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<br />Groundwater Dams - Rainwaterharvesting.org <br /> <br /> <br /> <br /> <br />TRADITIONAL <br />Indigenous <br />systems <br /> <br />MODERN <br />Contemporary <br />systems <br /> <br />HARVESTERS <br />Profiles <br /> <br /> <br /> <br /> <br /> <br />Page 1 of3 <br /> <br />,\ <br /> <br />Any land anywhere can be used to harvest r <br />The fundamental reason: extend the fruits 01 <br />The basic principle: Catch water where it fc <br /> <br />:Em ~mmm .R::.~....-."... <br /> <br /> <br />. ~ '.: ....,...,.... -.'~ - ... '~"""" .~ <br /> <br /> <br />-- I:: n:: G <br /> <br />4 <br /> <br />.,.; <br /> <br /> <br />ll.t\ 'r <br /> <br />.Im..... <br />y'.. ";1:1 ~-:':i ~.~. :!: :::. ,', .~_: <br />.'" :'.:.,.;i~,i~,; '"l' . f <br /> <br />Groundwater dams are structures that intercept or obstruct the natural flow <br />of groundwater and provide storage for water underground. They have been <br />used in several parts of the world, notably India, Africa and Brazil. Their <br />use is in areas where flows of grou~dwater vary considerably during the <br />course of the year, from very high flows following rain to negligible flows <br />during the dry season. <br /> <br />The basic principle of the groundwater dam is that instead of storing the <br />water in surface reservoirs, water is stored underground. The main <br />advantages of water storage in groundwater dams is that evaporation losses <br />are much less for water stored underground. Further, risk of contamination <br />of the stored water from the surface is reduced because as parasites cannot <br />breed in underground water. The problem of submergence of land which is <br />normally associated with surface dams is not present with sub-surface <br />dams. <br /> <br />There are two main types of groundwater dam: the sub-surface dam and the <br />sand storage dam. <br /> <br />A sub- <br />surface <br />dam <br />intercepts <br />or <br />obstructs <br />the flow <br />of <br />an aquifer <br />and <br />reduces <br />the <br />variation <br />of the <br />level of the groundwater table upstream of the dam. It is built entirely under <br />the ground (see figure 1). <br /> <br /> <br />Ground'tvater level <br /> <br />~ <br /> <br />A sub-surface dam <br /> <br />The sand storage dam is constructed above ground. Sand and soil particles <br />transported during periods of high flow are allowed to deposit behind the <br /> <br />http://www.rainwaterharvesting.org/methods/modem!gwdams.htm <br /> <br />11/1/2006 <br />