Avaliação da qualidade da água em uma lavoura de arroz através de parâmetros físico-químicos e de sensoriamento remoto

Abstract

The rice is widely used as a basic food in many countries. It is cultivated in many parts of the world, being Rio Grande do Sul (RS) in Brazil, the primarily responsible for producing it. The water used in its production must have quality parameters between potability limits.The goal of this work is to perform a morphometric characterization of the study area, a geostatistical analysis including the spatial variation of the physicochemical analysis of water and the gray level (NC) of pixels from satellite images and correlate them. The study was conducted in a crop of 25.5 ha located in the municipality of Itaqui Latitude S 29 ° 08 ' 42’’ and longitude W 56 ° 31' 05". Data from electrical conductivity (EC) and dissolved oxygen (DO) was collected in the years 2010/2011 (5 samples) and 2011/2012 (4 samples), in 3 points and 9 points respectively, including entry, middle and exit of crop water. Landsat 5 satellite images and radar images (SRTM) were used in the work. The geostatistical analyzes were performed with the aid of the Spring program. The maps created using the values collected at different points of the crops were presented in two classes: with and without water potability, using the limits established by law. We also performed a comparison between chemical and physical parameters of the NC pixels of satellite images. Data from gray level of points corresponding to physicochemical data collections was picked from the satellite images and this information was correlated graphically. We performed a morphometric characterization of the study area by produzing a slope map and a level map (hypsometry). It was concluded that the the area has a slope less than 4% and about 63% of the area has slope less than 2%. From hypsometry analysis it can be seen that inside the box there is a difference of 12 meters in altitude quota and during the period of the study the area presented EC levels above 100 us / cm at the beginning and end of the cycle. At intermediary dates the EC presented EC levels below 100 us / cm. During the two crop seasons, the variable OD remained without drinkable water level, in areas greater than 58% of the study area, which had values of OD equal or less than 5 mg / l. From the comparison between NC and physicochemical parameters of pixels it is concluded that the variable OD showed strong correlation with NC and EC showed no correlation.