Rainwater harvesting: Better alternative to seawater desalination for Jaffna Peninsula

Annually Jaffna district receives around 1.36 billion cubic meters of water through rainfall (Land area 1,025 square km and average annual rainfall of 1326 mm (average 2006-2020)). If at least 30% of this rainfall is collected, retained and recharged the amount of water would be 407 million cubic meters per year. This amount will provide 1.8 cubic meters or 1800 liters of water daily for each of the 613,083 people (according to Census 2021) living in the district.

Seawater Reverse Osmosis Desalination (SWRO) plant is under construction with funds from the Asian Development Bank at the cost of 266 Mn USD to provide domestic water to 300,000 people in Jaffna Peninsula. The capital cost to provide water for each person is Rs 280,000 (@Rs 320 per USD). In addition to the SWRO plant, the project cost involves construction of water towers, laying of pipelines, land acquisition, and maintain the RO plant. All these activities involve a substantial amount of finances to be obtained on loan by the government of Sri Lanka.

Initial investment to install a simple roof rainwater system is less than Rs 200,000 which will provide free supply of water at the door step with minimal maintenance cost. Additionally total number of wells recorded from Jaffna district is 131,000 (according to Water Resource Board), which has the potential to recharged to improve on water quality as well as quantity. Study conducted in Poonakary in Kilinochchi district by Lanka Rainwater Harvesting Forum showed that by simple recharging of wells from rainwater, there is a substantial improvement of the quality and quantity of well water in 8-12 months period.

An appreciable part of the water needed for domestic purposes of the district can be met by harvesting rainwater, thereby reducing the cost. The amount of water to be supplied per year by the SWRO project can be obtained at a much lower cost by collecting roof rainwater. It does not involve laying pipe lines and installing sea water desalination plant and maintaining it. Moreover, if there is no rainwater collecting system installed most of this amount of rain water will run-off to the sea, to be desalinated at higher cost and brought back again.

Benefits of Rainwater Harvesting

Rainwater harvesting plays a crucial role in addressing various water-related challenges. By capturing and storing rainwater, it is possible to supplement the water supply, particularly in regions where water scarcity is a pressing concern.

Implementing rainwater harvesting systems offers many benefits. Among these are reducing the demand for groundwater and surface water sources, minimizing storm water runoff (thus reduce flooding), replenishing groundwater aquifers ensuring the sustainability of these crucial water sources. In addition there is a significant savings on water bills, reduce the need for costly infrastructure investments, saves energy on treatment and pumping and improves water security. By understanding the diverse benefits of rainwater harvesting, we can better appreciate the value of incorporating this sustainable practice in our homes, businesses, and communities, ultimately contributing to a more sustainable and resilient future.

Lanka Rainwater Harvesting Forum