Abstract:
Scarcity of water is the most severe constraint for traditional agriculture in semi-arid
areas of Ethiopia. Precipitation is extremely variable, thus water harvesting is crucial for
ensuring improved crop production. A study was carried out to identify potential
rainwater harvesting systems for improved crop production under climate variability in
Adulala watershed, central rift valley of Ethiopia. Primary and secondary data together
with other relevant information through a well-structured questionnaire were collected
and analyzed to charachterize climate variability and water harvesting structures and to
estimate runoff and crop water requirement. The inter annual rainfall variability showed
a significant (p<0.05) increasing trend of 1.86 mm per year. The variability in the start
of the season was non significant while increasing at a decreasing trend of 0.042 days
per year. In the watershed, there are 38 water harvesting structures of which 34 are
hemispherical and 4 are rectangular with storage capacity of about 90 and 320 m3each
respectively. The average monthly and annual surface runoff were found to be 3.05 and
36.6 mm respectively. The total irrigation volume required to supplement both major
crops and vegetables per farmer was found to be 3285.9 m3to cover 2 hectares
.Considering the situation, additional storage structures for supplementary and full
irrigation are necessary. Irrigation for small vegetables could be encouraged with the
current storage volume and use of early maturing varieties should be considered under
variable climate
