Through the ages, urban wetlands have been the lifeline of most cities in India. They were preserved and looked after by the people as their main source of water supply for drinking and irrigation. These wetlands are found all over the country and are either natural or built by people. Over the years, they have gradually depleted, leading to a number of problems in urban areas such as flooding, water scarcity, and water logging.
Tanks were constructed in the catchment areas of cities that were not located near a river or a large lake. Rainwater or run-off would collect during the monsoons and be stored for the rest of the year in these tanks and lakes. The city would get its water supply from these.
In southern India, the towns were built around a temple, which always had a tank at the centre. Wells were located in the tank, which served as a link with the aquifers. There were innumerable tanks dug by the rulers, most of which have been destroyed. In fact, in some areas tank building by the ruler was considered a noble deed.
In Karnataka, the Hoysalas built tanks all over the state. Some of these still exist. Festivals were organized around tanks; cleaning and de-silting the tanks were a part of the rituals. But over the years, human activity steadily destroyed these wetlands. In Bangalore, the city bus terminus has been built on the Dharmambudhi tank. A part of the Sampangi tank has given way to the Kanteerva stadium and the remaining to a housing colony. Another lake was filled up to house the city market.
Pollution levels in the Hussain Sagar Lake in Hyderabad has been going up over the years. There are more than a thousand polluting industries located around the lake, a large number of them pharmaceutical industries. Untreated effluents from the industries and domestic sewage have deteriorated the water quality in the lake. The lake gets little chance to rejuvenate itself as a run-off happens only once a year during the monsoons, whereas pollutants flow in throughout the year.
The Cholas were well known for the construction of tanks in the state of Tamil Nadu. But today, despite heavy rains, Chennai reels under severe water crisis along with flooding. A number of housing colonies have been built on tanks and over the years the numbers are increasing. This is the case in most large cities in the country.
In Calcutta wetlands, both artificial and natural, have been a part of the city system. The main drainage for the city has been the Hooghly River; but the incline of the city is eastwards and this has led to the creation of the East Calcutta Wetlands. The Salt Lake is one of the largest wetlands in the city and serves as a flood cushion for the city. Calcutta has no sewage treatment plant. The sewage is treated in the sewage-fed fisheries; the process is cost-effective and lasting. A number of the fisheries purify this water through a series of sedimentation tanks and use the water for fish cultivation and agriculture.
Indore’s water needs were met by a large numbers of wells and tanks located all around the city. But over the last few years, the tanks have gradually dried up, including the largest of them, the Yashwant Sagar Lake. Vegetable and fruit cultivation along the banks of the lake has caused pollution due to run-offs from the fields. This has caused eutrophication and contamination.
There are no rivers in the vicinity of Bhopal and the city depends entirely on lakes to meet the water needs of the city.Over the years, these lakes have become polluted due to the dumping of sewage into them. The government recently announced the Bhuj Wetland Project, a scheme to prevent the flow of liquid and solid waste into the lakes and also to de-silt them. More than 2000 ha of land around the upper lakes, which feed water to the lower ones, is to come under plantation.
Once upon a time, these urban wetlands maintained a steady supply of water for the city, recharged the groundwater, cooled the city, and prevented flood as they were a natural drainage system. Over the years, these very tanks and wetlands have been neglected, encroached upon either to accommodate more houses or to dump waste. Our wetland are under threat now.This has caused large-scale water crisis and monsoon flooding and water logging, leading to misery and disease. These wetlands that have been protected for centuries are now being ravaged and destroyed in the name of development.
People in the urban areas must learn to live in harmony with nature in their own habitat. The wetlands, the green belts, and the flora and fauna of these areas have to be preserved for urban areas to survive and remain healthy.
In earlier times, we in India,practiced water harvesting systems. Perhaps it is high time to revive at least some of them,if not all.