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 contributed
by evapotranspiration from the same region. It is the interaction between terrestrial hydrology
and atmospheric processes, and plays a crucial role in forming local water resources and
affecting local climate. Up to date, global moisture recycling at regional and continental
scales has been understood relatively well, the patterns of local moisture recycling and the
main variables impacting it remain unclear. For wetlands, the evaporation alters local climate
by re-precipitation in surrounding regions, which can also be analysed from the viewpoint of
moisture recycling. Yet, there is rare research has been done in this viewpoint to analyse and
manage water resources of wetlands. It is thus of importance to carry out such research to
unveil it. As the largest wetland in Africa, the Sudd region has relatively large precipitation
recycling contributed by the surrounding regions, as well as large swampy areas of upper
Nile 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 and
complex system. In this article, we will present multi-year hydro-climatology patterns of
Sudd, and the calculation results from Water Accounting Model-Two Layers (WAM-
2layers), including water vapor sources of its precipitation, and the reprecipitation of its
evapotranspiration. We will also analyse their spatial distributions, origin and destination, and
find the multi-year average moisture recycling ratio of the basin. From our calculation, it is as
high as 24% in some regions. In summary, this work shows that Sudd region is of great
significance to the neighbouring regions in terms of moisture recycling, and this would be
also useful to provide a practical basis for planning by considering local land-atmosphere
interaction.