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2011-03-10

River authority looks at aquifer storage & recovery system

By Carolyn B. Edwards BCC Staff writer

The Bandera County River Authority and Groundwater District (BCRAGD) Board of Directors voted unanimously to look into the feasibility of initiating an Aquifer Storage and Recovery (ASR) project for Bandera County.
Director Gene Wehmeyer of Bandera presented the item during the Feb. 17 called meeting. "The district had a study done some years ago [2009] by Guyton [LBG-Guyton Associates] that said it was feasible," said Wehmeyer. ASR is a process of pumping surface water from rivers, lakes or rainfall into an aquifer for later use. The City of Kerrville uses ASR to replenish its aquifer.
The introduction to the Guyton study said, "The City of Bandera and many other residents of Bandera County rely on the Lower Trinity Aquifer for municipal, domestic and irrigation water-supply needs, and the demand from the Lower Trinity is projected to increase as the population increases.
"Because the water level in the Lower Trinity has declined about 350 feet in City of Bandera wells since pumping started in the 1950s, there is concern that continued withdrawals from the aquifer may negatively impact the aquifer's ability to meet the long term water supply needs of the area. The purpose of this project is to investigate the feasibility of constructing and operating an aquifer storage and recovery (ASR) facility using treated surface water from the Medina River and stored in the Lower Trinity Aquifer."
The Guyton study presumes the availability of "the county's 5,000 acre feet [of water from BexarMet]." The BexarMet Water District controls the rights to water in Medina Lake and the Medina River watershed. In 1997, Bandera County and Springhills Water Management District, a precursor to BCRAGD, signed an agreement with the Bexar-Medina-Atascosa Water Control and Improvement District #1 (BMAWCID#1), which has subsequently come under the control of BexarMet, for a surface water supply of 5,000 acre feet per year.
Wehmeyer said he was thinking in terms of something much smaller. "We want like 500 acre feet. The committee could research it. I don't want the district to get into the water-selling business."
Committee members appointed were Wehmeyer, Sides, Don Sloan and Andy Lautzenheiser.
According to the Edwards Aquifer Authority website, "ASR technology addresses one of the region's biggest problems: there are hardly any storage locations where water can be put in times of plenty for later use. One big advantage of storing water [underground] instead of a reservoir is that no water evaporates."
Washington State Department of Ecology explains ASR as "a water bank. Deposits are made in times of surplus ... and withdrawals occur when available water falls short of demand."
ASR systems reduce the need to build expensive surface reservoirs, which are also more susceptible to tampering.
ASR technology has been used from Florida to California and there are two operating ASR facilities in Texas - one in south Bexar County operated by the San Antonio Water System since 2004, and another in Kerrville operated by the Upper Guadalupe River Authority since the early 1990s.
The City of Kerrville provides 1.4 billion gallons of potable water to its customers. Eighty percent comes from a water treatment plant, 10 percent from ASR and 10 percent from seven groundwater wells. The city also operates an effluent system that delivers treated water from the sewer plant to local golf courses and schools for lawn watering.
Concerns about ASR systems include the possibility of pumping polluted water into the aquifer storage area. In systems where water is pumped from wells during high aquifer levels to be stored elsewhere for times of need, local residents feared the levels of their private wells would subsequently be lowered during the pumping.
Like Kerrville, Bandera is only 60 miles from the Chihuahuan Desert that runs south from West Texas into Mexico. The county's average rainfall is just 31 inches a year. Most municipal and private wells tap into the Trinity Aquifer Group, a multi-layered series of underground water pools that some estimate recharge at the rate of 50 to several hundreds of years. Those stats should make water conservation a year-round concern for all residents.