Impact of effective rainfall on net irrigation water requirement: The case of Ethiopia
Andualem Shigute Bokke, Keneni Elias Shoro
Abstract
Irrigation is one means to increase food supply besides the rain fed agriculture. During designing irrigation schemes most of the time effective rainfall is needed to be estimated in order to know the amount of water that should be supplied from irrigation. The problem is which effective rainfall determination method to be used is not clear among the available four built in methods in CROPWAT 8.0. Therefore, in this study analysis was made for Ethiopia case by considering selected 11 (eleven) small scale schemes from different parts of the country designed by different consultant companies. The finding shows most of the schemes designed in Ethiopia use either USDA-SC method (gives minimum net irrigation water requirement) or dependable rain method (results maximum net irrigation water requirement) in determination of effective rainfall. Moreover, additional study need to be conducted to test using soil–water balance method to identify which effective rainfall determination is the correct in planning and designing of irrigation schemes.