Environmental problems in Delhi, India, are a threat to the well-being of the city's and area's inhabitants as well as the flora and fauna. Delhi, the sixth-most populated metropolis in the world (second largest if the entire NCR is included), is one of the most heavily polluted cities in India,[4] having for instance one of the country's highest volumes of particulate matter pollution.[5] In May 2014 the World Health Organization announced New Delhi as the most polluted city in the world.[6]
Overpopulation and the ensuing overuse of scarce resources such as water put heavy pressure on the environment. The city suffers from air pollution caused by road dust and industry,[7] with comparatively smaller contributions from unclean engines in transportation, especially diesel-powered city buses and trucks, and 2-wheelers and 3-wheelers with two-stroke engines.[8]Another known cause of pollution is slow moving traffic due to pedestrians crossing the road just about anywhere. Noise pollution comes mainly from motorcycle and automobile traffic.[9] Water pollution and a lack of solid waste treatment facilities have caused serious damage to the river on whose banks Delhi grew, the Yamuna. Besides human and environmental damage, pollution has caused economic damage as well; Delhi may have lost the competition to host the 2014 Asian Games because of its poor environment.[10]
Water pollution
Yamuna river
The river Yamuna, the reason for Delhi's existence, has suffered heavily from pollution. At its point of entry into Delhi, at Wazirabad, its dissolved oxygen (DO) content is 7.5 milligrammes per litre. At its point of exit from city limits, the DO level is only 1.3 mg/l. Similarly, coliform counts jump from 8,500 per 100 ml at entry to 329,312/100ml at exit (for DO 5 mg/litre is the norm and for coliforms 500/100ml).[11] In 2007, roughly half of all the city's raw sewage went straight into the river. 55% of the city's 15 million people are connected to the city's sewer system and its treatment plants, but because of corrosion and clogging in the system many of the treatment plants do not run at full capacity. Waste from 1,500 unplanned neighborhoods runs straight into the river.[12]
The Supreme Court of India took up the issue in 1994 after reports in the press,[12] and since 2001 is actively monitoring the river and the city's efforts to clean it; in 2011, the national government announced a Rs 1,357 crore drain interceptor plan (all waste water is to be cleaned before it reaches the river) that would clean up the river by 2014.
Water sources
Underground hydrological resources are a substantial supplemental source of water in Delhi, especially in the affluent sections of the city. In the residential plots called the 'farmhouses' almost every household draws from this resource. Though water-storing rocks, i.e. aquifers, are renewed as surface rain-water percolates down, they are not inexhaustible. Delhi's aquifers stand in danger of depletion on account of excessive use. Furthermore, rampant construction activity has contaminated them with cement, paints, varnishes and other construction materials; leaky, poorly constructed and maintained sewage lines have added to the contamination. This is an irremediable loss, as aquifers, once polluted, cannot be decontaminated; they have no exposure to air and sunlight or to micro-organisms which clear-up chemical or biological pollutants.[13]
Contributing further to underground water degradation are Delhi's mushrooming landfill sites. Waste material leeches underground, contaminating aquifers. Besides, land-fill sites degrade land. Delhi has twenty-five landfill sites, and more are planned.[14]
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