EFFECTS OF ROOFING SHEETS ON HARVESTED WATER RUN OFF

CHAPTER ONE
INTRODUCTION
1.1 .0 Background
Water is essential for all life and used in many different ways, it is also a part of the large ecosystem in which the reproduction of the biodiversity depends. Fresh water scarcity is not limited to the arid climate regions only, but in areas with good supply the access of safe water is becoming critical problem. Lack of water is caused by low water storage capacity, low infiltration, larger inter annual and annual fluctuations of precipitation (due to monsoonal rains) and high evaporation demand (Sivanappan, 2006). The term water harvesting was probably used first by Geddes of the University of Sydney. He defined as the collection and storage of any form of water either runoff or creek flow for irrigation use. Meyer’s of USDA, USA has defined it as the practice of collecting water from an area treated to increase runoff from rainfall. Recently Currier, USA has defined it as the process of collecting natural precipitation from prepared watershed for beneficial use. Rainwater harvesting is a technology used to collect, convey and store rain for later use from relatively clean surfaces such as a roof, land surface or rock catchment (Khoury-Nolde,). Rainwater harvesting (RWH) is the collection and use of rainwater falling onto buildings which would otherwise have gone down the drains, been lost through evaporation, or soaked into the ground. Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops, the land surface or rock catchments using simple techniques such as jars and pots as well as more complex techniques such as underground check dams (Srinivas, 2009). Now days water harvesting has become a general term for collecting and storing runoff water or creek flow, resulting from rain in soil profile and reservoirs both over surface /under surface previously this was used for arid and semi arid areas, but recently their use has been extended to sub humid and humid regions too. Nowadays, rainwater harvesting and re-use are more and more encouraged, mainly for countries where water resources are rare, since they may prove to be a possible solution. As such, a lot of systems have been created to collect these waters (Voorde et al., 2009).