To demonstrate the application of WaPOR data at the scheme level, the KnoWat project conducted a water productivity assessment in the Nasho irrigation scheme in the Lower Akagera catchment in collaboration with the RWB, the Nasho Cooperative and the Rwanda Agriculture and Animal Resources Development Board (RAB).

The scheme comprises an area of 1 173 hectares irrigated by pivot systems, serving 2 099 smallholder farmers.

The assessment focused on maize that was cultivated in Season B (February–June) during the period 2016–2021. In the Nasho irrigation scheme, maize has an average yield of 6.5 tonnes per hectare and it is mainly irrigated through centre pivot sprinkler systems. The maximum yield is 10 tonnes per hectare.

The study revealed a high spatial variability in both yield and water productivity throughout the six years under examination. This appears to be due to the varied levels of expertise of farmers working in the scheme and the different agricultural practices applied during the growing season.

The assessment revealed important information on the performance of the irrigation system, identifying land and water productivity gaps. It also exposed bright spots, i.e. fields where water productivity is exceptionally high, and hot spots, where water productivity is low. Season 2021 experienced higher yields (average 7 tonnes per hectare) and water productivity (2 kilogrammes per m3) as well as lower spatial variability, probably due to the favourable rainfall and more efficient agricultural practices.

The challenges identified by the assessment included uncertainties in the land cover maps provided by WaPOR, which may have been affected by the high cloud cover of the satellite images during the main growing period, and by the size of the fields, which were often too small (less than 1 hectare) to be detected by remote sensing.