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2012-09-20

Gates closed at Medina Dam

By Carolyn B. Edwards BCC Staff Writer

It's the end of the season, and due to serious drought conditions, the Bexar-Medina-Atascosa Water Control and Improvement District, the owner and operator of Medina Dam, opted to close the dam's two gates on August 21.

"We're done with irrigation and SAWS says they don't need any more water this year," said BMA Manager Ed Berger. SAWS, the San Antonio Water System, has a contract with BMA to use Medina Lake water for San Antonians.

"They're working on a plant down there, and say they won't need anything before the end of the year," said Berger.

Berger, like everyone in the Texas Hill Country, is looking for rain. "Hopefully, El Niño will help us out."

Since the dam, which recently celebrated its 100-year anniversary, was built by an irrigation company as a business venture to provide water for irrigation purposes downstream, water levels have always been "up down, up down, up down," said Berger.

According to Berger, the lake loses 40-50 acre feet of water a day from evaporation or leaks through geological strata, "even when we aren't taking water out for irrigation."

During his 8-year tenure at BMA, Berger has overseen several major projects. "We're 100 percent conservation minded now," he said. "We only used a third of our water this year." Projects included a half-million dollar clean out of the first three siphons on the canal system which had about 30 leaks on each side, he said, and were about 80 percent blocked with debris. Pearson Lake was completed so that unused water from 26 miles of canal systems can now be recaptured. BMA completed a 2-mile $380,000 pipeline and just completed a rehab on the dam itself, "so it's good for another 100 years."

People below the dam expressed concern that closing the dam gates would dry up the lower reaches of the Medina River. Berger explained that the lower Medina is kept running "basically from the recharge zone. It doesn't get water from Medina Lake."

BMA has managed the irrigation system since 1950. Some years ago, BMA sold part of their interest and control of Medina Lake Water to Bexar Metropolitan Water District, a utility district serving portions of San Antonio. Money from the sale helped finance those long-over due repairs to the irrigation system.

As an interested party, Bandera County negotiated at that time to set aside some of the lake water for the county.

In 2012. Bexar Met was absorbed by San Antonio Water System (SAWS).

The Medina Lake irrigation system delivers water to 34,000 acres of farmlands below the Balcones escarpment around Castroville, La Coste, Natalia, and Devine. Portions of the canal extend to urban San Antonio, just outside Loop 1604. At the time it was constructed, it was the biggest irrigation project west of the Mississippi.

At spillway capacity, Medina Lake covers about 5,575 acres, has a length of 18 miles, a maximum width of three miles, 110 miles of shoreline, and a storage capacity of 254,843 acre-feet. In addition to the main dam, there is a smaller dam about four miles downstream that creates Diversion Lake, from which discharges are made to the canal system.

According to USGS data posted Thursday, Sept. 13, the surface level was at 999.69 feet. Elevation of the lake to the crest of the spillway is 1064.2 feet. That makes the lake down a little over 65.5 feet. Acre feet of water remaining in the lake is 33,740.

USGS data shows the lake hit a surface level of 1,074.65 feet in July of 2002 with a maximum content of 322,700 acre feet of water. That's just a couple of feet below the top of the dam, which stands at 1076.2 feet.

The historic low was recorded in April, 1948, with only 780 acre-feet of water in the basin at a surface level of 936.2 feet.

According to County Commissioner Bobby Harris, the County Park on PR 37 is now open only on weekends and is basically usable only for picnicking. Boat launching is no longer possible.