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Rainwater harvesting 2111 2005 Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Total World Water Supply Location Oceans Ice caps and glaciers Atmosphere Rivers and Streams Lakes (Fresh water) Groundwater (Shallow to depth of 0.8 km) Water Volume (km3) 1,230,000,000 28,600,000 12,700 1,200 123,000 % of Total Water 4,000,000 0.31 97.17 2.5 0.001 0.0001 0.009 Over 70% of our Earth's surface is covered by water More than 97% of Earth’s water is in the oceans, 2% is in ice and glaciers- (Both are unsuitable for human use because of Salinity (Ocean Water) and location (ice caps and glaciers) The total amount of water for which all the people, plants and animals on Earth compete is much less than 1% of the total www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES The Water Cycle 1- Precipitation 2- Infiltration- contributes Ground water sources 3- Transpiration 4- Surface runoff – contributes to surface water sources 5- Evaporation 6 - Condensation www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Rainwater harvesting- Alternative water source Technology used for collecting and storing rainwater for human use from rooftops, land surfaces Decentralised system – Installed in houses, Institutions, community www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Where rainwater harvesting is particularly attractive ? – Rural area with no surface water sources – Supply from surface and groundwater sources cannot meet the water demand (Urban area) – Groundwater contaminated with Arsenic – Household do not have capacity to pay for centralised water supply system www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Benefit of Rainwater harvesting Has multiple uses– Domestic consumption – toilet flushing, sprinkling, – ground water recharge, – reduces urban storm runoff and associate flooding and errosion Low maintenance www.umb.no NORWEGIAN UNIVERSITY OF LIFE SCIENCES Department of Plant and Environmental Sciences Component of Rainwater harvesting www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Typical Domestic Rainwater Harvesting System Source: http://www.eng.warwick.ac.uk/DTU/rainwaterharvesting/index.html www.umb.no NORWEGIAN UNIVERSITY OF LIFE SCIENCES Department of Plant and Environmental Sciences Ground Catchment System 9 www.umb.no NORWEGIAN UNIVERSITY OF LIFE SCIENCES Department of Plant and Environmental Sciences Ground Catchment System 10 www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Typical Domestic Rainwater Harvesting System Source: http://www.eng.warwick.ac.uk/DTU/rainwaterharvesting/index.html www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Conveyance Gutters and Downspouts Gutters are installed to capture rainwater running off the eaves of a building. Semi-circular gutters of PVC material www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Storage Storage tank, acts to flatten out any fluctuation in rainfall and usage allowing water use to be, to a greater or lesser extent, independent of rainfall. Types – Ferrocement tank - cement-rich mortar reinforced with layers of wire mesh, – Fiberglass www.umb.no PVC NORWEGIAN UNIVERSITY OF LIFE SCIENCES Department of Plant and Environmental Sciences Storage Tanks Concrete tanks www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Sizing of storage tank Demand side approach A very simple method is to calculate the largest storage requirement based on the consumption rates and occupancy of the building. – Consumption per capita per day, C – 20 litres – Number of people per household, n – 6 – Longest average dry period – 25 days Storage requirement = C x n x 25 = 3000 litres www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Quality of rainwater The quality of rainwater is relatively good but it is not free from all impurities. Depends upont type and condition of the catchments and the storage tank Dust from the soil, and droppings of birds and animals could be the source of contamination by the bacteria. www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Method to enhance quality The first run off from the roof should be discarded to prevent entry of impurities from the roof. In case of difficulties in the rejection of first flow- Clean the roof and gutter at the beginning of the rainy season www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Method to enhance quality Cleanliness of roof and storage tank is critical in maintaining good quality of rainwater. The storage tank requires cleaning and disinfection when the tank is empty or at least once in a year. www.umb.no NORWEGIAN UNIVERSITY OF LIFE SCIENCES Leaf Eater®/Leaf Beater®/Leaf Catcha® 19 Source: http://www.rainharvesting.com.au www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Disinfecting Rainwater Rainwater can be used for drinking, if it is clear, has no or very little taste or smell and is from well maintained system Rainwater may not meet WHO drinking water quality standards, specifically microbiological quality standards, hence some disinfection is recommended. Disinfection can be done by: – boiling the water in before consumption – adding chlorine compounds/bleaching powder in required quantity to the water stored in the tank. – using slow sand filtration – solar disinfection (SODIS) www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Rainwater Harvesting from Domed Stadium in Japan 21 Source: Zaizen et al. (1999) www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES 22 Bibliography Rainwater Harvesting and Utilization. An Environmentally Sound Approach for Sustainable Urban Water Management: An Introductory Guide for Decision-Makers. IETC-UNEP, Japan. Rainwater catchment systems for Household Water Supply (1991). Environmental Sanitation Reviews No No 32. ENSIC, Bangkok, Thailand. UNEP-IETC (1999) Proceedings of the International Symposium on Efficient Water Use in Urban Areas - Innovative Ways of Finding Water for Cities. (8 to 10 June 1999), Kobe, Japan. Gould, J. and Nissen-Petersen, E. (1999) Rainwater Catchment Systems for Domestic Supply. IT Publications, London Hasse, R. (1989) Rainwater Reservoirs- Above Ground Structures for Roof Catchment. GTZ. NGO Forum and SDC (2001) Rain Water Harvesting System. NGO Forum for Drinking Water Supply and Sanitation and SDC, Bangladesh. www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Web Resources on RWH (1) International Rainwater Catchment Systems Association http://www.eng.warwick.ac.uk/ircsa/ American Rainwater Catchment Association http://www.arcsa-usa.org/ Centre for Science and Environment (CSE), India http://www.rainwaterharvesting.org Development Technology Unit, School of Engineering, University of Warwick, UK http://www.eng.warwick.ac.uk/DTU/rwh/index.html 23 Chennai Metrowater, India http://www.chennaimetrowater.com/rainwaterfaqs.htm Rainwater Partnership http://www.rainwaterpartnership.org/ www.umb.no Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Web Resources on RWH (2) Lanka Rainwater Harvesting Forum http://www.rainwaterharvesting.com International Rainwater Harvesting Alliance http://www.irha-h2o.org/ Greater Horn of Africa Rainwater Partnership (GHARP) http://www.gharainwater.org/ The Web of Rain http://www.gdrc.org/uem/water/rainwater/rain-web.html 24 www.umb.no