[2009.04.11] Sin aqua non 用水之过

Apr 8th 2009 | ISTANBUL
From The Economist print edition

Water shortages are a growing problem, but not for the reasons most people think
水资源愈发短缺，原因却不如众人所料

THE overthrow of Madagascar’s president in mid-March was partly caused by water problems—in South Korea. Worried by the difficulties of increasing food supplies in its water-stressed homeland, Daewoo, a South Korean conglomerate, signed a deal to lease no less than half Madagascar’s arable land to grow grain for South Koreans. Widespread anger at the terms of the deal (the island’s people would have received practically nothing) contributed to the president’s unpopularity. One of the new leader’s first acts was to scrap the agreement.
三月中旬，马达加斯加总统下台，水资源问题难逃其咎——韩国水资源问题。韩国大宇物流集团由于担心国内水资源缺乏，粮食短缺日益严重，便租用马达加斯加近一半面积的可耕种土地，用作韩国人民粮食供给。协议中的条款引起举马达加斯加不满（因为人民几乎一无所获），总统的支持率跌至谷底。新总统上任后第一把火，就是撕毁协议。

Three weeks before that, on the other side of the world, Governor Arnold Schwarzenegger of California declared a state of emergency. Not for the first time, he threatened water rationing in the state. “It is clear,” says a recent report by the United Nations World Water Assessment Programme, “that urgent action is needed if we are to avoid a global water crisis.”
此事三周前，在世界另一端的加利福尼亚，州长阿诺.施瓦辛格宣布事态紧急，扬言要在州中分区供水——这已经不是第一次了。联合国世界水资源评估方案最近报道也称：“显然，如果我们希望避免全球水危急，就必须采取紧急行动。”

Local water shortages are multiplying. Australia has suffered a decade-long drought. Brazil and South Africa, which depend on hydroelectric power, have suffered repeated brownouts because there is not enough water to drive the turbines properly. So much has been pumped out of the rivers that feed the Aral Sea in Central Asia that it collapsed in the 1980s and has barely begun to recover.
地方水资源短缺现象日益严峻。澳大利亚干旱十年，依赖水电的巴西和南非也因为缺水，涡轮不能正常运转，只得受限电之苦。河流抽水过量，中亚咸海供水不足，20世纪80年代发生了生态灾难后，一直没能恢复。

Yet local shortages, caused by individual acts of mismanagement or regional problems, are one thing. A global water crisis, which impinges on supplies of food and other goods, or affects rivers and lakes everywhere, is quite another. Does the world really face a global problem?
个人行为管理不善或者区域问题引发地方性短缺是一回事，然而危及粮食和其他产品供应，影响各处河流湖泊的水危机，则另当别论。现在的世界，当真面临着一个全球性问题吗？

Water, water everywhere…
水，无处不在……

Not on the face of it. There is plenty of water to go around and human beings are not using all that much. Every year, thousands of cubic kilometres (km3) of fresh water fall as rain or snow or come from melting ice. According to a study in 2007, most nations outside the Gulf were using a fifth or less of the water they receive—at least in 2000, the only year for which figures are available. The global average withdrawal of fresh water was 9% of the amount that flowed through the world’s hydrologic cycle. Both Latin America and Africa used less than 6% (see table). On this evidence, it would seem that all water problems are local.
表面看来，并非如此。环顾四周，水源充足，人类也并未使用如此之多。每年，雨雪和融冰所带来的淡水资源有几千立方千米。2007年一项报道称，海湾地区之外的大部分国家最多也只使用所得水资源的1/5。世界水循环中，每年平均只有9%的淡水流失。拉丁美洲和非洲所用淡水都不过6%。这表明水资源问题，只有在地区内发生。

The trouble with this conclusion is that no one knows how much water people can safely use. It is certainly not 100% (the amount taken in Gulf states) because the rest of creation also has to live off the water. In many places the maximum may well be less than one fifth, the average for Asia as a whole. It depends on how water is returned to the system, how much is taken from underground aquifers, and so on.
此种结论的问题在于无人了解多少水资源能够供人们安全使用。当然，这一比例不会是海湾地区国家所称的100%，因为其他生物也需要靠水才能够生存。许多地区，最多也只有不过1/5的水源能够放心使用——整个亚洲地区的平均值即是如此。多少水能够回归生态系统，人们从地下蓄水层中又抽取多少等，均为其决定因素。

