1 There was volcanic activity on the earth several million years ago. Hydrogen and oxygen escaped from the volcanic activity. The two then joined to give rise to water.
2 Comets had been entering the earth's atmosphere over several million years. The ice carried by the comets evaporated and became water vapour. This water vapour had then condensed to fall as rains to the surface.
The two activities go on in the other planets as well. Yet, there are no water bodies in these planets. Why? It is because the atmosphere that envelopes the earth is not found in these planets. The earth's atmosphere captures the water vapour. The temperature regime of the atmosphere helps to keep most of the water vapour in the liquid form. Hence, there is opportunity for the development of water on the surface of the earth. It is primarily for this reason, our planet earth is known as the ' water planet'.
Water is the earth's foremost problem. Of the earth's water, 99 per cent is not available for direct use by humans. Salinity and the form in which it is available and location, (glaciers, ice caps) are the primary reasons for such a state of affairs. For 1.0 per cent of the world's water, the entire humanity is in competition. Table 8.1 gives the relative share of water by the sources.
More than 97 per cent of the water on the earth is salt water. This is not directly used by the humankind. The remaining 3 per cent is freshwater. The quantity of water directly available for human consumption is 0.014 per cent to the total. The rest is found in some seas, lakes, rivers, glaciers and icecaps as well as underground.
Surface water is about 230,250 ckm, of which freshwater lakes hold 125,000 ckm, saline lakes and backwaters 104,000 ckm and rivers and fountains 1,250 ckm. Groundwater is about 8.41 million ckm, of which soil humidity is 67,000 ckm, sub-groundwater and deep water 417,000 ckm. While the groundwater accounts for less than one per cent of the total water (in fact, 0.625 per cent), the surface water accounts for a negligible proportion only (0.0171 per cent). Ice and glaciers account for 2.15 per cent of the total waters (or 29.18 million ckm) while atmosphere for 0.001 per cent (13,000 ckm).
How does the quality of freshwater decline? What are the causes of such declines? Let us look at these questions.
When the humans began to settle down permanently in some areas, the waters in those areas declined in quality through their economic activity. Increasing population, agriculture, industrial activities and urban needs make a large demand on the freshwater sources. With the changing climate, there is a general decline in rainfall as well. Besides these, bio-degradation, salination through irrigation and such other events cause declines in quality. Nowadays, the wastes or effluents disposed from the industries such as the solid wastes, heavy metals, radioactive materials, nitrates and minute carbon pollutants create problems in water quality. Acidification of the waters of the lakes and streams and declines in oxygen content in the coastal waters are expected to create major problems in water quality in the near future.
We have now seen how the water quality declines due to various reasons. Our life is intertwined with the protection of the water resources. A quality assessment of the freshwaters made by the World Watch Institute has indicated to the declining quality worldwide. This assessment has also indicated to improving quality of the freshwater in some of the industrialised countries. It is pointed out that the quality of freshwater and the protection to it are still not adequate worldwide. The controls remain weaknesses. Just as quality, quantity has also become a worldwide problem. Increasing population further compounds this problem. Water scarcity is likely to become a Crisis of the Future
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