<p>The Mahanadi River Basin (MRB) faces significant hydro-climatic alterations, necessitating a comprehensive understanding of their underlying drivers and impacts on the hydrological cycle. This study integrates multi-site trend analysis of rainfall, maximum temperature (T_max), minimum temperature (T_min) and streamflow to unravel the complex links between meteorological forcings and anthropogenic disturbances on the MRB’s streamflow regime. This study employs the Mann-Kendall (MK) and Modified Mann-Kendall (MMK) tests for detecting long-term trends, Pettitt’s test for identifying change points, and a Vector Autoregression (VAR) framework incorporating Granger Causality and Impulse Response Functions (IRFs) to quantify predictive relationships between the hydro-climatic variables. The findings of this study reveal a highly heterogeneous, site-specific alteration in the MRB’s streamflow regime. Many stations show substantial reductions in high (Q₁₀) and medium (Q₅₀) flows, including a -64.05% reduction in Q₁₀ at Jondhra. Concurrently, the Kantamal and Kesinga stations show remarkable increases across all quantiles, with Kesinga’s low flow (Q₉₀) increasing by 109.34%. This complex hydrological response is linked to climatic drivers: most of the meteorological stations (54.73%) exhibit statistically significant decreasing trends in annual rainfall, while annual T_max shows a strong increasing trend across 90% of stations. Granger causality analysis confirms that rainfall is the dominant predictive driver of streamflow alteration, showing statistical significance at 14 (87.5%) of the 16 stations. These findings highlight that declining rainfall and rising temperatures are driving complex, site-specific alterations in streamflow regimes throughout the MRB. This evolving hydro-climatic context poses significant challenges for sustainable water resource management and effective flood risk mitigation in the region.</p> Graphical Abstract <p></p> <p><b>Graphical abstract description: </b>This graphical abstract illustrates a comprehensive hydro-climatic analysis of the Mahanadi River Basin, dissecting the impacts of both climate and anthropogenic changes on water resources. The methodology integrates multiple advanced statistical techniques to provide a holistic understanding of the system’s dynamics. Initially, the long-term trends in rainfall, temperature (T_max, T_min), and streamflow are evaluated using the Mann-Kendall and Modified Mann-Kendall test. The results are visualized in a heatmap, revealing significant decreasing rainfall trends and widespread warming across the basin. To unravel the predictive relationships between climatic factors and hydrological responses, a Vector Autoregression (VAR) framework, incorporating Granger Causality and Impulse Response Functions, is employed, confirming precipitation as the primary driver of streamflow. The study further quantifies shifts in the river’s flow regime by identifying abrupt change points using Pettitt’s test and subsequently analysing Flow Duration Curves (FDCs). A three-dimensional plot of these curves highlights the spatially heterogeneous impacts on high (Q₁₀), medium (Q₅₀), and low (Q₉₀) flows. The analysis highlights a substantial reduction in high flow at the Jondhra station (-64.05%), while the Kesinga station shows a notable increase (49.76%), underscoring the complex and varied responses within the basin influenced by climate shifts, land use changes, and reservoir regulation.</p>