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It also explains the various laws that have been put in place to increase groundwater replenishment.
With this information, the author makes a series of proposals to recharge the groundwater in the NCR. The NCR consists of parts of the states of Rajasthan, Haryana and Uttar Pradesh, besides New Delhi itself. The rapid urbanisation of these areas is leading to water being consumed at a pace, far greater than its replenishment.
The report has been divided into 10 chapters plus an annexure. These help build a case for groundwater recharge and for the recharge systems proposed. The chapters are:
The NCR covers an area of 33578 sq km, and according to this report the urban growth rate was 56.25% during 1991-2001. This area is dependent on groundwater, not only because of inter-state water disputes but also because of high pollution levels in the Yamuna and uneven if not low rainfall. Though there have been traditional water management techniques, these have not been able to resolve the demand for water and the resulting over-exploitation of ground water.
It is important to understand that groundwater depletion today is a classical case of 'tragedy of the commons'. As there is no resource ownership, but is dependent on rules of capture, there is no will to conserve it for future use. Thus there has been a steep decline in groundwater in these regions. Though there is natural replenishment of groundwater, it has not been able to keep pace with its extraction. There is therefore need to artificially replenish groundwater through human interventions like rain water harvesting etc.
There are many ways to divide the NCR. This region can be divided according to sub-regions i.e according to the states. Thus we have the Haryana sub-region, UP sub-region etc. Geo-morphologically it can be subdivided into alluvial plain areas, flood plain areas, structural hills mostly represented by the Aravallis, and Oxbow lakes and isolated water bodies located in depression. Such a sub-division is of great use when planning groundwater recharge. The NCR can also be divided into rural and urban areas which in other words is according to land use. Such differentiation helps in proposing recharge techniques most suited for that area.
The suitability of an area for setting up groundwater recharge systems is dependent on many factors - some of them are the rock types, the availability of source water. This chapter discusses the prevailing natural conditions (soil, climate etc) in the NCR.
Though rainfall is the major source of water, there are also a number of major and minor rivers. Ganga, Yamuna, Hindon and the river Sahibi, all pass through this region. There are also smaller streams but these are mostly in Uttar Pradesh. Parts of this region are covered by Alwar group of rocks and Ajabgarh group of rocks which are precambrian rocks. The presence of quaternary alluvial deposits, gives this area a lot of potential of creating structures for replenishing ground water.
The Central Ground Water Board and other agencies have undertaken exploratory drilling in this region. They have found that individual tube-wells drilled to more than 300 meters depth in the districts along the Ganga and Yamuna yield more than 150 m3/hour. While the transmissivity of aquifers varies between 1000 to 3000 m2/day. In other areas, yields range from 50-150 m3/hour.
This chapter also discusses the groundwater regime and groundwater quality in this region. Details of the climatic conditions, rainfall variations and temperature also figure here.
This chapter deals with assessing the water availability in the NCR; this is key to creating a recharge plan. This region has quite a few sources of water which include rainfall, groundwater, river basins, canals and surface water bodies, treated sewage water for recycling etc.
The NCR receives between 850 mm of rainfall in the east to 300 mm in the west. Interestingly, the report has been able to get information on the amount of rainfall on cultivable and non-cultivable land - in the Khariff season the rainfall occurring over cultivable land is between 352.0 MCM/ year to 2481.9 MCM/ year, whereas over non-cultivable land, it ranges from 83.9 MCM/ year to 1334.7 MCM/ year. The built-up area of Delhi receives 344.1 MCM/ year, which can be utilised for rainwater harvesting. In totality the amount of rainfall received for an average year is 22542 MCM of water of which 16906.5 MCM is received in the monsoon season.
A table breaks down rainfall distribution in the various sub-regions of the NCR. The surface run-off is determined by factors such as land use and land cover pattern. The NCR loses 6272.3 MCM/ year of water. Information on these losses are provided in a tabular form.
The report also mentions the non-use of flood waters in another table for each sub-region of the NCR.
Groundwater is a major source of water and has been over extracted. According to the Central Ground Water Board, though the net ground water availability for the NCT of Delhi is 0.28 BCM, annual groundwater extraction is estimated to be 0.48 BCM. Information on groundwater availability and extraction for the different sub-regions of the NCR Delhi and the NCT Delhi is also provided.
Mention is also made of minor rivers and various lakes and water bodies in these sub-regions and their carrying capacities.
The amount of wastewater recycled and used and its latent potential is also discussed in this chapter.
