Analysing the Flow Regime Changes in Three Major River Basins of Central and East India Using the Dynamics of Hydrologic Alteration Indices

ABSTRACT Several natural and anthropogenic factors have altered natural flow regimes, leading to severe ecological consequences. Quantifying deviations from natural baselines is essential to find a balance between development and environmental conservation. This study evaluated flow regime changes across 26 stream gauge stations in three major river basins of peninsular India—Mahanadi, Godavari and Brahmani. Significant change years were identified and alterations were analysed using the Indicators of Hydrologic Alteration. Change points were obtained between the late 1980s and early 1990s. The most significant alterations were observed in the mean monthly flows and extreme minimum flows. Maximum flows were also affected, though to a lesser degree. The Godavari basin shifted to a more regulated flow regime, with augmented low flows, attenuated high flows and reduced rates of hydrograph changes. Brahmani basin has become wetter while the Mahanadi basin showed mixed responses. Across much of the study area, frequency of high pulses increased and its duration decreased. This indicates a greater likelihood of high intensity short duration streamflow extremes, particularly in Brahmani and Mahanadi basins. Principal component analysis (PCA) resulted in two major axes along which the alterations varied. A PCA‐weighted Hydrologic Alteration Severity Index was developed, which revealed that the Mahanadi basin had more severe alterations despite high variability. Godavari basin was also heterogeneous with low to moderate alteration severities, while Brahmani basin was more homogeneous with moderate severities. Thus, this study provides useful insights for assessment of hydrologic alterations and river basin management.