Ethiopia lies in the northeast part of Africa, north of the equator, covering a total area of 1,221,900 km2. It’s topography is composed of massive highlands along with complex mountains and dissected plateaus divided by Great Rift Valley running from northeast to southwest. Elevation varies from a height at below sea level in the northeastern part of the country to higher than 3500 m above sea level in the northern highlands. Climate of Ethiopia is a typical of equatorial regions, but topography complicates its pattern and character. It creates diverse microclimates ranging from hot deserts over the lowlands to cool, very wet over highlands. Ethiopia’s rainfall is highly variable both in amount and distribution across regions and seasons. There are regions that experience three seasons (bimodal type-1 ) with two rainfall peaks (where one peak is more prominent than the other) while some regions have four seasons with two similar rainfall peaks (bimodal type-2). There are still some regions which have two seasons with single rainfall peak (monomodal rainfall type). On the other hand, some areas have rainfall for 10 consecutive months; others receive rainfall for just a few months; while still others are characterized by three distinct rainfall seasons. Mean annual rainfall distribution over the country is characterized by large spatial variations which range from about 2000 mm over some areas in the southwest to less than 250 mm over the Afar and Ogaden low lands.