Abstract

The overall objective of this present research is assessment of rice-water requirement in Cyabayaga wetland of Nyagatare District in Rwanda. Specific objectives of this research project were to collect and analyze weather parameters, of soil physical properties, crop-water requirements and to recommend efficient water management of the study area. Research design, data collection and field observations were made during July, 2019 to January, 2020. The experiment was carried out in Cyabayaga marshland and was especially based on the assessment of rice water requirement, weather parameters and hydraulic parameters like measurement of soil infiltration rate, soil hydraulic conductivity, flow discharge in irrigation channels, water loss, conveyance efficiency and application efficiency. Evapotranspiration and irrigation needs were determined by Cropwat 8.0 software. Conveyance efficiency (Ec) was found to be 70.05% and 30% of water was lost through seepage and evapotranspiration through weeds in unlined channels. The overall deep percolation, seepage and evapotranspiration losses were found to be 25 mm/day. Considering the highest potential crop evapotranspiration (ETc) of 4.8 mm, it was indicated that huge water loss of 20.2 mm/day was caused by seepage and percolation within the soil. The application efficiency (Ea) was found to be 23.8%. Hence, the overall efficiency was 16.7%. With the current rice yield of 4.25 t/ha, a low water-use-efficiency of 0.089 kg/m³ was found.

Key words: Cropwater requirements, rice, irrigation requirements, water use efficiency and Cropwat.