The flowing fluid electrical conductivity (FFEC) logging method has been used in deep boreholes to obtain estimates for the transmissivity, salinity of formation water, hydraulic head, and formation water flow rate of hydraulically conducting layers. In this paper, we proposed a modified FFEC logging procedure, involving a setup of a string of EC/T probes in the borehole, to passively monitor long-term temporal changes in local flow rates in a brine formation composed of multiple layers with different transmissivities over a period of months or years. The local flows in the layers can vary over time, for instance, as a result of seasonal or climatic changes. In the case of supercritical CO2 storage in the deep subsurface, the local flow pattern of the storage formation will be disturbed and furthermore it may change with time as the low density and low viscosity CO2 enters more and more into the transmissive layers and interacts with in situ water and rock. The present paper explores the possibility of using the FFEC method for such long-term monitoring in an observation well. The feasibility is demonstrated with field data from the Outokumpu test site in Finland.