8
Recording types
of rain gauges records in a sheet of paper directly the amount
of rainfall over a period of time, generally of very short duration. Types of
recording rain gauges are :
i)
Weighing bucket rain-gauge.
ii)
Tipping bucket rain-gauge.
iii) Float type rain-gauge.
Snow fall and Snow melt
Snowfall is the next important component of precipitation. Snow fall
occurs at high altitude and is seasonal. In India, heavy show falls occur in the
upper reaches of the Himalayan rivers, such as Ganga, Yamuna, Brahmaputra
during December, January and February. The snow melts during summer
season and sustains the perennial river flow in the major rivers.
Snow fall can be measured either for individual snow fall or for seasonal snow
fall. Snow gauges are used for measurement of both types of snow fall by
measuring the depth of snow, actually collected on a level platform or by
measuring the depth of the snow, caught in a shield gauge vessel, after leveling
the accumulated snow. Unlike rainfall, the amount of snow fall may vary within a
very short distance. One of the methods adopted is snow survey which is
carried out in a pre-determined snow courses in a particular season or weekly
or daily basis. The measurement of snowfall is necessary for anticipating the
stream flow during dry seasons. There are few empirial formulae for
determining the snow melt, of which mention may be made of U.S. Army Corps
of engineer's equation. According to this equation : (Source : S.K. Garg, 1988)
(a)
For open sites :
M
24
= 0.03 (9 Tm + 40); and
M
24
= 0.02 (Tmax + 25)
Where
M
24
= daily (24 hrs) spring time snow melt
Tm = Mean daily temperature in
0
C
Tmax = Maximum daily temperature
0
C
(b)
For forested sites :
M
24
= 0.025 (9 Tm); and
= 0.02 (9 Tmax - 50)
