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大峽谷水流狂洩 復育生命綠洲

2008年03月11日
摘譯自2008年03月07日ENS美國,亞歷桑納州,佩奇報導;游珮綺編譯;莫聞審校

水將從格蘭峽谷水庫流出。圖片來源:DOI靠近亞歷桑納州和猶他州邊境的包威爾湖(Lake Powell)現在每秒有超過30萬加侖的水穿越大峽谷滾洩而下,目的在於力求復育本土植物和魚類賴以生存的沙洲地。

美國內政部長坎培松(Dirk Kempthorne)3月5日拉開格蘭峽谷水庫(Glen Canyon Dam)的閘門進行洩洪,開始為期60個小時的『高流量水流測試』。由此造成的洪水水流預期可以將沙子推到河道的底部,並沿著河道形成一連串的沙洲和沙灘,使被阻擋在水庫內的沉積物能重新注滿河流。

坎培松表示,該水庫水流洩出的速度足以在20分鐘內把帝國大廈都灌滿,也能夠運送足夠的泥沙填滿100英尺深的足球場。

這個測試是由美國地質調查所(U.S. Geological Survey, USGS)、負責科羅拉多河格蘭峽谷水庫運作的美國開墾局(Bureau of Reclamation)、以及管理大峽谷國家公園的國家公園管理局(National Park Service)等3個內政部機關所共同主導進行的跨部會研究。

而高流量水流也可以創造低流量區域或迴水,能復育年幼的本土魚類,特別是瀕危的弓背鮭(humpback chub),牠是4種大峽谷僅存的本土魚類之一。

美國地質調查所科學家也將監控高流量水流,對年幼弓背鮭的存活數量所造成的影響。

科羅拉多河所造成的宏偉峽谷。圖片來源:USGS調查員將會收集沙洲在洩洪改變前後與期間的相關資料,將有助改善現有對沉積物模型的預測能力,並決定未來測試的理想洪峰流量。

但是各部會間對於未來的高流量水流測試的衝突,卻造成了內政部內部的分裂。

根據自然資源機構公務人員組織表示,美國開墾局目前正在推行一項與水電利益有關的計畫,此舉卻與國家公園管理局產生對立,因為國家公園管理局認為這個計畫將危及大峽谷國家公園的野生物及其棲地。「環境責任公職人員組織」(PEER)上週公佈這份文件,披露這個跨部會間的衝突。

Water Rushes Down Grand Canyon in High Flow Experiment
PAGE, Arizona, March 7, 2008 (ENS)

More than 300,000 gallons of water per second is now gushing through the Grand Canyon, released from Lake Powell near the Arizona-Utah border in an effort to restore sandbars needed by native plants and fish.

Interior Secretary Dirk Kempthorne Wednesday pulled a lever at Glen Canyon Dam to release the water for a 60-hour "high flow test." The flood of water is expected to push sand built up at the bottom of the river's channel into a series of sandbars and camping beaches along the river, replenishing the sediment that has been held back behind the dam.

"The water will be released at a rate that would fill the Empire State Building within 20 minutes," Kempthorne said. "It will transport enough sediment to cover a football field 100 feet deep with silt and sand."

The experiment is an inter-agency research effort conducted by three Department of the Interior bureaus ?the U.S. Geological Survey, USGS; the Bureau of Reclamation, which operates Glen Canyon Dam on the Colorado River; and the National Park Service, which manages Grand Canyon National Park.

High flows also create areas of low-velocity flow, or backwaters, used by young native fishes, particularly endangered humpback chub, one of four remaining native fish in the Grand Canyon.

USGS scientists will be monitoring how the high-flow releases affect the survival of a population of young humpback chub.

Researchers will collect data on the changes in sandbars before, during, and after the high flow. This data will be used to improve the predictive capabilities of the existing sediment model and determine the optimal peak flows of future high-flow experiments.

But a conflict over future high-flow experiments has caused a rift within the Department of the Interior.

The fight pits the U.S. Bureau of Reclamation, which is pushing a plan supported by water and power interests, against the National Park Service which says the plan will harm wildlife and habitat in Grand Canyon National Park, according to a national organization of government employees in natural resource agencies.

Public Employees for Environmental Responsibility, PEER, released documents last week that illuminate the intra-agency conflict.

全文及圖片詳見:ENS