Out of 629 water bodies in Delhi, very few remain, and those that remain are dying. Scientists and environment experts believe the atmospheric catastrophe that played out for a week after Diwali in the capital could have been controlled had these local water bodies been preserved.
According to experts, water bodies play an important role in controlling pollution. In fact, during the medieval period, besides the natural water bodies, the city had a large number of stepwells or baolis (man-made water tanks surrounded by steps). These played a special role in cleaning up the air. But they no longer exist.
Professor SC Rai, head of department, Geography, Delhi University, explains, “Water bodies play a major role in filtering the particulate matter -- they aid evapo-transpiration. It is a process by which the moisture from the surface is transferred to the atmosphere by evaporation of water and transpiration from plants. As the suspended particulate matter becomes moisture laden, they become heavy and settle down. Hence, the ponds, lakes and rivers are important in controlling pollution."
The point is further elaborated by Dr Shashank Shekhar, the assistant professor of Geology at Delhi University. He elaborates, “Besides recharging groundwater, natural water bodies help develop forests with native species. These water bodies, together with the vegetation, create micro-climatic zones with relatively distinct ecological patterns or signatures. They also act as receptacles for particulate atmospheric dust. Furthermore, the oxygen released by the surrounding trees purifies the ambient air quality. This makes a strong case for preservation of water bodies in land-locked Delhi."
Former scientist E of the Indian Meteorological Department, Vinod Kumar, says, “I followed the whole episode of pollution -- and its severity -- in Delhi post Diwali. It happened due to temperature inversion, caused by formation of an anti-cyclone or a high-pressure system in the lower troposphere over Delhi. When this happens, temperature of the atmosphere increases with altitude and cold air underlies warmer air. This severely hampers air circulation, as cold air is unable to rise. At such times, pollution released into the atmosphere gets trapped, and can be removed only by strong winds. As soon as the system dissipates, air circulation begins and slowly the atmosphere clears out. Had water bodies been there, the situation wouldn't have been this grave, since they would not have allowed so much of particulate matter to remain trapped in the air in the first place."
Gauhar Raza, former chief scientist of the Council of Scientific and Industrial Research (CSIR), emphasises, “Had Delhi maintained its water bodies, the situation would not have turned so bad. Continuous evaporation would have maintained high levels of water vapour in the atmosphere, which would have turned the dust particles heavy and helped them settle down. High levels of humidity also reduce the dissolvable gases and remove them from the air. It's almost like washing out the unclean air. Also, high levels of evaporation aid saturation and cloud formation. And rains help in clearing out the atmosphere.”
In Delhi, there had been many water bodies, including ponds, lakes, wells and rivers. But now, most of them are dead, or are dying. Convener of Citizens' Front for Water Democracy (CFWD), SA Naqvi, says, “According to government records, there are 629 water bodies. But, ironically, very few have water in them. The city's water bodies are dying, thanks to the lackadaisical approach of the administration."
Naqvi adds, “The biggest problem is that the water bodies in Delhi are not under the jurisdiction of one department. About 406 water bodies are with the flood control department, some 115 to118 with the DDA and the rest with gram sabhas, the Delhi Jal Board, the Public Works Department, and others. Of the 629, most have been encroached upon and quite a few have been levelled off for parks. The ignorance of the agencies and the administration is to be blamed for this dire situation."
To reduce the impact of urbanisation and maintain the ecology, water bodies in the Delhi-NCR must be urgently revived, feels Naqvi. He laments, "You can clearly see the lungs of this city struggling. The Yamuna is dying, Sahibi river is dead, and Badkhal and Surajkund lakes are dying! The government should wake up to the reality."
According to Naqvi, the Delhi government had made a list of 80 water bodies to be revived, but nothing happened. “No details are available on the government's website. No mapping of the exact area of water bodies has been done till now by any government."