Sustainable Micro Water Resource Management in ...

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Areas: The Gariahat Shopping Mall-A case in point. Authors: Arindam Biswas, Ranajit Gupta. INTERDESIGN, 220/2,Panditya Road Extension. Calcutta-700 029 ...
Title: Sustainable Micro Water Resource Management in Urban Areas: The Gariahat Shopping Mall-A case in point Authors: Arindam Biswas, Ranajit Gupta. INTERDESIGN, 220/2,Panditya Road Extension. Calcutta-700 029, WB, INDIA. 40 Word Summary: The water problem is becoming more acute in Metropolitan areas. An alternative solution (rainwater harvesting) along with controlled water management and Groundwater recharge via Rainfall has became an environmental and civic duty. Brief Description of Workshop Problem to be addressed: Most Metropolises face a water crisis. The traditional recourse to centralized supply or tapping of groundwater resources have failed. Alternative sources such, as rainwater is important. However its collection/supply requires integration into the overall water management of cities. Key Words: water scarcity, treatment plants, rainwater collection, aquifer recharge. Crisis in the Metropolis: The Calcutta metropolis area although endowed with ample water resources, is in the midst of serious water scarcity problem particularly in relation to filtered water. Large-scale abstraction has led to a lowering of the aquifer, soil subsidence and the infiltration of dangerous salts (Arsenic) from lower layers, in the ground water. The political shyness to levy water charges is also telling on the authorities quest for an overall solution. In this context it is important to seek nontraditional solutions and invest in micro projects. Facilities, Water Resources & Water Quality: Most modern commercial facilities and high rise complexes in the metropolis have to set up their own treatment plants, to assure a modicum of quality for Air condition plants, fire fighting systems, etc. These treatments are usually expensive and consume a large part of the municipal supply Moreover the quality of water is extremely poor with average TDS above 450 and iron content ten times above norms though Rainwater, which after first flush is well up to WHO standards, is drained off year after year to the rivers and deltas.

Rainwater harvesting diagram. Alternative Approach-Rainwater Harvesting: An alternative approach to water supply has to be found if the problem of scarcity and quality is to be addressed in developing mega cities. Treated water is expensive and capital intensive and cannot be wasted. Small-scale rainwater collection and subsequent recharge are two pronged strategies to relieve the water stress in these cities, particularly in the more affluent locality. The aim of this project is to prove that a viable economic solution can be found even on micro scales in the design of individual buildings and site. The Case Study At Jamir Lane: Located in the prime commercial area of south Calcutta the Mall would require substantial water resources at international quality levels.

Municipal supplies are limited and the existing small tube well cannot be re-dug. A quick tally of resources available has shown the importance of rainwater collection. The cost of storage is high, but then the statutory requirements the fire (125,000 ltr.) and domestic (40,000 ltr.) tanks largely offset this capital cost on reservoirs. The strategy is how best to store, mix and use the various qualities of water available. Water Requirement: The sanitary and plumbing system of the shopping complex have been designed on the basis of 28,000 LPD. The statutory requirement for fire fighting (500 GPM system i.e. 1800 LPM) is a static reserve of 250,000 lts . A water-cooled air conditioning plant was selected for economy of operation if soft water is available. Its peak load of 330 TR (ton refrigeration) consumes around 25 LPM. ,a total evaporation loss (requirement) of 12,000 LPD, considering 8 hours operation per day. Climatic Inputs: A hot and humid environment with rainfall nearing 1500 mm per annum. The wet monsoon months are June to October but the pre-monsoon months of April and May cannot be discounted nor November showers. There is low collection in the months February, March and April; this is due to limited showers. Demand Assessment: The consumption of water for toilets etc. has been assessed at 525,000 lts per month. Qualitatively this water could be poor grade municipal supply. The soft water requirement is mainly for the a/c plant condenser units and works out to 12,000 LPD at peak consumption. The tube well which will be operated only in emergencies, maybe recharged from yard wastewater.

Rainfall Collection Diagram Supply Management: On the supply side the options are limited to municipal water and rainwater harvesting, the tube well being an emergency option only. The municipal supply varies between 12,000 LPD and 16,000 LPD. The balance is taken care by stored rainwater. Rainwater harvesting is based on the collection factors for the various months and varies between 11,000 lts and 245,000 lts. Per month. The shortfalls or surplus in both municipal and rainwater against the projected demand allows us to size the rainwater tank. Rainwater and It’s Engineering: The rainwater collection peaks in October and then declines till the monsoon. The total storage of 340,000 lts. takes care of redundancy. A sand pile bore system recharges the aquifer with the yard drainage water (nearly 800,000 lts.). The tube well is kept as emergency supply in the month of May. Conclusion and Recommendations: It is possible to implement alternative(rainwater) technologies even in standard urban complexes to mitigate the stress on water resources. . The recharge of aquifer should become a statutory requirement.

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