So how does the Edwards Aquifer actually work?


    As the old saying goes, "It's a pretty deep subject for such a shallow mind." That describes me perfectly when it comes to understanding the vastness of the aquifer.

    And with all the rain that fell across the area during the first several days of July, there are questions about how it will help aquifer levels.

    So I went to the Edwards Aquifer Authority and spoke to the experts. They actually have a mock up of what it actually looks like down there and where the water goes.

    Many think the aquifer is a vast underground lake, but it's not.

    It's actually made of complex layers of limestone, with small cracks, crevices and sinkholes that filter the water as it passes through.

    According to information on the Edwards Aquifer website, here is how it works:

    Water circulates through the Edwards Aquifer as part of the hydrologic cycle from recharge areas to discharge locations (springs and wells). Approximately 1,250 square miles of Edwards Limestone is exposed at the ground surface and composes the Recharge Zone where water enters the Aquifer. Surface water from springs and streams originating on the Contributing Zone reaches the Recharge Zone where much of the flow sinks into the Edwards Limestone. Some water also enters the Edwards Aquifer through interformational flow (from rock formations adjacent to the Edwards Limestone) and from direct precipitation on the Recharge Zone.
    Water from the Recharge Zone flows down gradient to the Artesian Zone where the Aquifer is contained between less permeable beds of the Del Rio Clay (above) and the Upper Glen Rose Limestone (below). Portions of the Artesian Zone are as much as 3,400 feet below the surface where it still contains fresh water. The southern boundary of the Artesian Zone marks the Aquifer’s transition from freshwater to saline water (water with a total dissolved solids concentration greater than 1,000 mg/L). Groundwater moves through the Artesian Zone and ultimately discharges from a number of locations, such as Leona Springs in Uvalde County, San Pedro and San Antonio springs in Bexar County, Hueco and Comal springs in Comal County and San Marcos Springs in Hays County. In addition, domestic, livestock, municipal, agricultural and industrial wells throughout the region withdraw water from the Aquifer. The residence time of water in the Aquifer ranges from a few hours or days to much longer, depending on depth of circulation, location and other aquifer parameters.

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