Ibtissem Triki - Academia.edu (original) (raw)

Papers by Ibtissem Triki

A Decision Support System (DSS) for groundwater resources management is developed for the Monasti... more A Decision Support System (DSS) for groundwater resources management is developed for the Monastir region. It is a hydrogeological relational database joined with a Hydrogeological Information System (HISM) which enables fast and effective processing of large volumes of spatial data from multiple sources. The HISM has a great management capacity; it ensures the conversion from the geographic coordinates to the planimetric coordinates. It allows adding, modifying, deleting and editing data (Rainfall, piezometric and geochemical). It also ensures the storage and editing of the digitized and/or generated cartographic database.

Revue Internationale de Géomatique, 2019

Le système phréatique du sahel de Sfax (Tunisie) constitue une source importante d’approvisionnem... more Le système phréatique du sahel de Sfax (Tunisie) constitue une source importante d’approvisionnement. Ces eaux ne cessent d’être menacées par la pollution nitrique. Dans le but de protéger cet aquifère, une étude de la vulnérabilité intrinsèque a été effectuée. Pour cela on a eu recours à l’utilisation de la méthode SI (Susceptibility Index) qui prend en considération les différents critères de vulnérabilités, régissant le processus de transfert de contaminants. Il s’agit des facteurs géologiques, hydrogéologiques, d’occupation du sol, de la topographie, ainsi que de la météorologie. Dans la présente étude, une modification de la méthode SI a été faite. Une méthode dérivée du modèle SI est présentée (SI modifié). Elle repose sur une démarche qui intègre la modélisation hydrologique sous Agriflux et les SIG. Le divers recours aux SIG a permis l’exécution des différentes opérations de calcul de débits, la création de bases de données ainsi que la cartographie des paramètres influençan...

The approaches for groundwater monitoring network design can be classified as hydrogeologic and s... more The approaches for groundwater monitoring network design can be classified as hydrogeologic and statistical.

Journal of Geographic Information System

In Tunisia and particularly in Monastir region, groundwater constitutes the main source of water ... more In Tunisia and particularly in Monastir region, groundwater constitutes the main source of water supply systems. A lot of problems are facing the water management authorities. In fact, the Moknine coastal aquifer highlights several qualitative and quantitative anomalies due to the irrigated perimeters extension (Teboulba, Bekalta), releases of harmful products from the textile industry (Ksar Hellal and Moknine), intense overexploitation and seawater intrusion. Thus, for groundwater resources management, a Decision Support System (DSS) is developed for the Monastir region. This Decision Support System (DSS) brings together, on a digital support, the data descriptive and graphical component for groundwater management. It is a hydrogeological relational database joined with a Hydrogeological Information System for the Monastir region (HISM) which enables fast and effective processing of large volumes of spatial data from multiple sources. The implementation of the Hydrogeological Information System is assured using Object-Oriented Programming (OOP). The "Unified Modeling Language" (UML) is an Object-Oriented Design (OOD) methodology which is choiced for data modeling. The application interfaces have been developed in Visual Basic (VB.net) within the Integrated Development Environment (IDE) from Microsoft Visual Studio. "DotSpatial" library integrated is used to manage the geographic information layers. The HISM contains thematic layers acquired through the vectorization of 22 topographic and geologic maps (1/50,000 and 1/25,000

