Exploring relationships between drought characteristics and environmental flow conditions in Indian catchments

Environmental flow plays a crucial role in the sustainability of rivers and aquatic ecosystems. Reduction in the flow of rivers degrades its ecosystem functions and health, resulting in severe impacts on aquatic ecosystems. Additionally, meteorological drought, which occurs due to a substantial reduction in normal rainfall, subsequently affects the river flow. To understand such consequences, long-term observed flow data are required, which is not readily available for geographically different catchments. The present study is an effort to explore the relationship between the drought characteristics based on percent rainfall departure (%RD) and average annual flow (%AAF) based environmental flow conditions. Drought characteristics and the environmental flow conditions have been assessed for 17 Indian catchments from 5 different river basins of India, namely Godavari, Mahanadi, Tapi, Brahmani-Baitarini and Mahi. Relationship analysis showed a coefficient of determination (R²) value of more than 0.55 for 11 out of 17 catchments, showing satisfactory results. Furthermore, the analysis represents that %AAF and %RD are positively correlated. The explored relationships can be useful for assessing environmental flow conditions in Indian catchments without discharge data. Also, the study approach is extendable to understanding drought linkage to environmental flow conditions for the ungauged catchments with rainfall departure records only.