Samuel Taylor Coleridge’s verse could describe Chennai and most Indian cities. Every four-five years, Chennai gets a cyclone, floods and waterlogging. Yet, come summer, colourful plastic water pots lined in front of street taps tell another tale. The rainwater is let out into the sea: It has nowhere to go.
Chennai once had over 250 waterbodies, including eris and temple tanks. Now there are a mere handful, the rest having been encroached upon by private citizens and government offices or become garbage dumps, filled and sold to contractors. Chennai also has two freshwater rivers—Adyar and Cooum—which have shrunk into rivulets of sewage.
In Tamil Nadu, every political party promises to clean Chennai’s rivers and desilt the tanks, but does nothing when in power. This is not the fate of Chennai alone. Much of India depends on rainfall, but does little to catch and store the water.
Rainwater is a clean source of water, but its distribution is neither uniform nor assured in all parts of the country. India receives about 400 million hectare metres (mham) of rain per year over an area of 329 million hectares (mha). The rainfall ranges from 100 mm per annum in the Thar to 15,000 mm in the Northeast. Despite a complex network of rivers, vast stretches of India have neither rivers nor lakes for water. Fresh water is fast becoming a scarce commodity.
Floods and droughts were a regular occurrence in India. In the Rig Veda, Indra the rain fights Vritra the drought. By 3000 BCE, wells had been dug in the Indus–Sarasvati cities. The “Great Bath” of Mohenjo Daro was obviously a water storage tank, while excavations reveal deep rectangular constructions that were probably the earliest water harvesting structures in India.
Dholavira, laid out on a slope between two stormwater channels, is an example of sophisticated engineering. The cities of the Indus civilisation had excellent systems of water harvesting and drainage. In 300 BCE, Kautilya in his Arthashastra mentions water harvesting systems. There is archaeological evidence of dams, lakes and irrigation systems built in the time of Chandragupta Maurya.
In 100 BCE, Sringaverapura near Allahabad had a sophisticated water harvesting system, while in the 11th century CE, King Bhoja of Bhopal built India’s largest artificial lake (65,000 acres) fed by streams and springs. In arid and semi-arid regions, water was diverted through channels to storage tanks. In the flood plains, several unique systems to control and harness the floodwaters were devised. In the coastal areas, where there is danger of saltwater intrusion, several methods came up to regulate the flow of saline water.
Throughout India, several ingenious methods were devised to catch and store rainwater for future use. They are known as traditional water harvesting systems. Each region has given their tanks a distinctive name, from the dong of Assam to the vav of Gujarat, from the eri of Tamil Nadu to the baoli of Delhi and Rajasthan. Today, most are silted and unsanitary. Temple tanks, maintained out of faith, are important water harvesting structures used for drinking and ritual purposes and maintaining groundwater levels. They too are filthy and silted.
Rain enters the ground, so there is more groundwater than surface water. Groundwater is a reliable and unpolluted source of water. India uses only 10–20% of its annual rainfall of 400 mham. When it rains, only a fraction of the water percolates and reaches the groundwater aquifers, while the increasing numbers and depth of bore and open wells and their unrestricted use threaten India’s groundwater resources. Lack of adequate storage facilities is a major problem.
The problem of groundwater depletion can be best tackled by harnessing every drop of rainwater through artificial recharge. The main objectives of rainwater harvesting are to conserve the surface run-off, recharge aquifers, prevent flooding and stagnation of water during monsoon, and prevent saltwater intrusion. If this were done, we need not shift coastal populations to schools every time there is heavy rain. If the rainwater and the consequent overflow of streams and lakes could be stored, the water could be used throughout the year.
Even annual rainfall as low as 100 mm, if harvested properly, can meet drinking water requirements, as in the Thar where it sustains the Bishnois, the wildlife and plants. But maintenance of water harvesting structures is essential. At least 15% of Chembarambakkam lake is filled with silt. The release of water from the lake could have been avoided if it had been desilted regularly, as an official confessed after Cyclone Nivar. This is the story of most waterbodies.
In the past, villages managed them through kudimaramath, a system of voluntary labour undertaken by village communities, which ended when the British took control of the waterbodies. Now neither people nor governments maintain them. Indian urban planning creates housing colonies without provisions for harvesting rainwater.
In response to a PIL that sought direction to protect disappearing waterbodies, the Madras High Court directed all district collectors to deepen and desilt waterbodies in their districts. But this involves money. State governments should construct and maintain rainwater harvesting structures in urban and rural areas. Harvesting and conserving water is essential in today’s crowded cities with their growing populations. In India, water is considered to be sacred, but there is nothing sacred about our treatment of water. Every drop of rainwater is precious—save it. It might be the drop that will quench your thirst one day.
NANDITHA KRISHNA (firstname.lastname@example.org)
Historian, environmentalist and writer based in Chennai