Advances in Remote Sensing

Soil salinity limits plant growth, reduces crop productivity and degrades soil. Multispectral dat... more Soil salinity limits plant growth, reduces crop productivity and degrades soil. Multispectral data from Landsat TM are used to study saline soils in southern Tunisia. This study will explore the potential multivariate statistical analysis, such as principal component analysis (PCA) and cluster analysis to identify the most correlated spectral indices and rapidly predict salt affected soils. Sixty six soil samples were collected for ground truth data in the investigated region. A high correlation was found between electrical conductivity and the spectral indices from near infrared and shortwave infrared spectrum. Different spectral indices were used from spectral bands of Landsat data. Statistical correlation between ground measurements of Electrical Conductivity (EC), spectral indices and Landsat original bands showed that the near and shortwave infrared bands (band 4, band 5 and 7) and the salinity indices (SI 5 and SI 9) have the highest correlation with EC. The use of CA revealed a strong correlation between electrical conductivity EC and spectral indices such abs4, abs5, abs7 and si5. The principal components analysis is conducted by incorporating the reflectance bands and spectral salinity indices from the remote sensing data. The first principal component has large positive associations with bands from the visible domain and salinity indices derived from these bands, while second principal component is strongly correlated with spectral indices from NIR and SWIR. Overall, it was found that the electrical conductivity EC is highly correlated (R 2 = −0.72) to the second principal component (PC2), but no correlation is observed between EC and the first principal component (PC1). This suggests that the second component can be used as an explanatory variable for predicting EC. Based on these results and combining the spectral indices (PC2 and abs B4) into a regression analysis, model

Journal of Arid Land

In arid and semi-arid areas, artificial recharge is a key technology in groundwater resources man... more In arid and semi-arid areas, artificial recharge is a key technology in groundwater resources management, and a reliable estimate of artificial recharge is necessary to its sustainable development. Several methods are available to estimate the artificial recharge; however, most of them require field data or model parameters, thus limiting their applications. To overcome this limitation, we presented an analytical method to estimate the artificial recharge through monitoring the water release by piezometer and analysing the controlling factors of the artificial recharge from a hill dam in Tunisia. A total of 97 measurements of water flow in the streambed recorded from 4 gauging stations were analysed. Results indicated that the average infiltration velocity ranged from 0.043 to 0.127 m/d and the infiltration index varied from 7.6 to 11.8 L/(s•km). Pearson's correlation coefficient analysis shows that the infiltration index, the stream gradient, the thickness of unsaturated zone, the number of infiltration pond, the stream geometry, and the water flow rate were found to be the main factors in determining the infiltration. The high correlation coefficients (0.908 for the number of infiltration pond and 0.999 for the stream geometry) mean that the number of infiltration pond and the stream geometry are the most influential factors. Time variations of groundwater level were used to analyze the recharge effects on the piezometry of aquifer. The analysis showed that during the artificial recharge, the water table increased at a rate of 5 mm/d and that the increase was limited to the area surrounding the recharge site. Based on the results of the study, building infiltration ponds along streambed and improving the potential of rainwater harvesting over the study area are recommended.

Environmental Earth Sciences, 2016

Any hydrogeological conceptual model of an aquifer requires a piezometric map to enable defining ... more Any hydrogeological conceptual model of an aquifer requires a piezometric map to enable defining flow direction, hydraulic gradient, groundwater recharge and discharge zones. Thus, the piezometric head calculation requires an accurate assessment of the elevation and the depth to water in monitoring wells. The main concern of aquifer managers remains the elevation estimate with a satisfactory accuracy, particularly in developing countries, where a lack of well surveying data is frequently encountered. A solution to this situation may be found in the use of digital elevation models (DEMs). In the present paper, a methodology to extract well elevations from DEMs based on datasets from Shuttle Radar Topography Mission (SRTM), Google Earth and digitized topographic map is presented. Statistical analyses of the elevations derived from a topographic field survey and the relative DEMs and piezometric map comparisons are used to assess the elevation accuracy. The DEM generated from the topographic map (TopoDEM) resulted in the closest match to the surveyed one with a correlation coefficient of 0.98 and a root mean square error of 0.76. The elevation from SRTM and Google Earth DEMs lead to an underestimation of the piezometry with the poorest performance from Google Earth DEM.

