Dosiers en curso
2008 / 2009
dph participa en la coredem
Availability, usage and problems
06 / 2009
India has about 4% of world’s freshwater resources ranking it among the top ten water rich countries. Despite this, according to the Working Group II report of the Fourth Assessment of the Intergovernmental Panel on Climate Change, India is designated a ‘water stressed region’ with current utilisable freshwater standing at 1122 cubic meter (cu m) per year and per capita compared to international limiting standards of 1700 cu m. In future, at the current rate it is expected that India with high demands will be termed a ‘water scarce region’ as utilizable freshwater falls below the international standard of 1000 cu m per year and per capita. Water demand is on a high due to rapid urbanization and industrialization along with the traditional demand for agriculture. Overall, every year, precipitation in the form of rain and snowfall provide over 4000 cu km of freshwater to India, of which 2047 cu km return to oceans or is precipitated. A small percentage is stored in inland water bodies and groundwater aquifers. Topographic constraints, distribution pattern, technical limitation, and poor management do not allow India to harness its water resources efficiently.
In India, rivers have been the lifelines of growth and culture. India is drained by twelve major river systems with a number of smaller rivers and streams. Major river systems in the north are the perennial Himalayan rivers – Ganga, Yamuna, Indus and Brahmaputra. The south has the non-perennial but rain fed Krishna, Godavari, and Cauvery while central India has the Narmada, Mahanadi and Tapti.
The Ganges-Brahmaputra and the Indus systems are the largest as they drain almost half of the country carrying more than 40% of the utilisable surface water from the Himalayan watershed to the ocean. Over 70% of India’s rivers drain into the Bay of Bengal, mostly as part of the Ganges-Brahmaputra system. The Arabian Sea receives 20% of the total drainage from the Indus and other rivers. The remaining 10% drains into interior basins and natural lakes.
Flow in India’s rivers is strongly influenced by monsoon resulting in an annual peak in most rivers. The northern rivers with sources in the Himalayas see an additional peak during the spring snowmelt. Because of this, water levels increase and flooding is a common phenomenon that also leads to yearly calamity in states like Bihar and Assam. During the dry season, the flow diminishes in most large rivers and even disappears entirely in smaller tributaries and streams. Due to low rains, and dry rivers, drought is another common calamity across vast areas, especially the Deccan trap. Hence, some parts of India suffer from flood and some parts from drought.
Apart from the floods and droughts, most Indian rivers are cesspools of waste dumped from various urban and industrial centres. In 1995, the Central Pollution Control Board identified severely polluted stretches on 18 major rivers in India. The pattern of destruction is similar for any river - industrial and domestic pollution, jagged urbanization and encroachment, agricultural fertilizer and pesticide runoffs, erosion and silting, over withdrawal of water, and inconsiderate religious practices. All 44 rivers in Kerala face extinction through deforestation, sand mining, riverbank brick making and pollution.
The rivers are the sources of drinking water for urban and rural areas, raw water for industries, and irrigation. The demand for water is ever increasing leading to over-extraction. This abstraction of water in excess from the river lessens the flow in it. It is very important to maintain the flow as it helps in diluting and carrying the sewage and pollutants away. Irrigation canals and industrial units extract huge volumes of water, and in return, discharge agricultural runoff waste and poisonous effluents. Many rivers suffer from silt deposition in its bed — reducing flow, and disturbing the ecosystem. Deforestation near the source of the rivers, is leading to soil erosion, landslide, floods, silt formation and sedimentation in rivers. In Indian rivers, siltation rate is among the highest in the world. It has been estimated that about 135 thousand million metric tonnes of sediment load and 32 thousand million tonnes of soluble matter enter into ocean through various rivers. Water flowing through Indian rivers is 5 % of the water flowing through all the river of the world but carry 35 % of sediments. To regulate the flow in these rivers and store water and divert water for irrigation, and generate power, a number of large dams and barrages have been built on many rivers. However, these measures have been detrimental to the flow of water resulting in silt deposition. With the storage of water, the natural flow in rivers is obstructed affecting the ecosystems.
Apart from rivers, India is house to some of the most beautiful lakes of the world, some natural, others artificial. They are there in the high Himalayas under the ice sheath, in the virgin northeast, semi-arid deserts of Rajasthan, coastal zones, or in metros, small towns and villages.
In India, lakes serve as source of water for drinking, agriculture, and even industries. It acts as sewage absorbers, flood cushions and recharge zones for groundwater aquifers. It is an ecosystem where a variety of birds and animals breed; pisciculture, and aquaculture thrive leading to a source of income for people. Lake tourism is an immensely profiting sector. In India, there are urban and rural lakes along with natural water bodies which have been categorized under the Ramsar Convention on Wetlands (1971) and are important mostly from ecological sustenance and as a source of livelihood for many people.
