Over the last fifty years, the majority of water wastage and water pollution has been from agricultural irrigation practices. Since the Green Revolution, the area of the world which is irrigated has tripled – from 90 million hectares in 1950 to over 270 million hectares in 2000. On a global scale, over 85% of water is utilised to irrigate crops.
There is more than enough water for everyone. The problem is one of distribution, poor management and wastage. Modern society has lost its reverence for water's place in the cycle of life. This loss of reverence has allowed human beings to abuse it. Only by redefining our relationship to water and recognising its essential place in nature, can we begin to solve the problems of water mismanagement.
The technical problems of water management have for the most part been solved. Water wastage and pollution is primarily a political problem. Governmental policies and decisions favour industry and economic growth. Large-scale hydrological projects, displacing millions of people and destroying the environment, are favoured over small-scale projects.
Natural hydrological systems have been radically altered to provide water for the production of food for a continually increasing urban population. The majority of the world’s productive terrain depends upon irrigation. Artificial irrigation has become necessary component of food production.
The number of people, their levels of consumption and the technologies that they use determines how rapidly and to what extent resources are being utilised. The greater the number of human beings, the greater the demand on water supplies. In many parts of the world, people are withdrawing water from rivers, lakes, and underground sources faster than they can be replenished.
With the increase in the human population, water demand for consumption also increases. The world has a finite supply of fresh water and there are too many human beings, placing a great strain on water supplies. Global population projections suggest that the world population of over 6 billion people in 2000 will increase by 20% to over 7 billion by 2015, and to 7.8 billion by 2025 – a 30% rise. Enormous strains will be placed on existing services, and substantial increases in the provision of water and sanitation will be required to meet the needs of an ever-growing population. As populations increase and demands for water and other services expand, pollution levels will rise, which will in turn reduce the availability of water for human consumption.
Most irrigation practices are extremely unsustainable. Less than half of the water applied actually benefits crops; much of it is lost through surface runoff.
The perceived inexpensiveness of fresh water has led to a great deal of wastage. Governmental subsidies on water and electricity supply for farmers in many nations – for example, the Punjab – has resulted in the wasteful application of water for irrigation for many years.
Water resources are poorly managed or abused. Water is constantly wasted and polluted through the input of inefficient irrigation practices, large-scale government schemes, industry and domestic use. The world’s under-privileged are particularly subject to water shortages and pollution. In addition to the obvious causes such as over-use and pollution, there are many indirect causes of water shortage, such as salinity, soil erosion, climate change and flooding. Private ownership is also a factor – driving up costs and limiting water supply.
Most rivers in developing countries are polluted with untreated sewage and many people are obliged to drink water from them. As a consequence, million of people, mostly children, develop diarrhoeal diseases and die each year. In addition the sewage degrades the environment and destroys fisheries.
Nitrates and phosphates from fertilisers contaminate lakes, rivers and groundwater. In hot conditions toxic algae can grow in water enriched with these fertilisers, making the water unsafe to drink. Other contaminants include cadmium, mercury, Dioxins and PCB’s.
Over-irrigation of shallow rooted crops can bring salt to the surface and rain may wash it into rivers. The salt destroys productive farmland, wetlands and other habitats.
The single, most influential factor related to the sustainable provision of basic water and sanitation services, is that of poverty. The lack of availability of basic services is a primary measure of poverty, and poverty is the primary obstacle in the provision of basic services. Poverty affects basic water supply and sanitation in a number of ways; ultimately becoming all-encompassing with the result that that it overwhelms the application of even the very best practice incorporating all the lessons learned. It is therefore important to understand the full significance of poverty.
The provision of basic services is a ‘people’ affair. At this stage in the 21st Century, there is little that cannot be achieved technically. Providing services requires the interaction of many people in all spheres of life. Such interaction is governed by politics – the politics of the allocation of resources, establishment of priorities, interaction between institutions and engagement of those most directly affected.
We need dams and the many benefits that their reservoirs offer all over the world, by their storing of water in times of surplus, and dispensing it in times of short supply. Dams prevent or mitigate devastating floods and catastrophic droughts. They adjust natural runoff with its seasonal variations and climatic irregularities, to meet the pattern of demand for irrigated agriculture, power generation, domestic and industrial supply, and navigation. They provide recreation, attract tourism, promote aquaculture and fisheries, and can enhance environmental conditions. Consequently, dams and reservoirs have become an integral part of our engineered infrastructure and of our fabricated basis of survival.
More dams will be required in the future for adequate management of the world's limited, unevenly distributed, and in many places acutely scarce water resources. However, we are also increasingly recognising an urgent requirement to protect and conserve our natural environment as the endangered basis of all living things. Increasing numbers of dams have had a devastating impact on the environment. From 1880 to 1994, the salmon harvest from the Columbia River in the USA dropped from 19,500 tons to a total of 401 salmon. Approximately 99% of the salmon killed in rivers is a direct result of dams and general human alteration. In the interests of financial gain, dams in Laos that cater for Thailand’s growing electricity demand have displaced people and have caused enormous environmental damage.
In addition, there is a social side to the comprehensive conception of environment – the people, their land and settlements, economy and traditions. The impact of dams and reservoirs on this environment is inevitable and undeniable; land is flooded, people re-settle, the continuity of aquatic life along a river is interrupted, and its runoff modified and often reduced by diversions.
Great care must be taken to protect the environment from all avoidable harm or interference. We must cooperate conscientiously with nature's inherent fragility, as well as its dynamism, without ever overtaxing its powers of regeneration and its ability to adapt to a new but ecologically equivalent equilibrium.
One of the main problems with dams is their size. Environmental destruction and social disruption can be minimised by reducing the size of dams. Several small dams situated in river tributaries are preferable to one large dam blocking a major river.
The World Bank and IMF continue to finance the construction of ecologically unsound, large-scale dam projects. They focus on the financial aspect too much, and on giving loans for large-scale projects, whilst neglecting environmental and sustainable aspects, and desperately needed small-scale village projects.
Positive and negative aspects of dams