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Geographical
Description of Basin
Physical:
The Narmada basin extends over an area of
98796 Sq.km. and lies between east longitudes 72o
32' to 81o
45' and
north latitudes 21o
20' to 23o
45'lying
on the northern extremity of the Deccan Plateau, the basin covers large
areas in the states of M.P., Gujarat and a comparatively smaller areas
in Maharashtra.
The Narmada basin is bounded on the north
by the Vindhyas, on the east by the Maikala range, on the south by the
Satpuras and on the west by the Arabian sea. The basin has an elongated
shape with a maximum length of 953 Km. from east to west and a maximum
width of 234 Km. from the north south. The basin has five well defined
physiographic zones. They are (i) the Upper hilly areas covering the
distt.
of Shahdol, Mandla, Durg, Balaghat and Seoni (ii) the Upper Plains covering
the districts of Jabalpur, Narsimhapur, Sagar, Damoh, Chhindwara,
Hoshangabad, Betul, Raisen and Sehore (iii) the middle plains covering the districts
of East Nimar, part of west Nimar, Dewas, Indore and Dhar (iv) the lower
hilly areas covering part of the west Nimar, Jhabua, Dhulia and parts
of Baroda and (v) the lower covering mainly the districts of Broach and
part of Baroda. The hilly regions are well forested. The upper, middle
and lower plains are broad and fertile areas well suited for cultivation.
The Narmada basin consists mainly of black soils. The costal plains in
Gujarat are composed of Alluvial clays with a layer of black soils on
the surface.
Climate:
The tropic of Cancer crosses the Narmada
Basin in the Upper plains area and a major part of the basin lies just
below this line. The climate of the basin is humid and tropical, although
at places extremes of heat and cold are often encountered. In the year,
four distinct seasons occur in the basin. They are (i) Cold weather (ii)
Hot weather (iii) South west monsoon and (iv) Post monsoon.
In the cold weather, the mean annual temperature
varies from 17o 5 C
to 20o C and in the
hot weather from 30oC
to 32o 5C. In the South
west monsoon the temperature ranges from 27o
5 C to 30o C. In the
post monsoon season, the temperatures between 25 C to 27.5 C are experienced.
Rainfall:
According to the Indian Meteorological Deptt.,
there were ten rain gauges in 1867 in the entire Narmada basin. The number
rose to 21 rain gauges in the year 1891, the year from which published
rainfall data are available. Thereafter, there has been a study growth
of the rain gauge network in the basin. In 1965, the number of reporting
rain gauges above Garudeshwar was 69.
Nearly 90% of this rainfall is received during
the five monsoon months from June to October about 60% is received in
the two months of July & August.
The rainfall is heavy in the upper hilly
and upper plains areas of the basin. It gradually decreases towards the
lower plains and the lower hilly areas and again increases towards the
cost and south western portions of the basin.
In the upper hilly areas, the annual rainfall
is, in general, more than 1400 mm (55") but it goes up to 1650 mm
(65") in some parts. In the upper plains from near Jabalpur to near
Punasa dam site, the annual rainfall decreases from 1400 mm (55")
to less than 1000 mm. (40") with the high rainfall zone around Pachmarhi
where the annual rainfall exceeds 1800 mm (70"). In the lower plains
the annual rainfall decreases rapidly from 1000 mm. (40") at the
eastern and to less than 650 mm. (25") around Barwani, and this area
represents the most arid part of the Narmada Basin in the lower hill areas,
the annual rainfall again increases to a little over 750 mm. (30")
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