2017-Recharge-Report

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2017 GROUNDWATER RECHARGE

November 2018

Recharge to the Edwards Aquifer originates as precipitation over the drainage area and re- charge zone of the aquifer, or as interforma- tional flow from adjacent aquifers. The EAA maintains a joint funding agreement with the U.S. Geological Survey (USGS) to provide sur- face recharge estimates for eight of the nine major drainage basins with streams that flow on to the Edwards Aquifer recharge zone (Fig- ure 1). Recharge is estimated using a water- balance method that relies on precipitation and streamflow measurements across the region. Based on the USGS methodology, the Guadal- upe River Basin does not appear to provide sig- nificant recharge to the Edwards Aquifer, so re- charge is not estimated for that drainage basin. Table 1 lists estimated annual recharge by drain- age basin for the period of record from 1934 through 2017 based on USGS calculations. Es- timates of total annual recharge ranged from 43,700 acre-feet at the height of the drought of record in 1956 to 2,486,000 acre-feet in 1992, as shown in Figure 2. In 2017, total estimated recharge was 487,000 acre-feet, which is be- low both the mean annual recharge of 704,000 acre-feet and the median annual recharge of 557,000 acre-feet for the period of record. In an effort to enhance recharge, the EAA oper- ates four recharge structures in Medina County on the Edwards Aquifer Recharge Zone (yel-

low triangles in Figure 1). The total amount of enhanced recharge for each site is estimated using data from stage recorders near these structures. Enhanced recharge refers to the estimated amount of additional recharge attrib- utable to these structures above the amount of recharge that would have occurred naturally in the absence of these structures. Table 2 shows the estimated annual enhanced recharge for each site starting in 2014. Recharge estimates for prior dates reflect total annual recharge at each site. The total estimated enhanced re- charge for these structures in 2017 was 35 acre-feet, all of which occurred at Parker Dam. Enhanced recharge is generally a small fraction of total recharge and tends to be greater in wet years when natural recharge is also high. Recharge resulting from interformational flow in adjacent aquifers such as the Trinity Aquifer is not estimated annually. Estimates associ- ated with interformational flow are variable and range from 5,000 to 100,000 acre-feet per year in different publications. Estimated interfor- mational recharge is not included in recharge values provided in this report. Edwards Aqui- fer Authority is presently conducting an Inter- formational Flow Study that may help to better quantify the amount of water that may enter the Edwards Aquifer from Trinity Aquifer for- mations to the north.

E DWARD S AQU I F E R AU THOR I T Y

Caldwell

Hays

Guadalupe

Wilson

Comal

Atascosa # * EAA-Operated Recharge Structure Drainage Basin Boundary County boundaries Aquifer Zones Drainage Area Recharge Zone Artesian Zone

Blanco

Bexar

Legend

Kendall

San

Geronimo Creek Verde

# * # * # *

Miles

0 10 20 30 40 5

Gillespie

Creek

# * # * # * # * # * # *

Frio

Medina

Creek

Parker

# * # * # *

Bandera

Kerr

2 3 4

Seco

Creek

Uvalde

Zavala

Real

Edwards

Kinney

Figure 1. Major Drainage Basins and Edwards Aquifer Authority-Operated Recharge Structures in the San Antonio Segment of the Balcones Fault Zone Edwards Aquifer.

Maverick

Nueces-West Nueces River Basin Frio-Dry Frio River Basin Sabinal River Basin

Area between Sabinal and Medina River Basin Medina River Basin

Guadalupe River Basin* Blanco River Basin

and Cibolo/Dry Comal Creek Basins

Cibolo and Dry Comal Creek Basins** Area between Medina River Basin

* The current method of estimation does not attribute any net recharge to this basin. **Recharge is reported as a single basin for these two basins.

Key to Basins

20 17 GROUNDWAT E R R E CHARG E

TABLE 1. ESTIMATED ANNUAL GROUNDWATER RECHARGE TO THE SAN ANTONIO SEGMENT OF THE BALCONES FAULT ZONE EDWARDS AQUIFER BY DRAINAGE BASIN, 1934–2017 (IN THOUSANDS OF ACRE-FEET).

