Lingza - Ministry of Power

39
Preliminary Feasibility Report
Lingza HE Project (3 x 40 MW)
also supported by the narrow width of the catchment for which the effect of any system
lasts for a shorter duration. No storm of longer duration than 3 day is reported. Majority
of the storms have been reported in July & August. It has also been concluded that rain
storms over this catchment occur in association with any of the following synoptic
situations:
(i) Break monsoon conditions i.e. shifting of the axis of trough close to the
foothills of the Himalayas.
(ii) Eastern end of monsoon trough lying north of Latitude 24 0 N.
(iii)Movement of trough in west lies across the eastern Himalayas ; and
(iv) Low pressure system lying over or to the west of the catchment.
Many of the rainstorms studied by the authors were seen to occur due to either of the first
two synoptic situations in July & August. A combination of first three synoptic situations
is also a common feature over the area, giving rise to heavy precipitation.
5.2.4.1 Rain Gauge Network
As per the paper of Sh. B.Biswas and C.V.V Bhadram, the network density of rain
gauges in the basin works out to be one raingauge per 300 Sq.km of the basin area. The
data used by them is of 42 raingauge stations working under Indian Meteorology
Department (IMD) and Central Water Commision (CWC), 24 of which are equipped with
self recording raingauges. The rainfall data availability status of the raingauge stations in
the catchment upto Teesta-V H.E project, with NHPC, is shown in Table 5.3.
Table 5.3
Data Availability Status Of Raingauge Stations Upto Teesta-V
S.No Name of station Period of data availability
1. Lachung Jul 57 to Dec 58, 1960 to 1964,1970 to 1981,
Feb 91 to Dec 97
2. Chunthang Apr 57 to Dec 58, 1960 to 1964,1970 to Jul 85,
1991 to 1997