Variações sazonais nas composições química e isotópica das águas superficiais na Bacia do Rio Jacaré-Pepira/SP

• Autor(a) principal: Farinha, Bárbara Saeta [UNESP]
• Data de Publicação: 2016
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/155818; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2017-08-30/000889836.pdf
• topic: Hidrogeologia; Águas subterrâneas; Águas superficiais; Bacias hidrograficas; Chuvas; Nitratos; Geoquimica; Aquífero Guarani; Jacare Pepira, Rio (SP)

In a watershed, the surface flow in the river channel is the sum of the contribution of groundwater (base flow) and surface flow (run-off), each one contributing in different proportions throughout the year. The use of isotopic and chemical tracers to quantify these contributions in watersheds of various scales is a widely used tool worldwide, but much less used in Brazil. Seasonal variations of the chemical and isotopic compositions of surface water in two small catchments in the Alligator-Pepira River watershed in the city of Brotas (SP) were evaluated, in order to determine the contribution of each of these components in surface flow. Monthly samples of surface water and rainfall were collected between the months of December / 2014 and November / 2015. Rainfall had poor isotopic composition during the rainy season (Dec / 2014 to April / 2015) and higher values for the remainder of the period, without recognizing the effect of the quantity on these values. During the period, the electrical conductivity of surface water showed values of 16,25S cm -¹ for point 1, and 78.09S cm -¹ for point 2, reflecting different degrees of mineralization, associated with differences in the geological substratum of the watershed. Surface waters were classified as bicarbonate sodium-calcic in point 1 and bicarbonate calcic in 2. During the monitoring period there was a negative correlation between precipitation and nitrate concentrations measured in surface waters, indicating that the major contributions of this compound are associated to the discharge of the groundwater. The observed variations in the isotopic composition of precipitation are reflected in the surface water, with surface waters having higher variations in isotopic composition during rainy periods. Also, both points presented similar and stable isotopic compositions during the dry season, indicating the discharge contribution of groundwater flow in maintaining the channels...