Rain water harvesting for water efficiency and management

Abstract

Water being one of the world’s basic resources and one of the most essential needs to life, could be considered the nature’s precious gift to the living being. Although this resource was available in plenty till recently, due to urbanization, increase in population, industrialization and for large scale enterprises the shortage of water in the world has become evident. Furthermore, due to implications of climate change on rainfall patterns, with extremities of weather giving rise to floods and droughts there is growing concern globally about appropriate strategies to be adopted as far as the built environment is concerned for proper management and harvesting of rain water. Thus globally a Millennium Development Goal has also been set and rain water harvesting has emerged as an important issue in the international scenario. It has been highlighted at the third World Water Forum held in Kyoto, Japan, in the context of Millennium Development Goals and the issue of sustainability, at the Global Ministerial Environmental Forum in Korea, which has led to formulation of many networks and policies. The famous proclamation by King Parakramabahu the Great in (1153-1186 AD) could be considered as one of earliest policy statements, on water resources development and management in Sri Lanka, which highlights rain water harvesting. “Let not allow a single drop of water falling as rain flow into the sea without being used for the benefit of mankind”. This shows the wisdom and commitment of ancient kings and people to conserve and efficiently manage water resources by building tanks specially in the dry zone and the design and construction of complex water collection and distribution systems such as in the Sigiriya rock fortress. The Government of Sri Lanka in June 2005 accepted a “National Policy on Rain Water Harvesting & Strategies”. Sri Lanka has used rain water for both domestic and agricultural purposes for many centuries and the institutionalized rain water harvesting became a practice in Sri Lanka in 1995, under the World Bank funded Community Water Supply and Sanitation Project. This project initiated the emergence of the Lanka Rain Water Harvesting Forum (LRWHF). A major challenge is the need to have a delivery of the stored rain water, for which gravity flow and hand/manual pumping has been the economic option the use of Solar Energy is being promoted specially in rural areas where there is no main grid power available. Another challenge is the public Health concern due to the comparatively stagnant nature of rain water harvesting. There has been a significant increase in the use of rain water harvesting in Sri Lanka, which has proved to be a boon to rural people, particularly for domestic water supplies in water scarce situations. An estimated thirty thousand systems are presently in operation, scattered over a large number of districts. Interestingly, several large scale projects have also been implemented in the urban context, and this too is likely to increase in the future. With a National policy on Rain Water Harvesting and other legislation in effect, Sri Lanka stands to benefit significantly by the appropriate use of this technology.