Environmental Earth Sciences, 2016

Due to increase in population and agricultural activities, the Sfax coastal aquifer is under trem... more Due to increase in population and agricultural activities, the Sfax coastal aquifer is under tremendous stress and seawater intrusion becomes a serious concern. This situation needs an assessment of aquifer vulnerability and seawater intrusion risk. A new approach for vulnerability mapping using GALDIT, groundwater quality index for seawater intrusion (GQISWI), geostatistics, the Ghyben–Herzberg model and GIS was developed. The model is used to determine the trend of groundwater contamination by seawater intrusion in the coastal aquifer in Sfax basin (Tunisia). Vulnerability assessment method is recognized through assessing weight and ratings of the GALDIT relevant parameter. A second vulnerability map was realized based upon the groundwater quality index for seawater intrusion integrating the water quality parameters for delineating seawater intrusion in the aquifer. The validation of GQISWI and GALDIT vulnerability maps was undertaken through comparison of areas of high Jones Ratio, chloride and TDS concentration and their relative vulnerability index. The Ghyben–Herzberg model has been used to predict the actual seawater intrusion extend and evaluate the freshwater–saltwater dynamics. The results reveal that the coastal area is currently undergoing seawater intrusion and its northern part is the most affected one by this contamination.

Water and Environment Journal, 2012

In many developing countries, the groundwater monitoring network is randomly designed, and conseq... more In many developing countries, the groundwater monitoring network is randomly designed, and consequently needs to be revised and optimised to reduce operation time and cost, remove redundant piezometric data, and strengthen sparseness data zone with supplementary observation well. The geostatistical approach used in this work is based on the universal kriging variance combined with crossvalidation test. Hence, a rational interpolation of water table elevations was performed to evaluate the accuracy of data employed in the piezometric head modelling. In this study, the groundwater monitoring network of the Sfax superficial aquifer in the south east of Tunisia was optimised. The elimination of five observation wells induces the invariability in the variance of estimate due to their less contribution in interpretations of the groundwater level behaviour. However, 38 wells were added at areas of high variance of the kriging in order to ameliorate the spatial coverage of the monitoring network.

Desalination and Water Treatment, 2014

In this study, we investigate the ability to combine a multivariate statistical analysis with the... more In this study, we investigate the ability to combine a multivariate statistical analysis with the cokriging method to point out the groundwater salinization in the coastal Sfax aquifer (eastern Tunisia). First, multivariate statistical analysis such as principal component analysis (PCA) and cluster analysis were performed on 75 water samples. PCA identifies three main processes influencing groundwater chemistry which are seawater intrusion, water-rock interaction, and contamination by nitrates, these three factors accounted for 76% of total variance of the groundwater. Furthermore, cokriging is applied to take into account spatial dependence between the studied variables. Five variables were processed: concentration of sulfates, chlorides, sodium and the sodium adsorption ratio, as primary variables, and the more numerous data for total dissolved solid, as auxiliary variables. The generated spatial variability maps highlighted the high-risk zone of groundwater contamination of the superficial aquifer of Sfax. The effectiveness of the high estimation capability of the cokriging is demonstrated by cross-validation. Compared with ordinary kriging for a single variable, cokriging can provide an improvement of the uncertainty in terms of reducing the mean-squared error and mean error.

Environmental Monitoring and Assessment, 2014

In this paper, the pattern of groundwater level fluctuations is investigated by statistical techn... more In this paper, the pattern of groundwater level fluctuations is investigated by statistical techniques for 24 monitoring wells located in an unconfined coastal aquifer in Sfax (Tunisia) for a time period from 1997 to 2006. Firstly, a geostatistical study is performed to characterize the temporal behaviors of data sets in terms of variograms and to make predictions about the value of the groundwater level at unsampled times. Secondly, multivariate statistical methods, i.e., principal component analysis (PCA) and cluster analysis (CA) of time series of groundwater levels are used to classify groundwater hydrographs regard to identical fluctuation pattern. Three groundwater groups (A, B, and C) were identified. In group "A," water level decreases continuously throughout the study periods with rapid annual cyclic variation, whereas in group "B," the water level contains much less high-frequency variation. The wells of group "C" represents a steady and gradual increase of groundwater levels caused by the aquifer artificial recharge. Furthermore, a cross-correlation analysis is used to investigate the aquifer response to local rainfall and temperature records. The result revealed that the temperature is more affecting the variation of the groundwater level of group A wells than the rainfall. However, the second and the third groups are less affected by rainfall or temperature.

