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Climate change forces us to recognise new normals PDF Print E-mail
Written by John Olszewski   
Friday, 08 May 2009 11:08
China’s Yellow River and the Australian Murray-Darling cannot be relied upon to flow into the sea: the estuaries have to be dredged. The water flow, from considerable catchment areas, is depleted.
For the past 2 years, World Water Day on 25 March was hardly noticed by us here in Namibia. Two consecutive rainfall seasons providing astonishing results have largely overshadowed our usual concern about water.
The dismal 2006/2007 season had been largely forgotten, so why should there be concern? Quite recently, though, elsewhere in the world a different situation arose. Perhaps for as much as a generation, there have been distressing signs concerning the general subject of water from many parts of the world.
Some 60 years ago, the landmark work of Hendrik van Loon noted the importance of water during the formative evolution of planet Earth. Ages and ages later, as the planet was achieving a form and geography that we can recognize today, the planet’s hydrology was in place.
But through misuse in man’s more recent history, the hydrological cycle, the natural mechanism by which water is deposited on land and returns to the sea by rivers, is failing in many important aspects.
Too much water had been used, too much vegetation destroyed and the natural pattern was disrupted. Rainfall was affected.
The availability of underground water, seemingly an inexhaustible source, was proved far from limitless. The term “fossil water”, to describe its origins, became a term of practical proportion.  Although the hydrological cycle does return water to the water table, the constant depletion of the source far exceeds the moderate input.
Further, because modern man used river water for such purposes as irrigation, this sector of the hydrological cycle developed a puncture.
Today, the situation is such that the inland Aral Sea is some 90% dry. China’s Yellow River and the Australian Murray-Darling cannot be relied upon to flow into the sea: the estuaries have to be dredged. The water flow, from considerable catchment areas, is depleted.
Across the last few centuries, the population explosion and survival rates have demanded food supplies be multiplied and diversified. The agricultural demand to meet this taps any and every available water source.
In the December edition of the magazine Optima, Fred Pearce notes that while compared to a mere generation ago, the available food supply has doubled; the water requirement for this food supply has trebled. In the same article, this long-experienced author notes at some length the water requirements for a broad range of staple crops. The demand figure takes the imagination to the extremes of reality.
Yet food shortages persist. So too, do rainfall shortages, just as much as river and underground water sources fail.
The fact of the matter is that when climate change is considered, the risk of rainfall variability, drought occurrence or just depletion of rainfall values all has to be taken seriously.
That Namibia has, in the past dozen years, seen most of these years provide adequate rain in amount, time and area distribution is fortunate, but at the same time, highlighting an experience which is at variance with world-wide occurrences.
By world standards, the 500mm isohyet divides crop from pastoral agricultural potential. Precious little of the country’s area lies on the crop side of this divide. Our established crop areas produce a small volume of cereal but their overall contribution to our food needs is insignificant.
And suppose we have another dry year, like 2007?
Suppose there are a couple more soaking months like both this year and last year around the corner of the next 3 or 4 seasons? Would the available cropland still have seasonal value?
Despite the flooded areas, despite the grassland condition, the precariousness of our water availability requires us to adjust to a new normal. The averages of the past, as reflected in our rainfall statistics of around one hundred years, no longer apply and we are slowly realising, a new graph is being drawn. Pro-active management and further development of our water resources are the only way to approach this uncertainty.
 
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