Area between Medina River and Cibolo Creek/ Dry Comal Creek Basins

Nueces River/ West Nueces River Basin

Area between Sabinal River and Medina River Basins

Frio River/ Dry Frio River Basin

Cibolo Creek/ Dry Comal Creek Basin

Blanco River Basin

Sabinal River Basin

Medina River Basin

Year 1934

Total a

8.6

27.9 192.3 157.4 75.7 69.3 49.5 60.3 151.8 95.1 42.3 76.0 71.1 54.2 77.7 25.6 86.1 35.5 28.4 15.7 15.1 31.6 22.1 133.6 300.0 158.9 128.1 151.3 46.6 27.0 57.1 83.0 134.0 137.9 176.0 113.8 141.9 212.4 144.6 256.9 4.2

7.5 56.6 43.5 21.5 20.9 17.0 23.8 50.6 34.0 11.1 24.8 30.8 16.5 16.7 26.0 31.5 13.3 7.3 3.2 3.2 7.1 0.6 1.6 65.4

19.9 166.2 142.9 61.3 54.1 33.1 56.6 139.0 84.4 33.8 74.3 78.6 52.0 45.2 20.2 70.3 27.0 26.4 30.2 129.5 294.9 96.7 127.0 105.4 23.5 10.3 61.3 104.0 78.2 64.8 198.7 84.2 81.6 155.6 154.6 286.4 4.4 11.9 7.7 3.6

46.5 71.1 91.6 80.5 65.5 42.4 38.8 54.1 51.7 41.5 50.5 54.8 51.4 44.0 14.8 33.0 23.6 21.1 25.4 36.2 25.3 16.5 6.3 55.6 95.5 94.7

21.0 138.2 108.9 47.8 46.2 9.3 29.3 116.3 66.9 29.5 72.5 79.6 105.1 55.5 17.5 41.8 17.3 15.3 50.1 20.1 175.6 190.9 57.4 89.7 69.3 16.7 4.2 4.3 2.0

28.4 182.7 146.1 63.9 76.8 9.6 30.8 191.2 93.6 58.3 152.5 129.9 155.3 79.5 19.9 55.9 24.6 12.5 102.3 42.3 10.0 397.9 268.7 77.9 160.0 110.8 24.7 21.3 51.1 115.3 66.5 57.3 120.5 99.9 113.8 82.4 104.2 211.7 3.3 2.2

19.8 179.6 39.8 1,258.2 42.7 909.6 21.2 400.7 36.4 432.7 11.1 399.0 18.8 308.8 57.8 850.7 28.6 557.8 20.1 273.1 46.2 560.9 35.7 527.8 40.7 556.1 31.6 422.6 13.2 178.3 23.5 508.1 17.4 200.2 10.6 139.9 20.7 275.5 24.9 167.6 10.7 162.1 9.5 192.0 76.4 1,142.6 70.7 1,711.2 33.6 690.4 62.4 824.8 49.4 717.1 18.9 239.4 16.2 170.7 22.2 413.2 66.7 623.5 34.6 615.2 19.0 466.5 49.3 884.7 46.6 610.5 39.5 661.6 22.2 925.3 33.4 756.4 82.2 1,486.5 8.2 43.7

1935 411.3 1936 176.5

1937 1938 1940 1941 1943 1944 1945 1946 1947 1948 1950 1951 1952 1953 1954

28.8 63.5 50.4 89.9 36.5 64.1 47.3 80.9 72.4 41.1 41.5 18.3 27.9 21.4 61.3

1939 227.0

1942 103.5

1949 166.0

1955 128.0

1956

15.6

1957 108.6 1958 266.7 1959 109.6

223.8 61.6 64.9 57.4

1960 1961 1962 1963

88.7 85.2 47.4 39.7

104.0 88.3 57.3 41.9 43.3 54.6 50.5 44.7 59.9 55.4 68.0 68.7 87.9 97.6

4.3 5.0

9.3 35.8 78.8 44.5 30.2 83.1 60.2 68.8 81.4 74.3

1964 126.1

16.3 23.2 37.7 30.4 66.4 30.7 35.4 39.2 49.0

1965

97.9

1966 169.2

1967

82.2

1968 130.8 1969 119.7 1970 112.6 1971 263.4 1972 108.4 1973 190.6

123.9

237.2

E DWARD S AQU I F E R AU THOR I T Y

TABLE 1. CONTINUED.

