Water-Data Report 2013 08179500 Medina Lake near , TX San Antonio Basin Medina Subbasin

LOCATION.--Lat 29°32′24″, long 98°56′01″ referenced to North American Datum of 1927, Medina County, TX, Hydrologic Unit 12100302, at gate-operating platform, 576 ft from the left end of on , 4.2 mi upstream from Medina diversion dam, 13 mi north of Castroville, 28 mi west of San Antonio, and 70.4 mi from mouth. DRAINAGE AREA.--634 mi².

SURFACE-WATER RECORDS PERIOD OF RECORD.--May 1913 to Sept. 1994, Aug. 1997 to current year. Prior to Oct. 1965, end of month contents only from records provided by Bexar- Medina-Atascosa Counties Water Control and Improvement District No. 1. PERIOD OF RECORD, Water-Quality.-- CHEMICAL DATA: Oct. 1969 to Sept. 1984. REVISED RECORDS.--WSP 1923: 1953(M), Drainage area. GAGE.--Water-stage recorder. Datum of the gage is NGVD of 1929. Prior to Oct. 1999, datum of gage was 7.81 ft higher. Satellite telemetry at station. REMARKS.--Record is rated good. Some records listed in the "Period of Record" for surface water and water quality may not be available electronically. The lake is formed by a gravity-type concrete dam, 1,580 ft long. The dam was completed and storage began May 7, 1913. The uncontrolled spillway is a cut through natural rock 880 ft long, with a 3-foot wide cutoff wall, located near right end of dam. The dam and lake are owned and operated by Bexar-Medina-Atascosa Counties Water Control and Improvement District No. 1. Water is released downstream to Medina Diversion Lake where it is diverted into Medina Canal by the Water District. Capacity table based on survey made by the Water Development Board, July 1995. Conservation pool storage is 254,843 acre-ft. Data regarding the dam are given in the following table:

Elevation (feet) Top of dam 1,076.2 Crest of spillways 1,064.2 Water-supply outlet pipe (invert) 958.7 Lowest gated outlet (invert) 912.2

EXTREMES FOR PERIOD OF RECORD.--Maximum contents, 322,700 acre-ft July 5, 2002, elevation, 1074.65 ft; minimum contents, 780 acre-ft, Apr. 11, 1948, elevation, 936.2 ft (present datum). EXTREMES FOR CURRENT YEAR.--Maximum contents, 34,170 acre-ft, Oct. 2, gage height, 1,000.00 ft; minimum contents, 10,950 acre-ft, Sept. 20, 30, gage height, 978.27 ft.

U.S. Department of the Interior Suggested citation: U.S. Geological Survey, 2014, Water-resources data for the United States, Water U.S. Geological Survey Year 2013: U.S. Geological Survey Water-Data Report WDR-US-2013, site 08179500, accessed at http://wdr.water.usgs.gov/wy2013/pdfs/08179500.2013.pdf Water-Data Report 2013 08179500 Medina Lake near San Antonio, TX—Continued

RESERVOIR STORAGE, ACRE FEET WATER YEAR OCTOBER 2012 TO SEPTEMBER 2013 DAILY MEAN VALUES Day Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

