Why we need

Need for Artificial Recharge

Natural replenishment of ground water reservoir is a slow process and is often unable to keep pace with the excessive and continued exploitation of ground water resources in various parts of the country. This has resulted in declining ground water levels and depletion of ground water resources in such areas. Artificial recharge efforts are basically aimed at augmentation of the natural movement of surface water into groundwater reservoir through suitable civil construction techniques. Such techniques interrelate and integrate the source water to ground water reservoir and are dependent on the hydrogeological situation of the area concerned. Occurrence of rainfall in India is mostly limited to about three months in a year. The natural recharge to ground water reservoir is restricted to this period only in a major part of the country. Artificial recharge techniques aim at extending the recharge period in the post-monsoon season for about three or more months, resulting in enhanced sustainability of ground water sources during the lean season. In arid regions of the country, rainfall varies between 150 and 600 mm/ year with less than 10 rainy days. A major part of the precipitation is received in 3 to 5 major storms lasting only a few hours. The rates of potential evapotranspiration (PET) are exceptionally high in these areas, often ranging from 300 to 1300 mm. In such cases, the average annual PET is much higher than the rainfall and the annual water resource

Planning has to be done by conserving the rainfall, by storing the available water either in surface or in sub-surface reservoirs. In areas where climatic conditions are not favorable for creating surface storage, artificial recharge techniques have to be adopted for diverting most of the surface storage to the ground water reservoirs within the shortest possible time. In hilly areas, even though the rainfall is comparatively high, scarcity of water is often felt in the post-monsoon season, as most of the water available is lost as surface runoff. Springs, the major source of water in such terrains, are also depleted during the post monsoon period. In such areas, rainwater harnessing and small surface storages at strategic locations in the recharge areas of the springs can provide sustainable yields to the springs as well as enhance the recharge during and after rainy season.

Ground water management is the foremost challenge being faced today by the organizations dealing with ground water in India. The activities and policies affecting ground water need to reflect the priority issues with the overall objective of providing water security through ground water management in a major part of the country. Central Ground Water Board, being the apex organization at the central level with vast experience in the ground water sector, has taken a proactive role in identifying various key issues, which need immediate attention. These issues are discussed below in brief.

Ground Water Depletion

Indiscriminate ground water development has led to substantial ground water level declines both in hard rocks and alluvial areas threatening sustainability of this resource. Long-term decline of ground water levels is being observed in many areas, mostly in the states of Rajasthan, Gujarat, Tamil Nadu, Punjab, Delhi and Haryana. Apart from this, in most of the cities depending on ground water for drinking water supplies, water level declines up to 30 m and more have been observed. Traditional water harvesting methods, which were in vogue in arid and semi-arid areas of the country have either been abandoned or have become defunct in most cases. There is an urgent need to revive these methods.

In some parts of the country like Rajasthan, Gujarat, Haryana and Delhi, the in-storage or static ground water resources are also limited and depletion in ground water level is resulting in ground water drought scenario. In such areas, it may become very difficult for the State to provide water security for various users. Excessive groundwater development has resulted in deterioration of ground water quality in coastal areas due to saline water ingress. Ground water development, therefore, needs to be regulated and augmented through suitable measures to provide sustainability and protection. Dependence on use of ground water for agriculture due to monsoon failures is accelerating ground water depletion. Excessive withdrawal of ground water is further compounding the stress on ground water system due to free/subsidized power in some States. In order to tackle the burgeoning problem of water level decline, it is necessary to take up schemes for water conservation and artificial recharge to ground water on priority.

Ground Water Pollution

Ground water resources in several areas of the country are getting polluted due to over application of fertilizers and pesticides, indiscriminate disposal of effluents from industries and urban sewerage. Surveillance studies to determine the type and migration of pollution and measures for its control have become an absolute necessity from the point of view of long-term sustainability of ground water resources. Purpose driven studies need to be undertaken to find suitable mitigation measures to combat this problem.

Presence of naturally occurring Arsenic, Fluoride and Iron in ground water in excess of permissible limits recommended for human consumption prohibits its use for drinking purposes in several states of India. Research and Development studies need to be taken up for finding cost-effective solutions to this problem. Dilution of pollutant concentration through ground water recharge can be one of the effective ways to mitigate the hazards of high concentration of these constituents. It is also desirable that rural water supply schemes be formulated and arrangements made to utilize fluoride / arsenic rich water for purposes other than drinking.

Drinking Water Shortage in Urban Areas

There are several urban areas in the country where water supply systems are based mainly on ground water resource. Sustainability of urban water supply is one of the core issues the planners across the country are facing at present. The problem may get aggravated in near future with the rapid pace of urbanization being witnessed in India. Potable drinking water is an important input for providing municipal supply to the urban complexes. Due to steep increase in population, the stress on ground water system has increased tremendously resulting in steep water level declines in and around these cities. These problems could be solved to some extent by

• Shifting of ground water pumpage from the center of the cities to flood Plain areas having proven capabilities of sustaining high yielding tube wells wherever possible.
• Recycling and reuse of water
• Dual water supply systems for drinking and other domestic uses
• Roof Top Rainwater Harvesting and
• Regulatory measures through proper pricing and metering of water supplied.

Seawater Ingress in Coastal Aquifers

The unconsolidated deltaic and coastal sediments form thick and regionally extensive aquifers having prolific yield potential that can sustain deep, moderate to high capacity tube wells. Although considerable fresh ground water resources have been identified in regionally extensive deltaic and coastal tracts, particularly along the east coast, inherent quality problems restrict their development. The ground water in these aquifers exists in a fragile dynamic equilibrium with seawater. Indiscriminate exploitation of ground water from such aquifers can disturb this equilibrium and result in the development of landward hydraulic gradient, ultimately leading to seawater intrusion into the fresh water aquifers. Coastal aquifers in parts of Gujarat, TamilNadu and Andhra Pradesh are already suffering from the problem of salinity ingress. Measures to prevent/control saline water intrusion into coastal aquifers include

• Regulation of ground water development in coastal areas.
• Formation of a freshwater ridge parallel to the coast through artificial recharge.
• Formation of a pumping trough through a series of pumping wells aligned parallel to the coast

In Indian perspective, water shortage is one of the most difficult problems being faced in present time. Rainfall is quite erratic and non-uniform across the length and breadth of the country (Figure 1). About 80 –90% of the total rainfall is received during the summer monsoons (i.e. July to September) while rest of the period goes dry. Another serious repercussion of the problem is that every year almost 90 districts become drought affected and 40 million hectares in 83 districts get flooded. India receives about 34% of its freshwater from outside of the country and to fulfill the need, India is also withdrawing groundwater in an unsustainable rate. Many Indian states where the water table is going down with a speedy rate. In such a situation, it is necessary to save each and every drop of water through various means. Therefore, it is the utmost requirement that rainwater should not go in vain and it is to be collected efficiently.

The annual average rainfall for surat city is 1193 mm and the rainfall usually occurs for short duration but with high intensity. Such conditions result in the heavy flow of water leaving very little amount for the recharge of groundwater. Thus, groundwater does not get chance to replenish. Considering this situation, the rainwater harvesting (RWH) technique has emerged as a boon.