This chapter describes the South Koel River Basin and outlines the research framework. It details the basin’s geographical extension, geology, topography, hydrology, climate, soils, vegetation, land-use and land cover patterns and socio-economic setting. The chapter then presents the analytical methods: data sources and pre-processing, time series analyses, the SWAT hydrological model, ANCOVA statistical method and then connectivity assessment. It emphasizes integrating long-term hydro-meteorological data with simulation and statistical tools to capture the basin’s spatial heterogeneity and runoff dynamics as well downstream deltaic implications. By adopting trend and modeling techniques tailored to the basin’s characteristics, the methodology provides a rigorous foundation for the study’s analyses.