Rainwater Harvesting
Not merely a secondary source of water, but has many other benefits too

By GS Sethi
During 20th century, the world’s population increased three fold, while the utilisation of renewable water resources increased six fold during the same period, thus resulting in imbalance between availability and consumption of water. The gap is likely to get wider in future and will surely have an adverse effect on economic and social development and on environmental sustainability too.

Water Crisis
So far as India is concerned, it supports about 1/6th of world population but has 1/50th of world’s land and 1/25th of world’s water resources. Many environmentalists foresee a catastrophic water shortage in future and probably this would be the biggest threat that mankind will face. In fact what is decreasing in present days is the clean water availability per person and what is increasing is the sewage generated per person. It is perhaps in consideration of such a catastrophe that India has decided to set up National Water Mission - one of the eight missions planned under National Action Plan on Climate Change. To begin with, the Prime Minister’s Council on Climate Change has agreed that all the data on water should be put in the public domain to help mobilise better action on water conservation and augmentation. It is intended to focus on areas, where groundwater is overexploited and also to raise water use efficiency by 20% through water-positive and water-neutral technologies.

The recently reported row between farmers and Coca Cola in Guntur district of Andhra Pradesh has water as the root cause. What the report says is that while several villages in the area grapple with acute drinking water shortage and farmers want better irrigation facilities, the Government has allotted 21.5 lakh litres of water from the river Krishna per day to Hindustan Coca Cola Beverages Pvt. Ltd at its plant in Atmakuru village.

Reduce Wastage
The solution to the problem needs to be looked into from two angles - how to reduce wastage of water and how to conserve the sources of water.

With regard to reducing wastage, it is more of a mindset and needs educating general public. The means are all well known but little put to practice. The steps such as - avoid leakage of water from the taps, turn the tap off when not in use like while brushing your teeth, check hidden water leaks, don’t throw away water on the roads and better use it for gardening or cleaning, use minimum water for bathing, don’t leave tap running while washing dishes in the kitchen etc. are quite well understood, but not many are conscious of misuse. For example drops of water from a leaking tap can add up to loss of 10,000 litres in a year.

A novel way of educating students in a school is said to have been done through celebration of a NGO-organised ‘Water Audit Week’. Students were motivated to observe ‘Water Audit’ in their households by taking note of consumption of water in cooking, gardening, leaking taps, bathing, brushing teeth, shaving, using toilets or washing of vehicles in open spaces. Thereafter they were asked to come up with ideas to reduce the consumption by 20 to 25%.

The obvious benefits of reduction in water consumption are reduced water bill, reduced waste water flows, less of overflowing gutters, less environment contamination, and in the long run improving the quality of drinking water.

Municipal Corporation of Greater Mumbai (MCGM), as a part of its ‘Save Water’ campaign, decided to paste one lakh stickers on auto rickshaws and taxis remind the citizens about the importance of water. Earlier too, with the same motive, MCGM had shot an advertisement with Sachin Tendulkar urging Mumbaikars to save water.

Rain Water Conservation
With regard to conservation of water sources, let us see one method which is being very much promoted and that is rainwater harvesting. It implies nothing but accumulation and storage of rainwater for later use. One of the greatest examples of rainwater harvesting is that employed in Rashtrapati Bhawan. Although it has been traditionally used in rural areas for long, but now it is becoming vitally important in urban areas too, mainly in view of alarming rate of groundwater depletion. Besides being a secondary source of water supply and that too at lower cost, rainwater harvesting reduces top soil loss and improves plant growth. Other benefits of rainwater harvesting are: it checks the declining water table, is environment friendly, reduces flood flows, improves quality of ground water through dilution mainly of fluoride, nitrate, and salinity. According to health experts, the presence of nitrate beyond 45 mg per litre in drinking water is of concern and it arises from risks of methemoglobinemia - a disorder in which an abnormal amount of haemoglobin builds up in blood.

According to an estimate by going for rainwater harvesting, about 50 to 60% of our annual water requirement can be satisfied. Bangalore Water Supply and Sewerage Board (BWSSB) regulations have made rainwater harvesting mandatory for new buildings on sites measuring 1,200 sq.ft. and above, and on existing sites of 2,400 sq.ft. and above. Many other States like Andhra Pradesh, Haryana, Himachal Pradesh, Tamil Nadu, Punjab, Rajasthan, Maharashtra etc. have also made roof-top rainwater harvesting mandatory. But unfortunately after building plans in urban areas are passed, there is no monitoring whether rainwater harvesting is actually working or not. Still Delhi and Chennai are said to have some good examples of rainwater harvesting.

