Mohamed Ouessar

Water and Land Security in Drylands

Climate change (CC) is a main issue of interest at the international as well as the national levels. It is important at this stage to do research to analyze impacts and adaptation strategies. The objective of this study was to evaluate the water stress of olive groves within the context of CC in the South East of Tunisia (watershed of Oum Zessar, Medenine) using hydrological modeling (HidroMORE model). Data on rainfall and temperature were collected from available stations, while those for future scenarios (Horizons 2030 and 2090) were obtained using the Coupled Model Intercomparison Project Phase 5 CMIP5 (GFDL HIRAM C360). In comparison with the reference period (1996–2005) and projecting increases in temperature of 1 and 5 °C, as well as rainfall decreases of 5.4 and 20%, reference evapotranspiration (ETo) was simulated to increase by 3–9% and evapotranspiration under non-standard conditions (ETCadj) was reduced by 13% and 30%, respectively, for the 2030 and 2090 horizons. Thus, it is expected that the land suitable for olive cultivation will experience shrinkage and this cropping system would become increasingly problematic.

An Integrated Cost–Benefit and Livelihood Approach for Assessing the Impact of Water Harvesting Techniques (WHTs) on Livelihoods: A Case Study in the Oum Zessar Watershed, South-East Tunisia

Despite broad interest in use of water harvesting techniques (WHTs) to reduce pressure on natural resources in arid zones, few ex post assessments are available on how WHTs impact livelihood sustainability. This paper assesses the impact of WHTs on the livelihood conditions of inhabitants in the Oum Zessar watershed in south-east Tunisia. We used an integrated impact assessment (IIA) framework incorporating extended cost–benefit analysis (ECBA) and the sustainable livelihoods approach (SLA). The former internalizes environmental impacts while the latter enables assessment of the contributions of WHTs to rural livelihoods in the watershed. We began by using ECBA to estimate the profitability of investments in WHTs. We then scaled up our impact perspective from the local level to the watershed level using SLA based on survey data from beneficiary households upstream, midstream and downstream. Our goal was to better understand and evaluate changes in livelihoods and associated environmental effects. We focused on the links between cost–benefit of WHTs and sustainable livelihoods, looking in particular at the capitals that connect the two. Our ECBA results suggest that WHT techniques did benefit the local population at both the private and the social level (IRR > 20%; NPV > 2000 TD/ha). Sensitivity analysis confirmed this result. SLA findings point to a central role of social capital in promoting sustainable livelihoods, followed by physical capital enhanced by WHTs construction, especially in the upstream and downstream segments of the watershed. Recommendations were derived from these outcomes for more integrated watershed management policy.

Un système d’information pour le suivi opérationnel de la désertification à l’échelle locale (prototype SIELO)

Developper des modeles capables de fournir des indicateurs integrant des dimensions socio-economiques et environnementales dans leur diversite spatiale et temporelle, traitant de phenomenes a l’echelle locale, et mobilisables dans des systemes d’aide a la decision, reste un challenge d’actualite pour comprendre, spatialiser, suivre, evaluer et anticiper les dynamiques complexes de la desertification. Cet article presente la demarche modelisatrice imaginee, et la plateforme logicielle prototype intitulee « systeme d’information pour le suivi operationnel de la desertification a l’echelle locale » (SIELO) pour repondre a cet enjeu scientifique. Ce systeme tente de creer le lien entre : i) des indicateurs spatialises de risque de desertification prenant en compte la complexite systemique de la desertification ; et ii) le Land Cover Change observe. Le premier type de donnees est issu de modeles systemiques preexistants dans le SIEL. Le second type de donnees est extrait d’images satellites acquises selon des pas de temps reguliers. La demarche s’appuie sur des approches de spatialisation des connaissances, qui mobilise le « paysage » notamment. Dans cet article, nous mettons l’accent sur la description de la demarche proposee pour etablir ce lien, et sur les specificites qui la mettent en capacite d’alimenter un suivi operationnel de la desertification dans le cadre d’observatoires a l’echelle locale. Nous illustrons la faisabilite et l’operationnalite de sa mise en œuvre avec une premiere application a une zone aride tunisienne via un logiciel prototype developpe.