But there is some admittedly patchy evidence that, given current patterns of use and abuse, the amount now being withdrawn is moving dangerously close to the limit of safety—and in some places beyond it. An alarming number of the world’s great rivers no longer reach the sea. They include the Indus, Rio Grande, Colorado, Murray-Darling and Yellow rivers. These are the arteries of the world’s main grain-growing areas.
但一些零散的证据却不置可否：按照现在滥用水源的方式，水流失之量正逼近安全限度——而在某些地区已经超过。许多世界大河未曾入海就已断流，数量相当惊人：印度河、格兰德河、科罗拉多河、墨累-达令河和黄河莫不如此——而这些都是世界主要粮食种植地区的大动脉。

Freshwater fish populations are in precipitous decline. According to the World Wide Fund for Nature, fish stocks in lakes and rivers have fallen roughly 30% since 1970. This is a bigger population fall than that suffered by animals in jungles, temperate forests, savannahs and any other large ecosystem. Half the world’s wetlands, on one estimate, were drained, damaged or destroyed in the 20th century, mainly because, as the volume of fresh water in rivers falls, salt water invades the delta, changing the balance between fresh and salt water. On this evidence, there may be systemic water problems, as well as local disruptions.
淡水鱼数量急剧下滑。世界大自然基金会称，自1970年起，河流湖泊内的鱼类资源已有大约30%灭绝，比丛林、温带森林、大草原和其他大型生态系统中动物消失数量还要多。据估计，20世纪中，世界上的一半湿地都已干涸、毁坏或惨遭破坏，原因主要在于河流中淡水资源减少，咸水趁势侵入三角洲，打破淡咸水平衡。如此看来，水资源问题和地区性破坏问题，都可能会系统化。

Two global trends have added to the pressure on water. Both are likely to accelerate over coming decades.
两项全球性趋势也给水问题带来了压力——而这两项趋势在未来几十年中都有加速倾向。

The first is demography. Over the past 50 years, as the world’s population rose from 3 billion to 6.5 billion, water use roughly trebled. On current estimates, the population is likely to rise by a further 2 billion by 2025 and by 3 billion by 2050. Demand for water will rise accordingly.
其一是人口。过去50年中，世界人口从30亿飙升到65亿，用水量增加两倍。按照目前估测，截至2025年世界人口将再增20亿，到2050年增加30亿。水需求也会随之增加。

Or rather, by more. Possibly a lot more. It is not the absolute number of people that makes the biggest difference to water use but changing habits and diet. Diet matters more than any single factor because agriculture is the modern Agasthya, the mythical Indian giant who drank the seas dry. Farmers use about three-quarters of the world’s water; industry uses less than a fifth and domestic or municipal use accounts for a mere tenth.
确切地说，是随之加速增加——突飞猛进地增加。造成用水显著变化的并非是人口的绝对数量，而是人们的生活饮食习惯。饮食堪称最主要的因素，如果类比印度神话，农业就好比当代喝干海水的阿加斯提亚。农业用水占到世界用水总量的3/4，工业用水不及1/5，而生活和城市用水仅占1/10。

Different foods require radically different amounts of water. To grow a kilogram of wheat requires around 1,000 litres. But it takes as much as 15,000 litres of water to produce a kilo of beef. The meaty diet of Americans and Europeans requires around 5,000 litres of water a day to produce. The vegetarian diets of Africa and Asia use about 2,000 litres a day (for comparison, Westerners use just 100-250 litres a day in drinking and washing).
不同是食物从根本上也会使用不等量的水资源。种植一公斤小麦需要大约1,000升水，但生产一公斤牛肉则需要15,000升。按照欧美人士以肉食为主的饮食习惯，每天需要5,000升水，而亚非人民的素食食谱每天只需2,000升（西方人每天饮用和洗刷的水只有100-250升）。

So the shift from vegetarian diets to meaty ones—which contributed to the food-price rise of 2007-08—has big implications for water, too. In 1985 Chinese people ate, on average, 20kg of meat; this year, they will eat around 50kg. This difference translates into 390km3 (1km3 is 1 trillion litres) of water—almost as much as total water use in Europe.
因此，素食习惯向肉食的转变不仅是造成2007-08年食物价格上涨的原因，而且对水也起着至关重要的作用。1985年，中国人平均每人消费肉类20千克，今年则估计达到50千克。也就是说，390立方千米（一立方千米=一万亿升）的水因此消失，相当于欧洲的总用水量。

