Chilika Lake, (19⁰ 28' N - 19⁰ 54 ' N; 85⁰ 06' E - 85⁰ 36') on the Orissa coast, India, is one of the unique ecospheres in the world. It is the largest brackish water lagoon with estuarine character. On account of its rich biodiversity and socio – economic importance, it is designated as a ‘Ramasar site'- a wetland of international importance. Based on the circulation / hydrodynamics of the lake, the lake is divided into four sectors. The northern sector receives discharges of the floodwaters from the tributaries of the river Mahanadi. The southern sector is relatively smaller and does not show much seasonal variation in salinity. The central sector has features intermediate of the other sectors. The eastern sector, which is a narrow and constricted outer channel, connects the lagoon with the Bay of Bengal and the tidal effects are important in that area. Thus, due to its complicated geomorphology, the circulation in the lake corresponding to the different sectors is very complex. Interest in detailed analysis of the circulation, biotic and abiotic factors affecting the lake and its limnology is due to the threat to the lake from various factors – Eutrophication, weed proliferation, siltation, industrial pollution and depletion of bioresources. The present paper deals with the numerical simulation of seasonal circulation in the lake. The theoretical formulation leads to a vertically integrated non-linear model, which includes the effects of wind in two different seasons on the circulation of the lake. In addition, the effect of the complicated boundary as well as the different type of circulation in different sectors of the lake is evaluated. The model is capable of accurate simulation of tidal elevations throughout the lake.   A physico - biological model that incorporates the present dynamical model can be used to study the distribution of nutrients and chlorophyll in the lake.

Center for Atmospheric Sciences,
Indian Institute of Technology,
Hauz Khas, New Delhi – 110 016.

† Department of Marine Sciences,
Berhampur University,
Berhampur – 760 007, India.