Fadoua Hamzaoui-Azaza

Geochemistry and quality assessment of groundwater using graphical and multivariate statistical methods. A case study: Grombalia phreatic aquifer (Northeastern Tunisia)

The Grombalia coastal aquifer, situated in Northeastern Tunisia, is a water source for public, agricultural, and industrial supplies in the region. The overexploitation of this aquifer, since 1959, and the agriculture activities led to the degradation, by places, of the water quality. The present study implemented graphical, modeling, and multivariate statistical tools to investigate natural and anthropogenic processes controlling Grombalia groundwater mineralization and water quality for promoting sustainable development. To attempt this goal, groundwater was collected from 33 observation wells in January 2004, and samples were analyzed for 10 physicochemical parameters (temperature, pH, salinity, Na+, Ca2+, K+, Mg2+, Cl−, HCO3−, and SO42−). Hydrochemical facies using Piper diagram indicates a predominance of a mixed facies, of the Na-Cl-HCO3 type, or Na-Ca-Cl-SO4 type, and, with less expansion, Na Cl type. The main factors controlling Grombalia groundwater mineralization seem to be mineral dissolution of highly soluble salts especially, the halite dissolution existing in the surface salty deposits and, with less importance, the ion exchange and reverse ion exchange process with clay minerals existing in the aquifer. The comparison of the major ions of the Grombalia groundwater, with the World Health Organization norms of potability (WHO 2004), reveals that these waters cannot be used for human consumption without any treatment. Most waters of the Grombalia aquifer, with a relatively high salinity, are not suitable for irrigation, in ordinary conditions. Nevertheless, they can be used for permeable soils, with an adequate drainage and applying an excess of leaching water.

Application of multivariate statistical analysis and hydrochemical and isotopic investigations for evaluation of groundwater quality and its suitability for drinking and agriculture purposes: case of Oum Ali-Thelepte aquifer, central Tunisia.

Groundwater plays a dominant role in arid regions; it is among the most available water resources in Tunisia. Located in northwestern Tunisia, Oum Ali-Thelepte is a deep Miocene sedimentary aquifer, where groundwater is the most important source of water supply. The aim of the study is to investigate the hydrochemical processes leading to mineralization and to assess water quality with respect to agriculture and drinking for a better management of groundwater resources. To achieve such objectives, water analysis was carried out on 16 groundwater samples collected during January–February 2014. Stable isotopes and 26 hydrochemical parameters were examined. The interpretation of these analytical data showed that the concentrations of major and trace elements were within the permissible level for human use. The distribution of mineral processes in this aquifer was identified using conventional classification techniques, suggesting that the water facies gradually changes from Ca–HCO3 to Mg–SO4 type and are controlled by water–rock interaction. These results were endorsed using multivariate statistical methods such as principal component analysis and cluster analysis. The sustainability of groundwater for drinking and irrigation was assessed based on the water quality index (WQI) and on Wilcox and Richards’s diagrams. This aquifer has been classified as “excellent water” serving good irrigation in the area. As for the stable isotope, the measurements showed that groundwater samples lay between global meteoric water line (GMWL) and LMWL; hence, this arrangement signifies that the recharge of the Oum Ali-Thelepte aquifer is ensured by rainwater infiltration through mountains in the border of the aquifer without evaporation effects.

An integrated statistical methods and modelling mineral–water interaction to identifying hydrogeochemical processes in groundwater in Southern Tunisia

Abstract Groundwater is the most precious and valuable natural source of water in the southeast of Tunisia. The aim of this study is to find an adequate combination of methods for a qualitative description of geochemical processes into the Zeuss-Koutine, a Triassic and Miocene groundwater system, the unique source of water for this region of the Mediterranean (Medenine, Jerba, Zarzis and Jorf cities).Conventional classification techniques, statistical analyses and kriging methods were used to identify mineral processes distribution. This study finds that water chemistry is mainly dominated by dissolution/precipitation of minerals (calcite, dolomite, aragonite, anhydrite, gypsum and halite). Results obtained from principal component analyses (PCA) demonstrate that the variable responsible for water quality are largely related to soluble salts species (Na+, Cl-, Ca2+, Mg2+and SO42-). On the basis of the hierarchical cluster analysis (HCA), three groundwater clusters have been distinguished : cluster 1 is low TDS (<1000 mg L-1) Ca2+= Mg2+- Na+- SO42- waters which degrades into predominantly Na+-Ca2+-Cl--SO42- more saline groundwater (cluster 2) (TDS>3000 mg L-1) resulting from replacement of Ca by Na through cation exchange process on clay minerals. Cluster 3 is high TDS (>7000 mg L-1) NaCl waters from the aquifer system under confined conditions. Clusters 1 and 2 are located in preferential recharge zones whereas cluster 3 characterises downstream of the study area. Overall, a groundwater quality decrease has been observed similarly with a salinity increase from downstream to upstream towards the coast, where cation exchange processes and salinisation due to the long residence times appear to be the main processes responsible of more salty waters.

