Geoscience Reference
In-Depth Information
11.2 The Study Area and Climate
The Orissa state lies on the east coast of India, adjacent to the north Bay of
Bengal and close to the south of the normal position of monsoon trough with
17 o 47-22 o 33 N latitude and 81 o 31-87 o 30 E longitude (Fig. 11.1). The
geographical area of Orissa is 1,55,707 km 2 (cultivated area 62,000 km 2 ;
forest area 58,130 km 2 ). The state has a coastline of 384 km. The long-term
average annual rainfall is about 1482 mm, and the mean air temperature
ranges from a minimum of 12 °C to a maximum of 39 °C. The area is featured
by the presence of mountains, hills, hillocks, rivers and rivulets. The
predominant physiographic zones are: the coastal zone having undivided
districts (Balasore, Cuttack, Puri, Ganjam), the eastern ghat zone (Koraput,
Phulbani, Kalahandi), the central table land (Bolangir, Dhenkanal, Sambalpur),
and the northern plateau (Keonjhar, Mayurbhanj, Sundargarh). Overall slopes
of the area are from northern and northeast direction to west and southwest,
and from southern and southwest direction to east and then to the coastal
plains. The river system and their tributaries of the state carry an annual
surface runoff of 132 ×10 9 m 3 (95 ×10 9 m 3 from Orissa) (Lenka, 2001). The
Mahanadi is the largest river of the area, which drains 42% geographical area
with a length of 494 km in Orissa. The Mahanadi River branches off into
several streams at the Naraj gauging station, and carries an annual runoff of
66.88 ×10 9 m 3 . The Brahmani River drains 14% geographical area with a
length of 541 km. The annual runoff of the Brahmani River is 28.48 × 10 9 m 3 .
The major hydrogeologic settings, covering 80% of the geographical area, are
pre-Cambrian hard-rock formation, which includes granites, gneisses, schist,
khondalites and charnockites.
Variability of both rainfall and the total cyclonic disturbances has been
above normal since the 1960s, leading to occurrence of more droughts and
floods in the study area. However, the extreme events of the late 1990s have
been more severe. A record-breaking heat wave in 1998 claimed 2200 human
lives, which has been linked to the El Nino. The super cyclone of 1999 was
the strongest and deadliest of the region with a recorded wind speed of about
356 km h -1 and sea water surge of 8-10 m high (Mirza, 2003). Over 10,000
people were killed, and the coastal ecosystem in particular was seriously
affected due to the cyclone. Further, the droughts in 2000 and 2002, and
floods in 2001 and 2003 have also affected the economy and environment of
the state.
11.2.1 Anthropogenic Activities
The Orissa state is rich in minerals and ores having deposit of iron ore, coal,
bauxite, chromites, nickel, lead, copper and limestone. The state accounts for
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