Save Water: The Flow Need Not Stop

By M H Ahssan

Push water conservation before it’s too late

India’s water resources are depleting quite rapidly. Rainfall is, after all, limited in quantity and the availability of water in our rivers and lakes is decreasing rapidly as populations grow, agricultural and industrial usage increases and lifestyle changes occur. Also, the waters we pollute become unavailable for beneficial uses. In short, we are running out of water.

Availability of fresh water per person in some Indian rivers today is only half, or less, than what it was just 30 years ago. Lakes in India suffer a loss of 30 per cent or more of their volume merely through annual evaporation thanks to our tropical climate. Local bodies incur a further loss varying from 20 to 40 per cent in distributing water to urban consumers. In effect, for every glass of water we drink, roughly two glasses are lost for various reasons.

Yet water conservation is not seriously practised in India. This is one among few countries allowing farmers use of free electricity to pump up groundwater for irrigation. We are in a bind: it would be bad politics to increase the price of water or control its use in a country like India; at the same time, water being so cheap, its conservation is not taken seriously. Meanwhile, water scarcity is increasing rapidly in many parts of India.

The municipalities exert pressure on consumers to increase their water resources themselves either through rainwater harvesting or treatment of wastewater for reuse. Both methods have their limitations.

In India, water has been reused for agriculture for over a hundred years. With some treatment, wastewater has been reused in industry and commerce, especially since the early 1960s. From 1993 onwards, reuse expertise took on an entirely new approach to meet community uses. This remarkable development has gone almost unnoticed. Hussain Sagar Lake in Hyderabad was the first to use the technique of treating city sewage to replenish the lake’s evaporation losses.

Hyderabad uses as much as 20 million litres per day of the city’s treated sewage to make up for evaporation losses in its famous lake. Sewage is treated to a high degree in a special treatment plant and used to keep the lake topped up at all times. This frees it from odours caused by anaerobic — devoid of oxygen — conditions in the lake water in summer, conditions that would generate greenhouse gases and contribute to global warming. Moreover, evaporation laid bare some land along the lake’s shrinking periphery, encouraging public encroachments. Controlled reuse with treated sewage has been going on for nearly a decade now to protect the lake environment. Treated sewage could be used since the lake supplied water only for non-potable purposes. A foreign agency is now funding the system’s expansion.

Sewage and industrial wastewater find their way into most of India’s already highly polluted lakes. In many cases, lakes, especially the smaller ones, would dry up without wastewater. So, wastewater inflow cannot be stopped unless the dried up lake area is intended to be converted into a new building construction site and sold to builders. More logical would be to pre-treat wastewater to maintain a relatively clean lake people can benefit from. A few lakes in Thane and Navi Mumbai in Maharashtra are being taken up for protection in this manner. Many other lakes in India, both large and small, could be similarly saved.

Rajasthan is presently developing a lake area, with local funding, where water is badly needed for tourism development. Sewage will be brought from Jaipur city after high-level tertiary treatment to replenish evaporation and other losses. However, as some body-contact sports may be played in the lake water, the tertiary treated wastewater will be further treated by a ‘natural’ wetland treatment to simulate nature. The success of this project, backed by extensive analytical monitoring work, will take us a step further in the art of reuse.

Whether a lake is large or small, its sustainability is assured if it becomes a source of income for the people who look after it. Tourist activities around a clean lake as well as aquaculture and reuse bring income. Income is the key that motivates caretakers. If it goes to the government or local authority, neglect sets in.

For a country like India with its large population, existing water resources will never be enough and treated wastewater will someday have to be used on a much wider scale for replenishing potable water supply lakes. Can this be done? The US, Europe and Israel are already doing it in certain areas. Singapore has started reuse. Desalination of seawater is not always the answer since it is often more expensive. In most cases, wastewater is first treated well in a mechanised treatment plant and then made to flow underground for ‘natural’ treatment, as is planned for Jaipur. In flowing underground through soil and aquifer, the wastewater’s micro-pollutants are removed and quality is further improved. Groundwater may be re-treated just before supply, if necessary.

We have to utilise our reuse expertise to overcome heavy evaporation losses usually occurring in tropical lakes. Nowhere in the world is treated sewage being used to replenish lakes. Treatment has to be both mechanical and natural. That way, we will be able to turn our tropical climate to our advantage and conserve our water resources.