Introduction
Water is an important brick in the life support system (land, water and air). Water constitutes more than two-thirds of the composition in the human body. In almost every religion, there is mythological description of a flood, either at the beginning or towards the end of life, which underscores the significance of water for life. It is due to this very fact that rivers have always been the cradles of civilisation throughout the world. More than 75 per cent of the landmass is under water, under oceans and seas. The freshwater available in lakes and rivers is only 0.3 of the total fresh water available and amounts to less than one half of one per cent of all the water on Earth. Fresh water is renewable only by rainfall, at the rate of 40-50,000 cubic kilometres per year.1
Freshwater resources are under severe and increasing environmental stress. At a global level, two thirds of the withdrawals are used for agriculture and one fourth for industry. By the end of the century, withdrawals for agriculture have increased slightly whereas industrial withdrawals have probably doubled.2 Industrial development and population growth have also added pollutants to the freshwaters as governments have failed to boost their efforts to treat freshwater or prevent pollution.
The world's supply of freshwater is unevenly distributed and frequently unreliable. Water shortages are already acute in many regions, chronically so in East and West Africa. Consumption is outstripping supplies in Northern China. These shortages could reach crisis proportions in the Middle East and North Africa where the water issue is further compounded by political tensions. Globally, pollution has emerged as the severest threat to the quality of freshwater as 95 per cent of urban sewage is discharged untreated into surface waters. Loaded with bacteria and viruses, these waters have become a major threat to human health.
Another major contributor to freshwater pollution is agriculture, which accounts for a large share of pollution from heavy metals and toxic chemicals. These chemicals not only pollute the water but leach sub-surface and deteriorate groundwater bodies and contaminate the soil as well, eventually affecting its natural fertility. Logging operations and agriculture add sediment and organic matter, which adversely affect the habitats of river organisms and can smother coastal fishing grounds hundreds of miles away.
A. World's Freshwaters: An Overview
About half of the world's river basins are shared by two or more countries. In this backdrop, dealing with pollution and contamination of fresh water resources becomes a political as well as an economic and technical challenge. International co-operation in the management of the river basins is not easy, yet it is not impossible too. For example, in the case of River Rhine in Europe, it has produced some measurable environmental benefits.
Water is the most abundant resource on Earth, covering about 71 per cent of the planet's surface. The total volume of water on the Earth's surface is immense - about 1.41 billion cubic kilometres. If it is spread evenly over the Earth's surface, it would form a layer of nearly 3,000 metres. About 97 per cent of this volume is in the world's oceans and inland seas that is too salty for drinking, growing crops, or for industrial uses. Desalinisation of this water is very uneconomic at present. The remaining three per cent is freshwater, but about 87 per cent of this is locked in ice caps or glaciers, in the atmosphere or in the soil, or deep underground.3
Humankind's primary supply of freshwater is from rivers, lakes and reservoirs. About 2,000 cubic km of freshwater is flowing through the world's rivers at any one time; nearly half of this is in South America and another one fourth is in Asia. The actual amount available for use annually is much greater, because waters in rivers is replaced roughly every 18-20 days.4 Over a full year, the total amount of freshwater flowing through rivers is about 41,000 cubic km, including about 28,000 cubic km of surface runoff and about 13,000 cubic km of "stable" underground flow into rivers. Only about three-fourths of the stable underground flow - 9,000 cubic km - is easily accessible and economically usable. An additional 3,000 cubic km of useful capacity is available from man-made lakes and reservoirs.5
The primary source of freshwater is precipitation. Global precipitation totals about 500,000 cubic km per year, but only about one fifth of this amount - 110,000 cubic km - falls on land. About 65 per cent of the continental rainfall evaporates and is thus transported back to the atmosphere. The remaining precipitation either stays on the surface - in rivers, lakes, wetlands, reservoirs - or flows into the ground, where it is stored in groundwater aquifers.
Global precipitation varies considerably. Heavy rainfall is characteristic of Amazon Basin and parts of South and Southeast Asia. Meager rains typify Middle East, North Africa, North-Central Asia and Central Australia.6 Areas of low rainfall also tend to be the areas with unreliable precipitation. Reduced precipitation is a threat in many regions. At least 80 arid and semiarid countries, with about 40 per cent of the world's population, have serious periodic droughts.7
Global warming is likely to lead to increased evaporation from the sea and hence to increased precipitation. Global circulation models generally predict that precipitation will gradually increase by four to 12 per cent, if carbon dioxide levels in the atmosphere double, with potentially greater increase in the higher latitudes.8
Human use of water has increased more than 35 fold over the last three centuries. In recent decades, water use has been increasing at about four to eaght per cent per year, with most of the increase occurring in the developing world. Water use is getting stablised in the industrialised nations and the rate of increase of withdrawals has declined to two to three per cent annually in the 1990s.9 Annual average per capita water use varies widely: 1,692 cubic metres in North and Central America, 726 in Europe, 526 in Asia, 476 in South America and 244 in Africa.10
Globally, 3,240 cubic km of freshwater are withdrawn and used annually. 69 per cent of this is used for agriculture, 23 per cent for industry and only 8 per cent for domestic uses. In Africa, Asia and South America, agriculture is the primary use. Asia uses 86 per cent of its water for irrigation
B. The Hydrological Cycle
The total quantum of water on Earth can be represented by the Hydrological Cycle (Fig. 1) or in simple words the water cycle. The Hydrological Cycle implies that water is in constant motion from place to place and from one state to another.11 Water, as a whole, on the Earth is neither lost nor gained and hence this movement must be cyclic. The cycle can conveniently be taken to start with the condensation of water vapours in the air and its precipitation on the Earth as rain or snow. In the full cycle, water runs over or through the Earth to the ocean from where it evaporats becoming water vapour again, though there are a number of possible short cuts. For example, the water may evaporate from the surface of the ground, or even from the raindrops during their fall, and never reach the sea, or rain may fall directly on the sea and evaporat without benefiting the land areas.