1 34,120 31,130 27,600 24,230 22,280 19,680 16,610 14,070 13,900 13,350 12,420 11,400 2 34,120 31,000 27,500 24,120 22,200 19,570 16,520 13,880 13,910 13,320 12,380 11,370 3 34,100 30,880 27,400 24,010 22,120 19,470 16,510 14,000 13,910 13,280 12,350 11,340 4 34,080 30,750 27,300 23,930 22,050 19,370 16,420 14,000 13,880 13,240 12,310 11,310 5 34,070 30,620 27,190 23,850 21,970 19,260 16,310 13,970 13,850 13,210 12,270 11,280 6 34,050 30,480 27,080 23,730 21,890 19,140 16,210 13,950 13,830 13,180 12,240 11,270 7 33,990 30,340 26,980 23,640 21,810 19,050 16,110 13,920 13,800 13,150 12,200 11,240 8 33,930 30,220 26,890 23,580 21,710 18,950 16,020 13,890 13,790 13,120 12,170 11,210 9 33,900 30,100 26,790 23,670 21,610 18,880 15,930 13,880 13,770 13,100 12,130 11,180 10 33,880 29,970 26,580 23,660 21,540 18,880 15,810 13,890 13,770 13,070 12,100 11,180 11 33,860 29,850 26,530 23,610 21,450 18,770 15,720 13,900 13,740 13,040 12,070 11,180 12 33,830 29,690 26,430 23,590 21,380 18,670 15,620 13,880 13,750 13,000 12,040 11,160 13 33,810 29,540 26,320 23,460 21,280 18,570 15,510 13,850 13,860 12,970 12,000 11,130 14 33,790 29,430 26,200 23,480 21,190 18,470 15,410 13,820 13,860 12,930 11,970 11,100 15 33,750 29,320 26,120 23,390 21,100 18,380 15,310 13,810 13,870 12,890 11,940 11,070 16 33,710 29,210 26,020 23,400 20,990 18,280 15,210 13,800 13,850 12,870 11,900 11,040 17 33,700 29,110 25,910 23,350 20,890 18,190 15,110 13,800 13,830 12,860 11,870 11,020 18 33,650 29,000 25,790 23,290 20,800 18,100 14,970 13,810 13,810 12,860 11,830 11,000 19 33,580 28,910 25,700 23,230 20,700 17,990 14,880 13,800 13,780 12,850 11,790 10,980 20 33,490 28,820 25,410 23,160 20,600 17,890 14,760 13,790 13,740 12,820 11,760 11,070 21 33,380 28,720 25,420 23,100 20,520 17,780 14,650 13,770 13,710 12,790 11,730 11,160 22 33,230 28,610 25,310 23,060 20,410 17,690 14,540 13,750 13,670 12,760 11,700 11,120 23 32,880 28,510 25,220 22,950 20,310 17,590 14,420 13,720 13,630 12,720 11,670 11,100 24 32,520 28,390 25,120 22,890 20,210 17,460 14,220 13,740 13,600 12,690 11,640 11,070 25 32,160 28,270 24,900 22,820 20,130 17,350 14,180 13,790 13,550 12,660 11,600 11,050 26 31,850 28,180 24,800 22,750 19,990 17,230 14,130 13,810 13,520 12,630 11,570 11,020 27 31,690 28,050 24,750 22,690 19,890 17,120 14,110 13,940 13,490 12,600 11,540 10,990 28 31,560 27,920 24,630 22,630 19,780 17,010 14,090 13,940 13,450 12,560 11,510 10,980 29 31,440 27,800 24,500 22,570 --- 16,910 14,060 13,930 13,420 12,530 11,490 11,000 30 31,330 27,700 24,410 22,470 --- 16,810 14,080 13,930 13,390 12,490 11,460 10,970 31 31,230 --- 24,330 22,370 --- 16,710 --- 13,920 --- 12,450 11,430 --- Mean 33,250 29,350 25,970 23,310 21,100 18,230 15,250 13,870 13,730 12,900 11,910 11,130 Max 34,120 31,130 27,600 24,230 22,280 19,680 16,610 14,070 13,910 13,350 12,420 11,400 Min 31,230 27,700 24,330 22,370 19,780 16,710 14,060 13,720 13,390 12,450 11,430 10,970

Calendar Year 2012 Water Year 2013 Mean 44,320 19,170 Max 58,990 34,120 Min 24,330 10,970

— 2 — Water-Data Report 2013 08179500 Medina Lake near San Antonio, TX—Continued

35,000

30,000

25,000

20,000 RESERVOIR STORAGE, ACRE FEET ACRE STORAGE, RESERVOIR

MEAN

15,000

10,000 O N D J F M A M J J A S 2012 2013

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