Physicochemical Parameters Assessment and Seasonal Variations of Surface Water Quality of the Volta Lake in Ghana

Abstract

Data for nine (9) physicochemical parameters (EC, SAL, ERes, Turb, pH, DO, TDS, Temp and % sat of DO) were investigated from 13 sampling locations of the Volta Lake, to assess the seasonal and spatial variations in surface water quality, using multivariate statistical techniques (PCA and EFA). The range of the assessed parameters were observed to have seasonal significant difference for EC (76.20 - 124.09 µS/cm), SAL (36.15 - 52.56 mg/L), ERes (10.0 - 16.44 KΩ.cm), Turb (0.44 - 13.98 NTU), pH (6.18-8.17), DO (3.22 - 6.90 mg/L), TDS (30.59 - 49.24 mg/L), Temp (23.6 - 32.9 °C) and % sat of DO (60.4 - 89.2 %), of which, pH, DO (% Sat), Temp and SAL were observed to be maximum, though marginal, in the Dry season. From the entire stretch of the lake, all the parameters recorded mean maximum values from the UVS, except for ERes (15.15 KΩ.cm) and Temp (31.8 °C), whose mean maximum values were respectfully recorded from the MVS and LVS. Conversely, the UVS recorded mean minimum values of pH (6.9), ERes (11.16 KΩ.cm) and Temp (26.6 °C) throughout the 2 seasons. But, that of SAL (37.7 mg/L), EC (82.91 µS/cm), TDS (33.18 mg/L) and Turb (4.91 NTU) were observed at the MVS (all in the Dry Season). For the LVS, DO (5.0 mg/L) and % sat of DO (74.3 %) were observed in the Dry season. The PCA/EFA showed both spatial and seasonal variations for the parameters at all the 13 sample locations. The seasonal correlations according to the PCA and EFA, slight changes were observed in the selection of the most significant parameters (EC, DO (% Sat), DO, SAL, TDS and ERes) responsible for seasonal variations of the Lake’s water quality based on a rotated factor correlation coefficient selection criterion. In view of this, seasonal variations of parameters must always be considered in water quality assessment when selecting parameters for environmental monitoring purposes in the reservoir because, parameters considered significant in contributing to water quality variations in a particular season may, or may not, be considered important in another season. Due to the unique biodiversity the reservoir supports, and the socioeconomic services it provides to thousands of surrounding communities, extensive monitoring network throughout seasons should be encouraged since changes in land-use practices and climate variability can significantly affect the reservoir.