Rain water --- a prospective source of water security

Wasi Ahmed   | Published: July 06, 2021 21:52:30

Rain water --- a prospective source of water security

Monsoon this year has approached quite timely.  The Bangla month of Asar known for refreshing showers has been true to its characteristic heavy downpour since the very beginning of the month, around three weeks back. The regular and at times incessant downpours throughout the nights as well as in the late afternoons have already been the cause of flash floods in low-lying and haor areas. The city roads including those of the capital are experiencing water-logging. The latter, however, is not so much the fallout of the rains but an unmistakable accomplishment of our city corporations and the utility services' fancy for development work at this time.

Water-logging apart, the most noticeable thing one must not miss out during the monsoon is that there is no effort on anybody's part to make use of this abundant water.  In other words, there is no initiative to stop wastage of water.  It is often said: water these days is precious--- too precious to be wasted, and in reality, increasingly scarce to be wasted. But are we up for any plans to make use of the plentiful water in ways that are practised in many countries?   Globally, water management has assumed an extremely important role as it relates to one of the most critical human needs--- water security. While we speak of food security, we tend to forget that the security of water precedes the security of food for the simple reason that the grains we call food are fed on water.

Every year with the beginning of summer we routinely face two perennially worrying problems --- water and power. Frequent cuts on power supply seriously affect irrigation as watering the standing crops is a supreme priority at this time of the year. But this is only one side of the problem. While the irrigation requirements are barely met with the diverted and inadequate supply of electricity, the casualty on the other side is the availability of water in urban locations in the country. There is not enough flow of water to rush into the overhead or underground tanks meant to be reservoirs to meet all kinds of household needs. In the capital Dhaka, ground water level is falling at an alarming annual rate of around 3.0 per cent, experts say. Unsustainable extraction of fresh water and other human interferences with the water cycle is the immediate cause of water scarcity. Over-extraction has its most direct manifestations on the level of aquifers and underground reserves. If withdrawals exceed the natural rate of recharge, the level of an aquifer will fall, eventually drying up altogether.

For sometime now, there has been an increasing emphasis on storing rainwater --- better known as rainwater harvesting ---  during the monsoon. In simple terms, rainwater harvesting is the accumulation and storage of rainwater for reuse before it reaches the aquifer. It can be used to provide water for various typical household uses and irrigation. Rainwater collected from the roofs of houses can make an important contribution to the availability of drinking water as well.

According to experts, rainwater harvesting systems are simple to construct from inexpensive local materials and are potentially successful in most habitable locations. Roof rainwater may not be potable and may require treatment before consumption. Since some rooftop materials may produce rainwater that would be harmful to human health as drinking water, it can be useful in flushing toilets, washing clothes, watering the vegetation and so on. There are several types of systems to harvest rainwater, ranging from the very simple home systems to complex industrial systems. The rate at which water can be collected from either system is dependent on the plan area of the system, its efficiency and the intensity of rainfall.

It is indeed curious to note that in the Indian state of Tamil Nadu rainwater harvesting has been made compulsory for every building to prevent ground water depletion. It produced excellent results and few other states were quick to replicate the model. Since the implementation, a neighbouring state Chennai saw 50 per cent rise in water level in five years and the water quality also improved significantly. Harvesting method varies from country to country depending on the uses of rainwater and technologies applied for storing and purifying are also diverse.

Rainwater could be a prospective source for a variety of uses in our country, say experts. Many of us may not be aware that Dhaka WASA undertook a rainwater harvesting scheme in 2009 but the scheme did not progress. Later, the WASA authorities are said to have undertaken an action plan to recharge underground aquifers. Similarly, the Rajdhani Unnayan Kartripakkha (RAJUK) was reportedly contemplating on the amendment of the Building Construction Rules-2008 incorporating a mandatory provision for harvesting of rainwater for all upcoming building structures in the city. As a starter, we may try to replicate the easiest and cheapest of the methods and see how it works. Non-governmental organisations (NGOs) will be very well placed to give it a try in the rural areas where they have a network of working with the people in a host of areas. Experts are of the opinion that with an average 2,000 mm of annual rainfall in the country, the government can take up a policy to sensitise the people on the use of rainwater in the wake of potable water crisis.

There are reports of isolated moves in the southern region of the country to harvest rainwater but in the absence of required support including strong advocacy to sensitise the people, these have fallen short of the expected outcome. In view of the proven benefits of the system, it is imperative that the government, especially the local government agencies, embark on a country-wide programme to encourage harvesting of rainwater during the monsoon as a viable means of mitigating water scarcity to a great extent. With technology far more easily and cheaply accessible now, it is important that the plans earlier taken to harvest rainwater are revisited in order to bring those into the fold of a national planning. 




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