Protection against floods of the urban watersheds of Sidi Thabet in the lower valley of the Medjerda catchment (Tunisia)

This paper aims to protect against floods of the area of Sidi Thabet, which is located in the Lower valley of Medjerda catchment in the North of Tunisia and known by its wide variability of runoff between dry and wet seasons, with a diffuse distribution of urban and rural areas and the abundance of undeveloped water courses often causing flooding annoying to people and infrastructure. To identify the area of intervention and to propose the suitable accommodations in these ones, we was based on a refined cartography by using GIS tool, on a detailed hydrological study of the zone of the project, on a statistical analysis of the rainfall data using the statistical software HYFRAN, besides the application of the CAQUOT model to obtain the dimensioning flows of the projected hydraulic equipments. The protection primarily consists on establishing different collectors in the five sub-catchments responsible for channeling and routing the storm water to its natural discharge point and replacing the existent equipments unable to forward the flow with a return period (RT) of twenty years. The nature of the proposed channels depends on the area that they traverse, between buried collectors inside the city to especially solve the problems of water stagnation, open concrete and masonry channels in the towns and cities, and earth channels are projected in the areas non-urbanized in order to minimize the estimated cost of the proposed equipments, instead of respecting the width of the streets while avoiding establishing collectors in the narrow ones

Impact of climate change on the hydrological regime in the medium valley of Medjerda-Tunisia

Tunisia, as a Mediterranean region, is characterized by rainfall regimes and hydrometeorological phenomena variable in space and time. Climate change will increase this variability: extreme events such as droughts and floods can often a catastrophic situation

Drought assessment in a south Mediterranean transboundary catchment

Predicting the impacts of climate change on water resources remains a challenging task and requires a good understanding of the dynamics of the forcing terms in the past. In this study, the variability of precipitation and drought patterns is studied over the Mediterranean catchment of the Medjerda in Tunisia based on an observed rainfall dataset collected at 41 raingauges during the period 1973–2012. The standardized precipitation index and the aridity index were used to characterize drought variability. Multivariate and geostatistical techniques were further employed to identify the spatial variability of annual rainfall. The results show that the Medjerda is marked by a significant spatio-temporal variability of drought, with varying extreme wet and dry events. Four regions with distinct rainfall regimes are identified by utilizing the K-means cluster analysi. A principal component analysis identifies the variables that are responsible for the relationships between precipitation and drought variability

Water resources management in the Medjerda basin (Tunisia): assessment of hydrological impacts of climatic change in the Siliana and Béja catchments

Under the current conditions, water resources in Tunisia are intensively exploited and mobilized to meet the increasing demands of all water users. While these resources are limited, approximately estimated to 4,5 Milliards of m3, more than 50% of the total volume of renewable water is withdrawn and mainly used for agricultural purposes (80%). With almost 11 Million of inhabitants, the average of the annual available water volume per person is about 470 m3 which is clearly below the threshold of water scarcity sets to 500 m3/inh/year. Furthermore, water resources are unevenly distributed within the country. About 56% of available waters are surface waters against 44% of groundwater including deep and shallow aquifers. In addition, more than 80% of surface water is mainly from the North, 12% from the center and 8% from the south. One of the most important watercourses in Tunisia is the Medjerda. This river basin covers an area about 23,700 km2 and extends from across the border in Algeria up to the Gulf of Utica (Fig. 1). About 32% of the basin falls within Algeria and 68% in Tunisia (16,100 km2)

Water resources management in the Medjerda basin (Tunisia): assessment of hydrological impacts of climatic change in the Siliana and Béja catchments

Under the current conditions, water resources in Tunisia are intensively exploited and mobilized to meet the increasing demands of all water users. While these resources are limited, approximately estimated to 4,5 Milliards of m3, more than 50% of the total volume of renewable water is withdrawn and mainly used for agricultural purposes (80%). With almost 11 Million of inhabitants, the average of the annual available water volume per person is about 470 m3 which is clearly below the threshold of water scarcity sets to 500 m3/inh/year. Furthermore, water resources are unevenly distributed within the country. About 56% of available waters are surface waters against 44% of groundwater including deep and shallow aquifers. In addition, more than 80% of surface water is mainly from the North, 12% from the center and 8% from the south. One of the most important watercourses in Tunisia is the Medjerda. This river basin covers an area about 23,700 km2 and extends from across the border in Algeria up to the Gulf of Utica (Fig. 1). About 32% of the basin falls within Algeria and 68% in Tunisia (16,100 km2)

Gestion des ressources en eau dans la Medjerda: Modélisation hydrologique

La Medjerda est le seul cours d’eau pérenne en Tunisie. Le bassin versant est le plus important de la Tunisie en termes de ressources hydriques et contribue à près de 25% de l’ensemble des ressources mobilisables du pays. La compréhension fine de l’hydrologie de ce bassin versant anthropisé, dans un milieu fortement perturbé par des aménagements dont les objectifs sont parfois antagonistes (conservation, production, mobilisation,…), couplé à la problématique des changements climatiques dont plusieurs scénarios plaident en faveur d’une baisse significative des précipitations associée à un accroissement des températures, indiquant des ressources hydriques moins importantes pour des besoins plus élevés, reste donc un pré-requis à sa gestion durable

The added value of spatially distributed meteorological data for simulating hydrological processes in a small Mediterranean catchment

The purpose of this paper was to demonstrate the added value of the spatial distribution of rainfall and potential evapotranspiration (PE) in the prediction of the discharge for a small Mediterranean catchment located in the Medjerda basin in Tunisia, i.e. the Raghay. We compare therefore the performance of a conceptual hydrological model available in the ATHYS platform, using global and spatial distributed input data. The model was implemented in two different ways. The first implementation was in a spatially distributed mode, and the second one was in a non-distributed lumped mode by using spatially averaged data weighed with a Thiessen-interpolated factor. The performance of the model was analysed for the distributed mode and for the lumped mode with a cross-validation test and through several modelling evaluation criteria. Simultaneously, the impact of the spatial distribution of meteorological data was assessed for the two cases when estimating the model parameters, the flow and water amounts, and the flow duration curves. The cross-validation of the split-sample test shows a preference for the spatially distributed model based on accuracy criteria and graphical comparison. The distributed mode required, however, more simulation time. Finally, the results reported for the Raghay indicated that the added value of the spatial distribution of rainfall and PE is not constant for the whole series of data, depending on the spatial and temporal variability of climate data over the catchment that should be assessed prior to the modelling implementations

Assessing the goodness of fit of lumped and distributed implémentations of conceptual and global hydrological models of the Medjerda basin

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