Rainwater Harvesting – Sri Lanka
Notes : the following excepts are from the online editon of the Daily News in Sri Lankana sept 19 2009 Written by Dr Tanuja ARIYANANDA who is is Director, Lanka Rain Water Harvesting Forum, President, International Rainwater Catchments System Association
Development through rainwater harvesting
Sustainable social and economic development for resettlements in North and East through rainwater harvesting:
Sri Lanka’s three decades of conflict leaves the Northern and Eastern Provinces most affected, with infrastructure and institutions non-functional, homesteads in disrepair, livelihoods destroyed and most people unsettled and many traumatized. Now since the war is over and people and the land is free from the clutches of the terrorist, the battle is now on to rebuild infrastructure and houses, resuscitate the institutions, resettle and rehabilitate the affected and displaced people and help them redevelop their livelihoods.
Roof water harvesting system
It is only through social and economic development in these areas and people we can hope to bring ethnic harmony, trust and mutual respect among all communities to build a united Sri Lanka.
Any development activity cannot be done without water, which is not only a basic need of living beings, but also important for food production, sustenance of biodiversity, ecology and overall health of the environment.
The pressure in the available of water resource is ever increasing due to the rising population, pollution and climate change variability. Therefore, provision of water will be the greatest challenge for development activities in the North and East.
Water resources are limited in the North, Eastern, North Central and North Western Provinces.
Ground water is the only source of water in many of these areas and has also been over exploited. In many areas in the North, North Central and Eastern province and the water contains a high degree of fluoride in ground. Excessive use of agro chemicals and lack of sanitary facilities led to further pollution of ground water and high levels of nitrate and faecal Coliform are the evidence of poor quality ground water.
Potentiality of rainwater harvesting
In a crisis situation like this, the best option is to use the preserved rainwater for domestic and non domestic use.
Rainwater harvesting is accepted as a feasible water supply option in many countries and even in Sri Lanka, potentiality in rainwater harvesting is well documented in the National Rainwater Harvesting Policy.
Domestic rainwater (roof water) harvesting technology introduced in other areas with similar climatic condition offer reasonably good services to beneficiaries. Average annual rainfall experienced in the target areas range from 750 mm in Mannar to 900 mm in Anuradhapura district. The rainfall pattern in Sri Lanka is bi-modal and depends on the two monsoon seasons. The driest months of the year range from June- September in Anuradhapura district and May to September in Mannar district ( four to five months).
An average roof area of 50 m2 in Mannar district will provide the households with at least 40 litres of water per day with an 8,000 litre tank during the driest period from July to September. This will serve households with five people the minimum water requirement of the person which is eight litre per day for drinking and cooking. A tank of 8,000 litres will serve households with 40 litres per day for six to seven months.
Run off rainwater from the ground can also be collected and preserved in the home garden for agriculture purposes and to recharge the groundwater table. For example a two-acre land in an area, which receives annual rainfall of 1000mm, has the potential to store minimum 12,900 m3 of water annually through surface run off. A traditional ‘paththa’, a garden pond of 100 m3 volume can be filled very easily in an hour’s intense rain, and the water collected can be used for agriculture purposes effectively by using water conservation irrigation methods such as drip irrigation and pot irrigation, while the excess can be guided to recharge the groundwater table. A project implemented by the Lanka Rainwater Harvesting Forum in
Kotavehera D.S of Kurunegala District has shown increased availability of water for drinking and crop production through introduction of rainwater harvesting technologies. It has also brought many other social and economic benefits to households. It has reduce the daily average household time (mostly women’s) spend to fetching water from one hour and 20 minutes to average 12 minutes. Average annual income from home gardening has increased from Rs. 4,000 to Rs. 13,000.
Resources and readings from Lanka Rainwater Harvesting Forum
- What is Rain Water Harvesting?
- Construction Method for a 5 cubic metre Ferro-cement Pumpkin Shaped Aboveground RWH Tank
- Construction Method for a 5 cubic metre Brick Domed Underground RWH Tank
- Operation and Maintenance