Investigation of the Effect of Salinity on the Electrical Conductivity of Water Samples from the Lagos Lagoon

The electrical conductivity of water is a sensitive proxy for dissolved ion concentration and is closely linked to salinity, particularly in estuarine and lagoon environments where freshwater and marine sources mix dynamically. This study investigates the relationship between salinity and electrical conductivity in water samples collected from the Lagos Lagoon, South West Nigeria, across twenty-four sampling stations covering the full salinity gradient from freshwater tributaries to the ocean inlet at Lagos Bar Beach. Sampling was conducted during wet season and dry season campaigns to capture the seasonal influence of freshwater dilution from the Ogun and Osun rivers. Salinity was determined by the Mohr argentometric method for chloride content, while electrical conductivity was measured using a calibrated conductivity meter. Temperature measurements were made concurrently to apply temperature correction factors. The salinity-conductivity relationship was found to be highly linear across the 0 to 36 parts per thousand salinity range, with a regression coefficient of 0.998, confirming the applicability of standard conversion factors in the Lagos Lagoon context. Seasonal comparison shows a mean salinity reduction of 40 percent at central lagoon stations during the wet season peak runoff period. The study identifies salinity stratification at three stations near the Lagos Bar inlet, indicating incomplete mixing. Practical implications for water quality management, fisheries, and industrial water intake planning along the lagoon are discussed. Keywords: electrical conductivity, salinity, Lagos Lagoon, water quality, estuarine physics