The shift of diet will be impossible to reverse since it is a product of rising wealth and urbanisation. In general, “water intensity” in food increases fastest as people begin to climb out of poverty, because that is when they start eating more meat. So if living standards in the poorest countries start to rise again, water use is likely to soar. Moreover, almost all the 2 billion people who will be added to the world’s population between now and 2030 are going to be third-world city dwellers—and city people use more water than rural folk. The Food and Agriculture Organisation reckons that, without changes in efficiency, the world will need as much as 60% more water for agriculture to feed those 2 billion extra mouths. That is roughly 1,500km3 of the stuff—as much as is currently used for all purposes in the world outside Asia.
饮食习惯的改变不太可能逆转，因为此乃富裕化、城市化的产物。总体而言，饮食方面的“用水密度”随人们脱贫，达到最快速的增长，因为自此种情况下，人们摄入肉类增多。如果世界最贫困的地区生活水平再次上升，用水量就会飙升。加之从现在到2030年，全球预计增加的20亿人口，几乎全部处于第三世界城市中——而城市用水要多于农村地区。世界粮农组织认为，如果用水效率不加以改观，世界对农业的水需求要增加60%，才足够喂养多出的20亿张嘴巴。换句话说，用水量需要增加1,500立方千米——相当于亚洲地区以外全世界现在的用水总量。

The other long-term trend affecting water is climate change. There is growing evidence that global warming is speeding up the hydrologic cycle—that is, the rate at which water evaporates and falls again as rain or snow. This higher rate seems to make wet regions more sodden, and arid ones drier. It brings longer droughts between more intense periods of rain.
另一影响水资源的长期趋势即为气候变化。越来越多的证据表明，全球变暖正在加速水循环——也就是水蒸发后再度以雨雪形式返回生态系统的速率。速率变大，湿润地区就会更加潮湿，而干旱地区则更加干燥。干旱期会越来越长，而与其交叉的降水期则更加密集。

Climate change has three big implications for water use. First, it changes the way plants grow. Trees, for example, react to downpours with a spurt of growth. During the longer droughts that follow, the extra biomass then dries up so that if lightning strikes, forests burn more spectacularly. Similarly crops grow too fast, then wilt.
气候变化对于用水有三大影响。首先，它改变了植物的生长方式。树木遇到倾盆大雨，会迅猛增长。而在接下来的长期干旱中，超额的生物质量会干旱，如遇闪电，森林大火则更加严重。同样，庄稼生长也会过快，然后干旱枯萎。

Second, climate change increases problems of water management. Larger floods overwhelm existing controls. Reservoirs do not store enough to get people or plants through longer droughts. In addition, global warming melts glaciers and causes snow to fall as rain. Since snow and ice are natural regulators, storing water in winter and releasing it in summer, countries are swinging more violently between flood and drought. That is one big reason why dams, once a dirty word in development, have been making a comeback, especially in African countries with plenty of water but no storage capacity. The number of large dams (more than 15 metres high) has been increasing and the order books of dam builders are bulging.
第二，气候变化引发更多水资源管理方面的问题。管理措施高一尺，洪水声势高一丈。水库的储存量无法保证人们和植物度过更长的干旱期。除此之外，由于全球变暖，冰川融化，降雪量减少，降雨量增加。而冰雪是自然的调度站，冬日储水，夏天释放，如此一来，许多国家气候变化更为剧烈，常常在洪水过后经历干旱。于是曾经一度为发展所不齿的水坝现在也卷土重来，尤其是在水量充足却无储存能力的非洲。大型水坝（高于15米）数量日益增多，水坝建造公司现在订单应接不暇。

