Salt intrusion study in Cochin estuary - Using empirical models

Abstract

Intensive measurements of salt intrusion are taken at high and low waters during spring and neap tide for each month respectively from June 2007 to May 2008. Salt intrusion length at high water varied from 10 km in monsoon 2008 to more than 40 km in pre monsoon 2007. Salinity intrusion mostly depends on the fresh water discharge rather than spring-neap tidal oscillations. Stratification parameter of salinity varied with the distance along the estuary, tide and freshwater discharge indicating that the Cochin estuary experiences a transition from partially or well mixed estuary during post and pre monsoon to a strongly stratified estuary during the monsoon season. Instead of undergoing the entire process of data collection of all the parameters, for a prolonged period, which is quite expensive and time consuming, certain predictive models are preferred. A predictive model uses parameters which are measurable and quantifiable variables and determined through empirical relations. Four empirical models have been applied to the Cochin estuary in the present study to identify the most suitable model for predicting the salt intrusion length. Comparison of the obtained results indicate that the model of Van der Burgh (1972) is the most suitable empirical model for prediction of the salinity intrusion length in the Cochin estuary with the least RMS error of (6.1) and MAE of (4.8)