WATER QUALITY RESEARCHES: SPECTRAL VARIABILITY OF THE WATER BODY ANALYSIS TO DEFINE A SAMPLING SCHEME

Abstract

The characteristics variation of the water quality in reservoirs occurs in a complex way and usually the number of points surveyed in limnological researches is not enough to evaluate a significant number of parameters and theirs correlations. In this context, the aim of this work is to define a sampling scheme that considers an adequate number of points for the analysis of the water quality in water reservoirs.In this perspective, techniques of digital image processing were applied, a multitemporal analysis of satellite images in four distinct dates was carried out ad a scheme of sampling based on radiometric variations observed in the water body was defined.The study area is the Capivara Reservoir that belongs to the Paranapanema River Hydrographic Basin in the State of Paraná and São Paulo - Brazil, which is the limit border of the State of Paraná and an important integration axis between these two states. The sampling scheme applied to the area was based on the stratified random method, and stratification was defined for the spectral variability of the water body. The final size of the sampling scheme was 15 points, distributed throughout the course of the reservoir and in the tributaries. The sample points were precisely located by navigation GPS and GNSS. The limnological data was collected "in situ" in each point defined for the sampling scheme using GPS and GNSS receivers in order to guarantee fidelity in the tasks of data measures and collects.