A Decision Support System (DSS) for groundwater resources management is developed for the Monasti... more A Decision Support System (DSS) for groundwater resources management is developed for the Monastir region. It is a hydrogeological relational database joined with a Hydrogeological Information System (HISM) which enables fast and effective processing of large volumes of spatial data from multiple sources. The HISM has a great management capacity; it ensures the conversion from the geographic coordinates to the planimetric coordinates. It allows adding, modifying, deleting and editing data (Rainfall, piezometric and geochemical). It also ensures the storage and editing of the digitized and/or generated cartographic database.

Revue Internationale de Géomatique, 2019

Le système phréatique du sahel de Sfax (Tunisie) constitue une source importante d’approvisionnem... more Le système phréatique du sahel de Sfax (Tunisie) constitue une source importante d’approvisionnement. Ces eaux ne cessent d’être menacées par la pollution nitrique. Dans le but de protéger cet aquifère, une étude de la vulnérabilité intrinsèque a été effectuée. Pour cela on a eu recours à l’utilisation de la méthode SI (Susceptibility Index) qui prend en considération les différents critères de vulnérabilités, régissant le processus de transfert de contaminants. Il s’agit des facteurs géologiques, hydrogéologiques, d’occupation du sol, de la topographie, ainsi que de la météorologie. Dans la présente étude, une modification de la méthode SI a été faite. Une méthode dérivée du modèle SI est présentée (SI modifié). Elle repose sur une démarche qui intègre la modélisation hydrologique sous Agriflux et les SIG. Le divers recours aux SIG a permis l’exécution des différentes opérations de calcul de débits, la création de bases de données ainsi que la cartographie des paramètres influençan...

The approaches for groundwater monitoring network design can be classified as hydrogeologic and s... more The approaches for groundwater monitoring network design can be classified as hydrogeologic and statistical.

Journal of Geographic Information System

In Tunisia and particularly in Monastir region, groundwater constitutes the main source of water ... more In Tunisia and particularly in Monastir region, groundwater constitutes the main source of water supply systems. A lot of problems are facing the water management authorities. In fact, the Moknine coastal aquifer highlights several qualitative and quantitative anomalies due to the irrigated perimeters extension (Teboulba, Bekalta), releases of harmful products from the textile industry (Ksar Hellal and Moknine), intense overexploitation and seawater intrusion. Thus, for groundwater resources management, a Decision Support System (DSS) is developed for the Monastir region. This Decision Support System (DSS) brings together, on a digital support, the data descriptive and graphical component for groundwater management. It is a hydrogeological relational database joined with a Hydrogeological Information System for the Monastir region (HISM) which enables fast and effective processing of large volumes of spatial data from multiple sources. The implementation of the Hydrogeological Information System is assured using Object-Oriented Programming (OOP). The "Unified Modeling Language" (UML) is an Object-Oriented Design (OOD) methodology which is choiced for data modeling. The application interfaces have been developed in Visual Basic (VB.net) within the Integrated Development Environment (IDE) from Microsoft Visual Studio. "DotSpatial" library integrated is used to manage the geographic information layers. The HISM contains thematic layers acquired through the vectorization of 22 topographic and geologic maps (1/50,000 and 1/25,000

