The study of electrical conductivity of saline water: A case study of Lakes; Nakuru, Bogoria-Kenya and Nata Saltpan sanctuary-Botswana.

Abstract

Conductivity measurements have been used to estimate salinity, a feature of salt lakes and pans. Physical and chemical parameters with emphasis on the relationship between electrical conductivity (EC) and salinity were studied for brackish lakes Nakuru, Bogoria-Kenya and Nata saltpan sanctuary-Botswana during dry seasons of the hydrological cycle. Most of the measured variables, conductivity and pH, analyzed variables particularly Na+, HCO3- and CO32- in lakes Na+, Cl- and SO42- in Nata saltpan showed extremely high values due to the systems‟ low water volumes. Nutrients were found in significant concentrations in Lake Nakuru because of agricultural practices in the catchments‟ basin resulting to nutrient loading unlike Lake Bogoria and Nata saltpan. These studies were based on major ionic composition, which for Lakes Nakuru and Bogoria showed mean absolute salinity of 31.25 and 43.23 g/l respectively and 4.52, 14.80 and 5.54 g/l for the 1st, 2nd and 3rd saltpans respectively. Regression analysis was used to test the hypothesis that water of relatively high salinity has a different conductivity to salinity relationship than water of low salinity. Regression analysis using log10-log10 linear model provided an adequate approach to the study of the relationship between both variables Models, S = 0.6966K250.9981 R2 = 0.972, S = 0.6471K251.018 R2 = 0.967 and S = 0.7228K251.030 R2 = 0.745 for lakes Nakuru, Bogoria and Nata saltpan respectively were developed, where S is the salinity in g/l and K25 is conductivity at 25oC in mScm-1 to predict salinity from conductivity measurements for Kenya and Botswana saline waters with similar ionic composition. There was no statistical difference in the logarithmic relationship for waters of high and low salinities in the lakes and saltpans. From the concentrations of major ionic species in the lakes and saltpan waters, ionic strength (IS) for each was calculated. Ionic strength for the 1st, 2nd and 3rd saltpans were 0.038, 0.092 and 0.047M respectively whereas that of Lake Nakuru and Bogoria were 0.166 and 0.195M respectively.