Assessment of drought stress in arid olive groves using HidroMORE model

The olive tree is well known for being adapted to the arid conditions of the Mediterranean basin. However, prolonged drought periods which are expected to become more frequent because of climate change could result in severe water stress. In order to map the spatial distribution of drought stress in the olive groves in the arid regions of southeastern Tunisia (governorate of M denine), we made recourse to the HidroMORE model (based mainly on FAO56 ET, NDVI from Sentinel 2 images and other physical parameters) to compute the water balance in a GIS environment. The outputs were compared to in situ soil water content measurements in four selected sites representing the various agro-ecological zones (mountains, piedmont, inner plain and coast) of the study site during the observation period from January 2016 to December 2019. The model outputs performed relatively well (the overall correlation coefficient R2=0.72; index of agreement IA=0.76). The simulation results show that during normal years or average droughts, the water stress is least in the mountain and piedmont zones because of the additional runoff water supplied by the traditional water harvesting structures (Jessour and Tabias) and in the coastal zone, thanks to the higher air humidity and rainfall. In contrast, the olives in the inner plains are the most affected. Nevertheless, in case of severe droughts, the stress is generalised. Thus, the model could be used as a decision tool for prioritizing areas of intervention for drought control and mitigation (supplemental irrigation for trees safeguard, etc.)</jats:p

Groundwater vulnerability based on GIS approach: Case study of Zeuss-Koutine aquifer, South-Eastern Tunisia

Groundwater vulnerability mapping is largely used as a modeling tool to delineate areas susceptible to pollution and to protect groundwater resources from this threat. The Zeuss-Koutine aquifer, which constitutes an important source of drinking water in the Southeastern Tunisia, is subjected to an intensive exploitation and threatened by pollution due mainly to the industrial zone of Koutine. The groundwater circulates in fissured and karstified limestone. Aquifer vulnerability has been assessed using the SINTACS method. The different parameters of the SINTACS model were collected from several sources and converted into thematic maps using ArcGis. Each SINTACS parameter was assigned a weight and rating based on a range of information within the parameter. The weight of each parameter depends on the impact of potential pollution. The analysis of vulnerability map to pollution shows that the Southeastern part of the aquifer and the Wadis beds are more susceptible to pollution. The measured nitrate concentrations of two sampling campaigns carried out in high and dry water seasons are coherent with the SINTACS model results.</jats:p

Groundwater vulnerability based on GIS approach: Case study of Zeuss-Koutine aquifer, South-Eastern Tunisia

La cartografía de la vulnerabilidad del agua subterránea se utiliza como herramienta de modelado de contaminación y para proteger los recursos hídricos. El acuífero Zeuss-Koutin, que constituye una fuente primordial de agua potable en el sur este de Tunez, esta sometido a una explotación intensiva y amenazado de contaminación debido esencialmente a la zona industrial de Koutine. El agua subterránea circula a través de piedra calcarea fisurada y karstificada. La vulnerabilidad del acuífero se ha evaluado en los acuiferos Zeuss-Koutine utilizando el método SINTACS. Los distintos parámetros del modelo se obtuvieron de distintes fuentes y se hicieron mapas temáticos utilizando ArcGis. A cada parámetro SINTACS se le asigno un peso y una clasificación basados en una amplia gama de información del parámetro. El peso de cada parámetro depende del impacto de la contaminación potencial. El análisis del mapa de vulnerabilidad a la contaminación muestra que la parte sud-este del acuífero y los lechos Wadis son más susceptibles a la contaminación. Las concentraciones de nitratos medidas en dos campañas de muestreo realizadas en temporadas altas y secas en agua son coherentes con los resultados del modelo SINTACS. doi: https://doi.org/10.22201/igeof.00167169p.2017.56.2.176

Assessing pollution and water resources suitability for multiple uses under extended drought and climate change conditions: the case of the Grombalia aquifer in Tunisia

Climate change and human activities are increasingly impacting groundwater resources, presenting significant challenges for regions like Grombalia, Tunisia. This study investigates recent changes in groundwater quality and explores the potential long-term effects of climate change on groundwater levels until the end of the century. Twenty groundwater samples were collected to assess key hydrochemical parameters, including major ions, physical parameters, and chemical oxygen demand. Using geochemical modeling and multivariate statistical analysis, natural and anthropogenic processes influencing water quality were identified. The collected data serve to calculate the Drinking Water Quality Index (DWQI) and Total Hardness to determine the groundwater suitability for human consumption. Ten water quality parameters were used to assess the groundwater suitability for irrigation purposes and to calculate the Irrigation Water Quality Index (IWQI). Additionally, a proxy model was developed to forecast future groundwater levels using climate projections from an ensemble of regional climate models. This research underscores the growing pressures on groundwater systems in Grombalia, offering novel insights into the water resource sustainability of the region in the face of climate change and human activities. The findings contribute to a deeper understanding of groundwater vulnerability in this critical region, emphasizing the need for proactive management strategies