Hydrogeochemical and Isotopic Investigations for Evaluation of the Impact of Climate Change on Groundwater Quality, a Case Study of the Plaine of Kasserine, Central Tunisia

Located in arid region in Central Tunisia, the plaine of Kasserine is a deep Plio-Mio-Quaternary aquifer representing the most available source of water supply in the region. The increase of water demand with the impact of climate change caused a significance decline in the groundwater quality and quantity. The challenge of this study is to investigate hydrochemical and isotopic data for a better understanding of the groundwater mineralization mechanism and to highlight the link between the impact of global change and hydrochemical aspects in the plaine of Kasserine. To achieve these goals, 19 wells were sampled and several physico-chemical parameters (Temperature, pH, Salinity, Na, K, Ca, Mg, Cl, HCO3, SO4 and ∂2H and ∂18O) were analyzed. Conventional hydrogeochemical techniques and multivariate statistical analyses were performed. The water type of the plaine of Kasserine gradually evolved from Ca–HCO3 to Ca–Na–SO4 suggesting two possible main processes: dedolomization and cation exchange generated by the dissolution of gypsum and dolomite and the precipitation of calcite. Furthermore, data inferred from stables isotopes in groundwater samples indicated that direct infiltration principally ensure the recharge of this aquifer. However, as an arid region, the plaine of Kasserine is threatened by climate change, due to the low and the irregularities of precipitation, leading to the decrease of water table level and deterioration of its water quality. This study help understand the hydrochemical processes of the plaine of Kasserine and assess the impacts of climate change in this arid region for a better monitoring of these valuable resources.

Groundwater quality assessment of the Takelsa phreatic aquifer (Northeastern Tunisia) using geochemical and statistical methods: implications for aquifer management and end-users

The Takelsa phreatic aquifer (Northeastern Tunisia) is an important source of fresh water for different economic sectors in the region that are strongly dependent on groundwater resources but, the aquifer is showing increasing signs of groundwater quality degradation like many other regions in the Mediterranean Basin. By integrating geochemical and multivariate statistical investigation methods, this research aims to identify the main geochemical processes and anthropogenic activities that are responsible for regional groundwater quality evolution, identifying the origins of salinity and nutrients, and their implications for groundwater use forcropirrigation and drinking water supply in order to improve aquifer management practices. The results show that groundwater facies vary from Ca–Mg–SO4 to Na–Cl water type and that mineralization is strongly controlled by mineral dissolution and cation exchange. The isotopic analyses indicate that groundwater is recharged by rainwater infiltration at higher altitudes and that a cumulative evaporative effect may contribute to local increase of salt content in groundwater. The Water Quality Index (WQI) used to determine the suitability of the Takelsa groundwater for drinking purposes reveals that just half of the groundwater points sampled show good to excellent quality for human consumption. The groundwater quality is also limited for irrigation purposes due to anthropogenic activities existing throughout the region. As groundwater in the studied region is crucial for irrigation and human supply, the identified groundwater quality problems and the identification of the main processes responsible for them should contribute to improve the infrastructure and managementpractices to allow the region to sustainable exploit the available groundwater resources.

A GIS mapping assessment of the suitability of the Oued Rmel aquifer for irrigation in the Zaghouan district (north-eastern Tunisia)

A total of twenty-three water samples were collected in winter 2013 to assess groundwater quality in the Oued Rmel aquifer in the Zaghouan governate in Tunisia. These samples were subject to in-field measurements of some physico-chemical parameters (temperature, pH, and salinity), and laboratory analysis of major elements. Several parameters were used to assess the quality of water destined for irrigation, including electrical conductivity (EC) and sodium adsorption ratio (SAR). As part of this work, GIS was used to study spatial distributions of SAR, EC, residual sodium carbonate, sodium percentage (%Na), Doneen’s permeability index, Kelly’s ratio, and magnesium hazard and, therefore, evaluated the water quality of Oued Rmel (good, fair, or poor) regarding irrigation. The major ions most abundantly found in the waters of Oued Rmel were in the following order: Na+ > Ca2+ > Mg2+ > K+ and Cl− > SO42− > HCO3. 56% of water samples from the Oued Rmel aquifer showed a low alkalinization risk, where SAR was lower than 10, 39% have a medium soil destabilization risks (10 < SAR < 18), and just 5% indicated high alkalinity hazards (SAR > 26). Samples of water intended for irrigation showed a medium to high sodicity and alkalinization risk. It is expected that output may help in assessing the impacts of water quality of the Oued Rmel aquifer used for irrigation.