Abstract
Groundwater is the main supply of fresh water in many parts of the world. The intrusion of saline water into the fresh water is a serious threat to groundwater resources. Delineation of fresh-saline aquifer zones is essential to exploit the potable fresh water. The conventional method to differentiate fresh-saline water interface is to collect and test groundwater samples from boreholes using a number of laboratory tests. However, such techniques are expensive and time consuming. A non-invasive geoelectrical method, in combination with borehole data and physicochemical analysis, is proposed to assess the fresh-saline aquifers. This investigation was conducted in Jahanian area of Pakistan with forty-five vertical electrical soundings (VES) using Schlumberger array, nine bore wells and fifty physicochemical samples. The fresh-saline aquifers are delineated by aquifer resistivity and Dar-Zarrouk parameters namely transverse unit resistance and longitudinal unit conductance. The aquifer potential of fresh-saline water zones is estimated by the aquifer parameters namely transmissivity and hydraulic conductivity. Integration of subsurface resistivity with hydrogeological information reveals the subsurface formation of five layered succession, that is, topsoil having dry strata with resistivity greater than 30 Ωm, clay containing saline water with resistivity less than 15 Ωm, clay-sand with brackish water having resistivity between 15 and 25 Ωm, sand containing fresh water with resistivity ranging from 25 to 45 Ωm and gravel-sand having fresh water with resistivity greater than 45 Ωm. The geoelectrical columns and geological cross-sections constructed by the aquifer resistivity provide effectiveness of the interpretations for the evaluation of fresh-saline aquifers. The results of physicochemical analysis using WHO guideline validate the fresh-saline aquifer zones delineated by the geophysical method. This investigation contributes towards predicting the fresh-saline water interface using inexpensive geoelectrical method.
Highlights
Saline water intrusion is becoming a serious threat to fresh water supply for half of the world’s population that largely depends on groundwater resources [1]
Geoelectrical method measures the subsurface resistivity in the geophysical field survey which is known as the apparent resistivity or iso-resistivity
The geoelectrical method was performed for 45 sounding stations using
Summary
Saline water intrusion is becoming a serious threat to fresh water supply for half of the world’s population that largely depends on groundwater resources [1]. The saline intrusion is caused by a disturbance in the hydrostatic balance between the saline and fresh aquifers mainly due to the human action [2]. The main causes of saline water intrusion include intensive farming, industrial waste materials, overexploitation of groundwater resources, natural events and climate change and so forth [3]. The saline water intrusion is the displacement of fresh aquifer by saline aquifer caused by the. Water 2018, 10, 1548 excess withdrawal of groundwater including other human actions that can decline the groundwater table and result in saline water intrusion [4,5]. The saline water contains high salt concentration such as NaCl
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