The heavy rainfall that drenched San Antonio and caused deadly flash flooding also brought some relief to drought-stricken water supplies — although not nearly enough to fill them back to normal levels.
Groundwater and surface water sources have been depleted to record or near-record lows due to ongoing drought and increased demand due to population growth.
Five of the past six years have seen below average rainfall in the region, building up a major deficit that will take more than one big storm to recover, but this week's rainfall did help water levels climb in the Edwards Aquifer and area lakes.
READ MORE: Death toll rises: 8 dead, 6 missing in San Antonio floods. Here's what we know about victims.
Edwards Aquifer
The aquifer is a groundwater system that provides water for more than 2 million people, including more than half of the San Antonio Water System’s supply.
Water enters the aquifer through fractures in the ground’s surface, such as caves and sinkholes, in areas called the contributing and recharge zones. Those zones are to the north and west of San Antonio, so rainfall within the city limits doesn’t always make much of a difference to the aquifer’s water levels.
But the aquifer's recharge zone received enough rainfall to substantially boost the aquifer’s water level. The J-17 index well in Bexar County saw its water level rise 7 feet in two days, from from 630.79 feet on Wednesday to 637.8 on Friday.
It’s still about 24 feet below the historical monthly average, as multiple years of below-average rainfall have depleted the aquifer, but it’s a major improvement from just three weeks ago, when the well reached its lowest level since 1990 and the Edwards Aquifer Authority briefly implemented its most severe cutbacks.
The recharge zone stretches for more than 1,200 square miles, from Kinney County through Uvalde and Medina counties, across a swath of Northern Bexar County and into Comal and Hays counties.
READ MORE: Who is ‘Edwards,’ anyway? 5 things to know about the Edwards Aquifer.
Rainfall totals varied throughout that area. Concan, where the Frio River flows north of Uvalde, recorded 3.36 inches on June 11. Bandera, which sits in the contributing zone just above the recharge zone, tallied a lower amount, 2.66 inches on Wednesday and Thursday. The Stone Oak area in northern San Antonio, which is in the recharge zone, received 3.48 inches.
Rainfall totals were larger in the eastern parts of the recharge zone. Garden Ridge in Comal County saw 5.54 inches of rain on Wednesday and Thursday, and areas between New Braunfels and Canyon Lake recorded just under 5 inches.
Canyon Lake
It’s going to take a lot more than one heavy rain to refill Canyon Lake, a massive Comal County reservoir that’s less than half-full. The reservoir was created by damming the spring-fed Guadalupe River, and the amount of water flowing into the reservoir has been far below average for the past five years.
But the rain did bring some small improvement. The area received about 4 inches of precipitation, and the lake’s surface level climbed from 877.17 feet above sea level on Wednesday to just over 878 feet on Friday, a 10-inch increase, according to data from the Texas Water Development Board.
READ MORE: Photos reveal how the drought is affecting Central Texas lakes
When full, the lake can hold 378,781 acre-feet, a water industry metric that refers to the amount of water needed to cover 1 acre in 1 foot of water. One acre-foot is about 326,000 gallons.
On Friday, Canyon held about 176,234 acre-feet, or about 57 billion gallons of water.
Medina Lake
Medina Lake, a reservoir west of San Antonio, is just 2.4% full, according to the Texas Water Development Board data — but that’s an improvement from the 2.1% recorded on Wednesday.
Since then, the lake’s surface has risen about a foot, from 969.85 feet to 970.98 feet, thanks to about three inches of rain that fell near the lake and in upstream areas where the Medina River flows from.
Medina Lake has been less than 4% full since October 2023, and the last time it was full was in 2019.
The reservoir is currently holding 6,053 acre-feet; when full, it holds nearly 255,000.
June 13, 2025
Reporter
Liz Teitz covers environmental news and the Hill Country for the San Antonio Express-News. She writes about the San Antonio Water System, news in New Braunfels and Comal County and water issues around Central Texas. She can be reached at [email protected].
Liz joined the Express-News in June 2023. She has been a reporter for eight years, covering housing, government, education and other topics for the Ouray County Plaindealer, Hearst Connecticut Media Group and the Beaumont Enterprise. Liz grew up in Rhode Island and graduated from Georgetown University.