school energy&environment

Water waste

The gap between water supplies and water demand is increasing in many areas of the world: in those areas where water scarcity is already occurring, increasing drought will be the major constraint to agricultural growth and development. Climate changes will cause, above all, a decrease in annual water availability in many areas of the world. In Europe, especially in southern and central European areas, water availability will decrease more and more due to the constant decline of summer rainfall and high water demand for cultivations. Consider that the amount of water sufficient to irrigate one hectare of rice crop would also cover the needs of 100 nomads with 450 head of cattle over three years, or 100 urban families over a two-year period. Moreover, in southern countries of the world, water used for irrigation represents up to 91% of general water consumption (in comparison to a 39% share in high per capita income countries), but agricultural production is equivalent to a third of production in industrialized countries as half of the water destined for irrigation evaporates due to high temperatures or gets lost due to leaks in the water supply distribution networks.
To solve the problem of water waste it’s necessary to introduce more modern technologies as drip irrigation and renew distribution networks, but often serious financial and political problems limit these options. Men draw to irrigate much more water than the amount which the planet is able to provide: withdrawal for irrigation use, in fact, in many areas exceeds the water capacity of water flows, rainfalls and regeneration of nature reserves. Due to this imbalance, whenever delays in the arrival of rainfall occur, in comparison to natural cycles, events as famines burst out, as the one hitting some regions in Sub-Saharan Africa some years ago or, even if catastrophic events don’t take place, water reserves are slowly consumed until depletion: it is estimated that in Jordan within 35 years groundwater reserves will be completely depleted and that their renewal will take thousands of years. In the United States, since as early as 1960, the Colorado river doesn’t reach the sea anymore, save when exceptional rainfall occurs, because large quantities of water are drawn from the river before it reaches the Pacific Ocean.
In the African Sahel region, both due to extended drought and decreased inflow of rivers whose waters have been diverted for irrigation uses, the Chad lake has been reducing by 75% in the last 30 years. But the prime example is the drying up of the Aral lake (which was the world’s 4th largest lake) in the heart of Central Asian deserts. Some Asian republics of the former Soviet Union diverted the flow of two rivers that fed the lake to cultivate rice and cotton, two crops requiring large amounts of water, especially when grown in very dry lands.
This choice has reduced the surface of the Aral Lake by 70%; causing further salt concentration increases in its waters – which in the past were salty but very rich in fish – worsened by the presence of pollutants and pesticides, which have been carried for years into the lake by rivers or drained from cotton fields, and are now concentrated at the highest levels. Pollution is generating, besides the destruction of the lacustrine ecosystem, also serious health problems for local populations: anemia, infant mortality, rheumatoid arthritis, allergic reactions.