[미국] 콜로라도강 상류유역, 기후 변화에도 지하수 함양 유지

최근 미국 지질조사국에 따르면 콜로라도(Colorado)강 상류지역의 향후 강수량 증가가 계속되는 기온 상승에도 불구하고 지하수 함양 증가로 이어질 전망이다.

콜로라도 강은 미국의 3천500만 이상의 사람들과 멕시코의 약 3백만에 이르는 사람들에게 물을 제공한다. 최근 미국 지질조사소의 발표에 따르면 콜로라도 강 상류지역의 절반 이상에 달하는 물줄기가 지하수에서 기원하는 것으로 밝혀졌다. 얼마나 많은 지하수가 이용 가능하고 어떻게 보충되는지를 이해하는 것은 지하수와 표면수 모두를 현재는 물론 미래에도 지속 가능한 상태로 관리하는데 매우 중요한 일이다.

미국 지질조사소 과학들은 콜로라도 강 상류지역의 지난 1950년부터 2015년까지의 지하수 함양 데이터와 함께 2016년부터 2099년까지의 미래 기후 변화를 고려한 지하수 함양 모델을 구축해 종합적인 지하수 함양량의 변화를 추정했다. 시뮬레이션 결과, 2099년까지의 미래 지하수 함양량은 습윤한 기후가 예상됨에 따라 과거 평균치보다 다소 증가할 전망이다. 또한 지하수 자원은 기온 상승으로 인한 감소에도 불구하고 강수량 증가로 다시 보충될 것으로 예상된다. 전체 보고서는 ‘지질물리학 조사 보고서’에서 온라인으로 확인 가능하다.

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Groundwater recharge in Upper Colorado River Basin may hold steady under climate change

Future increases in precipitation in the Upper Colorado River Basin may increase groundwater recharge, offsetting reductions that would result from increased temperatures, according to a recent study by the U.S. Geological Survey and Bureau of Reclamation.

The Colorado River provides water for more than 35 million people in the United States and 3 million people in Mexico. A recent USGS publication suggests that as much as half of the water flowing in rivers and streams in the Upper Colorado River Basin originates as groundwater. Understanding how much groundwater is available and how it’s replenished is important to sustainably manage both groundwater and surface water supplies in the Colorado River basin now and in the future.

USGS and Reclamation scientists estimated projected changes in groundwater recharge for the Upper Colorado River Basin from recent historical (1950?2015) through future (2016?2099) time periods using climate projections and a groundwater-recharge model. Simulated future groundwater recharge through 2099 is generally expected to be somewhat greater than the historical average in most decades due to an anticipated wetter future climate in the basin under the most advanced climate modeling projections. Groundwater resources are replenished through increases in precipitation, which may offset reductions from increased temperatures. The full report is available online in the journal Geophysical Research Letters.

While recharge simulations from a majority of the projected climate data sets result in increased recharge in the Upper Colorado River Basin during most future decades, there were some that resulted in decreased future recharge relative to the historical climate period.

"You can’t manage what you don’t measure," said Fred Tillman, lead author and USGS scientist. "These results are the first step in understanding the quantity of groundwater we can expect in the Upper Colorado River Basin; however, further studies are needed to help more accurately forecast future groundwater availability."

"Future estimates of groundwater recharge are compounded by the large-scale of the Upper Colorado River Basin and the uncertainties of future climate projections," said Reclamation co-author Subhrendu Gangopadhyay.

"Given these uncertainties, multiple-future water supplies scenarios are used to inform Reclamation’s water management and planning within the Upper Colorado River Basin," Reclamation's Upper Colorado Region Water Resources Manager Malcolm Wilson added.

This study was completed with support from Reclamation’s Science and Technology Program to help meet objectives of the SECURE Water Act, which was created by Congress in 2009 as a framework for a programmatic approach to understand climate change impacts, and to develop adaptation and mitigation strategies. This act contains substantive mandates for both the USGS and Reclamation to help provide a more accurate assessment of the status of the water resources of the United States and assess the potential impacts of climate change on water management.

[출처 = Water World / 2016년 8월 15일]