Classification methods for detecting and evaluating changes in desertification-related features in srid and semi-arid environments

Land cover, land use, soil salinisation and sand encroachment, which are desertification-indicating features, were integrated into a diachronic assessment, obtaining quantitative and qualitative information on the ecological state of the land, particularly degradation tendencies. In arid and semi-arid study areas of Algeria and Tunisia, sustainable development requires the understanding of these dynamics as it withstands the monitoring of desertification processes. Two different classification methods of salt and sand features have been set up, using historical and present Landsat imagery. Mapping of features of interest was achieved using both visual interpretation and automated classification approaches. The automated one implies a decision tree (DT) classifier and an unsupervised classification applied to the principal components (PC) extracted from Knepper ratios composite. Integrating results with ancillary spatial data, we could identify driving forces and estimate the metrics of desertification processes. In the Biskra area (Algeria), it emerged that the expansion of irrigated farmland in the past three decades has been contributing to an ongoing secondary salinisation of soils, with an increase of over 75%. In the Oum Zessar area (Tunisia), there has been a substantial change in several landscape components in the last decades, related to increased anthropic pressure and settlement, agricultural policies and national development strategies. One of the concerning aspects is the expansion of sand encroached areas over the last three decades of around 27%. This work is partly supported and developed within the WADIS-MAR Demonstration Project, funded by the EU Commission through the SWIM Programme (www.​wadismar.​eu)

The SWAT model to assess hydrological processes in arid environment (SE Tunisia), in the frame of WADIS-MAR project

Arid regions of Maghreb (North Africa) suffer scarce water conditions and the erratic behaviour of rainfall events over brief intervals often produce short and intense floods events which converge into ephemeral wadi beds. The watershed of wadi Oum Zessar, in South-East Tunisia, is characterized by a rainfall rate of about 200 mm/year, overexploitation of groundwater resources and is highly exposed to climate change risk and desertification processes (Ghiglieri et al., 2014). This region represents one of the two study areas in the framework of WADIS-MAR demonstration project (www.wadismar.eu), funded by the European Commission under the Regional Programme SWIM (www.swim-sm.eu). WADIS-MAR Project aims: (i) to improve the traditional water harvesting systems (i.e. jessour and tabias) by applying “soft” modern rehabilitation interventions; (ii) to increase groundwater availability through managed aquifer recharge (MAR) systems (i.e. gabions, recharge wells, recharge trenches). Jessour andtabias capture surface runoff coming from degraded and rocky rangelands for crop production (fruit trees, mainly olives, and cereals) in upstream subbasins. The objective of this study was to assess the main hydrological processes and the sediment loads in this arid environment, by using the Soil and Water Assessment Tool (SWAT) model. Sediment load is an important parameter to be considered in the MAR systems because it may causes the clogging of the infiltrating surface, resulting in the reduction of water infiltration rates. The watershed delineation used the newly 2014 released SRTM 1 Arc-Second digital elevation model, available at www.earthexplorer.usgs.gov. A land cover classification obtained by visual interpretation of Landsat data was used for the modelling. Conversion to land use was supported by ancillary and detailed ground truth data. The classic version of SWAT was adjusted to adapt the model to this dry Mediterranean environment (Ouessar et al., 2009). In SWAT, subbasin may be divided into Hydrologic Response Units (HRUs) which possess unique landuse/management/soil attribute. Normally, the runoff from all HRUs is added directly to the outlet of the subbasin. In this study runoff is routed between HRUs within the subbasin. The main adjustment consists of allowing the simulation of the runoff collection behind the water harvesting structures by bringing the surface runoff and lateral flow generated by different HRUs within the same subbasin. Moreover, existing gabions and recharge wells were considered in the model for a more accurate simulation of the hydrological processes. Possible coupling with MODFLOW will be considered. After calibration and validation, the model will be also used for evaluating the efficiency of the MAR systems which are being realized within the WADIS-MAR project