Annual Report 2009-2010 - Ministry Of Earth Sciences

Fig. 7.5: Theoretical model to explain the open ocean blooms
7.5 Ecosystem Modelling
7.5.1 Ecosystem Modelling for Chilika Lake
The Chilika Lake productivity is governed by
catchment modifications together with the
opening of new mouths. In order to understand the
hydrodynamics and biogeochemical changes that
are prevalent in the ecosystem and the resultant
changes on productivity, the present project has
been taken up. The major aim of the project is to
develop an ecosystem model in stages to predict
primary, secondary and tertiary production and
changing environmental conditions.
a) Hydrodynamics modelling
A 2-dimensional depth integrated MIKE 21
hydrodynamic flow model was used to simulate
the water levels and flow field in the Chilka
Lake. The field data collected at five stations
simultaneously over a period of 30 days under
NE monsoon conditions was used for calibrating
and validating the model results. Based on HD
model results the tidal propagation into the lake
was studied. The tide excursion into the lake
underwent drastic spatial variations. Based on
the simulated hourly data over a period of 48
hours obtained from the model results, water and
salt fluxes across the four sector regions (open
channel, north sector, central sector and southern
sector) were calculated. Results indicate that a
net water flux of 413 cu.m/s and salt flux of 5797
cu.m/s was noticed in the central sector which
indicates that the central sector is favourable for
biological production when compared with the
other sectors. It is estimated that a quantum of
2196 Million cu.m. is discharged into the lagoon
from the gauged stream/ rivulets of the Western
Catchment during 2009-10.
44 Ministry of Earth Sciences : Annual Report 2009-10