Evaluating physio-chemical characteristics and water quality in the Rasik Beel Wetland complex in Cooch Behar district, West Bengal, India

Abstract Rasik Beel Wetland Complex is one of the most significant wetlands in the Teesta-Jaldhaka-Raidak basin. It is a part of the Government of India’s Wetland Development Project [18]. The present study aims to evaluate the physio-chemical characteristics of water in Rasik Beel , located in the Cooch Behar District of West Bengal, using the Water Quality Index (WQI) and Principal Component Analysis (PCA). In this context, water samples were collected from multiple locations (five sample sites) within the wetland over a specific period and analysed for key physico-chemical parameters. The analysis includes various parameters such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Alkalinity (AK), Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Hardness (HD), Chloride (Cl), Zinc (Zn), Copper (Cu), Lead (Pb), Iron (Fe) and Cadmium (Cd). The study computed the WQI to categorise overall water quality. The results reveal spatio-temporal variations in water quality, with specific parameters exceeding the permissible limits set by the World Health Organisation, the Bureau of Indian Standards (BIS), the Indian Council of Medical Research, and the Central Pollution Control Board. The WQI values indicated that the water quality ranged from excellent to unsuitable, with specific areas showing signs of ecological stress. Wetlands with excellent or good water quality are suitable for maintaining aquatic ecosystems, supporting fisheries, and providing irrigation and limited domestic uses after appropriate treatment. Wetlands with poor or very poor water quality require management interventions before utilisation. Water quality directly influences wetland ecological health, biodiversity and ecosystem services; therefore, maintaining acceptable water quality is essential for sustainable wetland conservation and resource utilisation. The average water quality index for the wetland complex is 73.34, indicating poor quality. S3 recorded the highest WQI value (215.03), indicating the most polluted water. S1 are showing very poor-quality water with a WQI value of 94.63. However, the water quality value in S2 is 47.85, indicating good quality. However, S4 and S5 exhibit excellent water quality, with WQI values of 3.39 and 5.79, respectively. The study emphasises the importance of continuous monitoring, sustainable management practices and policy interventions in preserving the ecological integrity of Rasik Beel .