Regional perspective on rainfall change and variability in the central highlands of Ethiopia, 1978–2007

Abstract

Rain-fed agriculture is the most common farming strategy in rural Ethiopia. A short rainy period called Belg (February–May) is caused by easterly winds from the Indian Ocean and a longer rainy season (Kiremt) which occurs between July and October is the result when the inter-tropical convergence zone (ITCZ) is located over the horn of Africa. The staple food is Injera preferably made from Tef (Eragrostis tef) but it is common to mix it with other cereals like Sorghum or Barley. The aim of this study is to analyse regional differences in yearly precipitation, seasonal, variability, intensity and the start of the short and the long rainy in the central highlands during the period 1987–2007. The analysis is done by comparing the three decades between 1978 and 2007. Analyses of total rainfall, seasonal changes, rainfall variability and rainy days were conducted from daily rainfall data from seven stations. Daily temperature data from two stations were used to calculate potential evaporation. Rainfall results show an increase in the annual rainfall and also in Kiremt season. The Belg rainfall has, on the other hand, declined during the 30 year period that has been analysed. High rainfall variability, more extreme rainfall during the start of the Kiremt season and more rainy days during the Kiremt season were found. The Belg season shows an increase in temperature and potential evaporation as well. The possibility to grow cereal during Kiremt season is considered to be more or less the same during the past 30 years but in the last decade it has become impossible in the southern part of the study area due to a shortening of the Belg season. Cereal production is considered to be a bigger problem in the last decade around some rainfall stations especially in South Wollo where population numbers are high and land is under greater pressure than the southern areas of the study region.