Rainwater harvesting

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Total World Water Supply LocationWater Volume (km3) % of Total Water Oceans1,230,000, Ice caps and glaciers28,600, Atmosphere12, Rivers and Streams1, Lakes (Fresh water)123, Groundwater (Shallow to depth of 0.8 km) 4,000, Department of Plant and Environmental Sciences  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

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Department of Plant and Environmental Sciences 1- Precipitation 2- Infiltration- contributes Ground water sources 3- Transpiration 4- Surface runoff – contributes to surface water sources 5- Evaporation 6 - Condensation The Water Cycle

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 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 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 Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Component of Rainwater harvesting Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Typical Domestic Rainwater Harvesting System Source: Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 9 Ground Catchment System Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 10 Ground Catchment System Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Typical Domestic Rainwater Harvesting System Source: 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. Department of Plant and Environmental Sciences Semi-circular gutters of PVC material

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 Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Storage Tanks Department of Plant and Environmental Sciences PVC Concrete tanks

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 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. 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 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. Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 19 Source: Leaf Eater®/Leaf Beater®/Leaf Catcha®

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) Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 21 Rainwater Harvesting from Domed Stadium in Japan Source: Zaizen et al. (1999) Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 22  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. Bibliography Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 23  International Rainwater Catchment Systems Association  American Rainwater Catchment Association  Centre for Science and Environment (CSE), India  Development Technology Unit, School of Engineering, University of Warwick, UK  Chennai Metrowater, India  Rainwater Partnership Web Resources on RWH (1) Department of Plant and Environmental Sciences

NORWEGIAN UNIVERSITY OF LIFE SCIENCES 24  Lanka Rainwater Harvesting Forum  International Rainwater Harvesting Alliance  Greater Horn of Africa Rainwater Partnership (GHARP)  The Web of Rain Web Resources on RWH (2) Department of Plant and Environmental Sciences