The study of groundwater is essential because of several reasons. Of the freshwater readily
available for human use (approximately 1% of the liquid freshwater available on the earth),
about 98% is groundwater and the remaining is surface water. Hence, groundwater serves as
a major source of water supply to life (humans, animals and ecosystems) throughout the
world. Because of its physical and chemical quality, groundwater provides a reliable source
of water supply in both humid and arid/semi-arid regions of the world and during
emergencies (e.g., droughts, earthquakes, etc.) as well as it sustains flow in rivers/streams
and lakes during dry periods. Thus, groundwater is one of the most valuable natural
resources of the earth, which supports human health, human livelihoods, socio-economic
development, and ecological diversity.
Besides the above-mentioned vital roles, groundwater also influences the design and
construction of engineering facilities such as dams, open-pit mines, tunnels, deep
foundations, and geologic storage of nuclear wastes or carbon sequestration. Groundwater is
also important due to its geologic role by supporting various geological processes such as
the formation of soils and their alternation, the development of landslides, rock falls, channel
networks and karst landscapes, oil formation and valuable mineral deposits. Thus,
groundwater plays a variety of roles on a global scale, which make this resource so vital for
human beings. However, the water resource and engineering aspects of groundwater
hydrology are the major focus of practice, though the groundwater hydrology field has a
rich relationship with other earth sciences.
Of the 37 Mkm3 of freshwater estimated to be present on the earth, about 22% exists as
groundwater (Foster, 1998). Although groundwater is the largest available source of
freshwater lying beneath the ground, its replenishment is finite and slow, and its quality can
be degraded by anthropogenic activities. Historically, groundwater has been a reliable, clean
and virtually unlimited water supply for much of the world population. However, with the
improvement in the knowledge of hydrogeology and advances in well-drilling and pump
technologies, massive groundwater withdrawal started from the 1950s in developed
countries and from the 1970s in developing countries. During the past 25-30 years, more
than 300 million wells have been drilled for water withdrawal in the world, and about one
million wells are drilled annually in the USA alone (Zektser, 2000). Consequently, the
worldwide groundwater overdraft or aquifer depletion, declining well yields, drying up of
springs, streamflow depletion, and land subsidence due to over-exploitation of groundwater
as well as the growing degradation of groundwater quality by natural and/or anthropogenic
pollutants and by saltwater intrusion are threatening our ecosystems and even the life of our
future generations (e.g., Brown, 2000; Zektser, 2000; Biswas et al., 2009). Excessive
groundwater depletion currently affects major regions of North Africa, the Middle East,
South and Central Asia, North China, North America, and Australia as well as localized
areas throughout the world (Konikow and Kendy, 2005). The key concern is how to maintain
a long-term sustainable yield from aquifers (Alley et al., 1999; Sophocleous, 2005). Global
climate change and socio-economic changes are expected to complicate the use of
groundwater and enhance stress on aquifer systems.
As to the groundwater scenario in India, firstly let‟s have a look on the rainfall characteristics
of India, which has far-reaching implications for groundwater. The mean annual rainfall in
India is estimated at 1,143 mm, which ranges from 11,489 mm at Mawsynram, a village in
Meghalaya (wettest place on the earth) to 217 mm at Jaisalmer, a district in the Thar Desert
of Rajasthan (Asawa, 1993). India is endowed with water resources only in very high rainfall
regions like the eastern Gangetic plains and the Konkan-Malabar coastal strip down below
the Western Ghat Mountains. Elsewhere, India’s water bounty is far from plentiful (Dhawan,
1989). Such a spatial variation in the water resources is inevitable for a country of continental
dimensions. What is truly striking is the temporal variation in water availability within the
year as well as from one year to another!
Out of the annual precipitation of about 4000 km3 in India, the accessible water is 1869 km3.
However, hardly 690 km3 water is currently used, and the remaining 1179 km3 of water
directly drains into the sea –– much of it in 100 days that define the India‟s wet season
(Aiyar, 2003). India‟s water problem basically stems from significant spatial and temporal
variations of precipitation, mismanagement, and the fact that while nearly 70% of
precipitation occurs in 100 days, the water requirement is spread over 365 days. In a number
of regions, water tables have been falling at an average rate of 2 to 3 m per year due to the
growing number of irrigation wells (Postel, 1993). Overuse of groundwater is reported from
different parts of the country such as Tamil Nadu, Gujarat, Rajasthan, Punjab, Haryana,
Orissa and West Bengal, among several other states (CGWB, 2006). A recent study based on
the analysis of GRACE satellite data revealed that the groundwater resources in the states of
Rajasthan, Punjab and Haryana are being depleted at a rate of 17.7 ± 4.5 km3/year (Rodell et
al., 2009). It indicated that between August 2002 to December 2008, these north-western
states of India lost 109 km3 of groundwater which is double the capacity of India‟s largest
reservoir „Wainganga‟ and almost three times the capacity of USA‟s largest artificial
reservoir „Lake Mead‟. In addition, the growing pollution of freshwater (both surface water.
and groundwater) from point and nonpoint sources and seawater intrusion into coastal
aquifers of the country are posing a serious problem of human health and hygiene. Thus,
increasing water scarcity and unabated water pollution threaten the sustainability of water
supply and environment in India (Aiyar, 2003; Garg and Hassan, 2007). Even water is
rationed in megacities such as Chennai, Bangalore, Mumbai and Delhi. Water tankers during
dry periods are the burning evidence of India‟s severe water scarcity! Consequently, India‟s
water security and food security are under a serious threat and the lives and livelihoods of
millions are at risk. More info: Perforacion de pozos profundos de agua
