Proposal for a remote sensing trophic state index based upon Thematic Mapper/Landsat images

Author(s)

Evlyn Márcia Leão de Moraes Novo ^[1] ; Luciana de Resende Londe ^[2] ; Claudio Barbosa ^[3] ; Carlos A. S. de Araujo ^[4] ; Camilo Daleles Rennó ^[5]

Affiliation

^[1] Instituto Nacional de Pesquisas Espaciais - Brasil

^[2] Centro Nacional de Monitoramento e Alertas de Desastres Naturais - Brasil

^[3] Instituto Nacional de Pesquisas Espaciais - Brasil

^[4] Instituto Nacional de Pesquisas Espaciais - Brasil

^[5] Instituto Nacional de Pesquisas Espaciais - Brasil

• Document type: Journal article
• Source: Rev. Ambient. Água; v. 8, n. 3, p. 65-82, 2013-12-00.

Abstract

This work proposes a trophic state index based on the remote sensing retrieval of chlorophyll-α concentration. For that, in situ Bidirectional Reflectance Factor (BRF) data acquired in the Ibitinga reservoir were resampled to match Landsat/TM spectral simulated bands (TM_sim bands) and used to run linear correlation with concurrent measurements of chlorophyll-α concentration. Monte Carlo simulation was then applied to select the most suitable model relating chlorophyll-α concentration and simulated TM/Landsat reflectance. TM4_sim/TM3_sim ratio provided the best model with a R² value of 0.78. The model was then inverted to create a look-up-table (LUT) relating TM4_sim/TM3_sim ratio intervals to chlorophyll-α concentration trophic state classes covering the entire range measured in the reservoir. Atmospheric corrected Landsat TM images converted to surface reflectance were then used to generate a TM4/TM3 ratio image. The ratio image frequency distribution encompassed the range of TM4_sim/TM3_sim ratio indicating agreement between in situ and satellite data and supporting the use of satellite data to map chlorophyll-α concentration trophic state distribution in the reservoir. Based on that, the LUT was applied to a Landsat/TM ratio image to map the spatial distribution of chlorophyll-α trophic state classes in Ibitinga reservoir. Despite the stochastic selection of TM4_sim/TM3_sim ratio as the best input variable for modeling the chlorophyll-α concentration, it has a physical basis: high concentration of phytoplankton increases the reflectance in the near-infrared (TM4) and decreases the reflectance in the red (TM3). The band ratio, therefore, enhances the relationship between chlorophyll-α concentration and remotely sensed reflectance. (AU)

• FAPESP's process: 08/56252-0 - Environmental and socioeconomic impacts associated with the production and consumption of sugarcane ethanol in south central Brazil
• Grantee: Evlyn Márcia Leão de Moraes Novo
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants