有關大壩的爭論

THE BIG DAMS DEBATE

　　"本世紀，美國人曾經認為建造水壩是正確的，因為水壩明顯地能帶來經濟利益，然而水壩漸漸成了大量花費納稅人錢的工程，後來對建造水壩的代價與收益評估也證實了這一看法。但是現在民眾知道了這些工程，長期以來，我們付出了很大代價。這些代價由以下幾點表現出來。大量魚群的迴游繁殖受到了破壞，氣溫的變化、河流內所包含的營養物質、和河流季節性的泛濫等方面改變了河川下游，以及由於缺乏淡水及受到海水的侵入，三角洲的溼地也退化了。在我父母那一代的人，以美國橫跨河流的水壩建設為榮。可是我們這一代卻看到水壩是如何改變、損害、摧毀這些河流。我們的下一代必須作出決定，看看這些水壩是否應當建造、如何建造以及在何處建造。"

　　在所有對河流產生影響或造成損害的方案中，大型水壩通常直接又深遠的影響湖川。因為它導致整個河流的水循環系統發生了重大的變化。整個流域和集水區都會受到影響。

　　在南非，通常人們以是否缺水來決定是否應該建造新的供水堤壩和河流改道工程。水壩顯然是貯存大量河水用於較乾旱時節的一個方法，這一點千真萬確。現代社會，用水量也急劇增加，這一點也是事實。本世紀的前80年，世界上人平均用水量增長了200%，導致世界上淡水資源的輸出使用速度顯著地增加了566%。但是水壩和水管並沒有真的創造出新的水來，他們不過是將水從一群用戶轉移到另一群用戶罷了-通常，是從最窮的到最富有的，或者換一種說法，從最節儉的到最奢侈的。

　　事實上，水壩甚至會減少飲用水的水源，因它們提供病菌的溫床，集中污染物質，與水庫中水的蒸發。舉例而言，納米比亞計劃建造的Epupa水壩蒸發的水量比溫得和克一年的水供應總量還多40倍。

　　世界各地對水需求量越來越大，這個問題非常嚴重，這並不僅僅是要解決太多人的飲水問題，問題還要複雜。逐漸升高的用水矛盾都是圍繞著公共資源的所有權、獲得公共資源的平等性這些較廣泛的問題而起的。在很多情況下，世界各地河流的大規模築壩活動已經導致了更大的用水不平等。 在過去的50年中，大壩（高度超過15公尺的水壩）數量已經增長了7倍多；大部分都是用於增加工業範圍內的農業灌溉。 在世界的乾旱地區，該用水量占了該地區水供應量的75-80%。事實上，大壩常常促使少數人用更多的水，也更奢侈地用水，而且這總是以農村地區的窮苦人家因這些工程而失去水、土地、漁場以及森林的代價。由於世界"用水不平等"現象的加劇，大壩所造成的損害比它所帶來的好處更多。如今，雖然大規模的水壩建設已達100年之久，13多億人仍無法取得淡水，30多億人的衛生狀況還遠遠不夠理想。

　　在許多工業化國家和非工業化國家，大型水力發電站已經是其發展策略必不可少的一部分，然而如今還有21億多人過著沒有的電的生活。十幾年來，水力發電站一直是爭論的中心。世界上約有78%的水能尚未開發利用，支持者們就紛紛提倡水力發電站是電的重要來源，但是，事實上，世界各地越來越多的人已經認識到，大壩造價極其昂貴，對環境具有破壞作用，還會造成社會不公義現象。

　　當社區的民眾表達如何使用他們集水區的意見時，他們不太可能批准可能對自然資源和文化資源造成傷害的工程，而大壩是會對自然和文化資源造成損害的。因為河流常常流經很多地方，穿過不同的省份地區，甚至還會越過不同的國家，流經利益各不相同的社區，所以在如何對待可能影響河流與集水流域開發的問題上就會產生矛盾。解決問題的一個方法在於許多國家政府把河流看作是一種資源來加以控制和開發，這樣發展往往忽視污染的發生、環境損害、社區破壞所產生的代價，或對具有巨大文化價值、精神價值和美學價值的地方的損失視而不見。

　　規劃者和政策制定者必須考慮過去與水力發電站相關的解決方法中有何問題，並重新考慮其未來作用。同時，國民們繼續要求參與規劃過程，這樣既能確定發電的合適方法，又能確定這些電力所要達到的目的的合適性。比方說是否還需要更多的電力？如果是的話，發電的最好方法又是什麼？這些都是我們需要提出的問題。

版權歸屬　國際河網　環境信託基金會(陶俊 譯，李堅、陳維立審校)

中英對照全文：http://news.ngo.org.tw/issue/water/
issue-water-irn00121801.htm

"In this century 〔in the US〕, dams that were clearly justified for their economic value gradually gave way to projects built with excessive taxpayer subsidies, then justified by dubious cost-benefit projections. The public is now learning that we have paid a steadily accumulating price for these projects, in the form of fish-spawning runs destroyed, downstream rivers altered by changes in temperature, unnatural nutrient load and seasonal flows, and delta wetlands degraded by lack of fresh water and saltwater intrusion. My parents' generation gloried in the construction of dams across America's rivers. My generation saw how those rivers were changed, deformed killed by dams. The next generation must help decide if; how and where those dams stand or fall."

Of all the ways to tamper with or harm a river, a large dam usually has the most immediate and far-reaching effects because of the huge changes it causes to a river's hydrology - its very circulation system. The impacts can be felt throughout the catchment.

Water scarcity is commonly used to justify new water-supply dams and river diversion projects in Southern Africa. It is certainly true that dams are an obvious way to store large quantities of water for distribution at drier times of the year. It is also a fact that water use has increased dramatically in modem times. The first 80 years of this century saw a 200 percent increase in the world's average per capita water use, which accounted for a remarkable 566 percent increase in withdrawals from the world's freshwater resources. But dams and pipelines don't actually create new water, they merely move it from one set of users to another - usually, from the poorest to the richest or, put another way, from the most frugal users to the most profligate.

In fact, dams can even reduce potable water supplies by creating better environments for disease organisms, by concentrating pollutants, and through evaporation from reservoirs. For instance, the proposed Epupa Dam in Namibia would evaporate more than 40 times Windhoek's annual water supply.

While the world's growing thirst is a serious problem, the story is more complicated than just too many people putting their straws in the glass. The growing conflicts over water use revolve around the broader questions about ownership of common resources, and equity of access to those resources. In many cases, large-scale damming of the world's rivers has led to greater water inequity. In the past 50 years, the number of large dams (those greater than 15 metres in height) has increased more than sevenfold; a high proportion of these were built to expand industrial-scale irrigated agriculture, which can use 75- 80 percent of the regional water supply in dry parts of the world. In fact, large dams have often promoted greater, more wasteful water use by fewer people, and usually at the expense of the rural poor who lose access to water, land, fisheries and forests to such projects. By adding to the world's "water inequity," large dams may do more harm than good. For today, despite a century of massive dam building, more than 1.3 billion people are still without access to fresh water, and more than 3 billion are without adequate sanitation.

Large-scale hydropower has been integral to development strategies in many industrialized and non-industrialized countries, yet more than 2.1 billion people remain without power today. Hydropower has been at the center of major controversy for more than a decade. With an estimated 78 percent of the earth's hydropower potential yet untapped, proponents continue to promote hydro as an important source of electricity, despite the fact that around the world there is growing recognition that large dams are vastly expensive, environmentally devastating, and can be socially unjust.

When local communities have a say in how their catchment is used, they are unlikely to approve of projects that could do the kind of lasting harm to natural and cultural resources that a large dam will. But because rivers often nm for long distances, across provincial and even national lines and through communities with many different interests, conflict often arises over how to handle development that can affect rivers and catchments. Contributing to the problem is that many national governments see rivers as assets to control and develop, and such development is often based on models that ignore the cost of pollution, environmental destruction, damaged communities, or the loss of places with great cultural, spiritual or aesthetic value. 

Planners and policy makers are having to consider the problems associated with the past approach to hydropower and to reconsider its future role. Civil society, meanwhile, continues to demand participatory planning processes that will identify not just appropriate means to generate electricity, but also the appropriateness of the goals that this electricity is intended to achieve. Is more electricity necessary? If so, what is the best way to generate it? These are the questions we all need to be asking.