06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation

Chilika Lake
30 km north with respect to its present
confluence of the Chilika lagoon. The area
between the palaeo lagoon boundary and the
present lagoon boundary is mud flat, which is
evident even now. The total area of this unit
extends approximately 400 sq. km. Some 'parts
of the area seem to be the reclaimed land. The
eastern most part of the Chilika lagoon is
bordered by a linear and spit or a barrier spit
which separate the lagoon from the Bay of
Bengal. The length of the spit extends for about
60 km with an average width of about 150m.
except at two places in the north-eastern part
where sea water flushes into the Chilika lagoon,
the barrier spit forms a continuous feature. The
shape of the bar is curvilinear, concave towards
the sea. From the earlier literature it is evident
that the inlets position and width changes due
to the influence of wave action, long shore
current in the form of littoral drift and the
influence of fresh water discharge and field
currents near the mouth of the lagoon.
c. Fluvial landform : The deltoid plain extends
between the river Daya and the coast. From the
alluvial plain with very gentle slope towards
southwest, most of the area is under 30 m
elevation. The land supports agriculture of
paddy crop.
d. Aeolian landform: Consisting the coastal sand
dunes, which lies all along the northern part
with width ranging from 1 to 8 km. The sand
dunes are discontinuous with their linear
direction paralleling the coast.
iv. Remote Sensing Information
Use of Remote sensing techniques for documenting
the bio-resources profile of Chilika lagoon is
limited. Recent studies depict the information on
vegetation, water quality, turbidity and sediment
load in the lagoon and their variability with time
(Mohanty et al., 2001; Pal and Mohanty, 2002).
Classified photomaps of Chilika lagoon during and
are shown in images. The images clearly depict
the variability of different lagoon features in the
time-space continuum. The images further
indicate the sediment load in the lagoon and their
temporal and spatial variability. Based on the soil
brightness indices Chilika lagoon itself can be
divided into three main regions namely, 1.
Productive eutrophicated region at the
northwest, 2. Turbid - drainage region at the
northeast and 3.Deep water region at the southcenter
of the lagoon.
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v. Limnological features
Limnology of Chilika lagoon has been extensively
studied by different groups in the past (Asthana,
1976; ZSI, 1995; Respond Project, 1998). Some of
the salient limnological features are as follows.
a. Tidal influx: The tidal inlet is a narrow
waterway connecting the lagoon with the ocean
and is maintained by the tidal flows. The
eastcoast of India is subjected to variable wave
climate, showing .the long shore sediment
transport towards north during March to
October and towards south during November to
January. Further, the annual long-shore
transport rate is observed to increase
northward along the east coast of Indi a
(Saxaena et al., 1976). The Chilika lagoon is
situated almost on the northern end of the Bay
of Bengal and the waves approaching from
u'orth are limited. The data on daily littoral
current observation showed that the long shore
sediment transport is northward throughout the
year along the shorefront of the Chilika lagoon.
The fresh water discharge during the southwest
monsoon flushes out the part of the sediment
deposited in the inlet mouth. The migration
rate of the inlet mouth is higher during the
southwest monsoon period. In the fair weather
season, the inlet mouth gets silted up since the
tidal prism becomes very low, the length of the
connecting channel between the sea and the
lagoon is too long, about 21 km, and the
hydraulic head loss due to the frictional effects
canses further reduction in the flood flow into
the lagoon. This has been one of the major
arguments in favour of an artificial mouth
opening near Satapada in order to increase
tidal prism (Chandramohan and Nayak, 1994).
The discharge of water from the lagoon into the
sea and the influx of water from sea to the
lagoon through this channel have been very
weak that resulted in the gradual siltation of
the lagoon over the years.
D. Bathymetry : The bottom is characterized by
loose mud and silt. The depth is uneven, the
northern broader part being the shallowest and
the narrower southern point being
comparatively deeper. Depth varies from sector
to sector as well as from season to season. In
summer the depth ranges between 0.94 - 2.63 m,
while the depth in the flood season varies from
1.78 to 3.70 m. The northern sector is the
shallowest with depth varying from 0.2 to 1.6 m.