A geospatial assessment of water quality in Tugwi Mukosi Dam, Zimbabwe

The graphical abstract shows in-situ data collection and use of remote sensing using Landsat imagery for a reservoir, the Tugwi Mukosi Dam for water quality assessment. Key results indicate high turbidity and increasing levels of nitrates and phosphates. Remotely sensed results showed a very strong positive relationship between measured and simulated values for turbidity (r = 0.95) and TDS (r = 0.80). Remote sensing for estimating water quality can aid in situ sampling techniques, which require more time and resources in data collection. The study evaluated the performance of existing remotely sensed-based algorithms in determining turbidity and total dissolved solids (TDS) concentration levels in Tugwi Mukosi Dam in Zimbabwe in reference to in situ validation measurements. The study further conducted trend analysis for nitrates, phosphates, turbidity, and TDS, focusing on the concentration levels from in situ water quality sampling. Landsat satellite monitoring indicated fluctuating water quality in Tugwi Mukosi between 2017 and 2025. The laboratory analysed water quality parameters, which exhibited varying concentrations. The average nitrate level was recorded as 0.002 mg/L. Phosphate concentration level increased from 2024 to 2025, while the average turbidity value exceeded the 5 NTU threshold. TDS average maximum value was 119.49 mg/L in 2024 and 64.66 mg/L in 2025. The study observed a strong and positive relationship between in situ and Landsat satellite-derived water quality parameters; turbidity (R2 = 0.91, r = 0.95) and TDS (R2 = 0.64, r = 0.80). The application of remotely sensed data and statistical models is useful for monitoring water quality parameters to trace trends in inland water bodies.