7

147.9 171.3 221.9 412.4 349.5 269.8 235.0 150.2 243.3 271.8 295.5 226.1 327.7 350.4 344.7 341.4 349.3 216.7 331.7 266.6 206.6 312.1 187.7 193.4 154.9 114.5 239.8 320.7 294.0 244.0 306.1

85.6 94.1

542.4 489.4 436.0 327.2 407.3 424.6 399.6 493.6 377.1 453.5 442.7 414.8 367.7 371.3 362.1 317.4 388.5 454.5 319.9 428.6 395.7 372.6 427.7 384.7 355.8 332.2 325.2 325.3 379.2 370.6 358.6

224.1 240.6 354.6 802.8 589.4 390.2 361.3 212.0 383.9 464.1 456.1 337.5 529.6 609.9 621.5 622.9 647.1 312.0 621.0 417.1 287.9 490.0 265.2 302.3 232.8 195.4 404.5 545.0 493.0 393.0 526.0 386.3 384.4

76.6 76.5

151.0 261.3 151.0 110.6 127.8 149.2 168.8 143.0 108.4 175.4 202.1 176.3 153.1 175.6 84.7

107.5

95.5 90.8

117.6

77.0

113.1 104.0

89.1 68.6 76.2 89.4 91.3

107.4 107.5

87.9

64.6

196.0 108.0

102.0

76.9 53.1 79.6 57.6 43.6 41.5 27.1 46.9 63.0 69.9 76.8

87.8

162.5

91.0

124.2

96.0 97.9

178.8 208.3 166.8 130.4 225.0

For period of record 1934–2019: Median 69.3 19.7

259.6 250.2

235.1 229.3

120.3 124.5

706.9 701.7

330.8 317.4

Mean

71.2

24.4

For last 10 years, 2010–2019: Median 55.4 42.4

272.3 271.7

241.9 222.6

146.5 139.0

746.7 747.9

364.6 363.2

398.8 384.7

Mean

55.9

41.0

Data source: USGS Letter Report to Edwards Aquifer Authority files, dated April 10, 2020. a = As of 2008, no longer includes Kinney County discharge; prior years include 1,900 acre-feet of discharge for Kinney County. b = Includes reports of Edwards Aquifer irrigators in Atascosa County. c = Includes reports of Edwards Aquifer industrial and municipal users in Guadalupe County. Differences in totals may occur due to rounding.

Table 2. Estimated Spring Discharge from the Edwards Aquifer in 2019 (measured in acre-feet)

Leona Springs and Leona River Underflow

Total Monthly Discharge from Springs

San Pedro Springs

San Antonio Springs

San Marcos Springs 15,700 13,800 14,700 14,200 16,700 15,600 14,000 13,100 11,500 11,000 10,600 10,200 161,000

Comal Springs 23,600 21,100 23,300 21,500 23,300 22,100 21,300 18,400 18,000 18,200 19,400 19,300

Hueco Springs 5,020 4,180 4,780 4,480 5,570 4,440 4,290 3,330 2,600 2,180 1,610 1,270

Month

January February March

3,050 2,900 3,000 2,810 3,060 2,830 2,540 2,010 2,280 2,470 2,600 2,660

901 783 758 605 740 659 620 246 191 282 400 357

6,500 5,130 4,640 3,180 4,530 3,590 3,180 57.2

54,800 47,900 51,200 46,800 53,900 49,200 45,900 37,100 34,600 34,300 35,400 34,500 526,000

April May June July

August

September October November December

0

160 819 682

Total

32,200

6,540

32,500

249,000 43,800

Data source: USGS letter report dated April 10, 2020. Totals might not equal sum of discharge values because of rounding to three significant figures.

Table 3. Comprehensive Discharge Summary for Calendar Year 2019 (in acre-feet) Reported Use (permitted wells) Unreported Use

Domestic, Livestock, and Limited Pumping*

Total Well Discharge

Total Wells and Springs

Federal Facilities*

Spring Discharge

County Atascosa

Irrigation Municipal Industrial

1,212 4,350

0

0

0 0

1,212

0

1,212

Bexar Comal

218,856

14,366 4,336

8,979

5,100

251,651 13,304 6,640 40,941 44,615 358,588 225

39,040 292,800

290,691 306,104 167,640 40,941 76,815 884,588 225

58

8,476

434 0 1 0

Guadalupe

0

11

213

0

Hays

147

4,027 7,152 2,966

1,271 3,516

901

294

161,000

Medina Uvalde Totals

29,086 38,876 73,728

1,187 0

0

101

2,672 14,174

0

32,200 526,000

241,489

23,803

5394

* Federal facilities and domestic and livestock wells are not required to report annual use; these quantities are estimated. Differences in totals may occur due to rounding.

