抗击500年来最严重的干旱，看美国加州如何用新技术节水

    最新评估显示，加州80%的地区目前处于极度干旱中。当地居民如今正经历的环境条件实际上2011年就萌芽了。但目前仍没有缓解迹象。毫不意外，当地用水成本高得吓人，但是加州所付出的代价，并非只是用水成本这么简单。加州中央谷地(Central Valley)农业今年将面临17亿美元的损失，原因在于该地区遭遇了据称是500年以来最严重的旱灾。这一地区的农业产值占加州半壁江山，占全美农业产值的5%，大约1.45万名工人也可能因农业萧条而失业。

    加州的出路在何方？专家表示，对于如此大范围的旱情来说，要找到解决办法不是件容易的事。但有一点是肯定的：科技将发挥重要作用。

    圣地亚哥市公用事业部门主管哈拉•瑞扎克向《财富》杂志(Fortune)透露，水源多元化一直是该部门工作的重中之重，因为圣地亚哥的九成用水都是从南加州市政水管区（Metropolitan Water District of Southern California）购买的。瑞扎克说，1990年也出现过旱情，当时我们明确地意识到现有的计划缺乏可持续性。旱情迫使政府官员重新审视替代水源的问题。

    自2007年以来，圣地亚哥人均用水量下降了27%。官员称，旨在改善用水效率的返利活动、工具和教育项目都是导致这一变化的因素。

    瑞扎克承认，“这些解决方案的科技含量较低。”这些办法并非那种全新的、昂贵的高科技解决方案，例如目前正在建设的反渗透海水淡化工厂。瑞扎克还说，由私营开发商波塞冬水务公司(Poseidon Water)新建的卡尔斯巴德海水淡化项目(Carlsbad Desalination Project)有望于今秋投入使用。该工厂每日供水量约为5,000万加仑，大约是该地区年用水量的10%。

    海水淡化是一个具有争议性的话题。虽然这是一种成熟的技术，而且长时间以来被用于为世界很多地区提供饮用水，尤其是中东地区，但它经常因高能耗而受到诟病。

    “圣地亚哥最昂贵的水源”

    非营利性组织太平洋研究所（Pacific Institute）所长皮特•格莱克表示，“我们从事海水淡化业务已经100多年了。我们对海水淡化技术了如指掌，但这并非长久之计，因为这一技术仍然非常昂贵。”该组织致力于与财富500强（Fortune 500）企业合作开发水务解决方案。

    格莱克说，与之前的技术相比，反渗透技术已帮助改善了海水淡化的能源足迹。即便如此，新建造的卡尔斯巴德工厂将“成为圣地亚哥最昂贵的水源。”

    在格莱克看来，那些“更世俗”的技术能帮助人们提升用水效率，包括节水马桶和灌溉设备在内的这些技术远比反渗透技术更为重要。“滴灌并不是什么新技术，节水马桶也不是，但是也有新的版本能够让我们以低廉的成本节约大量水资源。这些技术并不怎么吸引眼球，但它们实际上却是当前我们能够采取的最明智的办法。”

    More than 80% of California is now in a state of extreme drought, according to the latest assessment. The environmental conditions that residents are experiencing today actually began in 2011. Still, there seems to be no end in sight. Water costs are sky high, as you would expect, but Californians are paying the price in more ways than one. The state’s Central Valley agriculture industry, for example, stands to lose $1.7 billion this year as a result of what some believe is the worst drought to affect the region in 500 years. Some 14,500 workers could lose their jobs in an area responsible for half of the state’s agriculture and five percent of the entire nation’s.

    How will California survive? For a problem of such massive scope, the solutions will be complex, experts say. One thing is certain: technology will play a key role.

    Halla Razak is the director of public utilities for the city of San Diego. Diversifying the water supply has been a top priority, she tells Fortune, because more than 90 percent of San Diego’s water has historically been purchased from the Metropolitan Water District of Southern California. It became clear in 1990, when there was another drought, that the existing plan wasn’t sustainable, Razak said. It prompted officials to take a fresh look at alternatives.

    Since 2007, per-capita water use in the San Diego region has decreased about 27 percent. Officials point to rebates, tools, and educational programs aimed at improving water-use efficiency as factors in the change.

    “These are low-tech solutions,” Razak concedes. They are not like the brand-new and pricey reverse-osmosis desalination plant now under construction. The new Carlsbad Desalination Project, the work of the private developer Poseidon Water, is expected to open this fall. It will supply roughly 50 million gallons of water per day, which is about 10 percent of what the region uses each year, Razak says.

    Desalination is something of a controversial topic. Though it is an established technology that has long provided drinkable water to many parts of the world, most notably the Middle East, it is also frequently criticized for its high energy demands.

    ‘San Diego’s most expensive source’

    “We’ve been desalinating water for over 100 years,” says Peter Gleick, president of the Pacific Institute, a nonprofit that works with Fortune 500 companies on water solutions. “We know how to desalinate, but that’s not the long-term answer because it’s still extraordinarily expensive.”

    Reverse osmosis technology has helped improve desalination’s energy footprint compared with past alternatives, Gleick says. Even so, the new Carlsbad plant “will be San Diego’s most expensive source of water,” he says.

    In Gleick’s view, the “more mundane” technologies that help people use water more efficiently, from efficient toilets to irrigation equipment, are far more important. “Drip irrigation is not a new technology, toilets are not new, but there are new versions that let us save a tremendous amount of water cost-effectively,” he says. “They may not be sexy, but they’re frankly the smartest things we could be doing.”