Spatial behavior of chlorophyll-a in Itaparica reservoir, São Francisco River

ABSTRACT

In the analysis of trophic state of the water body is fundamental to know chlorophyll-a concentration. Thus, this work has as main aim to determinate and to assess the behavior of chlorophyll-a in the Itaparica reservoir, São Francisco river. This way, we used Landsat-TM imagery, in which it was used bands from 1 to 5 and 7. The algorithm used was written in LEGAL/SPRING 5.2. From the chlorophyll-a result was held slicing the water body in six concentration classes. As observed by histogram, the minimum value of Chl-a was < 1 mg/L and the highest was 249.5 mg/L. The classes that had the biggest area were Classe 01 (0-5 mg/L) with 27.4%, followed by Classe 02 (5-10 mg/L) with 24.6% of the total area of the study area. Through graphical analysis of points located along the reservoir it was possible to verify that chlorophyll concentration augmented from fluvial to lacustrine region and from the contact of streams with reservoir. In the next studies there is a need to validate the values with field data in order to verify the mapping accuracy in this reservoir, taking into account the day and also the transit time of the sensor.

Keywords:
water quality; remote sensing; landsat.