| Popis: |
The paper deals with the results of electrical resistivity and electromagnetic (EM) surveys conducted in the Abohar area, Ferozepur district, Punjab, for the demarcation of the fresh- and saline-water zones. It is brought out on the basis of the resistivity-depth probing that saline water is invariably at varying depths in the area surveyed, over which bodies of fresh water have developed, having thicknesses ranging from a few metres to more han 80 m. The area to the east and southeast of Abohar town appears to be most promising from the point of view of groundwater exploitation by tube wells. In addition, the existence of localized zones having appreciable thicknesses of fresh water bearing materials has also been indicated, and it is observed that such zones are located generally near canals and perennial tanks. It is inferred that the fresh-water bodies have developed due to the continuous percolation of rain and canal waters in the areas where coarer sediments predominate, resulting in the depression of an original saline-water table. The Em traverses conducted in selected parts of the area have indicated prominent anomalies in the out-phase component, and resistivity traverses over these zones of anomalies yielded lower resistivity values compared to those obtained in the zone where the EM profile is relatively flat. Thus the EM anomalies are attributable to the saline zones, and it is suggested that the EM method can be effectively used for delineation of fresh and saline-water zones and resistivity-depth probing can then be resorted to for quantitative estimation of the thickness of fresh water bearing material in the areas of promise, thereby considerably reducing the duration and cost of an exploitation programme. |