The prime reason of the apparently decreasing availability of freshwater is due to the fact that more and more water is getting polluted. This polluted water is rendered useless for human purposes, especially in developing countries, as there is no mechanism for secondary and tertiary recovery of water from water-based industrial waste, sewage plants and inefficient flood irrigation. In the light of the fact, that major population growth is taking place in the developing countries, sooner than later, these nations shall evolve such methods for greater availability of freshwater, which have already proved very efficient in developed countries. The industrialised nations are supplying increased amount of recovered water to their citizens. For example, in late 1980s the water recovered from wastewater treatment being supplied to the percentage of total population in some nations are as follows: Canada (73), USA (66), Austria (57), Belgium (72), Finland (75), France (52), Germany (80), Italy (60), Luxembourg (91), Netherlands (92), Norway (43), Spain (48), Sweden (95), Switzerland (90), UK (84), Japan (39).12 Obviously, most of the water being used in these countries is recovered water.
The hydrological process involves the sum of precipitation, evaporation, transpiration, infiltration and surface storage, soil water, groundwater, channel and lake-storage, snow and ice conditions. In a nutshell, all the problems related with water, right from quantity to quality, are the results of increased human intervention in this Hydrological Cycle, causing physical, chemical and biological effects. In this backdrop, many of the nations have started to evolve strategies to make this intervention as less disturbing as possible.
C. Fresh Water in India - An Overview
I. The Freshwater Resources of India
The total volume of water received annually in India is estimated to be around 330 million-hectare metres (mhm). Out of this, around 150 mhm enters the soil, which retains about 110 mhm as soil moisture and the remaining 40 mhm reach deeper strata in the form of groundwater. The remaining 180 mhm does not find its way into the soil, and thus constitutes the total annual runoff in our river systems. This water can efficiently be used through traditional methods. In fact all the post-1951 irrigation projects have so far been able to impound a mere 17 per cent of this run-off in their reservoirs, representing less than 10 per cent of the total runoff. The availability of water in the rivers of India is shown in Table 1.
The proper utilisation of fresh water in the country is further compounded by the fact that almost all the fresh water is received in only the four months of monsoon.13
II. Problems Related to Freshwater Resources of India
An overview of the problems associated with fresh water in India is presented here.
· The western model of annexing natural resources, especially water and forets, by the state has played havoc with the life and livelihood of millions of people as till 300 years back water and forests were community resources.
· The modern approach of impounding water in dams and reservoirs has caused numerous problems like, displacement, submergence of land and forests et cetera
· Throughout the country, the groundwater levels are falling sharply. Consequently, all along the coastline the sea wedge has intruded deeply and permanently.14
· Massive deforestation in the hill areas has decreased run-in and increased run-off many fold.
· The extinction of traditional water harvesting systems in desert ecosystems has caused grave problems for the population living therein.
· There is a great divide in the availability of water in urban and rural areas. For example, water availability per head per day in Delhi is 200 litres against a national availability of 25 litres. Even within a city, there is great inequality in different parts, e.g., in the slums and posh colonies, to the industrial areas and to the residential areas. For example, the total sum of water provided to the computer industry in Banglore exceeds the amount of water made available to the city dwellers.
· Practically all the water available to rural areas fall under the category of irrigation. More than 70 per cent of the villages in India have no potable water source.
· In the last 50 years, the population of the country has more than tripled, levels of urbanisation has gone up by about 400-700 per cent and industrialisation has increased many fold – putting enormous pressure on precious water resources, on the one hand, while heavily polluting freshwater and water sources on the other, including pollution of groundwater.
· The construction of more than 4,000 large dams and more than 50,000 medium and small dams in India, for dubious gains, have played havoc with the riverine ecosystems and natural drainage. At a global level, the same thing has happened as 50,000 big dams have been built on the globe in last 50 years, which have perpetuated the global fresh water crisis.15
· According to National Commission on Integrated Water Resource Development Plan, the total water resources of the country are 1953 cubic kms. Of this, the utilisable portion is estimated as about 690 cubic kms. In addition, there is a substantial replenishable groundwater potential in the country, estimated at 432 cubic kms.
· Freshwater has many critical linkages with other aspects of the environment. For example, forests play an important role in absorbing precipitation. Depending upon the location and species, trees in temperate North American forests may intercept 40 per cent or more of the annual precipitation, delaying runoff and greatly reducing the flow of pollutants to streams rivers and lakes. (op. cit. Ref. 5. P. 66). In the past two years, the importance of forests for controlling runoff has been illustrated in areas where acid rain or other factors have damaged trees. In the Black Forest in Germany, which has experienced severe tree damage, rainfall has remained fairly constant but runoff has increased considerably. Studies of a river basin in South Western Australia have found a similar link between deforestation and surface water runoff.16 This aspect has been dealt in more detailed manner, in the next chapter.