미국지질협회(U.S. Geological Survey, USGS)와 샌안토니오워터시스템(San Antonio Water System, SAWS)의 새로운 지하수 흐름 모델의 개발 덕분에 샌안토니오 및 텍사스 에드워즈 고원의 대수층 전체에 물이 흐르는 방법에 대해 보다 이해하게 되었다.

애드워즈 고원의 대수층은 세계에서 가장 물이 풍부한 대수층 중 하나이며, 샌안토니오와 오스틴(Austin)지역에서 소비되는 식수의 50% 이상을 제공하며, 중남부 텍사스 지역에 주거·여가·산업·농업 등의 용수를 공급한다. 멸종위기에 처한 동물들 또한 지하수에 의해 보호된다.

Thanks to a new groundwater flow model developed by the U.S. Geological Survey (USGS) in cooperation with San Antonio Water System (SAWS), scientists now have a better understanding of how water flows throughout the San Antonio, Texas, segment of the Edwards aquifer.

The Edwards aquifer is one of the most prolific aquifers in the world and provides more than 50 percent of the drinking water consumed in the San Antonio and Austin areas. The aquifer supplies water to south-central Texas for residential, recreational, industrial, and agricultural uses. Several endangered and threatened species are also sustained by groundwater discharged at Comal, San Marcos and Barton Springs.

The focus of the new USGS model is to simulate the interaction between fresh water and saline (salt) water and where the two mix, called the brackish-water transition zone. Model results indicate that effects on fresh water during a severe drought, such as the drought-of-record during 1950-56, would be minor.

This model improves on a previous USGS model that did not include analysis of the transition or saline zones. While this new model is capable of making predictions of spring flow, salinity concentrations and water levels in nearby wells, the reliability of these predictions are also measured through use of a tool known as uncertainty analysis, which few groundwater modeling studies currently provide.

The model, coupled with uncertainty analysis, improves understanding of the potential effects of severe drought on the movement of water within and between the different water-quality zones. The full USGS report on the model is available here.

"While the model shows little potential for movement of brackish water into fresh water, the research suggests there is a need for an improved understanding of some parts of the Edwards aquifer flow system," said USGS scientist Linzy Brakefield. "Better knowledge of how the aquifer is recharged and the relationship between recharge, pumping and spring flow is needed."

 

[출처 = Water World / 2015년 7월 23일]