Slowly, many of these prized possessions have vanished or are vanishing. Reasons: draining of lake water for real estates in cities and cultivable and factory land in villages; dumping of effluents — both domestic and industrial; agricultural runoff; encroachments, and general neglect. Earlier the farmers would take away the lake silt to their fields to fertilize the soil, but now with the usage of chemical fertilizers, the use of silt has stopped, leading to silt accumulation. Many cities of India like Hyderabad, Bangalore and Ahmedabad have a number of lakes, but there is a virtual seize on their survival.
In many lakes, uncontrolled tourism has resulted in disturbance to the biodiversity of flora and fauna — examples are the high altitude Tsomoriri and Tshangu glacial lakes. The coastal lakes have been seriously affected due to an imbalance in salinity levels. This is attributed to lack of balance between fresh water from the inland catchment of the lake and entry of seawater into the lake at the mouth of the estuary.
Other threats include water hyacinth growth which is common in many lakes resulting in breeding of vectors and consequently causing endemic diseases —Loktak Lake, Dal lake, and Ropar Lake are some examples. Or idols’ immersion in lakes during religious festivals in many cities like Bangalore, Bombay and Bhopal, leading to discharge of dyes and paints.
Water shortages in lakes, which sources of replenishment are seriously impaired due to encroachment and loss of catchments, have resulted in bird sanctuaries and fisheries getting seriously affected.
Regarding groundwater aquifers, in India, the mountainous regions of the north and west do not allow adequate infiltration and thus, groundwater availability is mostly limited to valleys and other low-lying areas. In peninsular India, the underlying geology limits the formation of large continuous aquifers. The overall yield potential in this region is low although some areas may see medium to high potential depending on the local hydro geology. Coastal regions are rich in groundwater owing to the largely alluvial terrain, but the aquifers risk being contaminated by saltwater ingress due to over pumping.
Groundwater development has been rampant across the country. About 80 % of irrigation and 90 % of drinking water comes from groundwater sources. It is contributing more than 85 % of the drinking water requirements of rural areas, about 58 % of irrigation requirements and more than 50 % of the urban and industrial water supplies. There are 20 million users of groundwater in the country. The incessant and mindless withdrawal over the past decades has suddenly triggered off a series of crisis. Foremost among them is the plummeting of the water table. This led to exploring of fossil aquifers that cannot be replenished. Excessive drilling of borewells, along with the use of mechanised pumping has led many parts of the country’s groundwater aquifers to go dry and have been declared as ‘dark zones’. The rate of extraction is alarming – for instance, the Central Ground Water Board has recorded a yearly 2.5-3 m drop in groundwater levels of Ahmedabad’s, urban areas where the rate of exploitation of the city’s aquifers is 123 %. The worst affected are the states of Rajasthan, Gujarat, parts of Andhra Pradesh and western Madhya Pradesh where water was abundantly available 10-15 years ago. The groundwater table in these areas has fallen below 300 m now, and drought has become a yearly phenomenon. Wells are drying at a fast pace – 25% of Rajasthan’s wells run dry every year. In the Indus basin as a whole, groundwater pumping is estimated to exceed recharge by 50 %. In India, the number of shallow tubewells used to draw groundwater was 3000 in 1960, and in 1990, reached 6 million.
Another major problem due to the abstraction of groundwater from the fossil aquifers resulted in chemical reaction of water with the rocks ushering in another contaminated water. The aquifer waters became contaminated with high levels of arsenic and fluoride from the rocky layers. People across many states are affected by diseases due to intake of fluoride or arsenic laden water. Again, excessive abstraction of groundwater especially in coastal areas has resulted in seawater ingression making the available water useless. The coastal metro of Chennai has been dependent on groundwater for decades, and now the table has plummeted to more than 80 to 100 m with water turning saline in many areas of the city.
The state of India’s water systems hangs in balance. It can either revive back to sustained system or plunge downhill. In a nutshell, the biggest threats faced by the aquatic ecosystem in India include over abstraction and river flow regulation, increasing pollution, encroachment and land use, degradation of watersheds, invasion by alien species, limited efforts at conservation and rising sectoral conflicts.
The urgency to conserve the water resources is enormous as the pressures are three fold. Firstly, water is becoming scarce both in terms of quality and quantity leading to a supply side shortage. Secondly, on the demand side, the requirement is increasing by leaps and bounds as India’s population, food demands, industrial requirements increase with development and economic activities lurching ahead. Thirdly, the loss or dwindling of these aquatic ecosystems will ultimately result in dry river and lakebeds, and parched aquifers.
To allay such scenarios, various efforts have been undertaken through the aegis of various government departments both at the centre and the states to conserve, revive, control and manage these aquatic systems. Apart from the government, NGOs and communities themselves are making active efforts to conserve water resources.
This sheet is also available in French : Les ressources en eau de l’Inde