Baseflow significantly contributes to river floods in Peninsular India

Abstract

Extreme rainfall prior to a flood event is often a necessary condition for its occurrence; however, rainfall alone is not always an indicator of flood severity. Antecedent wetness condition of a catchment is another important factor which strongly influences the flood magnitudes. The key role of soil moisture in driving floods is widely recognized; however, antecedent conditions of deeper saturated zone may contribute to river floods. Here, we assess how closely the flood magnitudes are associated to extreme rainfall, soil moisture and baseflow in 70 catchments of Peninsular India for the period 1979–2018. Annual flood magnitudes have declined across most of the catchments. Effect of flow regulations is also assessed to understand the impact of human interventions on flood characteristics. Reservoir regulation has positive effect by reducing the flood peak and volume, whereas the duration of flood events has increased after the construction of dams. Baseflow exhibits similar patterns of trends as floods, whereas trends in rainfall and soil moisture extremes are weakly correlated with trends in flood magnitudes. Baseflow is found to be more strongly influencing the flood magnitudes than soil moisture at various time lags. Further analysis with event coincidence analysis confirms that baseflow has stronger triggering effect on river floods in Peninsular India.

Optimal Baseflow Separation Through Chemical Mass Balance: Comparing the Usages of Two Tracers, Two Concentration Estimation Methods, and Four Baseflow Filters

“…Understanding the seasonal variability of baseflow and its contribution to streamflow is of utmost importance for a number of practices, such as the prediction of pollutant concentration and transport in river systems (Miller et al, 2017), planning of irrigation activities (Kourakos et al, 2019), and assessing ecosystem productivity (Palmer & Ruhi, 2019). Furthermore, the partitioning of streamflow is an essential function of the catchment system that is related to the propagation of hydrological extremes, for example, meteorological to hydrological drought, pluvial to fluvial (Sharma & Mujumdar, 2024;Yang et al, 2017). Therefore, understanding the potential impacts of climate change on the partitioning of streamflow is meaningful for mitigating hydrological hazard through the development of effective early warning systems (Barker et al, 2020;Hellwig & Stahl, 2018;Kreibich et al, 2022).…”