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
Three members of the Tunisian study team visited Princeton University’s African Drought Monitor (ADM) group February 5-14, 2014. Team members were trained about the science behind the Variable Infiltration Capacity (VIC) model. They learned how to download data for model processing and were trained in using visual tools to display climatic and hydrometric data, drought indices and surface fluxes. VIC calibration using data from a Tunisian watershed was performed as an exercise. The visitors also learned more about the various forecasting tools implemented in ADM.
Dr. Bargaoui and her team will be downloading and processing satellite data, comparing them with ground data, and selecting new observational sites in the coming months. They also plan to meet with farmers and local water resource administrators in preparation for their first model runs. A reciprocal visit to Tunis El Manar University by U.S. partner Kelly Caylor is scheduled during the summer of 2014. By that time, field sensors should also be purchased and installed.
Website of Princeton University’s African Drought Monitor
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