On the need of ensemble flood forecast in India

Floods affect a large fraction of the Indian population during the monsoon (June-September) every year. Floods disrupt all aspects of the socio-economic conditions and cause enormous damage to infrastructure and agriculture. Human mortality and economic losses due to floods have increased in India during recent decades. Moreover, floods are projected to occur more frequently in the future under the warming climate. Both structural and non-structural measures are common in India to mitigate the detrimental impacts of floods. However, the challenges and opportunities for operational flood forecast systems in India have not been carefully evaluated. Here, we review the current status and future requirements to strengthen the flood early warning systems in India. India made tremendous progress in developing the ensemble prediction system for precipitation forecast. Precipitation forecast is available at various spatial and temporal resolutions, which provides a skilful prediction of extreme precipitation at short (1–3 day) and longer (15–20 day) lead times. However, the spatial and temporal resolutions and lead time need to be improved for precipitation forecast in smaller catchments and urban areas, which are prone to flash flooding. There is a need to translate the ensemble weather and climate forecast to hydrologic ensemble prediction (HEP) system through the integration of improved meteorological forecast, hydrologic and hydraulic modelling, data assimilation, and post-processing. We also highlight the role of improved inflow forecast at the appropriate lead for reservoir operations as the decisions related to reservoir operations can be critical for flood management. We, finally, discuss the need for an integrated approach at various levels to enhance the operational flood forecast in India, which is essential for the development of an effective flood early warning system.