Testing utility of Landsat 8 for remote assessment of water quality in two subtropical African reservoirs with contrasting trophic states

Abstract

Water quality problems continue on a global scale and this creates the need for regular monitoring using cheaper technologies to inform management. The objective of this study was to test for significant relationships between the field-measured and Landsat 8 OLI sensor-retrieved water quality parameters. The study was carried out in two reservoirs with contrasting trophic states in Zimbabwe. Results show that the Blue/Red ratio had strong predictive relationships with Secchi disc transparency (R² > 0.70) and turbidity (R² ≥ 0.65). The Near-infrared/Red ratio was a strong predictor of chlorophyll-a in Mazvikadei (R² > 0.84) whereas in Lake Chivero, which is more polluted, the red band was the most useful predictor (R² = 0.69). Overall, our work demonstrates the utility of using Landsat 8 band ratios for remote assessment of water quality in African reservoirs as a value-addition to the traditional field-based methods, which are expensive resulting in data scarcity.

Keywords:

• Chlorophyll-a
• Lake Chivero
• remote sensing
• Secchi disc
• turbidity

Acknowledgements

We acknowledge the World Bank for funding this study. We also thank doctors Maxwell Barson, Amon Murwira, Christopher Magadza and Hudson Makurira of the University of Zimbabwe for technical assistance.