Estimating concentrations of chlorophyll-a and suspended sediments in a continental aquatic ecosystem using remote sensing

Abstract

Water is an important resource for life and as such, its monitoring is essential. The aim of this study therefore was to estimate concentrations of chlorophyll-a and total suspended solids (TSS) using orbital remote sensing data. The study area was the General Sampaio reservoir, located in the Curu River Basin, in the state of Ceará. The concentration of chlorophyll-a and sediments were mapped based on orbital images captured by the Operational Land Imager (OLI) sensor. The images were acquired on 14 September 2017 and 13 June 2018. The chlorophyll-a concentration was estimated using a model employing a ratio of the blue (450-510 nm) and green (530-590 nm) bands, and the TSS concentration was estimated from the red band (640-690 nm) of the OLI sensor. The chlorophyll-a concentration in September 2017 varied from 37.03 to 43.0 mg L-1, and in June 2018 it ranged from 42.9 to 62.2 mg L-1. The TSS concentration in September 2017 varied from 1.8 to 4.2 mg L-1, while in June 2018, a period that corresponded to the highest local rainfall, the variation was greater, between 2.1 and 17.73 mg L-1. The highest concentrations of suspended sediments were seen in the tributaries of the Curu River and the Salvação Stream. It was possible to estimate the concentrations of chlorophyll-a and TSS using orbital images. The reservoir water was classified as eutrophic throughout the study period.

Keywords

• Eutrophication. Limnology. Pluviometry.