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非洲南部的水問題專家一致認同：透過對水的需求實行管理，可以至少將大多數城市裏的水消耗量減少30%。而且，服務質量不必顯著降低就可以節省這麼多水，消費者也不必長期支付錢款。事實上，該地區有些城市已經藉由實行需求管理，明顯地節約用水。納米比亞的Windhoek市透過調整定價策略、設備升級、水的再利用以及其它措施，總共減少了33 %的用水量。節約這些用水開支成本，還不到開發新水源（比如從700公里之遙的Okavango河中用管道輸水）的十分之一。
在南非的Hermanus市，始於1996年的城市節水專案在第一年內就降低了32%的水量需求。Hermanus專案包括如下措施：促進智慧用水的園藝技術；改良水的計量系統；將耗水量大的外來植物從集水流域地區中移走；在學校和家庭開展用水的審計活動。這就是南非首次在一個市區內所開展的長期節水專案。專案的基礎是在Kruger國家公園取得成功的需求管理計劃。通過實施該計劃，Kruger國家公園將公園遊客的用水削減了73%（令人驚訝的百分比！），而且他們的用電量也減少了60%。
南非目前尚未建立一個全國性計劃來擴大執行Hermanus專案，但是水務部節水專案在1999 年5月發表了「節水和需求管理的國家策略計畫」，這篇報告將可引導南非水務規劃人員做出更明確的指導方針。報告指出，「降低水需求的增加，能使對於大型基礎建設的要求萎縮，如此便可省下了大筆資金‧‧‧而根據估計，如果Gauteng市的水需求成長無法降低，在未來20年裡，新建廢水處理廠就必須花掉100億蘭特（註），而新的增水計劃也會花去170億蘭特。單是將Gauteng市內所有新建的大型供水基礎設施專案延遲一年，可能產生的淨現值就超過20億蘭特。"
* （譯註：R = Rand 南非貨幣單位 。）
在節水方面取得進展的另一座城市，是辛巴威Bulawayo市。如同南部非洲其他許多城市，該市不得不對抗1991~1992年造成嚴重損失的旱災所造成的效應。該市大量用水大大提高的稅收率比例，對超量用水進行重罰。許多公司企業和家庭都安裝了新的量水錶，還建立自行車巡邏隊來檢查2,100公里長的配水管道，以防泄漏。透過這些措施，該市得以降低家庭用水需求30%以上，並減少工業需求至少40%。除此以外，該市90%人口都利用同一個污水處理系統，而經過廢水處理，該污水處理系統每天能夠提供8,000立方米的水，再度用於澆灌公園、運動場地和路邊的草木。然而，自從那場旱災之後，水需求幾乎已恢復到旱災前的成長曲線。
值得注意的是，儘管各種水需求管理的方法比較方便而且有效，但是這個（南非）地區極少數國家在有實際意義的規模上採用此法。在1999年3月的水需求管理會議上，來自該地區各個地方的水資源管理人員引證說，如今非洲南部地區無法實行大規模水需求管理的最大阻礙就是缺乏政治意願。要建立這種政治意願以改變目前的狀況，就需要讓公眾知道真相並站出來講話，形成一種壓力，要求將實施水需求管理作為未來數年內供水計劃的一個不可分割的組成元素。
這個問題的一部分在於，該地區最大的用水單位是頗具影響力的大型農業。非洲南部的農田耕種比其它行業的用水量要多得多：莫三比克和辛巴威的農業用水占全部用水的80%，納米比亞占66%，波次瓦納和南非則占50%。與此相反，這些國家的家庭用水和工業用水各自所占的比例通常還不到15%。灌溉損失往往非常嚴重，從水源中抽出來的水估計有將近一半都是浪費掉的。舉例而言，如果南非的灌溉設備能夠提高其效率，哪怕只是20%，可供城市或工業使用的水量也會增加一倍。顯然，透過節約農業用水就可以獲得大量的水，然而該地區迄今還沒有一個國家設法廣泛提高農業用水的效率。（作者 Steve Rothert ）
版權歸屬 國際河網IRN，環境資訊協會（陶俊 譯，吳國玢 、陳維立審校）
中英對照全文：http://e-info.org.tw/issue/water/2001/issue-water-irn01082001.htm
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Southern Africa water experts agree: water demand management can reduce water consumption by at least 30 percent in most cities. Moreover, these savings can be achieved with no noticeable reduction in quality of service, nor with any long term cost to consumers. In fact, some cities in the region have already achieved significant reductions through demand management. Windhoek, Namibia achieved 33 percent reductions through pricing strategies, appliance upgrades, water re-use and other measures. The cost of these savings was less than one-tenth the cost of developing new sources such as piping water from the Okavango River 700 kms away.
In Hermanus, South Africa, the city's conservation programme begun in l996 reduced water demand by 32 percent in the first year. The Hermanus programme included measures such as promoting water-wise gardening, improving the metering system, removing thirsty alien vegetation from water catchment areas and conducting water audits in schools and homes. This was South Africa's first longterm water conservation programme for a municipal area. It was based on a successful demand-management plan for Kruger National Park which managed to cut water use by park visitors by an amazing 73 percent, and electricity use by 60 percent.
Although South Africa does not yet have a national programme to replicate the Hermanus programme more broadly at this time, the Department of Water Affairs water conservation programme in May 1999 released the "Water Conservation and Demand Management National Strategy Framework," which may lead to more clearcut guidelines for South Africa's water planners. The report states, "Reducing the growth in demand can result in postponing large infrastructure requirements and wilt thus result in significant financial savings ... It is estimated that if the growth in demand in Gauteng is not reduced, over the next 20 years, R10 billion will have to be spent on new wastewater treatment plants and R17 billion will have to be spent for new water augmentation schemes. The net present potential value of postponing all new bulk water supply infrastructure projects in Gauteng by one year alone exceeds R2 billion."
Another city that has made progress with water conservation include Bulawayo, Zimbabwe. Like many other cities in Southern Africa, it had to battle with the effects of a crippling drought in 1991-92. The city implemented an aggressive increasing block-rate tariff structure, with heavy fines for excessive use. New metres were installed in many businesses and homes, and bicycle patrols were established to check the 2100-km water-distribution pipeline for leaks. The city was able to reduce domestic demand by more than 30 percent and industrial demand by 40 percent or more. In addition, the sewerage system serves about 90 percent of the city's population, and through reclamation, provides 8,000 m3/day used to irrigate parks, sports fields and road margins. Since the drought passed, however, growth in demand has nearly resumed the pre-drought trajectory.
Remarkably, despite the relative ease and effectiveness of water demand management approaches, very few countries in the region practice it at a meaningful scale. At a March 1999 water demand management meeting, water managers from across the region cited the lack of political will as the single biggest obstacle preventing widespread application of water demand management in Southern Africa today. Creating the political will to change this state of affairs will require an informed public that is willing to be outspoken in pressing for water demand management as an integral component in planning for water supply in coming years.
Part of the problem is that the region's biggest water user is powerful big agriculture. Farming in Southern Africa consumes more water than any other sector by a wide margin: 80 percent in Mozambique and Zimbabwe, 66 percent in Namibia and 50 percent in Botswana and South Africa. By contrast, the domestic and industrial sectors typically account for less than 15 percent each. Irrigation losses are often quite significant and it is estimated that less than half of water abstracted from water resources is wasted. If south African irrigators, for example, could improve efficiency by only 20 percent, water available for urban or industrial use would be doubled. Clearly, tremendous gains stand to be made through water conservation applied to the agricultural sector, and yet no country in the region widely promotes efficient water use in agriculture. (by Steve Rothert)
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