Though rainwater advocacy might take time, experts believe it is the finest way to mitigate the problem of water scarcity in the Valley.
“It can´t be a 100 percent solution but it does partially minimize the problem of water supply and if it meets the need for a certain period, we can surely make a difference,” says Ajay Dixit, a water resource analyst.
“A house with a two and half ana land area has the potential to accumulate 100,000 liters of water per year,” says Prakash Amatya, Executive Director of the NGO Forum for Urban Water and Sanitation. “One liter of water can be collected if we have 1 mm of rain in an area of 1 meter square,” he adds.
Currently, Kathmandu Valley has 250 swimming pools and 350 party palaces and these are the places that use water to the highest degree. Amatya believes that rainwater can be collected, recycled and reused at such places to ease the pressure on KUKL.
The Soaltee Crowne Plaza Hotel in Kathmandu has been implementing the techniques of rainwater harvesting.
The land absorbs only 10 percent of rainwater. According to Amatya the 90 percent of rainwater that does not go into the land but drains away can be harvested.
High infiltration rates are seen in places like Balaju, Naya Bazaar, Thapathali, Minbhawan and Asan in Kathmandu Metropolis, with the maximum infiltration of 1.59 cm per minute at Old Baneswor. Kalanki and Koteshwor heights have almost no infiltration during the monsoon. The infiltration rate at these places is 0.009cm/minute or lower.
Rainwater may also be used for groundwater recharge. First a recharge pit is dug to collect the runoff on the ground and it is then added to groundwater through pipes. Pits are a better alternative for recharging groundwater, especially for households.
Recharging water in dug wells will also help to upgrade the water table as they lead directly to the aquifers (porous underground rock formations from which groundwater can be extracted to the full through wells). However, recharging through wells alone has not much visible impact on the water table since digging a well is expensive and needs a lot of space. It is feasible only in large community spaces.
Municipalities like Lalitpur and Dharan encourage the general public to utilize rainwater. Dharan Municipality has announced a policy that involves 30 percent rebate on the building permit fee for houses that install rainwater harvesting systems.
Amatya suggests that the municipalities send rainwater underground. He says that if the government succeeds in re-popularizing indigenous technology, it could save as much as Rs. 2.8 billion annually in Kathmandu Valley by virtue of lessened demand alone.
“Lots of water has been extracted and this has resulted in fast depletion of the water table. Eventually this has resulted in water with high iron content,” says Dixit. Thus the need for recharging.
Use of groundwater with high content of ammonia, iron and nitrates could lead to serious illnesses like blue-baby syndrome in pregnant women where the newborn develop heart defects. Thus, experts suggest that recharging is imperative as dilution could help minimize the content of such chemicals.
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