Modeling of groundwater yield by the electrical method case of the Triassic sandstone aquifer (Tataouine South-Eastern Tunisia)

Houyem Khorchani,Samir Kamel

doi:10.2166/aqua.2021.011

Abstract

Abstract The method of electrical resistivity has proven very effective in the evaluation of groundwater. This specialized technique uses Dar-Zarrouk (D-Z) parameters in the estimation of longitudinal unit conductance, transverse unit resistance, and longitudinal resistivity to examine the groundwater level, to distinguish the fresh, brackish, and saline water interface, and to assess the storage capacity of groundwater in the Triassic sandstone aquifer system in the Tataouine region (South-Eastern Tunisia). In this context, 23 vertical electrical soundings (VESs) were carried out in the Tataouine region using the Schlumberger configuration with a current electrode with a maximum spacing of the current electrodes (AB) of 500–600 m. The results indicate that the study area consists of three types of aquifers: (i) silt/clay saline water (&lt;20 Ωm), (ii) a mixture of sand and clay freshwater (20–40 Ωm), and (iii) sand freshwater (40–200 Ωm). These sand freshwater aquifers are characterized by low longitudinal unit conductance (0–2.8 S), high values of transverse unit resistance (more than 9,000 Ωm2), and longitudinal resistivity (more than 35 Ωm) and are mainly concentrated in the north, south, and south-west regions of the study area. It should also be noted that the coefficient of anisotropy (λ) overlaps and does not clearly differentiate the characteristics of the aquifers of fresh, brackish, and saline water. An interpretation of VESs can also determine the storage capacity of groundwater by determining yield index values. Groundwater supply for the entire study area was classified as low yield, with a percentage of 13% and a maximum of 31% of the study area and 56% of moderate yield. Lastly, the real data from the drilling confirm all these results presented previously. The findings suggest that D-Z parameters are useful for making a distinction of various aquifer zones.

Highlights

In the Tataouine region, the sandstone aquifer of Triassic at the below-to-medium level constituted the most precious resources in terms of quantity and quality, giving a rich inventory of drinking water to the principal urban communities of the locale and providing an abundant supply of drinking water to the main cities of the region (Smar, Kirchaou, Tataouine city, Ghomrassen, and Bir Lahmer)
The study area is located in the Tataouine region in the extreme south of Tunisia
Triassic deposits are widespread in the Tataouine region, especially in Djebel Rehech, (Burollet ; Busson, ; Ben Ismail ; Bouaziz ); the lower to middle Triassic is filled with the sandstones of Sidi Stout (Scythian-Anisian) and Kirchaou sandstones (Ladinian) and the Upper Triassic is filled with Mekraneb dolomites, Touareg sandstone (Middle Carnian), and Rehech dolomites (Figure 2)

Summary

Introduction

In the Tataouine region, the sandstone aquifer of Triassic at the below-to-medium level constituted the most precious resources in terms of quantity and quality, giving a rich inventory of drinking water to the principal urban communities of the locale and providing an abundant supply of drinking water to the main cities of the region (Smar, Kirchaou, Tataouine city, Ghomrassen, and Bir Lahmer). This loss can be explained by the increase in the exploitation of groundwater (increase in the number of boreholes) (Duan a, b, ) accompanied by a succession of periods of drought

Methods

Results

Conclusion