抗击500年来最严重的干旱，看美国加州如何用新技术节水

    格莱克指出，加州整整80%的水都用在了农业领域。“农民知道如何使用滴灌技术。虽然这并不是什么新技术，但是他们在学习如何使用滴灌技术的新方法。”土壤水分检测器和智能仪表也能帮助降低水浪费。他说，“事实证明，在通过合理的途径获得正确的反馈之后，农民们减少了5%的用水量。虽然这看起来不多，但当旱灾来临时却能派上大用场。”

    但仅靠减少用水量是不够的。当极端旱情持续蔓延的时候，很多官员将目光投向了废水利用。在橘子郡，用过的水在处理后会重新注入地下，以补充当地的地下潜水层。格莱克解释说，“他们拥有创新的水处理厂，在那里，水在经过高标准处理后会被重新利用。在过去，这些水都会被排进大海。”

    太平洋研究所和自然资源保护委员会（Natural Resources Defense Council）上月发布的报告称，通过综合采用节水措施、废水利用和捕获雨水资源等方案，加州最多可节约1,400万英亩-英尺的未利用水源，足够满足加州所有城市一年的用水需求。

    “对于加州来说，这才是真正的出路”

    废水利用也是圣地亚哥关注的焦点。这座拥有130万人口的城市将效仿橘子郡的做法，目前正在酝酿一个名为“Pure Water”的项目。新项目呼吁更多地利用经城市净化处理后的废水，同时储存更多仅用于非饮用用途的水，例如灌溉用水。

    瑞扎克说：“圣地亚哥并没有橘子郡那么幸运，因为我们没有那么好的地下潜水层。但我们有大水库。”

    Pure Water计划涉及修建一座废水处理厂，并使用三种不同的废水处理技术：膜过滤、反渗透和紫外线消毒。为什么要采取这么多步骤？用瑞扎克的话来说，为了让水变得“尽可能纯净”。处理后的水将被注入当地的水库，在那里停留6个月。然后，它将被再次处理，并与其他的水源混合，供人饮用。

    最终，瑞扎克希望能跳过水库和后续的步骤，因为“在人们可接触到的所有美国水源中，这些水所接受的处理质量标准是最高的。”她指出，这些后续步骤“主要是为了打消人们对这种处理方式的抵触情绪罢了。”

    他们的目标是在2023年前实现1,500万加仑的日净化能力。瑞扎克说，从长期来看，官员们希望净化厂能够在2035年前负担超过三分之一的区域用水。

    她说：“我的确相信，这才是加州真正的出路。我们从河流和湖泊里获取原生态的水源，然后对其处理和净化，以供我们使用。随后，在将其排入大海和河流之前，我们又会以非常高的标准来处理废水。我们已经在这一过程中耗费了时间和能源，但是随后我们却让其流失掉了。对于加州来说，最好的办法在于，一旦我们获得了已经过高标准处理的水源，那么我们应该在使用之后进行再处理，再利用。”

    在资产管理公司Impax负责水策略业务的西蒙•格特利尔（Simon Gottelier）对这一观点表示赞同。他说：“这一举措在于回收原本应回归大海的已处理废水，并在大范围内加以使用。如果让我来回答加州在今后该如何应对这一挑战这个问题，我的看法是，这些废水再利用项目将成为加州可以采取的主要方法之一。”

    A full 80 percent of the water used in California goes to agriculture, Gleick points out. “Farmers know how to implement drip irrigation. It’s not a new technology, but they’re learning new ways to do it.” Soil-moisture monitors and smart meters also help reduce waste. “It turns out that with the right feedback delivered in the right way, people cut their water use by 5 percent,” he says. “That doesn’t sound like a lot, but in a drought it makes a big difference.”

    But reduction is not enough. As extreme drought conditions persist, many officials are looking at water reuse as an answer. In Orange County, used water is treated and fed back into the ground to replenish local aquifers. “They have innovative water treatment plants there and are treating it to high standards and then putting it to use,” Gleick explains. “In the old days, it would have been thrown into the ocean.”

    Through a combination of water-saving practices, water reuse, and recaptured storm water, California could save up to 14 million acre-feet of untapped water, enough to supply all of California’s cities for a year, according to a report published last month by the Pacific Institute and the Natural Resources Defense Council.

    ‘This is the real future for California’

    Water reuse is also a focus in San Diego. The city of 1.3 million is currently in the planning stages of an effort called Pure Water, which follows in the footsteps of Orange County. The new project calls for more reuse of the water the city has already been cleaning but reserving for non-potable uses only such as irrigation.

    “We in San Diego aren’t as lucky as Orange County in that we don’t have good aquifers underground,” Razak says. “But we do have large reservoirs.”

    The Pure Water plan involves building a plant that will treat used water with three different techniques: membrane filtration, reverse osmosis, and ultraviolet disinfection. Why so many steps? To make it “as pure as can be,” Razak says. The renewed water is then piped to local reservoirs, where it will sit for six months. Then it will be treated again before it’s mixed with other water sources for potable use.

    Eventually, Razak hopes to skip the reservoir and subsequent stages, since already “the water is being treated to the best standard of quality of any other raw water we get in the county.” Those later stages are “mostly to improve people’s acceptance of this process,” she admits.

    The goal is to purify 15 million gallons per day by 2023. Longer term, officials hope the purification facility supplies more than a third of the region’s water by 2035, Razak says.

    “I honestly believe this is the real future for California,” she says. “We take pristine water from rivers and lakes; we treat it and we clean it; and then we use it. Then we treat it again to a pretty high standard before we dispose of it in the ocean and rivers. We’ve already spent time and energy, but then we’re letting go of it. The best thing for California is once we already possess that water and it’s treated to a high level, to treat it further and reuse it.”

    Simon Gottelier, who runs the water strategy at the asset management firm Impax, agrees. “This is taking treated wastewater that would normally go out into the ocean and using it on a grand scale,” he says. “If I had to say how California will cope going forward, my sense is these water-reuse projects are going to be one of the major ways California can do it.”