Modeling the Sudd Wetland in South Sudan using Satellite Data

Motivation:

As part of her Ph.D. research, Dr. Di Vittorio developed a hydrologic model of the Sudd Wetland (South Sudan) using various satellite-based data sources. The Sudd is positioned downstream of the great equatorial lakes and is a critical component of the Nile River Basin. During the rainy season, inflow to the Sudd increases substantially and water overtops the main channel and spreads outward, causing the wetland to approximately double in size. The flood water mostly evaporates instead of flowing downstream to Sudan and Egypt, arid and water-scarce countries with increasing population growth and water demands. Egypt considered channelizing the Sudd to reduce evaporative losses and even began constructing the Jonglei Canal (Howell et al. 1988), but construction was halted due to the Second Sudanese Civil War. While this project would have augmented downstream flows, it would have also impacted the nearly 1 million people who live in the Sudd region. These nomadic communities have come to rely on the seasonal flooding to regenerate the grasslands that support their cattle, their primary source of food and income.

Dr. Di Vittorio’s Ph.D. advisor, Dr. Aris Georgakakos, has developed various decision support tools for the Nile River Basin stakeholders and a key limitation of these tools is the hydrologic representation of the Sudd. The tools simulate the total quantity of water flowing through the Sudd but lack a process-based model that simulates hydrologic variables that are important to local stakeholders, such as the time-variable flood extents. A more comprehensive and process-based wetland model would allow decision-makers to more carefully consider the Sudd response to alternative management and climate scenarios. However, the in-situ hydrologic data needed to develop an improved model is not available due to ongoing political conflict and limited financial resources. The overarching goal of Dr. Di Vittorio’s research was therefore to explore how satellite information could be leveraged to fill data gaps and develop a hydrologic model of the Sudd that could support long-term planning and management.

Research Goals and Objectives:

The Sudd hydrologic model was developed through three key research objectives, briefly summarized below. A full description of the first objective is available in Remote Sensing of Environment (https://doi.org/10.1016/j.rse.2017.11.001). A full summary of the second and third objectives is available through the Journal of Hydrology: Regional Studies (https://doi.org/10.1016/j.ejrh.2021.100922)

1) Developed a novel multi-temporal wetland land cover and inundation classification algorithm using MODIS optical imagery.

2) Estimated the key hydrologic fluxes, including flows, precipitation, and evapotranspiration, using limited in-situ data supplemented with various satellite-derived data sources.

3) Formulated and evaluated a hydrologic model of the Sudd in an iterative manner that emphasized uncertainties ingrained in the hydrologic data, the model structure, and the model parameters.