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“Well Recharging” through Roof Rainwater supports desalination of Coastal Ecosystems

IWRA World Water Congress 2017 - Cancun Mexico
2. Water quality, wastewater and reuse
Author(s): Jos Raphael
Jos Raphael

Keyword(s): Roof Rainwater Harvesting,Open Dug Well Recharging, Reduction in Saline ingress,Improving Water Quality, Coastal water bodies



It is a successful attempt of water solution implementation in improving water quality and quantity from open dug well recharging through roof rainwater harvesting in the coastal areas of Kerala State from India. It is based on the “Ghyben – Herzberg Equations” of saline ingress in Coastal areas.


Kerala state has long coastal belts and ecosystems facing Arabian Sea. 75% of the people mainly depend upon homestead open dug wells which is the traditional water resource for all water needs. Water quality issues out of excessive pumping is a problem in the coastal ecosystem. Joint efforts of farmers in building seasonal check bund to avert sea water intrusion during up-tide found declining. 


Procedures Used / Solution:

It is a solution implementation with action research. The solution of well recharging unit consists of a rain gutter of 10 to 15 metre length and nearly 10 metres of down pipes from house roof tops directed towards the well www.mazhapolima.org.  A rainwater filter unit is installed to filter the impurities from the roof rainwater. Also it includes a first flush system to flush out the dirt from the roof while diverting first shower of roof rainwater to open well.  Along with the implementation, scientific observations were also done with the support of Centre for Water Resources Development and Management www.cwrdm.org


Water Quality samples (pre monsoon and post monsoon rainfall) from the open wells were taken and tested in the Government Water Quality Laboratories. The test result shows high concentration of salt due to saline intrusion. And after diverting rainwater to the open wells, ie., from June 2009 to April 2015, open  wells turned useable for domestic uses evinced by the families those installed roof rainwater harvesting structures for well recharging.  And people recognize the taste of fresh water from their own homestead wells.  The communications from people to people across the area initiate all households themselves to adopt for such roof rainwater harvesting for well recharging as a multiplier effect. Apart from the water quality changes positively in the wells, this method of rainwater injection to the wells helps to raise the ground water level of wells in other parts of the district. CWRDM (2013) studied the impact of the project and found it replenishes the coastal aquifers and reduce saline ingress. There are about 20000+ units work to reduce saline ingress and to recharge the homestead open wells in Kerala.

Science & Policy Dimensions:

This innovative experiment of recharging wells with roof rainwater is successful cost effectively for less than 100 US$ or Euro for one roof structure of 1000 sq.ft. Practical application of this Gybhen-Herzberg equation based technique can be replicated in the coastal ecosystems of developed and underdeveloped countries where there exists roof rainwater harvesting structure and well /water body.  Moreover, it is a climatic change adaptation technique to save the high rain/flood while storing to use them in ground when there a low rainfall period. Indeed this would reduce ecosystem degradation while improving livelihoods, moving from vicious to virtuous cycles.

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