According to the Department of Hydrology and Meteorology, the Valley has a catchment area of 656 square kilometres and receives an annual rainfall of 1,500 mm. And 80 per cent of households can harvest rain. If rainwater harvesting is increased, groundwater can be recharged to a great extent

The Kathmandu Valley has been suffering from a crunch of water since the 1980s. The demand for water is going up in the Valley due to increasing population and settlements.

Now the demand for water is put at 400 million litres a day, whereas the supply stands at about 130 million litres a day in the summer and about 90 million litres a day in the winter.

This shows the glaring gap between the demand for and supply of water in the Valley. The Kathmandu Valley is fast growing in terms of both population and settlement.

It is estimated that 20 per cent of the country's population lives in the Valley.

Migration from other parts of the country to the Valley, especially Kathmandu, has been going on, especially since the Maoist insurgency. What with the haphazard construction of houses, buildings, complexes, roads, pavements and other structures and what with the rampant extraction of groundwater, recharge areas have got sealed, and aquifers have been affected. This has given rise to water woes in the Kathmandu Valley.

In a bid to address the water woes, the Kathmandu Upatyaka Khanepani Limited (KUKL) and other institutions as well as individuals are resorting to shallow and deep boring.

In the Tarai region, groundwater, both shallow and deep, is suitable for irrigation and drinking purposes.

Groundwater extraction is restricted to 250 metres.

The rate of recharge is 8,800 MCM (800,0000 circular mils) per year.

But the quality of groundwater in the Valley is such that it is suitable for irrigation, but treatment is required to make it suitable for drinking and industrial purposes. Groundwater is over-exploited in the Valley.

The rate of extraction of groundwater is 5.5 MCM (5,500 circular mils), which overweighs the rate of recharge.

This has contributed to depleting aquifers. As a result, a large number of wells, ponds, springs and stone spouts have dried up in the Valley.

It may be noted that groundwater may be unsuitable for use. Harmful chemicals like arsenic, ammonia and nitrates have been detected in deep aquifers in the Valley.

It is a matter of worry that extraction of groundwater in the Valley is so huge and rampant that aquifers are getting depleted year after year.

Both shallow and deep boring should be compensated through groundwater recharge, but it is not so in reality.

Extraction of groundwater in the Valley is as high as six times the rate of recharge.

As such, about two and a half meters of the water table is sinking every year in the Valley. Due to the presence of impermeable black clay in many parts of the Valley, the recharge of groundwater has proved to be a difficult proposition when deep boring is excessively resorted to.

In the past, there was no water shortage in the Valley.

There were stone water spouts, ponds, wells, springs and other water sources in large numbers here.

After the introduction of the piped (municipal) water system, such water sources were left neglected, and rainwater collection ponds and recharge areas got destroyed. A study shows that 400 stone spouts and several hundred wells have dried up in the Valley.

With water problems growing day by day, the importance of rainwater harvesting and groundwater recharge has been realised. Some organisations like the Centre for Integrated Urban Development (CIUD) have also engaged in this field. They have adopted several techniques for groundwater recharge.

Recharge trenches and permeable pavements are used to facilitate the percolation of water through the soil at shallower depths, while recharge wells are used for the percolation of water to greater depths.

Rain gardens are also used for groundwater recharge.

Rain gardens are constructed in a small pit and consist of native shrubs, perennials and flowers. But they can hold rainwater temporarily only during or after rainfall.

It is not too late to recharge groundwater in the Valley.

There are still many areas, both public and private, where groundwater recharge can be carried on.

Rainwater can be used to recharge groundwater.

Rainwater can be harvested from any building with a good catchment area.

According to the Department of Hydrology and Meteorology, the Kathmandu Valley has a catchment area of 656 square kilometres and receives an annual rainfall of 1,500 mm.

And 80 per cent of households can harvest rain. If rainwater harvesting is increased, groundwater can be recharged to a great extent.

Groundwater recharge has many benefits. It helps in restoring wells, ponds, springs and other sources of water. This will solve the water woes to some extent at a time when the Melamchi water coming to the Kathmandu Valley is still up in the air. It also helps in controlling floods during the monsoon and land subsidence, which is accelerated by excess groundwater extraction.

The Kathmandu Metropolitan City launched the Recharge Kathmandu Campaign in 2019. The aim of the campaign is to make the residents of the Valley aware of the importance of groundwater recharge.

Every household can dig a recharge pit and contribute to the campaign.

However, the campaign has not been effective. The campaign needs to be reactivated for the benefit of people in the Valley.

Experts warn that deep boring should be avoided as it would almost irreversibly deplete aquifers. However, deep boring is still practised without considering the dire consequences it will bring on in the future.

Such practices should be stopped by the government at any cost.

Rainwater can be harvested from any building with a good catchment area.

A version of this article appears in the print on February 2, 2021, of The Himalayan Times.