The history of human civilisation reveals that water supply and civilisation are almost synonymous. Water resources are sources of water that are potentially useful and essential for existence of life. Several uses of water include agricultural, industrial, household, recreational and environmental activities. The majority of human uses require fresh water which is scarce.
About 97% of the water on the earth surface is in the ocean and only 3% is fresh water. Slightly over two-thirds of this is frozen in glaciers and polar ice caps. The remaining 1per cent unfrozen fresh water is found mainly as groundwater, with only a small fraction present above ground which is suitable for human consumption.
The seas and oceans are the products of gigantic acid-base titrations during the early stages of formation of earth. Sea water contains about 2,000 times more dissolved salts than fresh water. The constant pH of sea water (8.1±0.2) all over the globe is due to ion exchange equilibrium of dissolved cations with silicate phase in the marine sediment. It is estimated that 8% of worldwide water use is for domestic purposes.
These include drinking water, bathing, cooking, toilet flushing, cleaning, laundry and gardening. Basic domestic water requirements are at around 50 litres per person per day, excluding water for gardens. Drinking water is water that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called as potable water.
In most developed countries, the water supplied to domestic, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation.
It is estimated that 70% of worldwide water is used for irrigation, with 15%-35% of irrigation withdrawals being unsustainable. It takes around 2,000-3,000 litres of water to produce enough food to satisfy one person's daily dietary need. This is a considerable amount, when compared to that required for drinking, which is between two and five litres.
Major industrial users of water include hydroelectric dams, thermoelectric power plants, which use water for cooling, ore and oil refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent. Water withdrawal can be very high for certain industries, but consumption is generally much lower than that of agriculture. Overexploitation of water use will cause the depletion of water resource from both surface and underground water.
The United Nations designated March 22 as the World Water Day in 1992 at the Conference on Environment and Development in Rio de Janeiro. This year's theme, 'Water and Climate Change', explores how water and climate change are inextricably linked. Water plays a pivotal role in how the world mitigates and adapts with the effects of climate change. Water is the primary medium through which we will feel the effects of climate change.
Climate change intensifies this cycle because as air temperatures increase, more water evaporates into the air. Warmer air can hold more water vapour, which can lead to more intense rainstorms, causing major problems like extreme flooding in coastal communities around the world. According to the World Health Organisation, increasing temperatures on the planet and more variable rainfalls are expected to reduce crop yields in many tropical developing regions, where food security is already a problem.
It is estimated that by 2040, one in four of the world’s children under 18 – some 600 million in all – will be living in areas of extremely high water stress. One of the most effective ways to protect children in the face of climate change is to safeguard their access to safe water and sanitation. The World Water Day has seen an increase in the quantity and quality of education initiatives within schools and universities, to raise awareness of the importance of conserving and managing water resources.
(Dr Senapati is Dean Science, Biju Patnaik University of Technology)