Estuarine characteristics of the lower reaches of the River Periyar (Cochin backwater)

Abstract

Lower reaches of river Periyar were studied to assess longitudinal extent of salt water intrusion into the system during different seasons and also its effect on the flushing of pollutants introduced by the industries. During SW monsoon season due to the influx of a large volume of fresh water longitudinal salinity gradient could be noticed only up to a few stations upwards from the barmouth. During postmonsoon season the estuary behaved like a partially mixed estuary with the saline intrusion extending further upstream up to 17 km. In the premonsoon season the intrusion length extended further upstream beyond 21 km. A steady down stream dilution of any pollutant introduced could be expected during these seasons. Fluoride concentration showed high values ( 1.5 mg.l -1) during Nov. to May and minimum from July to Sept.. The high values observed may be due to the effect of pollutants containing fluoride discharged into the river