Environmental Engineering Reference
In-Depth Information
1
The dry lands are characterized by a moisture deficit caused by relatively low
precipitation and high inputs of solar energy which lead to high levels of evaporation.
Natural levels of vegetation are controlled by moisture availability. There is a strong
seasonal cycle of growth associated with the wet season and generally a low density of
vegetation. Where water is available crop growth can be good, but it requires the
supply of adequate volumes of good-quality water.
2
Supplying water to dry lands can cause a wide range of problems. The most frequent
method is dam construction, but the resulting lake has many harmful effects and
incorrect use of the water can produce major problems of salinization. Under these
conditions the land can become sterile, as in parts of the Indus valley.
3
Soil erosion can be another major problem in dryland areas, where bare ground is easily
eroded by heavy rainstorms. It is made worse by deep ploughing and attempts at
intensive commercial agriculture.
4
Desertification has been threatening the drier margins of the dryland areas, though a
strict definition of the problem is difficult. As a result of overgrazing, coupled with
fluctuating rainfall levels, the vegetation of the drier margins may experience stress
and degrade in quality. This does not mean that the desert is advancing; it is a
reflection of recent pressures on the vegetation.
