VILSON SOUSA QUEIROZ JÚNIOR
Abstract:
The natural change of river courses for the construction and reservoir formation, represented here for power generation given the growing demand for electricity in Brazil, causes significant changes in aquatic environments and consequently in its surroundings, given the different characteristics depending, of flooded areas, the different types of water circulation, the period of residence, the flow of nutrients, in synthesis, limnological, standards setting different aquatic compartments, suggesting a certain importance for these environments. Limnological analysis of reservoir waters associated with remote sensing techniques in order to identify aquatic compartments represents an effective methodological set for desired results. With this in mind, the goal of the present work was to characterize the aquatic compartments of Caçu HPP reservoir, Goiás, Brazil, by limnological variables and spectral data associated with an analysis of the land use dynamics of the Caçu HPP watershed. Analyzing two distinct periods, one with the lowest rainfall, represented by August 2014 and the highest index, January 2015 according to the climatological average. The methodology consisted of collecting precipitation data, Suspended Solids Concentration (CSS), water transparency through Secchi Disc (DS), Chlorophyll - a (CHL - a) and land use classification. Spectral data were collected FieldSpec® HandHeld 2. Limnological and spectral data collection was performed at 35 sampling points evenly distributed throughout the reservoir. Limnological variables were spatialized by the Inverse Square Distance (IDW). Land use was made by Landsat 8 OLI satellite image classification, with the predominant class being Pasture with an average value for the fields of 74.11%, followed by the Vegetation class with 19.91%. From the results it was observed that the accumulated precipitation for the period of the field of January showed higher and for the field of August the lowest rainfall. The CSS presented variation from 0.17 to 4.5 mg/L for the field of August, for January from 0.5 to 18.83 mg/L. DS transparency was 0.9 to 2.5 m for August and January from 0.5 to 1.60 m. For the CHL - a in August field values were found from 0.0 to 6.32 µg / L and for January from 1.26 to 8.84 µg/L, with values varying along the reservoir, with parts with low values and others with high values (compared to the previous part), for both fields. For limnological variables, Person correlation tests were performed to understand their interdependencies, obtaining Strong inverse correlation for CSS and DS and Moderate correlation for CSS and CHL - a. For the field spectra, in general all showed similar behavior, varying only the reflectance rates between 0.5% and 2.5% for August and 0.3% and 3.4% and certain peculiarities. It was observed that there are absorption features, being approximately at 610 and 675nm, the latter being for Chlorophyll - a. According to the literature, the absorption band at 610 nm is due to absorption by phycocyanin. It presented spectral response to CSS in the red and near infrared bands. In general, from the results, based on the most relevant variables such as DS, CSS and CHL - a, the Caçu UHE reservoir presented three defined compartments, Lotic, Transition and Lentic A and B given their particularities of patterns. of limnological variables.
