Carrying Capacity Study of Teesta Basin in Sikkim - Affected ...

somewhat sub-tropical agro-climates prevailing. The temperature and
rainfall almost follow the altitude intensity of rise and fall and the major
determinant of the types of micro-climates of a place. The rainfall pattern
is also unique in itself, the heavy rainfall occurring in the mid and the
lowers hills while alpine, temperate and lower valleys get less rainfall.
The rainfall in these hills is again influenced by the direction of the wind
and the aspects of the hill slopes. It is generally observed that the
valleys along Teesta river and its tributaries receives good amount of
rainfall whereas the valleys of Rangit river and its tributaries receives
lesser or scarce rainfall one possible reason for less rainfall or some
times no rain in the region may be attributed to the Shadowing effect
exerted by the adjoining Darjeeling hills in this past of the south and west
districts.
Besides the above the monsoon rainfall is controlled also by north-
south oscillations of the monsoon trough and other perturbations in the
monsoon circulation such as the formation of depressions in the Bay of
Bengal and “Breaks” in the monsoon.
As the monsoon depressions bring fresh surges of the monsoon
air, they cause spurts in rainfall over the Himalayas in the longitudinal
belt covered by the field of depressions. During ‘breaks’ in the monsoon,
this part of the Lesser Himalayas (the Eastern Himalayas) gets heavy to
heavy rains which cause occasional floods and landslides in the Teesta
river basin. In such a peculiar situation, if the troughs in the upper
westerlies move eastwards, they interact with the monsoonal circulation
and cause very heavy rain in the mountainous terrain. Generally, the
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CISMHE