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Congress: 2008
Author(s): K.Aravindan and M.karthikeyan
Post gradute in the field of water resources. Currently working as wastewater modeller in Atkins India Pvt. Ltd.

Keyword(s): Chennai, Roof Top Harvesting (RTP), RTP legislation, RTP efficiency
AbstractEFFICACY OF CITY WIDE ROOF TOP HARVESTING SYSTEMS AND ITS LEGISLATION: A CASE STUDY OF CHENNAI M.Karthikeyan, K.Aravindan Contact Address: M.Karthikeyan, Wastewater modeler, Water and Environment, WS Atkins (India) Pvt. Ltd, Vectra House, 3rd Floor, #15, 1st main, 6th Cross, Gandhinagar, Bangalore-560009, Karnataka, India. Tel: 00 91 80 41530000 Fax: 00 91 80 22356289 Congress Sub-theme: Water conservation and demand management Introduction: Roof Top Harvesting (RTH) has been considered as a partial panacea for water problems in urban area of developing countries. Yet, it is imperative that RTH systems, and its associated law and policies designed without considering the interrelated aspects of local hydro-geological, socio-economic, political and cultural conditions will not yield desired results. As new wave of laws and policies for mandatory rain water harvesting in urban regions are implemented in wide scale from few didactic experience, insufficient knowledge of its competence in large magnitude, quantum of financial resources directed from individual households for implementation and its operational effectiveness to achieve designated objectives compel searching review of stemming experiences from implemented area. Objective: The purpose of this paper is to analyse the efficacy of wide scale implementation of RTH systems through legislation in Chennai city, India by mandatory means and not to question the rain water harvesting itself. Methods: This paper critically reviews the existing methodology for analyzing the efficacy of implemented RTH systems. Rather than seeking relation between ground water levels before and after implementation to evaluate its efficacy as per the conventional one, it proposes a new methodology by analyzing a set of rainfall data stretching over 20 years inclusive of 3 year coverage after implementation of RTH in Chennai. Rainfall pattern and its effects on recharge has been analyzed by correlating the groundwater levels with the rainfall data over time period so as to establish whether the implemented RTH systems in the city are significantly contributing to the recharge. Efficiency of the RTH system constructed has been calculated from survey of sampled households of various land uses and classes of property. Total cost of RTH system implemented in the cityís entire households has been found and correlated with quantum of recharge itís providing. It also explores the various possibilities and changes in RTH legislation and its on field implementation needed at different stages in the future for effective and efficient implementation. Conclusion: The paper concludes that by comparing only the ground water levels before and after implementation of RTH systems for determining the efficacy often mislead, since the rainfall pattern could be different in the after years of implementation contributing significantly even without recharge structures, and the quantum of recharge which is considered to be occurring because of RTH systems is not factual because of inefficient systems implemented for compelling legislation.
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