Utilização da resistência elétrica transversal para identificar áreas mais promissoras e estimativas de transmissividades hidráulicas no Aquífero Barreiras em área do baixo curso do Rio Maxaranguape-RN

Abstract

The cities on the east coast of the Rio Grande do Norte State are primarily supplied by the Barreiras Aquifer, which has a predominantly unconfined hydraulic character. However, the lack of reliable data about wells hinders to identify the most promising areas for future water exploitation, especially outside urban perimeters. To identify the most promising áreas for In this context, the present research was carried out in an area in the lower course of Maxaranguape River-RN, aiming to identify the most promising subareas to locate wells and estimates of hydraulic transmissivities of the Barreiras Aquifer based on geoelectric data. Thus, we adopted the methodology of the transverse electrical resistance (RT) parameter methodology through inverse models of vertical electrical soundings-VES, considering a previous geoelectrical calibration conducted adjacent to local research well with a defined lithological profile. The estimates of hydraulic transmissivities also resulted from the calibration between the transverse electrical resistance value and hydraulic parameters from the aquifer test in the referred well. Additionally, we conducted dependence degree analysis (linear regression - R²) between transverse electrical resistance (RT) values with the resistivity and the saturated zone thickness parameters in order to identify a possible local predominance of one or another of these parameters in the definition of areas with the most significant hydrogeological potential. The results obtained show a band in the center of the area with an NW - SE orientation and transverse electrical resistance values greater than 25,000 Ohm.m², associated with thicker sectors and/or average resistivities of the saturated zone. Thus, this subarea is the most promising in terms of hydrogeological potential. The mean thickness of the saturated zone showed values above 56m in the central and northwestern portions of the area. In contrast, the mean resistivity of the saturated zone showed values above 990 Ω.m in the extreme southwest and the central region. In this respect, analyzes based on linear regression demonstrate that average electrical resistivity exerts more significant influence on the transverse electrical resistance parameter in the study area, exhibiting a correlation factor R² of 0.88, in detriment of an R² of 0.39 of the ratio between saturated thickness and transverse resistance. The hydraulic transmissivity estimates map revealed higher values in the central portion of the area, highlighting the most significant transversal resistances associated with the highest hydraulic transmissivities. Therefore, this portion is the most promising for future well locations.