Figure 2. Historical Mean Annual Discharge at Comal Springs

Figure 3. Historical Mean Annual Discharge at San Marcos Springs

Figure 4. 2019 Discharge by Type of Use

Figure 5. Groundwater Pumping Compared with Springflow

Table 4. Annual Estimated Edwards Aquifer Groundwater Discharge by Use, 1955–2018 (measured in thousands of acre-feet) Year Irrigation Municipal Domestic/ Livestock Industrial/ Commercial Springs

1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

85.2

120.5 138.3 116.1 113.7 118.9 121.1 124.5 143.7 151.8 140.2 138.8 141.8 171.0 146.9 162.0 167.5 196.2 190.5 177.1 174.6 182.5 182.1 205.3 214.2 208.9 256.2 231.8 268.6 249.2 287.2 263.7 266.3 260.9 286.2 285.2 254.9 240.5 236.5 252.0

30.1 28.9 29.8 33.4 31.5 29.1 29.6 28.8 27.8 26.3 27.0 23.3 25.1 25.5 29.2 29.3 28.6 30.8 32.3 33.5 33.6 34.6 38.1 40.3 40.7 43.3 40.9 39.5 38.8 36.2 39.2 42.0 43.5 41.9 38.2 37.9 39.5 34.8 49.9

25.1 22.4 22.6 25.1 24.2 23.3 22.2 22.8 21.8 21.7 22.3 22.6 25.8 20.0 21.1 22.5 22.6 21.1 18.8 15.1 15.3 14.7 13.0 11.5 15.2 13.7 12.6 15.0 14.7 15.2 16.5 16.8 18.7 18.8 22.9 23.7 67.5 29.0 36.1 39.3 37.3 38.8

127.8

127.2

69.8

68.8 47.2 60.0 54.9 52.1 72.7 75.4 72.6 68.0 68.2

219.2 398.2 384.5 428.3 455.3 321.1 239.6 213.8 322.8 315.3 216.1 408.3 351.2 397.7 272.7 375.8 527.6 483.3 540.4 503.9 580.3 375.5 523.0 328.3 407.3 333.3 301.5 178.3 334.0 388.0 557.9 369.7 224.1 240.6 354.6 802.8 589.4 390.2 361.3 212.0

119.4

59.3 95.2

110.1 159.4 128.8

82.2

140.4

96.4

118.2 124.2 165.8 126.8 177.9 101.8 130.0 115.9 191.2 203.1 104.2 193.1 196.2 172.9 40.9

88.5 27.1 69.3

104.5

247.0 255.0 261.3

33.9

95.6

11.6*

181.3

12.3

(Table 4. continued)

Domestic/ Stock

Industrial/ Commercial

Year 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

Irrigation

Municipal

Springs

77.4 a/b

253.0 266.5 273.3 261.3 245.9 228.4 237.2 220.3 255.1 259.1 236.0 273.6 247.5 259.9 265.5 257.9 239.5 220.1 247.2 232.6 268.3 250.5 241.5

12.3 13.4 13.4 13.4 13.4 13.6 13.7 13.8 13.8 13.8 13.8 13.6 13.6 13.6 13.7 13.7 13.9 13.9 14.0 14.0 14.1 14.1

34.4 41.7 b 42.4 33.8 29.4 32.3 31.7 28.1 34.3 34.5 27.6 28.8 25.7 26.4 23.6 22.6 26.3 22.8 21.9 24.0 22.8 22.1 23.8

383.9 464.1 456.1 337.5 529.4 609.9 621.5 622.9 647.1 312.0 620.6 417.1 288.0 490.0 265.2 302.3 232.8 195.4 404.5 545.0 493.0 393.0 526.0

131.9 a 113.6 106.3

79.0 97.1 79.6 55.4 85.3

149.1

42.5

112.7 108.9

13.5 **

72.7

124.9

90.6 76.3 75.3 42.2 54.7 74.1 84.0 73.7

For period of record 1955–2018: Median 95.2 For 2009–2018 (last ten years): Median 74.7 Mean 101.2

237.2 216.8

28.8

22.8 24.8

384.5 393.6

26.2**

248.9 248.3

13.9 13.9

23.2 23.6

398.8 384.7

Mean

76.9

Data source: USGS unpublished report and Edwards Aquifer Authority files (2018). a = Includes estimates from Atascosa County discharge by Edwards Aquifer users. b = Includes estimates from Guadalupe County discharge by Edwards Aquifer users. * = In 1995 USGS revised the method of calculating domestic/livestock pumpage, which significantly decreased the estimated pumping; EAA believes the post-1995 estimates to be more accurate than the previous method. ** = In 2008, EAA began to estimate domestic/livestock pumping based on number of new wells permitted annually and discontinuation of Kinney County pumping in total. Period of record mean and median only include post 2008 estimates. Differences in totals may occur due to rounding.