Methodology of using electrical tomography in groundwater exploration in permafrost conditions on example of Bodaibo district, Irkutsk region

Growing current demand for new water supply sources determines the need to search for new sources of groundwater. Since well drilling is expensive and environmentally risky, it is becoming relevant to use geophysical methods, in particular electrical exploration. Electrical resistivity tomography allows a detailed study of geological structure and properties of aquifers, but there are no clear recommendations for conducting electrical resistivity tomography studies when searching for groundwater in various geological conditions. To improve the accuracy and efficiency of geophysical works, it is proposed to perform mathematical modeling of electrical resistivity tomography data, which allows to assess the method sensitivity and possible measurement errors as well as to ensure the most accurate results. The purpose of the conducted study is to develop an optimal technique for groundwater exploration using electrical resistivity tomography in the conditions of permafrost distribution in the Bodaibo district. The technique takes into consideration possible groundwater occurrence conditions and includes mathematical modeling to assess the impact of permafrost on the data obtained. Numerical modeling has proved the efficiency of the method in permafrost areas. Water-flooded fractured areas characterized by low values of specific electrical resistance have been reliably identified in all obtained modeling data. The results of solving direct and inverse problems of electrical exploration compared with the data of production works performed in 2020 in the Republic of Buryatia and in 2022 in the Irkutsk region have shown that electrical tomographic studies, which were successfully confirmed by drilling, make it possible to identify a productive water-flooded horizon with a very high degree of confidence.