Spatial Distribution Analysis of Seasonal Variation in Salinity Stratification at Vembanad Estuary, Kerala, India

Estuaries are among the most important interconnections between land and sea. The restricted exchange between estuaries and the open sea allows rapid changes in salinity, temperature, nutrients, and sediment load. This study focuses on spatial and temporal variation of salinity stratification of Vembanad Estuary, Kerala with reference to the seasonal variations and tidal effects. Water samples are taken from 20 locations along the Vembanad Estuary throughout the pre-monsoon, monsoon, and post-monsoon seasons for the year 2022. By application of stratification parameters, salinity stratification in the water column was determined. Linear regression analysis was applied to model the relationship between the salinity and distance from the estuary mouth. Spatial variations of salinity and temperature maps were prepared using ArcGIS software. Based on the field analysis and statistical studies it was found that horizontal salinity structure of the estuary was in homogeneous, such that the southern region was less saline than the northern region. The vertical profiles of salinity at the mouth region showed stratification, with a low saline water floating on the surface and high saline water at the bottom. These variations were influenced by the intrusion of up-welled waters from the Arabian Sea and by changes in the meteorology. Comparing the spring–neap salinity variation, it has been observed that spring tide phase is more saline than neap tide. Keywords: Vembanad Estuary, Salinity Stratification, Regression Analysis, GIS, Spring Tide