Third, climate change has persuaded western governments to subsidise biofuels, which could prove as big a disaster for water as they already have been for food. At the moment, about 2% of irrigated water is used to grow crops for energy, or 44km3. But if all the national plans and policies to increase biofuels were to be implemented, reckons the UN, they would require an extra 180km3 of water. Though small compared with the increase required to feed the additional 2 billion people, the biofuels’ premium is still substantial.
第三，因为气候变化，许多西方国家都被说服补助生产生物燃料——这为水带来的灾难不亚于它们对粮食造成的影响。眼下用来培养能源作物约占灌溉水的2%，也就是44立方千米。联合国称，如果所有国家增加生物能源的计划政策都加以实施，则需要另外180平方千米的水资源。同供给新增20亿人民粮食所用的水相比，这算不了什么，可是生物燃料需求还是不容小觑。

In short, more water will be needed to feed and heat a world that is already showing signs of using too much. How to square that circle? The answer is by improving the efficiency with which water is used. The good news is that this is possible: vast inefficiencies exist which can be wrung out. The bad news is it will be difficult both because it will require people to change their habits and because governments, which might cajole them to make the changes, are peculiarly bad at water policy.
总而言之，解决这个已经过度用水世界的“温饱”问题，还须更多水资源——这根本没希望的事情该如何解决呢？答案是提高用水效率。比较让人欣慰的是这不无可能：低效现象普遍存在，通过适当途径能够得以解决；然而也有坏消息：解决水问题需要人们改变生活习惯，加之政府虽然有可能设法让人们做出改变，却格外不擅长制定水务政策，因此这个问题还是相当棘手的。

…nor any drop to drink
无水可饮

Improving efficiency is doable and industrial users have done it, cutting the amount of water needed to make each tonne of steel and each extra unit of GDP in most rich countries (see first chart). This can make a difference. The Pacific Institute reckons that, merely by using current water-saving practices (ie, no technological breakthroughs) California, a water-poor state, could meet all its needs for decades to come without using a drop more.
改善用水效率，此法可行，而且工业中已经做到——富裕国家中，每吨钢铁和每单位GDP所需水量都已减少。这意义重大。太平洋研究所称，仅通过现行的节水方案（即在没有其他科技突破的情形下），水源匮乏的加利福尼亚可以不多使用一滴水，而满足接下来几十年的需要。

Still, industry consumes less than a fifth of the world’s water and the big question is how to get farmers, who use 70-80%, to follow suit. It takes at least three times as much water to grow maize in India, for example, as it does in America or China (see second chart). In some countries, you need 1,500 litres of water to produce a kilo of wheat; in others, only 750 litres. It does not necessarily follow that water is being used unsustainably in the one place and not the other; perhaps the high-usage places have plenty of water to spare. But it does suggest that better management could reduce the amount of water used in farming, and that the world could be better off if farmers did so. Changing irrigation practices can improve water efficiency by 30%, says Chandra Madramootoo, of the International Commission on Irrigation and Drainage. One can, for example, ensure water evaporates from the leaves of the plant, rather than from the soil. Or one can genetically modify crops so they stop growing when water runs dry, but do not die—they simply resume growth later when the rains return.
工业用水仍不及总量的1/5，现在一个很大的问题在于：如何让使用世界上70-80%水资源的农民们加入节水潮流。在印度种植玉米的用水量是美国或中国的三倍之多。某些国家中生产一公斤小麦需水1,500升，而另一些地方只需750升。这并不是说有些地方可持续用水而另外的地方不然，可能用水多的地方水源充足。但是这却表明我们可以通过更加有效的管理来减少农业用水量，如果农民们也能效仿此行，全球景况将会有所改善。国际灌排委员会主席曼德拉穆图说，改变灌溉方式，可以将用水效率提高30%。比如说，我们可以让水从植物叶面蒸发，而非土壤中；或者我们可以通过转基因，让植物在水源匮乏之时停止增长，而不死亡——再次降雨之时，它们可以再度生长。

The world might also be better off, at least in terms of water, if trade patterns more closely reflected the amount of water embedded in traded goods (a concept called “virtual water” invented by Tony Allan of King’s College London). Some benign effects happen already: Mexico imports cereals from America which use 7 billion cubic metres (m3) of water. If it grew these cereals itself, it would use 16 billion m3, so trade “saves” 9 billion m3 of water. But such beneficial exchanges occur more by chance than design. Because most water use is not measured, let alone priced, trade rarely reflects water scarcities.
如果贸易模式能够更好地反映货物中的含水量（伦敦大学国王学院的托尼.阿兰所发明的“虚拟水”这一说法），世界也会有所改善——最起码在水方面。一些良性效应已经有所体现：墨西哥从美国进口用水70亿立方米的谷类植物，相对自身种植所需160亿立方米，就能够通过贸易“节约”90亿平方米。但是此类有益的交流更多的是出于偶然，而非处于策划——因为大部分水都未曾经过测量，更不用说标价，因此水匮乏无从体现。

