Abstract
Shivaprasad, A.; Vinita, J.; Revichandran, C.; Manoj, N.T.; Srinivas, K.; Reny, P.D.; Ashwini, R., and Muraleedharan, K.R., 2013. Influence of saltwater barrage on tides, salinity, and chlorophyll a in Cochin estuary, India. Thanneermukkam Barrage (TB) is constructed in the southern arm of Cochin estuary. It prevents salt intrusion upstream and regulates river discharge downstream. Characteristics of the estuary when the barrage is opened and closed are discussed. The analysis showed that the closure of the barrage caused amplification of tides in the immediate vicinity and up to 10 km farther downstream. When the barrage was closed, the northern region of the TB transformed from an ebb-dominant system into a flood-dominant system. During high discharge periods, the barrage was opened and salinity intrusion was exponentially dependent on river discharge. During the dry period, the reduction in river flow compounded with closure of the barrage resulted in an increased salinity concentration downstream. Whereas oceanic salinity was observed at the ocean-end station, about 13PSU occurred at the river-end station when the barrage was closed. Hydrodynamic control on phytoplankton biomass was also evident. Higher surface chlorophyll a levels were observed at higher salinity during the closed barrage period, and residence time was estimated for 4 days during this period.