Rainwater harvesting can either be surface runoff harvesting or roof top harvesting. In the first system, rainwater as it flows away as surface runoff, is caught and used to recharge aquifers through suitable means. In the second system, the roof becomes the catchment, and the rainwater is collected from the roof of the building. It is either stored in a tank or diverted to artificial recharge system. Irrespective of the complexity, rainwater harvesting systems have 5 basic components, namely catchment, gutters and downtake pipes, filters and first flush devices, storage tanks, and delivery system.

Methods of Rainwater Harvesting
The traditional methods of rainwater harvesting include Kunds of Thar Desert, Bamboo Drip of Meghalaya, and Kul method of Himachal Pradesh.

Villagers of Thar Desert are using what is called as Kunds for rainwater harvesting. This has helped them tackle the problem of drinking water. This method is prevalent in regions where ground water is moderate to highly saline. A kund has a saucer-shaped catchment area with a gentle slope towards the centre where there is a tank located. A wire mesh is provided at inlet to the tank so that floating unwanted material does not enter the tank. The first known construction of a kund in Rajasthan was during 1607 AD by one Raja Sursingh in village Vadi-ka-Melan.

Bamboo drip method is prevalent in Meghalaya and is used to irrigate plantations (like betel leaf or black pepper) by use of bamboo pipes to tap stream and spring water.

In Spiti area of Himachal Pradesh, which is said to be a cold desert, Kul irrigation is used. Kuls are diversion channels, which carry water from glacier to village. Some kuls are 10 km long, and have existed for centuries. Kul’s head at the glacier is its crucial part which has to be kept free of debris. The Kuls are therefore lined with stones to prevent clogging and seepage.

Modern Methods
The modern methods of rainwater harvesting include groundwater dams and ferrocement tanks. Groundwater dams are structures meant to obstruct the flow of groundwater and act as storage for underground water. This method is very useful where there is wide variation of rate of flow during the year i.e. where there is heavy flow during rainy season and practically no flow during dry season. The dam stores water during monsoon period which can be used during dry season. In this method, evaporation loses are low and the chances of contamination of water are remote.

What is primarily required for rainwater harvesting is to have hygienic containers. Ferrocement, which is made of thin sheet of cement mortar reinforced with wire mesh and steel bars, is very suitable for this purpose and its cost is low too. This method is very much used in regions like Meghalaya, Arunachal Pradesh and Kerala, which have high frequency of rainfall.

International Experience
86% of Singapore’s population lives in high-rise buildings. A light roofing is placed on the roofs to act as catchment. Collected roof water is kept in separate cisterns for non-potable uses. The Ryogoku Kokugikan Sumo-wrestling arena, in Japan, built in 1985 utilises 8,400 m2 rooftop of this arena as the catchment surface of the rainwater utilisation system. In Berlin rainwater falling on the rooftops (32,000 m2) of 19 buildings is collected and stored in a 3500 m3 rainwater basement tank. It is then used for toilet flushing, watering of green areas and the replenishment of an artificial pond. Indonesian government has introduced a regulation requiring that all buildings have an infiltration well. The rainwater harvesting programme in Capiz Province of the Philippines is implemented as part of an income generation initiative. Under this arrangement, loans are provided to fund the capital cost of the tanks and related agricultural operations. In Bangladesh, rainwater collection is seen as a viable alternative for providing safe drinking water in arsenic affected areas. Rainwater harvesting has become an important option for Gansu Province (China) to supply drinking water, develop rain-fed agriculture and improve the ecosystem in dry areas. Rainwater collection is becoming more widespread in Africa with projects currently in Botswana, Togo, Mali, Malawi, South Africa, Namibia, Zimbabwe, Mozambique, Sierra Leone and Tanzania among others. Rainwater harvesting and utilisation is now an integrated part of educational programs for sustainable living in the semi-arid regions of Brazil.

Changing Job Market Scenario
Climate change has caught the attention of the world, though belated, but is now assuming great importance. The efforts being made are giving rise to new avenues of investments and employment opportunities. Any job which in one way or the other is concerned with preserving or restoring environmental quality, be it in manufacturing, servicing, research & development, or administration, falls within the broad category of green jobs. The core objective of such jobs is to protect ecosystems and biodiversity, reduce consumption of energy, material, water etc. through such high efficiency means which would reduce wastage of such resources on the one hand and conserve the same, on the other.

For example, a rooftop rainwater harvesting consists of elements like collection area, conveyance system, filtration/treatment, storage, usage/recharge etc. Construction, erection and maintenance of these elements are the areas requiring skilled workers. In a broad sense, each job can be made green to some extent, but would need skilled workers and professionals to handle them. Many experts foresee that green job sector would bring in the next big revolution in the job market.

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