Area between Medina River and Cibolo Creek/ Dry Comal Creek Basins

Nueces River/ West Nueces River Basin

Area between Sabinal River and Medina River Basins

Frio River/ Dry Frio River Basin

Cibolo Creek/ Dry Comal Creek Basin

Sabinal River Basin

Medina River Basin

Blanco River Basin

Year 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 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

Total

91.1 71.8 150.7 102.9 69.8 128.4 58.6 205.0 19.4 79.2 32.4 105.9 188.4 308.5 59.2 52.6 479.3 325.2 234.1 32.6 124.6 107.1 130.0 176.9 141.5 101.4 238.4 297.5 83.6 149.8 481.9 105.5 45.5 471.8 48.2 58.5 135.4 15.3 78.3 67.7 19.8 343.8 275.7 122.0

135.7 143.6 238.6 193.0 73.1 201.4 85.6 365.2 123.4 85.9 40.4 186.9 192.8 473.3 117.9 52.6 255.0 421.0 586.9 78.5 151.5 147.6 92.0 209.1 214.8 136.8 123.0 126.7 207.3 112.2 424.5 147.2 60.2 474.4 44.5 30.3 104.9 13.7 82.6 26.7 32.8 281.9 247.8 95.4

36.1 47.9 68.2 62.7 30.9 68.6 42.6

115.3 195.9 182.0 159.5 103.7 203.1 25.3 252.1 90.9 42.9 18.1 148.5 173.6 405.5 24.9 13.5 131.2 315.2 566.1 60.8 45.1 62.4 208.4 201.4 57.2 55.2 124.1 345.2 67.4 343.9 79.1 9.4 406.4 9.8 13.5 186.3 5.0

96.2 93.4 94.5 77.7 76.7 89.4 88.3 91.3 76.8 74.4 43.9 64.7 74.7 90.4 69.9 46.9 54.0 52.8 91.4 78.5 61.1 61.7 42.3 63.3 80.3 77.1 53.4 90.0 93.7 86.6 95.5 82.8 47.7 75.2 53.6 45.6 68.2 43.3 41.6 10.8 8.9 54.6 77.5 72.6

68.1 138.8 47.9 97.9 49.6 85.4 18.8 165.0 22.6 31.9 11.3 136.7 170.2 229.3 12.6 290.6 38.9 34.1 36.2 10.6 193.4 86.2 21.2 28.6 101.5 175.5 56.2 213.4 84.8 4.6 35.9 84.5

76.9 195.7 54.3 191.6 72.4 266.3 55.4 196.8 44.8 62.5 16.9 259.2 267.4 270.9 28.5 12.3 71.8 109.7 286.6 90.9 55.6 51.1 14.7 144.2 240.9 27.9 48.6 173.7 447.8 105.0 315.0 140.4 11.2 306.1 22.8 26.4 148.2 15.3 32.2 28.7 177.3 186.4 68.8 9.5

39.1 85.9 57.9 66.7 26.3 75.2 31.8 67.3 23.5 23.2 25.9 50.7 44.5

2.0

973.0 894.1 952.0 502.5

1,117.8 406.4 1,448.4 422.4 420.1 197.7 1,003.3 1,153.7 2,003.6 355.5 214.4 1,123.2 1,508.4 2,485.7 447.6 538.1 531.3 324.3 1,134.6 1,142.3 473.5 614.5 1,069.4 1,573.7 669.0 2,176.1 764.0 201.6 2,162.3 212.9 210.9 813.5 112.0 313.5 182.6 107.2 1,358.1 1,221.1 487.0

105.6 21.0 20.1

8.8 50.7 42.2

110.7 17.0 8.4 54.6 103.1 201.1 29.6 29.5 34.7 11.4 57.0 72.5 30.8 33.1 66.2 70.6 31.7 116.0 50.1

