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2009-01-22

Trinity not recharging-

By Stephanie Parker

A handful of people attended a Thursday, Jan. 8, Bandera County River Authority and Groundwater District (BCRAGD) meeting to hear the results of a Medina River surface water study that pinpointed Trinity Aquifer recharge zones along the river.

Directors with BCRAGD hired engineering consultant firm LBG Guyton Associates in 2005, to develop a comprehensive hydro-shed assessment for Bandera County.

With projections that the county’s population will triple over the next 50 years, BCRAGD board members, attempting progressive and forward thinking, requested a five-task surface water assessment to see how the Medina River impacts groundwater. Signs of drought-caused stress have already impacted the City of Bandera wells that draw from the Lower Trinity Aquifer.

United States Geological Survey engineer George Ozuna shared early results of the Guyton study with those attending last Thursday’s meeting. After taking measurements from 14 sites along the Medina River, Ozuna discovered the river is not recharging the Lower Trinity Aquifer. Instead, the shallow aquifer is feeding into the river.

“What this does for the water district,” he said, “is give them a sense of the areas that need protecting toward Medina. It will be interesting to see if more recharge occurs after a flood.”

The Medina River normally runs at 50 cubic feet per second. Drought conditions, however, have dropped that reading to 15 cubic feet per second.

Ozuna said that the water information gained could be used to pinpoint the best location for an early warning system portending floods.

BCRAGD directors and Ozuna discussed land clearing - especially cedar - as a proven method of enhancing water flow and creating new springs.

BCRAGD Manager David Jeffery said he wanted another series of river depth readings before rain arrives. “Twenty-eight inches of rain a year is normal for this area,” he said. “We got 13.5 last year. It takes three to three-and-a-half inches of rain to produce run-off when it’s this dry.”

BCRAGD President James Chastain called Bandera’s rain events, some of which produce 14 inches in one day, “run-off and run-out events.”