Hybridization of GALDIT method to assess actual and future coastal vulnerability to seawater intrusion

Contamination and seawater intrusion are esteemed as chief issues of coastal aquifers resulting from unscientific utilization, non-standard monitoring network and improper management. In the present study, an optimum monitoring network with appropriate numbers and standard spatial distribution was designed based on a vulnerability map of the Urmia coastal aquifer. A vulnerability map was extracted using a modified GALDIT-iP model and searching optimum network was done based on genetic algorithm (GA). The maximum value of the correlation between electrical conductivity (EC) and vulnerability index, the minimum number of monitoring wells and the highest value of Nash-Sutcliff were utilized for the simultaneous optimization model. The W-weighting coefficient was considered for economical goals and three targets were defined in a general objective function. The results showed that the W-weighting coefficient has a significant effect to determine optimal solution, and the best weighting was opted considering the most optimal response based on the precise of the monitoring network and vulnerability index. An acceptable optimization and validation process was obtained with the predictions of the validation results. For W = 1, the final value of the objective function was obtained 1.791 using 91 wells with a correlation coefficient of 0.935 and Nash-Sutcliff of 0.979, resulting in the appropriate spatial distribution of the wells and reduction of 18 wells from the existing monitoring wells. 

Optimization design of quality monitoring network of Urmia plain using genetic algorithm and vulnerability map

Optimal redesign of coastal groundwater quality monitoring networks under uncertainty: application of the theory of belief functions

Evolution of the fresh to salt water interface from electrical sounding near Oued Nador, Tipaza (North Algeria)

Maps of the vulnerability of groundwater to seawater intrusion were developed for the multi-layered coastal aquifer of Ouled Taoui—Ouled Boujemaa in Algeria. Groundwater in this area is threatened by the risk of salinization due to excessive groundwater use. To protect this aquifer, mapping the vulnerability to potential saline intrusion was carried out using a modified GALDIT index mapping model that takes into account six parameters, namely: (G) groundwater occurrence, (A) aquifer hydraulic conductivity or network development and persistence index (IDPR), (L) depth to groundwater level above sea, (D) distance from shore, (I) impact on the existing status of seawater intrusion in the area, and (T) It’s the thickness of the aquifer. A system for rating, weighting and classifying the GALDIT model according to the relative importance of these parameters was developed under a GIS environment. The compilation results illustrate that the underlying confined aquifer with clay levels characterizing a low hydraulic potential. It will be more vulnerable during excessive pumping and in the presence of karst conducts, which produces an impact of salinity decay as soon as one moves away from the shore. The assessment indicated that the vulnerability of the uppermost unconfined aquifer was particularly sensitive to changes in the weights of parameters (A), (L) and (D). Areas with a “high” vulnerability to seawater intrusion are located especially in the coastal fringe. The results of the vulnerability assessment were validated based on: the density and distribution of existing groundwater production wells, the land cover map, and the hydrochemical quality of groundwater. Finally, the identification of areas of “high” vulnerability to saline intrusion will serve as a tool for the management, control, and protection of coastal groundwater resources.

Mapping of the groundwater vulnerability to saline intrusion using the modified GALDIT model (Case: the Ain Temouchent coastal aquifer, (North-Western Algeria))

Bentekhici Nadjla

Papers

Mapping of the groundwater vulnerability to saline intrusion using the modified GALDIT model (Case: the Ain Temouchent coastal aquifer, (North-Western Algeria))