Decision of threshold values for extraction of turbidity for inland wetland using IRS P6 LISS III data

Wetland is a kind of natural resource with fast dynamic changes. Around 50% of the earth’s wetlands are estimated to have already disappeared worldwide over the last hundred years through conversion to industrial, agricultural, and residential developments. It is important for wetland protection and management to accurately map the wetland distribution by remote sensing and GIS. A study of the water turbidity and water quality of the wetland is essential to assess the fitness of the water for various purposes—irrigation, drinking, other domestic use, and industry. In the present study, an attempt has been made to know the inland wetland of Salem taluk of Salem district and to monitor changes in turbidity conditions for post-monsoon and pre-monsoon seasons. With the IRS P6 LISS III satellite image, indices images were generated for the extraction of water spread boundary. An automatic determination method of the threshold was examined to produce masks for the extraction of turbidity, and a turbidity map was generated which classifies turbidity into high, medium, and low. From the analysis, it has been observed that the inland wetlands of post-monsoon constitute 489 ha of the study area, of which 21.3% is subjected to high turbidity. Pre-monsoon spread constitutes 362.81 ha, of which 15.7% is subjected to high turbidity in pre-monsoon. Thus, this study highlights the usefulness of remotely sensed data for wetland mapping, seasonal monitoring, and characterization. The result indicates that turbidity conditions are moderate and low in pre-monsoon and moderate in post-monsoon seasons.