Developing an Impact-Based Combined Drought Index for Monitoring Crop Yield Anomalies in the Upper Blue Nile Basin, Ethiopia IHE Delft PhD Thesis Series

Having a robust drought monitoring system for Ethiopia is crucial to mitigate the adverse impacts of droughts. Yet, such monitoring system still lacks in Ethiopia, and in the Upper Blue Nile (UBN) basin in particular. Several drought indices exist to monitor drought, however, these indices are unable, individually, to provide concise information on the occurrence of meteorological, agricultural and hydrological droughts. A combined drought index (CDI) using several meteorological, agricultural and hydrological drought indices can indicate the occurrence of all drought types, and can provide information that facilitates the drought management decision-making process. This thesis proposes an impact-based combined drought index (CDI) and a regression prediction model of crop yield anomalies for the UBN basin. The impact-based CDI is defined as a drought index that optimally combines the information embedded in other drought indices for monitoring a certain impact of drought, i.e. crop yield for the UBN. The developed CDI and the regression model have shown to be effective in indicating historic drought events in UBN basin. The impact-based CDI could potentially be used in the future development of drought monitoring in the UBN basin and support decision making in order to mitigate adverse drought impacts.

Introduction
Spatio-temporal assessment of meteorological drought under the influence of varying record length
Comparison of the performance of six drought indices in assessing and characterising historic drought events
Developing a combined drought index and prediction model to monitor drought-related crop yield reduction using mainly hydrological model input variables
Application of Earth observation data for developing a combined drought index and crop yield prediction model
Summary, conclusions and recommendations

Yared was born in Ambo town in Ethiopia in 1979. He studied his Bachelor of Science (BSc) degree in Irrigation Engineering at the former Arbaminch Water Technology Institute (AWTI) the later Arbaminch University where he graduated in 2002. He joined Addis Ababa Institute of Technology (AAiT), Ethiopia for Maters studies in 2007, and graduated with a MSc degree in Civil Engineering, with specialization in Hydraulic Engineering in 2009. Yared pursued a PhD in the "sandwich programme" between IHE Delft Institute for Water Education/TU-Delft, The Netherlands, and Ambo University, Ethiopia and graduated in 2018. Since 2016, he has been working in the National Drought Mitigation Centre (NDMC) under the school of Natural Resources of the University of Lincoln-Nebraska, USA, as a visiting scientist.