Chapter 23 - Monitoring Drought with the Combined Drought Index in Kenya

Abstract

A first step in any drought management system is to monitor the state and the evolution of the drought. This study addresses the problem of nonexistent operational drought monitoring systems and presents a new methodology for monitoring the evolution and severity of drought with the new, Combined Drought Index (CDI). It is based on the fact that drought is a natural phenomenon created by a combination of several factors, such as deficiency in rainfall amount, persistence of below average rainfall, temperature excess and soil moisture characteristics. By combining the factors in the preceding text, the CDI compares present conditions with multiyear average (normal) conditions for the same time period. The methodology was applied at selected locations of different climate zones in Kenya. The results were compared with available official records of drought events (impacts), showing a very good positive relationship between the two. An attempt to detect the long-term trends of drought events using the CDI indicates that there is an increasing trend of drought events in the country, while the drought severity is not necessarily getting worse in all stations. The CDI method also revealed the possibility of drought early warning and drought-related climate change analysis in Kenya.