Water use and crop water productivity in farmer managed irrigation schemes across agro ecological zones of usa river catchment

A Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of Master’s in Hydrology and Water Resource Engineering of the Nelson Mandela African Institution of Science and TechnologyThe Usa River Catchment is the potential area dealing with traditional irrigated agriculture. This study aims to estimate the amount of water abstracted for and yield that reflect water values to enhance crop water productivity. The main objective of this study was to assess water use and crop water productivity in farmer managed irrigation schemes across agro-ecological zones of Usa River Catchment. The specific objectives were: (a) to determine crop water productivity, (b) to determine factors causing the variation of crop water productivity, and (c) conveyance efficiencies in the traditional irrigation schemes in the Catchment. The secondary and primary data were collected and analysed using Statistical Package for Social Science (SPSS) and R-program. Consequently, the average productivity obtained were 2.3 kg/ha, 1.9 kg/ha, and 3.4 kg/ha of maize for downstream, midstream, and upstream zones respectively. Similarly, at twenty (20) furrows, the conveyances efficiency of the water channels was 72%, which reflects the water loss in the conveyances of 28% on average. However, the water abstractions were 3500 L/s more than the permitted amount of 2856.2 L/s, which was against the established water abstraction laws and regulations leading to water shortage in downstream of the catchment. Traditional irrigation infrastructure in this study contributed more water losses and low crop water productivity compared to global average water losses in the conveyance and crop water productivity in irrigation schemes. This study recommends weirs with water control structures intakes to be constructed, canal lining and improve irrigation water management