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地下水補給
目前許多非洲南部國家的水供給大部分來自地下水。雖然有些國家的地下水資源非常豐富，其他國家卻體認到，在某些情況下，他們的地下蓄水層正在迅速耗竭。由於該地區的降雨毫無規律，經常管水的人會暫時從某個「地下水水庫」過度抽取地下水，以度過旱季，在降雨較多的年份再讓地下水庫補充水分。但是，長期過度抽取地下水，會導致水位下降（可至數百米），或使得含有鹽份的水流入地下水，使得地下水不能再被飲用，還會導致地面下陷。如果蓄水層能夠得到休息、補充的話，它們通常都是可以恢復的，但是如果水抽走後不能及時得到補充，它們會收縮，而無法恢復原來的蓄水能力。
納米比亞一直在研究把蓄水層作為地下水庫的可能性，這樣就可以擴大現有的地表水供應。Windhoek
市政府希望減少每年蒸發損失的水量，他們把淨化過的地表水人工注入某些蓄水層，以備以後使用。該市估計，用這個方法能節約超過10%的供水量。
在印度古加拉特，三分之二的村莊目前沒有永久性的可靠水源，其主要原因是地下水的過度開採。為了幫助解決這一問題，村民們在季節性河流上橫向建築小型的泥土攔水堤，以便在雨季期間形成小型水池，用來重新補充地下水供給量。雨季過後，水池漸漸消失。攔水堤只不過用來恢復地下水源，而從不直接將水攔截住用於供水。這項技術十分簡單，建造成本較低，維護修理也很方便。一個由政府出資的機構幫助村民設計攔水堤並支付所需費用。村民們則負責建造和維護他們的攔水堤，並負擔20%左右的建造費用。有一位印度工程師相信，此類工程項目最終能夠收集到多達該國降雨量50%的水。
地下水水壩提供了另一種補充地下水的方法。這些水壩是地下水的障礙物，它們將地下水攔截在一定的區域內，防止它們從地下流失。在某些地區，地下水水位下降幅度太大，即使下一場大雨也無法使水位回升。而在另一些地區，通過將雨水收集到地下水水庫中去，已使水位從深度200英尺上升到深度20英尺。印度沙漠地區的人們使用這種技術已經有幾個世紀的歷史了，如今這種做法被引進到山區。其中一個村的村長說道：「原來的枯井現在全年有水。」
雨水收集
在非洲和世界上其他一些地方，越來越多的社區正在回到小規模收集雨水的時代，人們通常使用一種收集屋頂雨水的系統。發表在1999年1月19日衣索比亞報紙《監督者》（The
Mornitor）上的一篇文章，介紹了一個成功的屋頂集水專案。該專案由衣索比亞農業部發起，並得到瑞典國際開發署（SIDA）和一個當地非政府組織「水行動」（Water
Action）的協助。文章中寫到：「這項新引進的技術，使許多家庭能省下可供維持長達5個月的飲用水，只需要一個普通尺寸的儲水箱。這些家庭甚至還能獲得一些多餘的水來澆灌他們花園中的植物。」文章並指出，對於大多數衣索比亞人來說，唯一的問題是費用。大多數農民負擔不起水箱、水管系統和水槽的費用。希望通過國際援助機構的資金援助能使該專案得到更廣泛的使用，也希望進一步的研究工作能使材料費用能夠降低。
一個南非團體「水資源與鄉村發展協會」（請見本手冊後方的聯絡方式），針對如何收集一般平房、學校、或其他種類建築屋頂上的雨水，列了一張資料表。這個團體計算出每30公厘的降雨量，落在50平方公尺面積的屋頂上，這屋頂透過特別的設計可引水流入水槽，這樣總共能收集到1,200公升的水。「水資源與鄉村發展協會」換算了用屋頂雨水收集法所得到的水量，結果足以讓到一個原本到當地取水地點取水的人來回少走16趟。該團體也估計了水槽的成本，製造商開出的價錢是，從180蘭德可以買到2,500公升水泥槽，到1,000蘭德買一個4,500公升的鋼製水槽。（編按：南非貨幣單位，Rand蘭德）
版權歸屬 國際河網IRN，環境資訊協會（金霞
譯，吳國玢、李瑞玉 審校）
中英對照全文：http://e-info.org.tw/issue/water/2001/issue-water-irn01100101.htm
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Groundwater Replenishment
Groundwater currently makes up a large part of the water supply of many Southern African countries. While some countries appear to have plentiful groundwater resources, others recognize that in some cases their water supply aquifers are being rapidly depleted. Because of the region's erratic rainfall pattern, it is not uncommon for water managers to temporarily over-extract water from certain aquifers to make it through dry periods, and allow aquifers to recharge during wetter years. But longterm over-pumping of groundwater can cause the water table to drop (up to hundreds of metres), or allow salty water to be move into the water table, making it unpotable or causing land subsidence. Usually aquifers will recover if allowed to rest and recharge, but they can compress when water is removed and never regain their previous storage capacity.
Namibia has been studying the possibility of using aquifers as underground reservoirs to stretch existing surface supplies. By artificially injecting certain aquifers with purified surface water to be extracted later, the Windhoek municipality hopes to reduce the amount of water lost each year to evaporation. The city estimates that it could save more than 10 percent of its water supply using this method.
In India, two-thirds of the villages in Gujarat now have no permanent, reliable source of water, mainly because of the over-exploitation of groundwater. To help solve the problem, villagers are building small earthen impoundments across seasonal streams to create a small pond during the monsoon, which is used to recharge groundwater supplies. After the monsoon, the pond gradually recedes. The impoundments are only used to restore the groundwater, and are never tapped directly for water supply. The technology is very simple, relatively cheap to build, and easy to maintain. A government-funded group helps villagers design and pay for the impoundments. Villagers are responsible for building and maintaining their impoundments, and about 20 percent of the building costs. One Indian engineer believes such projects could ultimately collect up to 50 percent of the water that falls on the state.
Groundwater dams provide another way to replenish groundwater. These are underground water barriers which trap groundwater in a certain area and prevent it from flowing away underground. In some areas the groundwater table has fallen so dramatically that even a good rainfall will not raise the water table. By collecting rainwater in these underground reservoirs, the water table in some places has risen from a depth of 200 feet to 20 feet. People in India's deserts have been using this kind of technology for centuries, and now this practice has been introduced to the hillsides as well. The head of one village stated, "Dried wells now hold water round the year."
Rainwater Harvesting
In Africa and elsewhere around the world, more communities are returning to small-scale water harvesting, often using a system that collects water from house rooftops. A January 19, 1999 article in the Ethiopian newspaper The Monitor describes a successful roof water harvesting programme begun by the Ministry of Agriculture with help from the Swedish International Development Agency (SIDA) and a local NGO called Water Action. "This new introduction can enable households to save water that they can use for drinking purposes for up to five months, and with an average size reservoir. Such households might even have some extra water to spare for garden plants." The only issue for most Ethiopians, the article notes, is the cost. The water tank, water conduit system and gutter cost more than most farmers can afford. It is hoped that the programme will get wider usage with the help of subsidies through international aid agencies, and research efforts to bring down the cost of the materials.
A South African group, Association for Water and Rural Development (AWARD - see Contacts), has created an information sheet on how to collect water from the roof of a house, school or other building. The group calculates that for every 30mm of rain falling, a house with a 50-square-metre roof designed to funnel it into a water tank could collect 1200 litres. AWARD estimates that this could save a person 16 trips to the local water-collection source. The group estimates tank costs at anywhere from R180 for a 2500 litre concrete block tank to R1000 for a 4500 litre steel tank purchased from a manufacturer.
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