- WHY TO SAVE GROUNDWATER?
DR. NITISH PRIYADARSHI
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become fully saturated with water is called the water table.
Our ancient religious texts and epics give a good insight into the water storage and conservation systems that prevailed in those days.
Groundwater development dates from ancient times. The Old Testament contains numerous references to groundwater, springs, and wells. Other than dug wells, groundwater in ancient times was supplied from horizontal wells known as qanats. These persist to the present day and can be found in a band across the arid regions of Southwestern Asia and North Africa extending from Afghanistan to Morocco. Qanats are laboriously hand constructed by skilled workers employing techniques that date back 3000 years.
Iran possesses the greatest concentration of qanats. Here some 22,000 qanats supply 75 percent all water used in the country. Lengths of the qanats extended up to 30 km, but most are less than 5 km. The depth of the qanat mother well is normally is 50 m, but instances of depths exceeding 250 m have been reported.
Some ancient Indian methods of water conservation
The Indus Valley Civilization, that flourished along the banks of the river Indus and other parts of western and northern India about 5,000 years ago, had one of the most sophisticated urban water supply and sewage systems in the world. The fact that the people were well acquainted with hygiene can be seen from the covered drains running beneath the streets of the ruins at both Mohenjodaro and Harappa. Another very good example is the well-planned city of Dholavira, on Khadir Bet, a low plateau in the Rann in Gujarat. One of the oldest water harvesting systems is found about 130 km from Pune along Naneghat in the Western Ghats. A large number of tanks were cut in the rocks to provide drinking water to tradesmen who used to travel along this ancient trade route. Each fort in the area had its own water harvesting and storage system in the form of rock-cut cisterns, ponds, tanks and wells that are still in use today. A large number of forts like Raigad had tanks that supplied water. In ancient times, houses in parts of western Rajasthan were built so that each had a rooftop water harvesting system. Rainwater from these rooftops was directed into underground tanks. This system can be seen even today in all the forts, palaces and houses of the region. Underground baked earthen pipes and tunnels to maintain the flow of water and to transport it to distant places, are still functional at Burhanpur in Madhya Pradesh, Golkunda and Bijapur in Karnataka, and Aurangabad in Maharashtra.
Ground-water development and quality consideration were getting sufficient attention as evidenced by Vrahat Samhita (550 A. D.) Water management and conservation, well organized water pricing system in 400 B.C. Construction methods and materials of dam, tanks etc., bank protection, spillways and other considerations mentioned in the ancient books reflect the high stage of development of water resources and hydrology in ancient India.
Groundwater Theories in Ancient Philosophy:
Utilization of groundwater greatly preceded understanding of its origin, occurrence, and movement. The writings of Greek and Roman philosophers to explain the origins of springs and groundwater contain theories ranging from fantasy to nearly correct accounts. As late as the seventeenth century it was generally assumed that water emerging from springs could not be derived from rainfall, for it was believed that the quantity was inadequate and the earth too impervious to permit penetration of rain water far below the surface. Thus, early Greek philosophers such as Homer, Thales, and Plato hypothesized that springs were formed by seawater conducted through subterranean channels below the mountains, then purified and raised to the surface. Aristotle suggested that air enters the cold dark caverns under the mountains where it condenses into water and contribute to the springs. The German astronomer Johannes Kepler (1571-1630) was man of strong imagination who linked the earth to a huge animal that takes in water of the ocean, digests and assimilates it, and discharges the end products of these physiological processes as groundwater and springs.
Importance of Groundwater:
Ground water is an important part of the water cycle. Ground water is the part of precipitation that seeps down through the soil until it reaches rock material that is saturated with water. Water in the ground is stored in the spaces between rock particles (no, there are no underground rivers or lakes). Ground water slowly moves underground, generally at a downward angle (because of gravity), and may eventually seep into streams, lakes, and oceans.
The importance of groundwater for the existence of human society cannot be overemphasized. Groundwater is the major source of drinking water in both urban and rural India. Besides, it is an important source of water for the agricultural and the industrial sector. Water utilization projections for 2000 put the groundwater usage at about 50%. Being an important and integral part of the hydrological cycle, its availability depends on the rainfall and recharge conditions. Till recently it had been considered a dependable source of uncontaminated water.
