Although the oceans cover 75% of the earth’s surface, the saltwater does not provide us with ready consumption. Fresh water accounts for only 3% of all the water in the world. Of this paltry percentage, 69% of the fresh water is locked up in polar ice and glaciers, and 30% in underground aquifers, which are difficult to extract. The remaining fresh water flows in rivers and lakes. This is the water ready for us to consume but also easy for us to pollute.
The world’s fresh water supply is approaching crisis level as seen in the drying wells, rivers and lakes in many places. The water consumed is not lost for it will eventually flow back to the sea and underground. The real problem is the pace of recycling falling behind human consumption due to population growth and rapid industrialization. Recycling consists of two aspects: natural and artificial, the former being overwhelmingly more important than the latter.
The human race has depended on natural recycling of fresh water since day one through precipitation in the form of rain or snow. Where does precipitation come from? It mainly comes from the sea as the sun evaporates some of the seawater to form clouds everyday. The sun’s heat also generates air currents (or winds) that carry the clouds inland and deposit them as rain or snow. By now you probably appreciate the vast ocean surface to enable sufficient clouds to form. You will also appreciate that water fulfills the precipitation requirement so easily due to its relatively narrow range between boiling and freezing. Of course, all these will not be possible without the sun acting as the engine of natural recycling for no cost at all.
In recent years, we are losing the dependability of this natural recycling. Global warming has increasingly disrupted the existing pattern of precipitation, resulting in cases of extreme drought and flood. This compounds the problem of limited fresh water supply. The consequences will worsen unless we find a way to reduce the amounts of CO2 and other greenhouse gases floating in the atmosphere.
As for artificial recycling, it is done in three ways: desalination of seawater, redistribution of fresh water from wet to dry lands, and change in lifestyle.
Desalination is operated in some countries such as Saudi Arabia, Singapore and Hong Kong. It requires access to the sea, and the ability to afford a desalination plant. For poor countries with a dry hinterland, desalination is out of the question.
At present, China is building two pipelines to transfer water from the wet south to the dry north. The US is considering a pipeline to carry the water from the Mississippi to the dry southwest region. This requires tremendous energy to pump the water. If the energy comes from burning fossil fuels, it will add to global warming that further disrupts the natural recycling process.
The third artificial method is cutting wastes of fresh water and adopting smart ways for collecting precipitation. As the price of fresh water rises, it will force people to think about how to save and recycle fresh water. In most developed countries, we have already seen a movement in this direction such as: water-saving toilets, automatic faucets in public washrooms, and regulations to limit the watering of grass lawns. In many new buildings, we also see smart designs for collecting rain and recycling fresh water.
Whatever we do artificially to recycle, the result is only marginal compared with the natural recycling process powered by the sun that we have taken for granted all these years. Now is the time to really think about minimizing the disruption of this natural process by reducing the emissions of greenhouse gases into the air.