The concept is to use the EC values of two streams converging into one to estimate the relative flows of those two streams using a simple mass balance approach (see Pinder & Jones 1969)*
Two streams, S1 and S2 (EC values 400 and 100 uS/cm) converge to form stream S3 (EC 125 uS/cm). “p” is the relative proportion of S1 in the water flow at S3; (p-1) is the relative proportion of S2.
*A keystone paper by noted US hydrologist GF Pinder, with Nova Scotian John F. Jones, the “Grandfather of Groundwater in Nova Scotia” as co-author and based on work in NS.(Canadian born Pinder’s first professional job was with the NS Dept of Mines, in 1968. Then the Yanks scooped him up, view cv)