Spatio–temporal water quality assessment of Chohal and Damsal dams located in Kandi region of Punjab, India by geospatial technique and on-site investigation

Effective monitoring of water quality in reservoirs is imperative to comprehend pollution sources and secure a sustainable water supply for various needs, notably irrigation. Thus, a case study was undertaken at Punjab Agricultural University, Ludhiana to provide a comprehensive understanding of the spatio-temporal water quality in Chohal and Damsal dam reservoirs located in the Kandi region of Punjab, India for facilitating informed decision-making for water resource management and environmental protection. The study employed multimodal technique based on satellite-based analysis (Normalize Difference Turbidity Index, NDTI) and on-site investigations (sample analysis and Water Quality Index (WQI) determination) to provide composite picture of water quality dynamics. NDTI values for 2016 and 2022 for Chohal dam ranged from −0.0034 to 0.4758 and −0.0107 to 0.2931, respectively. For Damsal dam for these years, values were −0.0313 to 0.3381 and −0.0539 to 0.1902, respectively. Consistently low NDTI values across both reservoirs indicated suitable irrigation water quality. Variations in NDTI values over time implied changes in water turbidity. Likewise, WQI values indicated water quality suitable for irrigation, but showed changes between pre- and post-monsoon periods, reflecting fluctuations. Average WQI values for Chohal and Damsal dams decreased by more than 20% during post-monsoon, implying worsened quality, likely due to monsoon related factors. Comparing pre- and post-monsoon water quality data helped to discern significant changes stemming from agricultural runoff, industrial discharges, and sediment transport. Identifying post-monsoon deterioration would help pinpoint pollution sources, crucial for water management. These findings provide valuable information for policymakers to protect the water quality of Chohal and Damsal dams, thus ensuring a consistent and trustworthy source of irrigation water.