Monitoring Water Quality in a Reservoir of the Semi-arid Region Using Remote Sensing

Aims: The aim of this study was to analyse the use of remote sensing as an alternative in monitoring water quality, and to analyse models that estimate the concentrations of chlorophyll-a (Chl-a) in a reservoir in the semi-arid region.

Place and Duration of Study: Field campaigns were carried out at the Pereira de Miranda reservoir, Pentecoste, in the State of Ceará (CE), at five sampling points, from December 2014 to December 2015.

Methodology: Limnological and spectral data were used, which were collected using a spectroradiometer. The limnological attributes of Chl-a and suspended sediments were analysed in the laboratory, and used to evaluate the spectral responses. Four three-band models were analysed for estimating the concentrations of Chl-a.

Results: The models of Lopes [11] and Gitelson et al. [15] gave the best performance, with respective satisfactory results for R2 of 0.75 and 0.79, MAE errors of 6.74 (μg.L-1) and 6.51 (μg.L-1), an NSE of 0.74 for both models, and RMSE of 9.01 (μg.L-1) and 8.93 (μg.L-1). From these results, the models were selected and applied in the campaigns of April and September 2015.

Conclusion: The use of remote sensing is therefore viable in estimating concentrations of Chl-a, collaborating to the development of research and in water resource management at lower cost.