9.1 NATURAL RESOURCES
Natural Resource Conservation includes management of water (surface and ground), air and noise.
9.1.1 WATER (SURFACE AND GROUND)
a) The surface water resources in Delhi are basically comprised of the river Yamuna, drains and the lakes/ponds. The groundwater in Delhi occurs in confined and semi-confined conditions, with depths varying from 1 m to 10 m below the ground level and in the alluvial terrain, several sandy aquifers occur at different levels up to a depth of 70 m.
Based on studies and statistics, some of the striking features that are revealed about the surface water resources in Delhi are:
i. The Yamuna river and the drains are highly polluted;
ii. The supply of water for human use is too much in absolute terms, but is characterized by iniquitous distribution in per capita terms in different areas, and significant wastage;
iii. Assuming that 80 percent of the water is converted into wastewater, the capacity to treat wastewater is grossly deficient; Various options for the re-use of treated wastewater must be explored and implemented.
iv. The actual quantity of waste water treated is much below the installed capacity on account of missing links in sewer connectivity between the generation points and treatment plants and choking/silting of sewer lines, etc. The missing links in sewer connectivity must be covered for its continuity from the generation point to the treatment plant.
v. The planned reuse of treated wastewater is minuscule;
vi. The treated wastewater is being largely put back into the drains and gets polluted again before flowing into the river Yamuna, which receives 70 percent of its waste from the 22 kms. of its flow through urban Delhi which, in turn, constitutes only 2 percent of the total length of the river basin stretching from its point of origin till its merger into the Ganga at Allahabad;
vii. A large number of the traditional water bodies in the form of ponds, etc. (excluding areas of unintended water logging along railway tracks, highways and canals etc.) have been encroached or have otherwise become defunct.
viii. The standards for STP / CETP developed by Central Pollution Control Board / Delhi Pollution Control Committee should be adhered to.
ix. The public participation and education programmes must be encouraged so that the sensitivity of the water resource is understood by the consumers, students and RWAs.
b) Groundwater is one of the major sources for water supply in many parts of the country. In Delhi too, groundwater contributes a substantial quantity of water supply. Especially in new development areas, groundwater is largely being used as drinking water resources. The Central Ground Water Board (CGWB) assessed the total groundwater potential to be 292 million cubic meters (MCM) in 2003 as compared to 428.07 MCM in 1983, showing an overdraft and reduction of around 130 MCM over the past 20 years. Out of the 6 blocks into which Delhi is divided, significant over drawl / reduction has been observed in the Najafgarh and Mehrauli blocks. Rapid urbanization leading to the reduction in recharge of aquifers, increasing demand in the agriculture, industrial and domestic sectors, the stress put on groundwater resources in periods of drought/deficient rainfall, and unplanned withdrawal from the subsoil aquifers, have been mainly responsible for the decline in groundwater levels.
The average annual rainfall in Delhi is 611 mm. However, recharge of groundwater gets limited due to decreased availability of permeable surfaces owing to urbanization, and the runoff getting diverted into the sewers or stormwater drains that convey the water into the river Yamuna. The annual rainwater harvesting potential has been assessed at 900 billion liters or 2500 million liters per day. If even 25% of this could be harvested it would imply availability of 625 mld, which would be nearly equivalent to the presently estimated deficiency. This is in addition to the potential for roof water harvesting assessed at around 27 mld.
The existing drainage basins shall have to be made self-sustainable in water management by integrating water-sewerage-drainage systems. New projects and up gradation of present infrastructure should be taken up in addition to promotion of water conservation through an integrated and a community-driven model. Complimentary short-term and long-term strategies as mentioned above will need to be initiated.
c) Development of parks and green corridors along the Nallahs should incorporate conservation of groundwater and water bodies. To recharge the groundwater, conservation of water bodies and rainwater shall be essential. The area near Najafgarh Jheel and its surroundings and the Ridge can also be used as the potential water conservation area.
d) To increase sub-surface soil water through seepage of rainwater, porous paving tiles should be used in the pavements and soft parking areas. All the new bridges/flyovers must have the provision for rainwater harvesting.
Water bodies, having a minimum size of the surface area of 1 ha., shall be preserved by the concerned authorities. Further efforts shall be made at the local level to retain smaller water bodies.