Advances in Remote Sensing

Soil salinity limits plant growth, reduces crop productivity and degrades soil. Multispectral dat... more Soil salinity limits plant growth, reduces crop productivity and degrades soil. Multispectral data from Landsat TM are used to study saline soils in southern Tunisia. This study will explore the potential multivariate statistical analysis, such as principal component analysis (PCA) and cluster analysis to identify the most correlated spectral indices and rapidly predict salt affected soils. Sixty six soil samples were collected for ground truth data in the investigated region. A high correlation was found between electrical conductivity and the spectral indices from near infrared and shortwave infrared spectrum. Different spectral indices were used from spectral bands of Landsat data. Statistical correlation between ground measurements of Electrical Conductivity (EC), spectral indices and Landsat original bands showed that the near and shortwave infrared bands (band 4, band 5 and 7) and the salinity indices (SI 5 and SI 9) have the highest correlation with EC. The use of CA revealed a strong correlation between electrical conductivity EC and spectral indices such abs4, abs5, abs7 and si5. The principal components analysis is conducted by incorporating the reflectance bands and spectral salinity indices from the remote sensing data. The first principal component has large positive associations with bands from the visible domain and salinity indices derived from these bands, while second principal component is strongly correlated with spectral indices from NIR and SWIR. Overall, it was found that the electrical conductivity EC is highly correlated (R 2 = −0.72) to the second principal component (PC2), but no correlation is observed between EC and the first principal component (PC1). This suggests that the second component can be used as an explanatory variable for predicting EC. Based on these results and combining the spectral indices (PC2 and abs B4) into a regression analysis, model

Journal of Arid Land

In arid and semi-arid areas, artificial recharge is a key technology in groundwater resources man... more In arid and semi-arid areas, artificial recharge is a key technology in groundwater resources management, and a reliable estimate of artificial recharge is necessary to its sustainable development. Several methods are available to estimate the artificial recharge; however, most of them require field data or model parameters, thus limiting their applications. To overcome this limitation, we presented an analytical method to estimate the artificial recharge through monitoring the water release by piezometer and analysing the controlling factors of the artificial recharge from a hill dam in Tunisia. A total of 97 measurements of water flow in the streambed recorded from 4 gauging stations were analysed. Results indicated that the average infiltration velocity ranged from 0.043 to 0.127 m/d and the infiltration index varied from 7.6 to 11.8 L/(s•km). Pearson's correlation coefficient analysis shows that the infiltration index, the stream gradient, the thickness of unsaturated zone, the number of infiltration pond, the stream geometry, and the water flow rate were found to be the main factors in determining the infiltration. The high correlation coefficients (0.908 for the number of infiltration pond and 0.999 for the stream geometry) mean that the number of infiltration pond and the stream geometry are the most influential factors. Time variations of groundwater level were used to analyze the recharge effects on the piezometry of aquifer. The analysis showed that during the artificial recharge, the water table increased at a rate of 5 mm/d and that the increase was limited to the area surrounding the recharge site. Based on the results of the study, building infiltration ponds along streambed and improving the potential of rainwater harvesting over the study area are recommended.

Environmental Earth Sciences, 2016

Any hydrogeological conceptual model of an aquifer requires a piezometric map to enable defining ... more Any hydrogeological conceptual model of an aquifer requires a piezometric map to enable defining flow direction, hydraulic gradient, groundwater recharge and discharge zones. Thus, the piezometric head calculation requires an accurate assessment of the elevation and the depth to water in monitoring wells. The main concern of aquifer managers remains the elevation estimate with a satisfactory accuracy, particularly in developing countries, where a lack of well surveying data is frequently encountered. A solution to this situation may be found in the use of digital elevation models (DEMs). In the present paper, a methodology to extract well elevations from DEMs based on datasets from Shuttle Radar Topography Mission (SRTM), Google Earth and digitized topographic map is presented. Statistical analyses of the elevations derived from a topographic field survey and the relative DEMs and piezometric map comparisons are used to assess the elevation accuracy. The DEM generated from the topographic map (TopoDEM) resulted in the closest match to the surveyed one with a correlation coefficient of 0.98 and a root mean square error of 0.76. The elevation from SRTM and Google Earth DEMs lead to an underestimation of the piezometry with the poorest performance from Google Earth DEM.

