Physical Resources / 95involves arduous hours of walking and carrying, mainly by women and children, and where debilitating
water-borne diseases are common.
The resource is renewable, but distributed unevenly, and its efficient management requires an elaborate
infrastructure of reservoirs, treatment plant, pipelines, and sewerage, coordinated within an overall
strategy by an authority with the power to prevent abuses. For people in those regions, improvements
in living standards depend crucially on the establishment of such strategies for water management,
and once living standards begin to rise it is inevitable that the demand for water will increase
substantially. As rising demand encounters limits in the supply available, conflicts may ensue, as
they have already between Israel and Jordan over abstraction from the river Jordan. This is one of the
most formidable challenges facing us. It is encouraging to note, however, that throughout history,
competition between nations for scarce water resources has almost invariably been settled peacefully.
23. Eutrophication and the life cycle of lakes
In the late 1960s there was widespread popular concern over the pollution of rivers, lakes, and
ground water by nitrate from sewage, farm effluents, but most of all by leaching from farmed land.
It was feared that high nitrate levels in water might lead to health problems (principally
methaemoglobinaemia, or ‘blue-baby’ syndrome) in infants less than 6 months old.
Methaemoglobinaemia is very rare, but between 1945 and 1960 about 2000 cases were reported in
the world as a whole, causing the deaths of 41 infants in the United States and 80 in Europe. The fear
was not unreasonable. Today, when nitrate levels in water exceed a permitted maximum parents are
advised to use bottled water for mixing infant foods and drinks. There were also fears that nitrates
might form nitrous acid (HNO
2
) in the body and react with amides (derived from ammonia by the
substitution of an organic acid group for one (primary amide), two (secondary), or all three (tertiary)
of its hydrogen atoms) or amines (also formed from ammonia, when one or more of its hydrogen
atoms are replaced by a hydrocarbon group). Amines and amides are common and the product of the
reaction would be N-nitrosamines and N-nitrosamides, which are known to cause cancer in
experimental animals. In fact, there is no evidence that nitrate causes cancer in humans (ROYAL
COMMISSION ON ENVIRONMENTAL POLLUTION, 1979, pp. 87–92). Indeed, dietary nitrates
have no adverse effect whatever on human health. Although nitrites remain impli-cated in infant
methaemoglobinaemia, it is now known that they are formed in feeding bottles by bacterial action on
nitrates contained in the food in the bottle. Nitrates in the water are not involved (L’HIRONDEL,
1999). In parallel with this there was also concern that the nitrate loading of waters would cause their
widespread over-enrichment (eutrophication).
Nitrogen is an essential plant nutrient and plants take it up readily in the form of nitrate (NO
3
) ions,
because all nitrates are highly soluble in water. Grass is present throughout the year, so its roots are
always absorbing nitrate. Arable fields, on the other hand, are bare for part of the year, often at times
of heavy rainfall. With no plant roots to intercept the nitrate, it is washed (leached) from the soil.
Nitrate pollution was perceived as a problem in the 1960s because of agricultural changes that had
taken place in Britain in the preceding years.
In 1938, the area of land growing arable crops in Great Britain was smaller than it had been at any
time since the middle of the last century. The depression of the 1930s had so reduced the profitability
of farming that large areas were almost abandoned, and as the Second World War began, with the
likelihood of a sea blockade to restrict the import of food, the British people faced real hunger.
Drastic steps were taken to increase agricultural output and after the war these continued as farming
modernized. A major consequence of these changes was a substantial reduction in the area growing