The demand for water has increased over the years and this has led to water scarcity in many parts of the world. The situation is aggravated by the problem of water pollution or contamination. World is heading towards a freshwater crisis mainly due to improper management of water resources and environmental degradation, which has lead to a lack of access to safe water supply to millions of people. This freshwater crisis is already evident in many parts of India, varying in scale and intensity depending mainly on the time of the year.
Groundwater crisis is not the result of natural factors; it has been caused by human actions. During the past two decades, the water level in several parts of the country including Jharkhand has been falling rapidly due to an increase in extraction. The number of wells drilled for irrigation of both food and cash crops have rapidly and indiscriminately increased. India's rapidly rising population and changing lifestyles has also increased the domestic need for water. The water requirement for the industry also shows an overall increase. Intense competition among users — agriculture, industry, and domestic sectors — is driving the groundwater table lower. The quality of groundwater is getting severely affected because of the widespread pollution of surface water. Besides, discharge of untreated waste water through bores and leachate from unscientific disposal of solid wastes also contaminates groundwater, thereby reducing the quality of fresh water resources.
The importance of the groundwater arises from the following considerations:
1. The quantity of groundwater up to drillable depth, is about seventy times more than all the waters in the rivers, lakes, reservoirs, etc. in the world put together.
2. The quality of groundwater is generally superior to surface water, because the soil column purifies the contaminants in water through processes such as anaerobic decomposition, filtration, ion exchange, etc.
3. Groundwater is the main source of potable water in most parts of the world (for instance groundwater is the source of 75% of the municipal water supplies in USA).
4. The world's rural population now exceeds 3 billion people. While the total is expected to stabilize over the next 30 years, the proportion from less developed regions will rise. Demand for groundwater for rural water supply will continue to grow because it is a resource that provides drinking water of acceptable quality with minimal treatment and at modest cost.
5. Groundwater already plays a key role in the provision of safe drinking water to rural populations e.g. already almost one-third of Asia's drinking water comes from groundwater, much of it supplying farms, villages and small towns. About 80 percent of domestic water use in rural areas in India is groundwater-supplied.
6.Rural dependency on groundwater is just as widespread in the developed world - in the United States, more than 95% of the rural population depend on aquifers to provide their drinking water.
7. While global population growth is increasingly concentrated in the world's cities, the demand for food will continue to rise, and much of this increase will need to be satisfied by irrigation-aided rises in agricultural productivity.
8. Irrigation, much of it drawn from groundwater, has made possible the already-enormous rise in food production during the last 30-40 years. Cultivators have become well aware, in terms of increased productivity, of the benefits groundwater offers: timely irrigation and security of application.
9.Groundwater is a scarce resource and needs to be managed. Inadequate control of the use of groundwater, indiscriminate application of agrochemicals and unrestrained pollution of the rural environment by other human activities is unsustainable in the face of the twin demand for water of good quality for domestic water supply and adequate volume for irrigation.
The use of groundwater for irrigation ranges from about 40% in the case of India, to about 70% in the case of Libya. As a consequence of excessive use of groundwater for drinking and irrigation purposes, the water table is going down 1-3 m per year in most parts of India.
In rural India, groundwater (GW) provides approximately 85% of the water used for domestic purposes, and more than 50% of that used for irrigation. These statistics, however underplay the larger role of groundwater within both, natural resources and socio-economic frameworks. Access to groundwater means reduced agricultural risk and an avenue for economic development. At the same time, increasing use of groundwater has resulted in various environmental concerns, the foremost being the depletion of groundwater resources and reduced base flows to streams and rivers.
The National Water Policy (1987) states that water is a prime natural resource, basic human need, and precious national asset. It gives special attention to drinking water for both humans and animals over its other uses. The policy calls for controls on the exploitation of groundwater through regulation and an integrated and coordinated development of surface- and ground-water. The central government has identified strategies for meeting drinking water needs and micro-watershed management and conducted pilot projects in different regions in the country. Even so, India is facing a freshwater crisis.
1. Todd, D.K. 1980. Groundwater Hydrology. John Wiley & Sons, New York.
2. Aswathanarayana, U. 2003. Natural Resources and Environment. Geological Society of India.