Dakshina Kannada, Udupi have been reeling under water scarcity for some years now. The government declared Mangaluru and Bantwal taluks in Dakshina Kannada and the entire Udupi as ‘drought hit’ for the first time in 2016-17. N.J. Devaraja Reddy, a Chitradurga-based hydrogeologist, rainwater harvesting consultant, expert and author, has been visiting the coastal belt for roof-water harvesting and borewell recharging for a decade. He spoke to The Hindu on water issues in the coastal belt.
The government, farmers, industries are after borewells as a panacea to meet water demand. Is this the only solution?
Drilling borewells is definitely not the permanent solution. The coastal belt has reached a point of no-return by believing so. Water is not being lifted but ‘mined’ in the coastal belt.
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A case in point: A farmer from Belthangady called me up sometime ago seeking a solution as all the 18 borewells on his land have become dry now. Borewells are not yielding even after digging 400ft.
Then what is the immediate feasible solution?
Store rainwater in geo-membrane tanks. Constructing them will be cheaper than drilling borewells and there will be no need to recharge them like borewells.
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As the coastal belt receives an annual average of 4,000 mm rainfall the tanks will easily get filled in the rainy season.
Such tanks are best suited to farmers. Drinking water needs can also be met, partially or fully.
Is water stored thus enough for farming?
Why not? Some farmers in Vijayapura are now growing grapes by using water collected in geo-membrane tanks. Even farmers in dry belts of Kalaburagi, Bagalkot, and Anantapur (Andhra Pradesh) districts are using water which are stored thus.
Can you quantify the amount of water which can be stored thus ?
It is possible to store 1 crore litres of water by building a geo-membrane tank in about 200 sq.mt. area depending upon (varying) its depth, length, and width. About 12 lakh litres of water can be stored in a tank which is 3m deep, 21m wide, and 21m long.
There has been some arguments that laterite soil structure is not suitable for groundwater recharging, especially in the coastal belt. What is your view on it?
It is a wrong concept. Recharging is definitely possible.
How can the water scarcity in the coastal belt be solved ?
It needs an integrated and site-specific approach. The practice of building the traditional ‘kattas’ (bunds) should be revived. Open wells and borewells should be recharged by harvesting rainwater. But recharging borewells should be done under the guidance of an expert. Otherwise the groundwater will get polluted, thus raising another issue. The coastal belt is already facing this threat with unqualified persons suddenly emerging as ‘experts’ for commercial reasons.
Are there enough qualified experts in State?
Yes. There are more than a dozen.