Environmental Earth Sciences, 2016

Due to increase in population and agricultural activities, the Sfax coastal aquifer is under trem... more Due to increase in population and agricultural activities, the Sfax coastal aquifer is under tremendous stress and seawater intrusion becomes a serious concern. This situation needs an assessment of aquifer vulnerability and seawater intrusion risk. A new approach for vulnerability mapping using GALDIT, groundwater quality index for seawater intrusion (GQISWI), geostatistics, the Ghyben–Herzberg model and GIS was developed. The model is used to determine the trend of groundwater contamination by seawater intrusion in the coastal aquifer in Sfax basin (Tunisia). Vulnerability assessment method is recognized through assessing weight and ratings of the GALDIT relevant parameter. A second vulnerability map was realized based upon the groundwater quality index for seawater intrusion integrating the water quality parameters for delineating seawater intrusion in the aquifer. The validation of GQISWI and GALDIT vulnerability maps was undertaken through comparison of areas of high Jones Ratio, chloride and TDS concentration and their relative vulnerability index. The Ghyben–Herzberg model has been used to predict the actual seawater intrusion extend and evaluate the freshwater–saltwater dynamics. The results reveal that the coastal area is currently undergoing seawater intrusion and its northern part is the most affected one by this contamination.

Water and Environment Journal, 2012

In many developing countries, the groundwater monitoring network is randomly designed, and conseq... more In many developing countries, the groundwater monitoring network is randomly designed, and consequently needs to be revised and optimised to reduce operation time and cost, remove redundant piezometric data, and strengthen sparseness data zone with supplementary observation well. The geostatistical approach used in this work is based on the universal kriging variance combined with crossvalidation test. Hence, a rational interpolation of water table elevations was performed to evaluate the accuracy of data employed in the piezometric head modelling. In this study, the groundwater monitoring network of the Sfax superficial aquifer in the south east of Tunisia was optimised. The elimination of five observation wells induces the invariability in the variance of estimate due to their less contribution in interpretations of the groundwater level behaviour. However, 38 wells were added at areas of high variance of the kriging in order to ameliorate the spatial coverage of the monitoring network.

Desalination and Water Treatment, 2014

In this study, we investigate the ability to combine a multivariate statistical analysis with the... more In this study, we investigate the ability to combine a multivariate statistical analysis with the cokriging method to point out the groundwater salinization in the coastal Sfax aquifer (eastern Tunisia). First, multivariate statistical analysis such as principal component analysis (PCA) and cluster analysis were performed on 75 water samples. PCA identifies three main processes influencing groundwater chemistry which are seawater intrusion, water-rock interaction, and contamination by nitrates, these three factors accounted for 76% of total variance of the groundwater. Furthermore, cokriging is applied to take into account spatial dependence between the studied variables. Five variables were processed: concentration of sulfates, chlorides, sodium and the sodium adsorption ratio, as primary variables, and the more numerous data for total dissolved solid, as auxiliary variables. The generated spatial variability maps highlighted the high-risk zone of groundwater contamination of the superficial aquifer of Sfax. The effectiveness of the high estimation capability of the cokriging is demonstrated by cross-validation. Compared with ordinary kriging for a single variable, cokriging can provide an improvement of the uncertainty in terms of reducing the mean-squared error and mean error.

Environmental Monitoring and Assessment, 2014

In this paper, the pattern of groundwater level fluctuations is investigated by statistical techn... more In this paper, the pattern of groundwater level fluctuations is investigated by statistical techniques for 24 monitoring wells located in an unconfined coastal aquifer in Sfax (Tunisia) for a time period from 1997 to 2006. Firstly, a geostatistical study is performed to characterize the temporal behaviors of data sets in terms of variograms and to make predictions about the value of the groundwater level at unsampled times. Secondly, multivariate statistical methods, i.e., principal component analysis (PCA) and cluster analysis (CA) of time series of groundwater levels are used to classify groundwater hydrographs regard to identical fluctuation pattern. Three groundwater groups (A, B, and C) were identified. In group "A," water level decreases continuously throughout the study periods with rapid annual cyclic variation, whereas in group "B," the water level contains much less high-frequency variation. The wells of group "C" represents a steady and gradual increase of groundwater levels caused by the aquifer artificial recharge. Furthermore, a cross-correlation analysis is used to investigate the aquifer response to local rainfall and temperature records. The result revealed that the temperature is more affecting the variation of the groundwater level of group A wells than the rainfall. However, the second and the third groups are less affected by rainfall or temperature.