In Tunisia, irrigation in the arid and semi-arid areas is often accompanied by sodicity and alkalinization of soils, leading to soil degradation a decreased crop yields. In this context, this study aims to analyze the spatio-temporal variation, and depending on depth of the water quality of the dam of Bezirk. Monitoring of physico-chemical parameters, concentrations of nutrients and major elements was performed to identify the factors and phenomena that govern their variations. Compilation and interpretation of all results show the main origin of the major elements is the chemical weathering of rocks exposed in the watershed and nutrients originate soil leaching and degradation of organic matter. The variation of the contents of dissolved inorganic nitrogen and phosphorus is linked to the level of dissolved oxygen, to the photosynthesis-respiration balance and to the degree of degradation of organic matter. The concentrations of the major elements are mainly controlled by dilution - evaporation balance, ion complexation and biologic activity.
The values of conductivity, alkalinity and SAR show that waters of Bezirk dam are of good quality for irrigation and can be used without risk, particularly for moderately salt tolerant plants.

The Triassic aquifer is an important hydrogeological entity in the Southeast of Tunisia, for satisfying drinking water and irrigation. For efficient and rational management of water resources and monitoring the chemical water quality of the Triassic aquifer, a geographic information system has been developed on ArcGis to elaborate a spatial, complete and well-structured database. This allows updating of the information and development of thematic maps, such as those relative to geology, hydrology and piezometric map of the study area. An attempt was made to study the chemical quality of the water table of the Triassic sandstones through the calculation of the index of water quality which has shown that 64% of the water of this sheet is good while 36% is poor.