Climate variability, climate changes and their impact on water cycles

Water availability in Pakistan particularly depends upon both summer and winter rainfall in plains and snowfall over the mountains. Climatically being located in subtropical region, the major amount of rainfall is in monsoon season, which extends from July, to September. Incidentally the deficient or surplus rainfall years are dependent upon intensity of Monsoon current. The same Monsoon current is also responsible for rainfall over the catchment area of eastern rivers i.e. Sutlej, Ravi, Chenab. These catchments are located across the border of eastern rivers. Westerly wave component is another aspect, responsible for rainfall in Jhelum and Indus River though some times Monsoon depressions penetrate up to Jhelum and give heavy rainfall along the route over the Eastern rivers causing the net surplus water availability. The rainfall pattern determines the agriculture output and the crops to be sown along with the area determination. This is particularly dictated by the different regimes of the Monsoon rainfall to mitigate both the surplus and deficient water availability, comprehensive study of statistical data indicates future reservoir/dam location, its construction, and a shift in crops pattern and water utility in commensurate with Climatological dictates in this region of south Asia. (Author)