Atmospheric moisture recycling and its influence in the Sudd Region in the Upper Nile Basin

Moisture recycling, is defined as the precipitation in a region which is partially contributedby evapotranspiration from the same region. It is the interaction between terrestrial hydrologyand atmospheric processes, and plays a crucial role in forming local water resources andaffecting local climate. Up to date, global moisture recycling at regional and continentalscales has been understood relatively well, the patterns of local moisture recycling and themain variables impacting it remain unclear. For wetlands, the evaporation alters local climateby re-precipitation in surrounding regions, which can also be analysed from the viewpoint ofmoisture recycling. Yet, there is rare research has been done in this viewpoint to analyse andmanage water resources of wetlands. It is thus of importance to carry out such research tounveil it. As the largest wetland in Africa, the Sudd region has relatively large precipitationrecycling contributed by the surrounding regions, as well as large swampy areas of upperNile Basin, which makes it an appropriate study case for the moisture recycling of wetlands.In this research, it is the first time to carry out atmospheric moisture recycling of Sudd region,considering anthropogenic activities such as engineering practices, hydro-politics andcomplex system. In this article, we will present multi-year hydro-climatology patterns ofSudd, and the calculation results from Water Accounting Model-Two Layers (WAM-2layers), including water vapor sources of its precipitation, and the reprecipitation of itsevapotranspiration. We will also analyse their spatial distributions, origin and destination, andfind the multi-year average moisture recycling ratio of the basin. From our calculation, it is ashigh as 24% in some regions. In summary, this work shows that Sudd region is of greatsignificance to the neighbouring regions in terms of moisture recycling, and this would bealso useful to provide a practical basis for planning by considering local land-atmosphereinteraction.