114.9 25.5 23.6 41.3 96.9 226.9 37.8 36.6 30.6 13.9 82.3 104.7 21.0 34.1 89.7 150.0 59.9 185.8 74.1 17.9 96.9 18.5 27.5 57.5 18.3 51.6 42.1 16.5 108.3 86.3 55.0

9.0

5.1

104.0

227.6

5.9 1.8

9.6 7.3

31.5 1.0 8.9 0.5 4.9 42.2 52.4 17.0

81.4 3.0 3.9 3.3 0.4

2.0 14.4 2.8 14.4

218.4 184.1 30.4

131.6 110.9 25.0

Recharge statistics for the period of record 1934–2017: Median 102.2 115.9 31.2 Recharge for the period of record 2008–2017 (last ten years): Median 73.0 63.55 7.4 Data source: USGS unpublished report (April 2017). a Totals may not exactly equal sum of all basins due to rounding errors. 76.3 110.6 Mean 127.9 137.5 41.0 14.4 67.6 Mean 116.5 96.1 16.6

60.5 61.4

49.9 70.7

77.4 109.8

36.5 557.0 47.5 704.0

49.6 47.7

8.45

30.45 71.6

46.85 263.0 48.2 502.0

37.6

20 17 GROUNDWAT E R R E CHARG E

2017

(502,000 AF)

(704,000 AF)

(487,000 AF)

1933 1935 1937 1939 1941 1943 1945 1947 1949 1951 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017

Total Annual Recharge

Historical Mean (1934-2017)

Ten-Year Mean (2008-2017)

Figure 2. Estimated Annual Recharge for the San Antonio Segment of the Balcones Fault Zone Edwards Aquifer, 1934–2017.

500

2500

2000

1500

1000

Thousands of Acre-Feet

E DWARD S AQU I F E R AU THOR I T Y

TABLE 2. ESTIMATED ANNUAL RECHARGE FROM EDWARDS AQUIFER AUTHORITY-OPERATED RECHARGE STRUCTURES (MEASURED IN ACRE-FEET).

Parker (April 1974)

Verde (April 1978)

San Geronimo (November 1979)

Seco (October 1982)

Annual Total

160 620

--- --- --- ---

--- --- --- --- ---

--- --- --- --- --- --- --- ---

160 620

2,018

150

248

2,315

1,725

4,040 1,274 4,102

371

903

772

1,923

1,407

3 0

112 254 246 440 889

0 0

206 254 640

0 0

251 232 217

143 643

1,097

2,412 3,649

963

1,580

2,104

4,141

1,176

12,915

20,336

0 0

176 966

479

745

647 723

1,647 2,874

2,160

5,420

2,775

14,631

21,003

0 0

334

508

842 164

159

880

1,028

2,941 a 1,469 a/b

2,154 b 1,160 b

1,579 b

7,515 b 3,796b

14,189 b 7,297 b

872 b

0 b

50 c

50 b/c

901 b 526 b

1,371 b

1,023 b 1,085 b/d

4,606 b 2,154 b/d

7,901 b 4,422 b/d

657 b/d

1,811

1,511

4,350

18,872

26,544

665

184 170

465

1,314

2,363

4,778

14,682

21,993

795

0 0

853

5,998

2,091

7,268

10,645

26,002

2.6

2.5

630

0.1

688

1,356

1,324

4,375

6,171

13,226

4.5

1.0

1.0 0.6

0 0 0

150

0.4

1.0

759 419

38.0

319

1,116 7,079 8,799

816 747

1,163 1,776

4,682 4,018

2,257

Data source: Unpublished Edwards Aquifer Authority files (2014). a =

Written communication from USGS, San Antonio Subdistrict Office.

= Determined by linear-regression analysis using rainfall data and historical recharge data. c = Linear-regression analysis indicates zero recharge; however, one recharge event was observed that was estimated to have recharged 50 acre-feet. d = Part of 2001 recharge estimate provided by HDR Engineering, Inc. (unpublished report). --- = Years prior to construction of recharge structure.

20 17 GROUNDWAT E R R E CHARG E

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