Nested hydrological modeling for flood prediction using CMIP6 inputs around Lake Tana, Ethiopia

Abstract

Study region: Tana basin is the origin of the Blue Nile Basin located in Ethiopia. The Lake Tana’s mean annual precipitation is approximately 1400 mm/yr and its outflow drains an area of about 15,096 km2. There is limited effort to apply nested hydrological models for flood prediction due to being poorly gauged for validation. Study focus: The objective of this study is to show how climate simulations can be used to generate reliable local predictions of flood and runoff for the Blue Nile in the Ethiopian highlands.In this study, outputs from the Coupled Model Intercomparison Project Phase 6 (CMIP6) were used to initialize a nested hydrological model to reveal long-term trends of runoff in flood-prone areas of the Lake Tana basin, Ethiopia. Available satellite and reanalysis datasets were used for selection of CMIP6 products and the five models with best validation were used to force a nested hydrological model: Known as Wflow_sbm. A model-independent multi-algorithm optimization estimation tool was implemented for calibration of Wflow with insitu observations. New hydrological insights for the region: In terms of simulating runoff and flood events, application of Wflow_sbm to the Lake Tana basin gave promising results. This study serves as a major step towards the development and implementation of global model-driven nested hydrological assessments of flood risk in future projections for Lake Tana basin.

Keywords

• Climate Projection
• GCMs-CMIP6
• WFlow_sbm model
• Flood prediction
• Lake Tana Basin
• Ethiopia