2.4
Productivity of Backwaters and Estuaries
S. Z. QASIM
The main reason why the backwaters and estuaries have been included in the Symposium on "The Biology of the Indian Ocean" is that, in certain regions of the Indian
Ocean, the backwaters with their associated river system form a fairly large part of the
inshore waters and influence the hydrography of the coastal water considerably. The term
Fig. 1. Map showing a portion of the backwaters around Cochin. The estuarine site to which the data
refer has been indicated by open circle. Inset shows the backwater system with its marine and
freshwater connections
"backwater" or "backwaters" is of local ongm and refers to a system of shallow,
brackish-water lagoons and swamps found in Kerala State along the SW coast of India.
They occupy an area of hundreds of square kilometers. Although the' backwaters have
their own physiography and geomorphology, most of them behave like estuaries. The
areas which are close to the permanent connection with the sea are influenced by the
regular tidal rhythm and have been referred to as tropical estuaries (QASIM et aI., 1969;
SANKARANARAYANAN and QASIM, 1969).
Fig. 1 shows the backwaters around Cochin, the main area under investigation
for several years. The connection between the Arabian Sea and thi s backwater is main-