Abstract:
Puttalam lagoon significantly contributes for the livelihood through fishing for the
economically deprived community in Puttalam District, Sri Lanka. Observable
anthropogenic activities and rapid urban development cause deterioration of water quality
and reduction of surface area of water body. The objective is to study the spatiotemporal
changes on the surface area and on surface temperature of lagoon. This study was done using
geographic information system and remote sensing approach for the six Landsat (3 TM, 1
ETM and 2 OLI) imageries and Water Ratio Index was applied to extract and quantify the
changes in the surface area and spectral radiance approaches to determine the land surface
temperature of the lagoon for the period of 1988, 1995, 2001, 2008, 2015 and 2019. The multi
temporal map of surface area and surface temperature maps were produced for the change
directions. The results revealed a significant decrease in surface area of the lagoon which was
nearly 8.7% of its surface area and an increase of temperature by nearly 5.2oC during the
period of study. Strong negative correlation (Pearson's correlation coefficient = 0.91) observed at 95% of significance level (p value = 0.01) between the surface area and
temperature of lagoon. It is essential to take conservation measures to sustain this lagoon at
Puttalam.