To make water use more efficient, says Koichiro Matsuura, the head of UNESCO, the main UN agency dealing with water, will require fundamental changes of behaviour. That means changing incentives, improving information flows, and improving the way water use is governed. All that will be hard.
处理水问题的主要联合国机构联合国教科文组织总干事松浦晃一郎说，要想更高效利用水资源，就需要我们在行为上做出彻底改变。这就意味着修订奖励方案，改善信息流通和水资源管理——这些都绝非易事。

Water is rarely priced in ways that reflect supply and demand. Usually, water pricing simply means that city dwellers pay for the cost of the pipes that transport it and the sewerage plants that clean it.
目前的水价格，几乎不反映供求。通常情况下，城市居民所支付的水价只不过是运输水的管道费用和污水处理厂的清理费用。

Basic information about who uses how much water is lacking. Rainwater and river flows can be measured with some accuracy. But the amount pumped out of lakes is a matter of guesswork and information on how much is taken from underground aquifers is almost completely lacking.
用水人，用水量的基本信息现在均不充足。雨水河水能够比较精确地测量，但是从湖中抽取的水量则纯属臆测，地下蓄水层的水量信息几乎空白。

The governance of water is also a mess. Until recently, few poor countries treated it as a scarce resource, nor did they think about how it would affect their development projects. They took it for granted.
水管理也是一团乱麻。就是现在，也很少有贫穷国家认为水资源稀缺，更不去考虑水资源会影响他们的发展项目。他们认为用水纯是理所当然。

Alongside this insouciance goes a Balkanised decision-making process, with numerous overlapping authorities responsible for different watersheds, sanitation plants and irrigation. To take a small example, the modest town of Charlottesville in Virginia has 13 water authorities.
除了以上所说的漠不关心，用水决策还如同巴尔干半岛国家一般——各司其职。不同的分水岭、公共卫生工厂和浇灌都由数不清的机关负责，其中职责难免重叠。稍微举个例子，在弗吉尼亚，规模不大的夏洛茨维尔镇上就有13个水务局。

Not surprisingly, investment in water has been patchy and neglected. Aid to developing countries for water was flat in real terms between 1990 and 2005. Within that period, there was a big shift from irrigation to drinking water and sanitation—understandable no doubt, but this meant less aid was going to the main users of water, farmers in poor countries. Aid for irrigation projects in 2002-05 was less than half what it had been in 1978-81. Angel Gurria, the head of the Organisation for Economic Co-operation and Development, talks of “a crisis in water financing”.
那么，水务投资零星不整，无人关注就不足为奇了。1990年到2005年间，世界对发展中国家的水援助实额完全没有增长；而且在此期间，灌溉、饮用和卫生方面都发生了可观的变化——当然这可以理解，但是这也意味着主要的水用户，就是贫穷国家的农民们，所得到的援助相应减小。相比1978-81年，2002-05年灌溉项目的支援降低一半之多。经济合作暨发展组织秘书长葛利亚称之为“水务融资危机”。

As is often the way, business is ahead of governments in getting to grips with waste. Big drinks companies such as Coca Cola have set themselves targets to reduce the amount of water they use in making their products (in Coke’s case, by 20% by 2012). The Nature Conservancy, an ecologically-minded NGO, is working on a certification plan which aims to give companies and businesses seals of approval (a bit like the Fairtrade symbol) according to how efficiently they use water. The plan is supposed to get going in 2010. That sort of thing is a good start, but just one step in a long process that has barely begun.
在处理废物方面，商业组织往往走在政府前面。诸如可口可乐之类的大公司已经为自己定下了目标，在生产过程中减少用水量（可口可乐计划截至2012年用水节约20%）。生态非政府组织“大自然保护协会”现在正在设计一项认证计划，希望经此以用水效率为参照，为公司和企业提供审批印章（形状貌似自由贸易符号），预计2010年开始实施。这样的做法的确是个不错的开端，但是在节水的漫漫长路上，这才刚迈出开始的一小步而已。