PI: Zoubeida Kebaili Bargaoui (Ecole Nationale d’Ingénieurs de Tunis)
U.S. Partner: Kelly Caylor (Princeton University)
Project Dates: August 2013 to July 2015
Tunisia is a primarily agricultural country with sub-humid, sub-arid, and arid climate zones. As a result, the country's economy is very sensitive to the impact of droughts, so research on drought alert systems to facilitate drought monitoring, mitigation, and adaptation programs could be very useful. The project aims to contribute to drought identification and alert in Tunisia using water budget modeling, which incorporates satellite information. It will leverage the experimental African Drought Monitor (ADM) system developed by Princeton University researchers in collaboration with UNESCO and installed in Niamey and Nairobi. North Africa is not currently well covered by ADM, so this PEER Science project intends to enhance drought monitoring in the region by using local observations that are currently unavailable to ADM. Actual prediction of the water balance terms is one point of departure in ADM. The Princeton researchers are using a variable infiltration capacity (VIC) land surface model as the computational basis for the water balance representation in ADM and for land surface temperature modeling. Climate and soil data including from remote sensing sources are used as model inputs to compute soil moisture content and resulting water stress indicators.
The Tunisian research team, on the other hand, has developed a water balance model in recent years using ground-based local precipitation, air temperature, and soil data for runoff and evapotranspiration prediction. In the first phase of the project, the Tunisian model will be compared with ADM/VIC results to reconstitute a historic period of observation using runoff data (1960- 2010). The next element of the project is to assess the quality of satellite estimates and reanalysis data (rainfall in particular) that feed the VIC model by comparing them with ground estimations (historic reconstitution). In addition, the ENIT team has developed an application using ground observations and water balance modeling to assess drought indices, some of which have already been implemented in ADM. However, the drought index based on soil moisture percentiles adopted by ADM is not included in the Tunisian applications so far. An assessment of the drought indices and evaluation of their quality and ability to identify well-known past drought periods will also be carried out as part of the PEER project. Data will be shared through a web-based interface that will be developed as part of the existing ADM web interface in order to display the results of the North Tunisia Drought Monitor. Users will be able to access maps of model outputs (mainly precipitation, evapotranspiration, surface runoff, and soil moisture) and to spatially averaged drought indicators. Overall, the project should help to facilitate drought mitigation and adaptation efforts.
Summary of Recent Activities
During the final quarter of 2014, Dr. Bargaoui and the project team continued their data collection and satellite and in person research of drought conditions in Tunisia. The team requested government rainfall data from the past decade to help in creating and verifying a Standard Precipitation Index for Tunisia. Additionally, the government provided GIS information concerning soil texture, soil occupation, and geological parameters needed for the BBH water balance model used in the ungauged basins of the upper Siliana basins of Wadi Messouge and Wadi Jbara and the dam controlled Lakhmess sub basin. A tutorial for the new BBH model was also written. The team carried out further data collection and modelling correction including implementing a correction procedure from Princeton University for the Drought Monitor. This will be applied by team member Saoussen Dhib for extreme events and the results will be sent to the Drought Monitor team to improve the rainfall database.
In addition to the data research, the team experienced a change-up in the form of new members. Hanen Ghanmi obtained an Assistant Professorship at Gafsa University and thus left the project team as an engineer. However she is continuing to work with the project team on the overarching objectives. She was replaced by Maher Hsouna whose work will also focus on Siliana watershed modelling using ground water information.
In the new year, the team plans to continue collecting data and calibrating their models for the region. The team will also acquire and install new sensors and plans on hosting the US based team in Tunisia.
Website of Princeton University’s African Drought Monitor
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