Hydrologic and Climatic Signatures of Reservoir Operations Using Long-term Panel Data

Reservoirs play a vital role in regulating the spatial and temporal distribution of water resources and meeting downstream demands. However, the impacts of reservoirs on hydrometeorological factors, and how they affect sustainable water management are mostly overlooked in the existing literature. Hence, this research investigates panel regression methodologies to analyze the impacts of reservoirs across 49 catchments in Peninsular India, with specific stress upon the synchronous and lagged impacts of reservoir expansion on groundwater storage, baseflow, and other hydrological states and fluxes. The study found that reservoir expansion had statistically significant effects on both hydrological and climatic factors in Peninsular India, with more than 65% of all tested relationships showing significance. Reservoirs were found to significantly increase evapotranspiration and groundwater storage during the monsoon and post-monsoon seasons. Fixed Effects models, which demonstrated significant basin-specific limitations on hydrological responses, received the majority of the support.  Reservoir operations were found to have an impact on regional temperature and precipitation in addition to groundwater, soil moisture, and evaporation. This demonstrates that there is a quantifiable feedback between the atmosphere and the land. In contrast, baseflow responses were feeble and mostly insignificant, reflecting the buffered nature of subsurface channels. Groundwater storage emerged as the most sensitive variable. As a result, the region's reservoirs mainly influence groundwater storage rather than surface factors, indicating a change in the water balance where reservoirs improve subsurface retention and mitigate seasonal shortages. This study highlights the need for integrated reservoir and climate management strategies by showing the potential of a strong novel approach based on panel regression for interpreting the effects of reservoirs on catchment-scale hydrology.