Rainwater harvesting is a familiar term for Bangladesh. People in areas that lack drinkingwater, particularly the coastal areas and the rural areas in the country, practice rain waterharvesting. The high annual rainfall in the country makes rainwater harvesting a logicalsolution for the arsenic contamination of ground water in Bangladesh (Rahman et al.2003). Also, the increasing population in the urban as well as rural areas is puttingincreased load on underground aquifers which is evident in the fact that the piezometriclevel in Dhaka has decreased by more than 65 feet in the last decade. The annual rain fallthat the city receives may be an effective answer to the recharge of aquifers. Rain waterharvesting during the rainy season can reduce the increasing load on groundwater levels.This study aims to provide some guidelines for economic rainwater harvesting system,especially for urban areas for specific user groups. These guidelines were formulatedthrough literature review, analysis of some case studies on rainwater harvesting, and, to acertain extent, practical experience of the researcher. Data from secondary sources havealso been used for the purpose. The guidelines have been formulated using existing dataon rainwater harvesting systems. Based on these guidelines, a mathematical model hasbeen developed to figure out cistern sizes for collection of rainwater. The solution isapplied to a typical plan of an apartment house in Dhaka (multistoried) usingprogramming and visualization so as to demonstrate the scope and benefit of integrationof rain water harvesting technique with the architectural design. The harvested rainwater definitely does not meet the basic domestic requirement, butsupplements it during the rainy season which, most importantly, is usable for individualhousehold use. Large-scale rainwater harvesting also, hopefully, results in a decrease ofseasonal flooding in the urban areas. The products of this research are a) a computerprogram for sizing cisterns and b) an animation of the proposed rainwater harvestingsystem that may be used as a tool to demonstrate the benefits of the technique.
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