Hydrogeochemical study and groundwater quality index of the Tinfouchy-Hassi Khebbi region (South-west Algeria)

Water is a natural resource essential to life. It is considered as a determining factor in the socio-economic development of a country. In the Tinfouchy-Hassi Khebbi region, groundwater is characterized by scarcity and its spatial and temporal irregularity forces us to think about a rational management of these resources in order to ensure water sustainability. Groundwater is the main resource to supply the water needs of the Tinfouchy-Hassi Khebbi region, which is located to the northeast of Tindouf (southwestern Algeria). In the considered region, where water quality control is infrequent, salt or non-potable water is a real public health problem. Water is considered to be fit for human consumption, if its physico-chemical components don’t exceed the standards of potability. In order to understand the hydrodynamic parameters, 18 boreholes were used for preparing a piezometric map. The objectives of this work are to produce a piezometric map for hydrodynamic study and prepare the assessment of groundwater quality of the Tinfouchy–Hassi Khebbi aquifer, using the Groundwater Quality Index (GWQI) model. The piezometric map obtained from the existing boreholes as well as the geological data reveals a clearly visible surface watershed line which is likely to coincide with an underground watershed. This phenomenon leads us to deduce an area of the aquifer of about 4000 km2 for an average aquifer thickness of about 70m. The GWQI values for this region range from 132.88 to 238.53. Based on the obtained results, it is concluded that 81.25% of the groundwater samples taken from the boreholes capturing the studied aquifer fall into the poor-quality category, while 18.75% of the samples fall into the very poor category. The assessment of water quality for agriculture was carried out based on SAR (sodium adsorption ratio), Kelly ratio (KR) and permeability index (PI). The obtained results revealed that the Tinfouchy – Hassi Khebbi aquifer waters are good for irrigation.