ROOF TOP RAIN WATER HARVESTING AND RUNOFF STORAGE SITE SELECTION IN MOUNTAINOUS AREA USING GIS & RS – A CASE STUDY OF PATIKA; MUZAFFARABAD

Abstract

The history of rainwater harvesting is centuries old in Pakistan. The technique is under practice in many parts of the country in different forms. These practices are entirely conventional in applications till the last quarter of 20th century. Roofs are the first candidates for rainwater harvesting especially in mountainous/hilly terrain. The study area selected was Sub Division, Naseerabad (Patika) which is a part of Muzaffarabad Division, AJ&K. To optimize the rainwater harvesting technique a study was designed to (a) estimate/quantify roof top rain water for domestic use and engineer a design and (b) identify the suitable and sustainable sites for storm water harvesting ponds. This research integrates GIS and remote sensing techniques to design rooftop rainwater harvesting and also ponding stormwater runoff sites in a mountainous/hilly terrain in a Monsoon-weather environment. A high spatial resolution (2.4 m) satellite imagery of QuickBird was processed for identification and mapping of CGI sheet rooftops areas. Digital Elevation Model (DEM) was used to determine the slope and aspect of the entire study area for mapping/locating the stormwater runoff ponds. The DEM was processed using ArcGIS extension Arc Hydro for determination of the points where maximum water is available in a stream; it was then analyzed for suitable poundage sites. The rainfall data was used to generate rainfall map which was overlayed using a statistical algorithms to calculate the rain water available for each rooftop. A rooftop rainwater harvesting design was develop for maximum utilization of the rooftop rainwater. Rainwater harvesting ponds were selected within 250 m maximum distance from communities. It is concluded that the quality of water collected from rain do commensurate with the WHO standards and is safe for drinking purposes however initial water flow from the roof tops is required to be diverted to avoid the dust and birds contamination after which CGI sheets will provide absolutely safe drinking water. However, storing water for more than 20 days there is a requirement of adding chlorine in the water storage tanks to eradicate bacteria’s and other microorganisms. The study was presented to AJ&K government for implementation at site thereby reducing economic impact on health and water supply schemes. It is recommended that the study can be used for implementation in urban areas thereby reducing the water supply schemes cost, reduction in storm water designs and sewerage systems.