With the information on various sources of water, the chapter also discusses the potential areas where recharge can occur. Thus the river flood plains, rural areas and their water bodies, the hills of the Aravalli range where trenches can be constructed along their fringes are some of the areas where recharge can occur. There is also discussion on rooftop rainwater harvesting techniques for urban areas, besides parks and abandoned quarries.
A discussion on the concept of water recharge begins this chapter. It is noted that there are four major aspects to water harvesting and run-off recycling, these are collection, efficient storage of harvested water, water application and utilization for maximum benefit. Various explanations of the term of 'artificial recharge' are also mentioned. It is noted that though recharge is in fact natural, it is the use of mechanisms to improve and accelerate the percolation of surface water to aquifers that makes it distinct from natural recharge.
Ancient water recharging practices and their success stories are also mentioned here. For example, the world's largest rainwater harvesting structure in Istanbul is noted.
Choice of artificial recharge techniques has many variables which include rainfall pattern, land use and vegetation, soil type and soil depth etc. Taking these into consideration, the chapter mentions various methods of rainwater harvesting and artificial groundwater recharge. These include surface spreading techniques under which structures like ditches and furrows, bench terracing etc are considered. Then there are sub-surface techniques like injection and gravity recharge wells.
Under rooftop rainwater harvesting systems (RRHS), the author first discusses where these techniques are most beneficial and their advantages over conventional water supply systems. Thus in rural areas where water bodies dry up in the summer, RRHS can play an important role in providing water. Some of the advantages include easy access to clean water, cost-effectiveness etc.
India does not have a comprehensive water law. There are various laws that deal with different aspects of water. The Indian Constitution has listed water in its State list in the 7th Schedule; thus issues relating to planning, management and development of water resources is the prerogative of the States.
The report lists out and explains the various laws related to water; for example mention is made of 1873 Northern India Canal and Drainage Act which deals with use and control of rivers, lakes etc. The Indian Easement Act of 1882 which gives the owner of a property right to collect and dispose the water under and on the land. Mention is also made of various Supreme Court rulings on water. Government policies on water are also discussed in this chapter. The National Water Policy which deals with development and exploitation of ground and surface water, and the National Environment Policy are discussed.
Existing laws and policies on rainwater harvesting and groundwater recharge for the region as a whole and sub-regions are covered. The Delhi Water Board Act and its various amendments is a case in point. The Haryana government has changed the building bye-laws to make it mandatory for all buildings to install rainwater harvesting systems, so have the UP and Rajasthan governments. A table provides information on such laws in other states of India.
Starting with the approach and methodology for groundwater recharge, the report says artificial recharge of aquifers can be achieved in three ways - surface spreading, watershed management (water harvesting) and recharge wells. However, the choice of an aquifer for recharge depends on surface material, which needs to be highly permeable, depth to water level should not be less than 7 to 10m, high transmissivity in aquifer etc.
Various types of flood plain recharge methods, like basin spreading recharge and stream channel recharge are given. It is explained that the the flood plain of the Ganga should be utilised. Other systems of recharge specific for ridges like 'Hill Toe Trenches', check dams etc, are also explained. Recharge systems for alluvial plains include dug wells, abandoned hand-pump and tube-wells, according to the report.
Percolation tanks can also be constructed in these plains. It is important to note that percolation tanks should be empty by February every year, with the water having percolated into the aquifer. The size of such a tank should be dependent on percolation capacity of the soil. These are suggestions for rural areas.
In the case of urban areas where there are more constructed areas and there is less surface water, rooftop rainwater harvesting is a suggested method of recharge. Use of parks to harvest water is also suggested and utilising storm water is an option too, by constructing recharge tubewells inside the drains itself. The use of mega urban structures like airports for rain water harvesting, can combine the different types of water harvesting methods mentioned above.
The reclamation and restoration of water bodies like lakes, tanks etc is also a form of recharge system. Besides restoration, the use of cut-off trenches (COT) on the upstream side of these water bodies enhance ground water recharge. Constructing recharge shafts to make use of excess water is another system. The use of treated sewage water for recharge is also suggested. However there is a lot of stress on treatment of this water type.
Importantly, the chapter lists out the impact of these different recharge systems which have been implemented in different parts of India. The artificial recharge structures have been able to recharge anywhere between 4500 cubic meters for a percolation tank, to 2 lakh cubic meters through a rainwater harvesting system.
This report has not only been able to provide an impelling case for recharge of groundwater but also gives a scientific method by which the recharge has to be carried out. By focussing on important preconditions like soil type etc, the report has ensured that recharge structures have more chances of success and that there will be a higher return on investments in terms of amount of water finally reaching the aquifer.
Download the report here: