Jamila Tarhouni’s research while affiliated with University of Carthage and other places

The present work seeks to characterize the water resources of the overexploited aquifer of Oued Chiba watershed, thus identifying the geochemical process controlling the mineralization. Physico-chemical analyses (T°C, pH, electrical conductivity and major elements) were carried out during two sampling campaigns. The piezometric study showed depressions at Tafelloune, Gsar Saad and Diar Hajjej, which were caused by the overexploitation of the aquifer. The results showed high values of total dissolved solids (TDS) and salinity, due to contamination by seawater intrusion; this is confirmed by negative values of piezometry and high concentration of chloride. The interpretation of the Piper diagram revealed that the water facies of the Chiba plain are chloride-sodium and mixed chloride and mixed sulphate. Subsequently, to understand the mechanisms governing the water quality of the region, we used the statistical tool especially the principal components analysis which showed that the two factors F1 (water mineralization) and F2 (anthropogenic activities) account for 65% of the total variance in groundwater quality.

The Plio-Quaternary aquifer in the Kairouan plain (central Tunisia, 3000 km2) represents a key resource for the agricultural development of the region. To date, hydrological studies consider that a part of the water of this large aquifer is discharging in the Sebkha Kelbia, topographic depression (120 km2). Regarding the continuous groundwater level drop observed since the 1970s, questions can be asked about the actual system functioning. This study investigates exchanges between groundwater and surface water and describes water flow paths in the Sebkha Kelbia basin by combined two approaches such are environmental tracers and geophysical investigation (TDEM). Two types of groundwater were distinguished in Sebkha Kelbia basin based on their piezometric and geochemical behaviors. Geophysical study shows that a deep fresh groundwater is confined below a clay layer and separated from shallow saline groundwater. According to stable isotopes (d18O, d2H), deep groundwater in the north of the Sebkha is characterized by enriched d18O and d2H contents, reflecting the existence of another source of recent recharge. Further south, the isotopic composition of deep groundwater is characterized by depleted isotopic levels of stable isotopes. This isotopic signature is very similar to that of the Plio-Quaternary aquifer, confirming that the Sebkha Kelbia is recharged by the groundwater of Kairouan aquifer in this area. Results make clear that, not the entire amount of groundwater of the Plio-Quaternary aquifer in Kairouan plain are discharged in the Sebkha Kelbia. A flow path from upstream to downstream of the Sebkha Kelbia is defined on the basis of the piezometric map, showing that groundwater continues partly towards the sea. This study highlights another role of the Sebkha Kelbia. It represents not only a discharge area of groundwater but can also recharges the shallow groundwater in the north of the basin.

Tritium is a well-known tracer, used to estimate the age of modern groundwater (<50 years) and consequently to capture information on the longer-term components of recharge in aquifers. However, its current low concentration in groundwater limits its usefulness for recharge assessment, which is more symptomatic of arid and semi-arid regions where the recharge is characterized by extreme spatial and temporal variability. Regions where groundwater tritium was studied at a time close to the peak of nuclear bomb testing (1963) would be worth studying again today to establish new information. This report describes the application of a radioactivity decay model to a long (up to 50 years) record of tritium in rainfall and the associated recharge to several aquifers in central Tunisia; these aquifers were sampled for tritium in 1967. The results show that the groundwater renewal rate has a large range: 0.06–2.2% of annual mean rainfall for Plio-Quaternary aquifers, 0.1–6.46% for Mio-Pliocene aquifers, and 0.1–1.5% for the upper Oligocene aquifers. A good agreement was found between the recharge estimated in this study and the recharge estimated in previous studies only for the upper Oligocene aquifers. This suggest that the methodology of recharge estimation, described in this report, is reliable only for aquifers of homogeneous lithology with a localized recharge area, but the method is less consistent for detrital aquifers, i.e. composed of lenticular sediments. The results also highlight the usefulness of historical (1950–1970) measurements of tritium in groundwater for the estimation of the groundwater recharge.

The aquifer of the semi-arid Kairouan plain has been exploited for decades to supply the growing irrigated agriculture and theneed of drinking water. In parallel, the major hydraulic works drastically changed the natural groundwater recharge processes.The continuous groundwater level drop observed since the 1970s naturally raises the question of groundwater storage sustain-ability. To date, hydrogeological studies focused on groundwater fluxes, but the total amount of groundwater stored in the aquifersystem has never been fully estimated. This is the purpose of the present paper. A complete database of all available geological,hydrogeological and geophysical data was created to build a 3D lithology model. Then, the lithological units were combined withthe hydraulic properties to estimate the groundwater storage. Over the 700 km2of the modelled area, the estimated storage in2013 was around 18 × 109m3(equivalent to 80 times the annual consumption of 2010) with a highly variable spatial distribution.In 45 years (1968–2013), 12% of the amount of groundwater stored in the aquifer has been depleted. According to these results,individual farms will face strong regional disparities for their access to groundwater in the near future

With water table drop, managers got extremely concerned about the future of the groundwater resources sustainability of the Sisseb El Alem Nadhour Saouaf aquifer (SANS). In order to understand the groundwater flow dynamic and to assess the functioning of the aquifer system, a three-dimensional (3D) regional geological model of the SANS basin was carried on. The 3D geological model was developed by the combination of 2D seismic reflection profiles, calibrated by wireline logging data of oil wells, hydraulic wells and geological field sections. The 3D geological model shows that the Oligo-Neogene and Eocene aquifers in the study area represent important geometric variations and cumulated thickness affected by intensive fractures. The modeled stratigraphic units were combined with the hydraulic properties to estimate the groundwater storage. The estimated storage in 2016 was around 11 × 10⁹ m³ and in 1971, it was 16 × 10⁹ m³, so, 30% of the groundwater stored previously was consumed in 45 years. Yet, a variable spatial distribution of storativity was demonstrated, ranging from 1 to 3.4 × 10⁶ m³/km². These results prove the importance of hydro-geophysical investigation and numerical modeling to depicting hydrostratigraphic trends and suggest, that the fate of groundwater resources in the SANS aquifer seems though to be more a matter of the disparity of the groundwater storage than a matter of quantity.

This paper describes an assessment of the climate change (CC) impacts on the Zeuss Koutine (ZK) aquifer in southeastern Tunisian using aDecision Support System(DSS). TheDSS is formedby a dynamic linkage between WEAP and MODFLOWsoftware. It includes allwater resources existingin the hydro-systemofMedenine’sgovernorate, at the scale of the Zeuss Koutine Watershed. This aquifer has been over exploited since 1986. It had an exploitation rate of 185% in 2010 with a monthly maximum of 220% in summer; which reflects the climatic effect on groundwater exploitation. The study area has an arid climate with an average annual rainfall less than 200mmand only 30 rainfall days per year in addition to a spatio-temporal irregularity. The average annual temperature is 21.4 °C with high potential evapotranspiration. These severe climatic factors are the major cause of water scarcity in arid regions. Therefore,modelinggroundand surfacewater resources taken intoaccount CCimpacts can be useful .