Recharging groundwater for enhanced water quantity and quality

Today is World Water Day


by Randima Attygalle

The wisdom of King Parakaramabahu the Great was such that centuries before phrases such as ‘climate change’ or ‘recharging ground water’ came into vogue, the farsighted monarch knew that ‘not a single drop of water should be allowed to flow to the sea without using it for human benefit.’ Centuries before the world came to talk of water and sustainable development at global forums, our own ‘dahasak wewu bendi rata’ or the dry zone of the island with thousands of reservoirs exemplified the value of retaining rain water for all forms of life and activity including agriculture. The age old concept which received royal patronage could be more localized through means of modern technology especially in a backdrop of global climate change.

Capturing the rain fall

"Recharging of ground water simply means increasing the ground water level or ground water table by capturing the rainfall run off which is about 60%," explains Dr. Tanuja Ariyananda, Executive Director, Lanka Rain Water Harvesting Forum (LRWHF). Of this, a larger part of the rainfall over the wet zone and the rest from the dry zone, flows to the sea without being used. By recharging ground water aquifers, this unconsumed water is retained. Recharging of ground water happens naturally when rain water gets into wells or reservoirs and deeper down into aquifers. However, to save the remaining water, artificial means or manual intervention is required. "Especially in urban areas, the surface soil is covered with concrete or tar and there is no way for the water to seep into ground. So in that case, we need to intervene artificially and recharge the ground."

The need for recharging of ground water is most felt in areas where it’s extracted intensively for day-to-day consumption, agrarian purposes and industrial needs. When water is so extracted, the time for recharging is less. "As Dr. Raghawan of the Rain Centre in Chennai puts it, one needs to treat the ground like a bank where you not only have to take out money, but you’ve got to deposit as well," says Ariyananda who explains several modern methods of recharging the water. In many parts of India these methods are used very intensively, she adds, since they need to dig as deep as 300 ft to get water. It has been found out especially in Chennai, that each year water levels go further down by about three meters.

Methods of recharging

Among the methods of recharging, having barriers against the flow of water is popular. This is largely followed in hilly areas by digging trenches along contours enabling the water to percolate into the soil from them. Digging boreholes deep into the ground and allowing the water to seep through them is also popularly used in India. "In the case of boreholes one needs to prevent contaminated water from flowing in. For instance, if water from an agricultural zone contaminated with fertilizer and pesticides is saved, precautions should be taken." Water could also be collected from roofs and redirected to a well which is also a method of recharging. "We have seen this successfully done in an ayurvedic hospital in Vavuniya," notes Ariyananda.

Recharging of ground water not only enhances the quality of water in the dry zone of our island but enhances the quantity as well. "Today with increased climate change, we are experiencing a very high rainfall for very short periods of time resulting in longer periods of drought and we need to store water as much as possible either in the soil in form of recharging or by harvesting," observes Ariyananda who goes onto note that such methods not only reduce wastage but act as buffers against floods as well.

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