Arid Land Development and Combating Desertification in Pakistan - Combating Desertification in Asia, Africa and the Middle East - page 229

Table 12.8 Area affected by wind erosion (000 ha)

Province

Tot al
Pakistan

Degree of erosion Punjab Sindh NWFP/FATA Balochistan Northern area

Slight 2251.4 295.0 13.1 36.0 - 2595.5

Moderate 279.1 70.2 3.8 143.6 - 496.7

Severe to very
severe

1274.0 1686.8 19.6 100.9 - 3081.3

Total 3804.5 2052.0 36.5 280.5 - 6173.5

Source: Reconnaissance Soil Survey Reports from 1965 to 1988

estimates the Indus is adding 500,000 tons of sediment to the Tarbela Reservoir ev-
ery day, reducing the life of the dam by 22 % and the capacity of reservoir by 16 %.

Water erosion: The soils in the Indus basin are recent and undeveloped. The
surrounding mountains have some of the world's steepest and largest slopes. Intense
summer rainfalls along with melting of snow in high mountains contribute to the
soil erosion hazards. Land use practices, vegetation cover, soil type and structures
are other major factors related to soil and water erosion.
In the northern mountainous areas with steep slopes, the water erosion is low in
the areas with permanently closed canopy forests, while the erosion is greater in
areas with arable crops on steep slopes. About 11 million ha are affected by water
erosion.
Sedimentation of canal irrigation system decreases water and land use efficiency.
Some 40 million tons of soils are brought into the Indus basin each year. It shortens
the life span of major reservoirs and reduces their efficiency. The upstream riverside
infrastructure is destroyed and top soil is washed away declining productivity of the
area. In downstream, the sediment reduces the efficiency of hydropower generation
and irrigation systems.

Wind erosion: Land degradation by wind erosion is quite common in the sandy
deserts of Thal, Cholistan, Tharparkar and sandy areas along Mekran Coast. Erosion
is significant in areas around habitations and watering points trampled by livestock.
Here the major degrading factor is the overexploitation of rangelands for fuel-wood
cutting and livestock grazing. The global impact of wind erosion is prevalent in areas
where sand dunes are leveled for irrigated cropping. These areas have assumed the
form of 0.5-4 m high moving sand dunes, posing danger for cultivated land and
infrastructure. Some 3-5 million ha are affected by wind erosion (Table 12.8 ). The
amount of soil removed by wind is about 28 % of total soil loss. High velocity
wind storms cause severe movement of sand dunes depositing thick layer of sand
on roads, railway tracks, croplands and threaten village inhabitants.

Deforestation: There is only 5.2 % area under forests, which is too low to meet
environmental as well as socio-economic needs of the country (Table 12.5 ). Due
to deforestation, forest cover is shrinking by 3.1 % annually and woody biomass
by 5 % annually. Natural vegetation reduces sedimentation in water reservoirs and
stabilizes sand dunes. The continuous destruction of forests is causing a substantial