CHAPTER II
DISCRIPTION OF STUDY AREA
CHAPTER II
DISCRIPTION OF STUDY AREA
Karnataka state, lying between longitude 74° and 78° East and latitude
110 and 18° North occupies central position in the south-western part of the
Indian Peninsula, with three natural geographical regions, viz., the coastal
strip (Paschima Karavali), the Sahyadri or the Western Ghat (Malnad) and the
Deccan Plateau (Maiden). Karnataka with a coastline of about 320 km.
extending from Majali, about 8 km. north of Karwar (near Goa border) to just
south of Dakshin Kannada (towards Kerala state) and a resourceful
continental shelf of 25,000 km. offers great scope for the exploitation of
marine and estuarine fishes.
Uttar Kannada District (Map 1) coast lies between 74° 91 to 75°101
East longitude and 13°351 to 15°311 North latitude. The district has a coastline
of about 144 km. and covers approximately an area 10327 sq.km, and is
largely influenced by several rivers flowing in to the Arabian Sea of West
Coast of India. There are many leading rivers, the Kali the north, the Bedti or
Gangavali about 32 km. south, the Aghanashini or Tadri rising far to the
south but falling into the sea only about 6 miles south of Gangavali, the
Sharavati or Gersoppa river, about 24 km south of Tadri, when it reaches the
foot of the hills and becomes a tidal creek and Venkatapur river south of
Sharavati and reaches to the Arabian sea. In the hilly region, the channels of
all rivers are broad and rocky, showing the force of their monsoon torrents. At
8
the foot of the hills, they are broad backwaters, the mouth stopped by bars of
sand, which during heavy rains block the passage of the flood waters till they
overflow the low lands along their banks.
At Gangavali at the river mouth there is a temple of goddess Ganga
where every year after Dipavali people organize Ganga’s marriage with Shiva
in the form of festival since thousands of years. Hindus worshipped Goddess
Ganga, as a manifestation of power, the conqueror of time. People see her in
the river hence the name Gangavali. The river originates near Dharwad
district where it is known as Shalmala River. The river runs about 68 km.
towards Yellapur with a winding westerly course to the western face of
Sahyadri. In Yellapur Shalmala River is called as Bedti River.
After winding westerly course from the Western Ghats, the Bedti river
falls down to Arabail Ghat at Magod and which is known as Magod falls. It is
one of the beautiful tourist places in Uttar Kannada district, from where the
river takes turn to southwest near village Sunkasal. Beyond this point, she
flows further 8 km. westwards and takes turn southward to reach Kavalalli
and takes turn north and reaches Gundabal to Magota and, runs westward to
reach Arabian Sea between Manjaguni and Gangavali village. Before joining
Arabian Sea it forms a beautiful small inhabited island is called Koorve.
The estuarine water reaches up to Gundabal about 15 km. The depth
in the estuary ranges from 4-8 meters at the mouth and about 3-5 meters
9
towards the riverine zone during high tide. The tides are of semidiurnal nature
and the time and range between two floods and two ebbs show marked
variations. It lies between the edges of the plateau near the Western Ghats.
The river mouth is rather narrow and thus allows moderate tidal limit in to the
estuarine regions. Topographical features exhibited are varied, mud mixed
sandy floor at the bottom region of the mouth to muddy to clayey towards the
southern stretches of the estuary to mud mixed sandy bottom towards the
northern stretches.
The climate of coastal Uttar Kannada is characterized by high humidity
nearly all around the year. The area is influenced by Monsoon and receives
more than 300 cm rainfall annually. An average temperature ranges from
25°C to 34°C. On the basis of the monsoon effect and associated climatic
conditions, a year can be distinguished in to three seasons as follows.
•
Pre- monsoon season -
February to May
•
Monsoon season
-
June to September
•
Post- monsoon
-
October to January
Hydrographically, the Gangavali estuary can be divided into four zones viz;
1. The euryhaline zone around the estuarine mouth extending upto about
1.5 kilometers from the river mouth.
2. The Polyhaline zone or the proper estuarine zone extending upto
about 6 kilometers from river mouth.
10
3. The Mesohaline zone from polyhaline zone extending to about 10
Kilometers.
4. Oligohaline zone, which is influenced by fresh water influx beyond
mesohaline zone.
River Gangavali flows in between Ankola taluk longitude 74° 18’ to
74° 42’, latitude 14° 29’ to 14° 48’ and Kumata taluk longitude 74° 24’ to 74°
34’, latitude 14° 17’ to 14° 35’. It has an estuary extending from Gangavali (S)
and Manjaguni (N) at the river mouth and tidal zone extends about 15 km. up
to Gundabal with remaining part being fresh water. Salinity of water varies
here frequently. In this area varieties of fishes have been found. The specialty
of these fishes is that, they can tolerate varied salinity changes. The
backwater extends to fresh water zone where salinity is almost 0.1 ppm. The
fishes, which are common in brackish water, were found rarely or
occasionally in this zone. Thus the character and hydrological parameters
varies from one zone to other. This variation has great influence on
distribution and abundance of zooplankton, benthos and fish resource along
Gangavali River. The abundance and distribution of zooplankton, benthos and
fin fishes was studied in various selected stations, which comprised study
stations related to all zones.
11
STUDY STATIONS
A preliminary survey of the estuary was made in the beginning and
four sampling stations were identified for hydrological studies. Water and
sediments samples were collected once in a month for a period of thirteen
months (2007-2008) for detail analysis. The four sampling stations represent
different zones of estuarine water body namely, lower reaches, lower middle
reaches, upper middle reaches and upper reaches.
Four stations were selected for monthly water and sediment sampling
based on accessibility strategic position, variation in salinity and type of
sediment distance from one to the other in order to obtain estuarine average of
different parameters on monthly and year basis, which are as follows:
Station: I.
Manjaguni
Station: II. Koorve
Station: III. Moralli
Statoin: IV. Gundabal
Station: I. Manjaguni
The Manjaguni is a small village on the northern side of the river
mouth which represents lower reach of the estuary. The southern side of the
river is bounded by Gangavali village and other smaller villages and paddy
fields. Bottom is generally a mixture of clay and sand, depth varied from 5-6
12
meters during high tide. This station is characterized by high saline water.
Prominent tidal effects are seen in the entire stretch of the sea and wave
action is barely visible. Manjaguni is rich in mangrove vegetation and diverse
group of mangrove and associates. However, in the recent years mangroves
are being destroyed everyday for firewood, timber and other developmental
and mining activities threatening the habitat. Manjaguni and Gangavali
village have sizeable population of fishermen for whom fishing is one of the
sources of livelihood.
Station: II. Koorve
Koorve is a small island surrounded by Gangavali River about 2.5 km.
from the mouth. Kangil and Hichkad are the villages on the northern bank
and Sagadgeri and Aggargone are on the southern bank. This represents lower
middle reach of the estuary. During rainy season some time floods force the
people of Koorve Island to migrate to Kangil. The island is about 1km. long
and 500 meter wide with a small population of fishermen. The sampling was
carried out at the eastern end of the island where it divides into two parts. The
salinity of this station is lesser than first station (Manjaguni). The nature of
the bottom is admixture of sand and mud with depth varying from 3-4 meters
during high tide. During low tide vast area on both banks get exposed and
also part of the western island where large scale of clams and oysters fishing
is seen through the year. The area is always full of activity with large number
of fishermen and other people occupied in various activities exploiting
riverine resources. Some fringing mangrove vegetation can be seen here.
13
Station: III. Moralli
Moralli is village on the southern bank of river and Vasarekudrage
village is on the northern bank of the river and bounded by smaller paddy
fields. The salinity of this station is lower than other two stations. The nature
of the bottom is admixture of sand and with depth 2-4 meters during high
tide. The area is always full of activity with large number of fishermen and
other people occupied in their various activities exploiting riverine resources.
The soil is mixture of sand mud. The station represents upper middle reach of
the estuary and is well known for estuarine fishes.
Station: IV. Gundabal
Gundabal is village on the southern bank of river. Other side of the
river is bounded by smaller villages and paddy fields. This station located
about 15 km. away from the river mouth and the river takes little turn to the
south from here. This is upper reach of the estuary where the salinity is very
low during high tide and almost nil during low tide. Salinity is zero especially
during monsoon months. The station is generally dominated by river water
and is good fishing area with sandy and clayey soil. Large rock on the river
bed help aeration on one side and separates estuarine water with fresh water.
This is a beautiful picnic spot for tourists and represents the upper reach of
the estuary.
Location of the study stations are shown in the Plate 1 to 4, while their
coordinates (Geographical position) are given in Table 2.
14
Map 1. Location of the study Stations
Table 2. Locations of Study area (GPS Reading)
SI. No.
Area
Lat.
Long.
Station 1
Manjaguni
14° 35' 52.85" N
74° 18' 02.82"E
Station 2
Koorve
14° 36' 30.54"N
74° 19' 42.24"E
Station 3
Moralli
14° 34' 01.34"N
74° 24' 55.98"E
Station 4
Gundabal
14° 38' 26.30"N
74° 25' 42.74"E
16
Plate 1. Station I - Manjaguni
17
Plate 3. Station II - Koorve
At High Tide
At Low Tide
18
Plate 4. Station III - Moralli
At LowTide
At High Tide
19
Plate 5. Station IV - Gundabal
At High Tide
At Low Tide
20