In cooperation with the International Water Management Institute (IWMI), the KnoWat project trained 30 experts from Sri Lanka to use and interpret WaPOR datasets. Developed by FAO, WaPOR monitors water productivity in near-real time through remote sensing, identifies water productivity gaps and proposes solutions to address these gaps. Key national partner institutions, including the Irrigation Department of Sri Lanka, the Department of Agrarian Development, the Department of Land Use Policy Planning, the Department of Census and Statistics and the University of Peradeniya, now have the tools to use WaPOR to better manage water resources. 

All WaPOR data are freely available on FAO’s WaPOR portal. Users can access data on evapotranspiration and water consumption by vegetation. Data are available for 10-day intervals, and aggregated by growing season, or every 10 days. This data can be used, for example, to analyse water productivity at irrigation scheme level or as an input to water balance studies at catchment or basin scales. FAO and its partners in Sri Lanka are currently discussing arrangements for WaPOR coverage beyond 2022. 

Project partners in Sri Lanka are currently studying the application of WaPOR for the System for Environmental Economic Accounting for Water (SEEA-W) as well as for monitoring Sustainable Development Goal Indicator 6.4.2 on water stress.  

To demonstrate the usefulness of WaPOR in areas of scare water resources, the KnoWat project carried out a crop water productivity assessment in the  Malwathu Oya southern catchment in 2022. 

One of Sri Lanka’s most important agricultural zones, the catchment area is prone to extreme weather events due to climate change. These include severe water scarcity and floods, which challenge farmers’ work and lives. Inefficient water use in agriculture, particularly in paddy, and poor irrigation infrastructure exacerbate the situation. 

The area covered by WaPOR extends over 779 km2 and includes the fields of more than 200 000 farmers. The water productivity assessment only considered only paddy rice cultivation, since this consumes the most water through irrigation. 

The water productivity assessment analysed rice yields in the project area during the Maha monsoon season (1 October–30 March) between 2015 and 2022. Yields of paddy rice ranged from 3.8 to 4.8 tonnes per hectare. The highest yield was achieved in 2017–2018. Yields are lower here than in other districts in Sri Lanka, but are around the global average of irrigated rice yield (4.5 tonnes per hectare). 

The project assessed irrigation performance indicators to discover the underlying causes of low water productivity of paddy in certain zones of the pilot area. The assessment revealed that irrigation is neither adequate nor uniform across the basin. Both land and crop water productivity of paddy rice cultivated during the Maha season in the Malwathu Oya southern catchment had a high spatial and temporal variability. These findings can be used by irrigation experts to identify hot spots and bright spots increase the water productivity in the Malwathu Oya basin. 

The assessment also analysed the yield assessment in the Nachaduwa irrigation area (left). In this area, irrigated crop yield reaches more than 6 tonnes per hectare, while farmers in the rest of the catchment produce less, between 2 and 5 tonnes per hectare. It would be interesting to study the reasons for the higher yields in Nachaduwa. Do farmers there apply good practices that farmers in other areas could benefit from? 

The assessment identified a number of challenges, including uncertainties in the land cover maps provided by WaPOR, which may have been affected by the high cloud cover of satellite images during the main growing period. In some areas, the fields were often too small (less than 1 hectare) to be detected by remote sensing at 30 metres resolution. Trustworthy local data on crop cover and crop calendar are needed to ensure reliable irrigation performance assessments. WaPOR works best on large fields with a uniform crop cover and calendar; such was the case in the Nachaduwa irrigation scheme. 

The application of WaPOR for water productivity and irrigation performance assessment should continue to improve, thanks to ongoing research by university students supported by the KnoWat project in collaboration with the International Water Management Institute (IWMI).