Carga de poluição difusa em bacias hidrográficas com diferentes impactos antrópicos

Abstract

The disordered occupancy of the soil with no suitable conservationist treatment and inappropriate human actions cause impacts in the local hydrology and, also induce the pollution of water resources. The objective of this study was evaluating load of diffuse pollution in four watersheds with different human impacts in distinct location of the Vacacaí Mirim River in Santa Maria, RS, to obtain an analysis of the factors that influence the pollution in the hydric flow as: precipitation, water discharge, soil use and occupation, basin area and, dry period preceding the event. The average concentration of events presented variability due to precipitation and intensity of precipitation, only the Alto da Colina basin presented correlation of the total solids, dissolved solids and, ammonia with the antecedent dry period. The diffuse load in the Rancho do Amaral basin, which has 55.8% of native forest, obtained the smaller charge of diffuse pollution in all analyzed parameters. The Alto da Colina basin, which is influenced by urban and agricultural areas, presented higher loads in all analyzed parameters, and it is the basin with the smallest area. The lower organic load of BOD5 was in the Rancho do Amaral Basin with 9 kg / ha / year and the highest was in the Alto da Colina with 202 kg / ha / year. The polutographs showed the variability of the pollutants in relation to the liquid discharge and greater wash load in urban areas. The difference in pollutant load is due to the high degradation process caused by human activities such as urbanization, agriculture and domestic effluent, different for each watershed.