Estimation of Hydrogeological Parameters Using Geoelectrical Methods and Evaluating Approximate and Exploitable Water Volume in Ghachsaran's Emamzadeh Jaafar Plain Aquifer

1- Introduction Estimating aquifer hydrogeological parameters (T, K, Sy, etc.) is essential for the assessment of groundwater resources and groundwater studies/management. There are several different methods such as pumping test, simulation or modeling of groundwater, geophisical modeling, etc. to estimate these parameters. Although analysis and evaluation of pumping test data is the best way to achieve this purpose, it is costly, time consuming and the gained results are from limited points. As a result, applying geoelectrical methods to estimate aquifer parameters in combination with pumping test method is very effective and economical. 2- Theoretical framework Since well-drilling for the hydraulic parameters calculation is often prohibitively expensive, the integration of aquifer parameters calculated from the existed boreholes locations and surface resistivity parameters extracted from surface electrical measurements can be highly effective for aquifer hydraulic parameters estimation. Geoelectrical exploration methods are based on the assumption that rocks are porous, the rock matrix is generally insulator, and electrical currents pass through because of water/moisture present in the pores. This shows that electrical measurements are mainly influenced by porosity and fluid resistivity in the pores. geoelectrical data recorded on the surface contain a lot of useful information about the aquifer which can be deciphered by experienced geophysicists. application of geoelectrical method has lead the workers to develop surface resistivity techniques for Estimation of aquifer hydraulic parameters from geophysical resistivity data. 3- Methodology In this paper, using the resistivity data obtained from 86 vertical electrical soundings (VES) with the schlumberger arry and considering the similarity of the groundwater flow (Darcy's law) and the electrical flow (Ohm's law) characteristics in porous media, the hydrogeological parameters of Gachsaran’s Emamzadeh Jaafar aquifer, located in south of Kohgiloyeh and Boyrahmad province, were estimated 4- Discussion Besed on the results of this research, the average aquifer porosity and specific yield (Sy) were estimated to be about 26% and 0.044, respectively. The average alluvial and aquifer thicknesses were estimated to be about 132 and 79 meters, respectively. The total volume of Emamzadeh Jaafar aquifer and the approximate volume of water within the aquifer were respectively calculated to be about 5.7 and 1.5 billion cubic meters and the volume of extractable water from the aquifer was estimated about 66.5 million cubic meters. 5- Conclusion and Suggestions The comparison of data from geoelectrical and pumping test methods indicate that the electrical resistivity method is able to provide a reasonable estimate of hydrogeological parameters of the aquifer. Therefore, with the combination of data from geoelectrical method and pumping test, desired results can be obtained while reducing the costs.