Dissertação
Influência dos constituintes opticamente ativos na reflectância espectral da água do reservatório Passo Real, RS
Fecha
2012-05-29Registro en:
SANTOS, Felipe Correa dos. INFLUENCE OF THE OPTICALLY ACTIVE CONSTITUENTS ON THE
SPECTRAL REFLECTANCE OF THE WATER OF PASSO REAL RESERVOIR, RS.. 2012. 89 f. Dissertação (Mestrado em Geociências) - Universidade Federal de Santa Maria, Santa Maria, 2012.
Autor
Santos, Felipe Correa dos
Institución
Resumen
The construction of dams results in hydrological impacts as they alter the natural flow of
water of a river. Remote sensing is a tool capable of helping the monitoring of water quality
by enabling acquisition of information for spatial and temporal analysis of its composition.
This paper presents the analysis of the Influence of the optically active constituents on the
spectral reflectance of the water of Passo Real reservoir. For this, limnological and spectral
data were collected in October 2009 and March 2010 in 31 sampling stations in the reservoir.
The limnological variables total of suspended solids (TSS), chlorophyll a (Chl a), dissolved
organic carbon (DOC) and water transparency were determined on field and laboratory.
Spectral data were acquired on field by using FieldSpec® HandHeld spectroradiometer.
Results showed the most concentration of TSS and Chl a in October may be related with
greater occurrence of rain in that period. TSS was greater in October resulting a reduction of
water transparency. DOC maintained similar average in both analyzed months, still it was
found that sampling points location with above average concentration were located in water
compartments with higher concentration of Chl a. Exclusively using Chl a as indicator of
trophic state we found environments between oligotrophic to hypereutrophic. Reflectance was
higher in October 2009 in all wavelengths, because of high concentration of TSS. Two
features of absorption were observed in both dates, centered in 610 and 675 nm due to the
presence of Chl a. On account of the great concentrations in some sampling points in October,
the peak in the infrared region presented higher magnitude than the peak in the green region
and in some cases the spectrum was similar to the earth vegetation spectral response. DOC
did not present enough concentrations to produce, significantly, spectrum alterations. Each
information extraction technique in spectral reflectance better showed certain spectral
characteristics. First derivative showed itself efficient on the characterization of Chl a effects,
this technique contrasted the influence of this pigment especially on the wavelengths of 438,
566, 685 and 700 nm and the absorption band through pure water in 740 nm. By applying
statistics tests, we could prove the influence of limnological variables on the reservoir water
spectral characteristics and identify wavelengths with strong correlation between variables. In
October we verified the joint acting of Chl a with TSS in water reflectance. Also, it was
proved the influence of Chl a on the spectral response of the reservoir water, especially on
greater concentrations.