|
Ground water resources are dwindling
The country's ground water resources are dwindling, at a much faster pace than they are being recharged,
naturally or otherwise. Against a backdrop of fast depleting groundwater reserves - in some villages, wells have now to be dug at over 200 meters to reach water.
Findings of a scientific study
The findings of a scientific study using satellite imagery, by the National Aeronautics and Space
Administration of the US, made public recently, show that 26 cubic miles of water has disappeared from under the surface of Punjab, Haryana,
Rajasthan and the national capital region during 2002-08. The aquifers are reducing by up to 1 ft a year because they are
getting depleted faster than they are being replaced. Hence, NASA issues a dire warning: “If measures are not taken to ensure sustainable groundwater use, the
consequences for the 114 million residents of the region may include a collapse
of agricultural output and severe shortage of potable water… The loss is particularly alarming because it occurred when there was no unusual trend in rainfall (during 2002-08).”
A long-term 'reservoir'
Groundwater is water located beneath the ground surface in soil pore spaces and
in the fractures of geologic formations. A formation of rock/soil is called an
aquifer when it can yield a useable quantity of water. The depth at which
soil pore spaces become saturated with water is called the water table. Groundwater
is recharged from, and eventually flows to, the surface naturally; natural
discharge often occurs at springs and seeps and can form oases or wetlands.
Groundwater is also often withdrawn for agricultural, municipal and industrial
use by constructing and operating extraction wells.
Groundwater can be a long-term 'reservoir' of the natural water cycle (with residence times from days
to millennia), as opposed to short-term water reservoirs like the atmosphere and
fresh surface water (which have residence times from minutes to years).
Groundwater is naturally replenished by surface water from precipitation, streams, and
rivers when this recharge reaches the water table. It is estimated that the
volume of groundwater is fifty times that of surface freshwater. Groundwater makes up about twenty percent of the world's fresh water supply,
which is about .61 percent of the entire world's water supply. The temperature of groundwater averages out climactic fluctuations to maintain a
relatively steady temperature.
Groundwater is a highly useful and abundant resource, but in arid or semi-arid
regions it is in a pre- development state. The most evident problem that may
result from this is a lowering of the water table beyond the reach of existing
wells. Wells must consequently be deepened to reach the groundwater; in some
places in India and Rajasthan the water table has dropped hundreds of feet due to well pumping. A lowered water table may, in turn, cause other
problems such as subsidence.
Sometimes the water movement from the recharge zone to the place where it is
withdrawn may take centuries (see figure above). When the usage of water is
greater than the recharge, it is referred to as mining water (the water is often
called fossil water, due to its geologic age). Under those circumstances it is not a renewable resource. |
