Assessment of moisture availability over semi-arid and arid zones of Ethiopia.

The amount of moisture available during the growing season has a direct influence on plant growth and crop yield. Water from rainfall is the major climatic factor that governs climatic adaptability and distribution of crops in t eh semi-arid and arid zones. Water availability from rainfall acts in different proportions as constrains in relation to year round rain-fed crop production. This availability doesn't depend on rainfall alone. The semi-arid and arid zones pose a unique set of climatic features. The rainfall is characterized by high spatial and temporal rainfall variability. The rainfall exceeds potential evapotranspiration (PET) only for less than 4 months. Shortage of moisture is the key limiting factor to stabilize and improve agriculture. The objective of this study is to assess the availability of moisture over the semi-arid and arid zones, which would help in planning the agricultural activities and identify the associated risks in crop production. In order to achieve the above objective a moisture availability model developed by FAO and application of the Markov Chain model in determining consecutive wet and dry spells are applied in this study. This study considered five stations from different moisture regimes in the country. The results of this study indicated that the first season over Combolcha and the second season over Neghelle are highly exposed to the effects of drought. On the other hand, over Gonder and during the second season over Combolcha drought risk is negligible. Therefore, it is possible to conclude that belg rain generally does not provide enough moisture to support crop production over combolcha. This rain is very important to carry out land preparation and planting of long maturing crops. It is possible for a farmer to take full advantage of Kiremt rain if he prepares the land during belg. However, if the belg rain fails, land preparation will start after the onset of Kirmet rains, which results in decreasing the period available for crop growth. This is mainly because land preparation is very difficult since the soils are dry during the belg season.