Water Balance in the Guarani Aquifer Outcrop Zone, Brazil
Water Balance in the Guarani Aquifer Outcrop Zone, Brazil
Presented on Wednesday, May 7, 2014
The Guarani Aquifer System (GAS) is the largest transboundary aquifer in South America with an area of 1.2 million km2 spread over four countries (Argentina, Brazil, Paraguay, and Uruguay). Despite the importance of the GAS as a major source of fresh water in the region, little is known about its recharge processes. The main recharge is supposed to occur in the outcrop zones of the Botucatu and Pirambóia Formations, representing approximately 10% of the total aquifer area. Aiming to estimate the groundwater recharge, a monitoring network has been deployed in the Ribeirão da Onça watershed, which appears to be representative for the GAS outcrop zones. Water table observation wells have been installed under different land uses (grassland, eucalyptus, sugar cane, and citrus cultures) and monitored since 2004. Direct recharge was estimated using a point-scale method (Water-Table Fluctuation) for each land use, after a careful determination of the specific yield. The average results indicate that the direct recharge strongly depends on the land use: eucalyptus forest (135 mm.y-1), sugar cane (248 mm.y-1), citrus (296 mm.y-1), and grassland (401 mm.y-1). The main climatological variables (precipitation, temperature, solar radiation, wind velocity) as well as the discharge at the draining creek have also been monitored, allowing the evaluation of the water balance in this watershed. The recharge contribution to the regional groundwater system was estimated to be approximately 3% of the annual average precipitation (1400 mm). The estimated recharge is important information for water management purposes since it can be used as an input parameter for regional groundwater models to predict water table levels and to assess potential future climate changes impacts in the GAS.
Edson Wendland
University of São Paulo (USP)
Edson Wendland has been a Professor in the Department of Hydraulics and Sanitary Engineering at the University of São Paulo since 2001. He holds a bachelor’s degree in Civil Engineering, an M.Sc. in Mechanical Engineering, and a Ph.D. in Civil Engineering. From 1996 to 1999 Wendland was Assistant Professor in the Department of Applied Geology at Ruhr University Bochum in Germany. His research and publications focus mainly on field experiments for water resources evaluation and numerical modeling of groundwater flow and solute transport.
Murilo Cesar Lucas
University of São Paulo, São Carlos-SP, Brazil
Murilo Lucas is a Ph.D. student in the Department of Hydraulics and Sanitary Engineering at the University of São Paulo. He has been involved with studies related to the impacts of land use on groundwater recharge and water balance in the Guarani Aquifer System. His current research focuses on the effect of fracture aperture and geometry on the fluid flow and mass transport in fractured media. Lucas develops experimental work and mathematical modeling in laboratory scale.
Davi de Carvalho Diniz Melo
University of São Paulo, São Carlos-SP, Brazil
Davi Melo is a Ph.D. student in the Department of Hydraulics and Sanitary Engineering at the University of São Paulo. He has been involved with studies related to the estimation of climate change impacts on groundwater recharge and water balance in the Guarani Aquifer System. His current research focuses on downscaling of Global Circulation Models for numerical modeling of groundwater flow in a watershed scale.
Rodrigo Lilla Manzione
São Paulo State University, Ourinhos-SP, Brazil
Rodrigo Lilla Manzione holds an MSc. in Agronomy and a Ph.D. in Remote Sensing. During a doctorate internship (2005-2006) he worked at Alterra Institute, Wageningen University, The Netherlands. Since 2008 he has been an assistant professor at São Paulo State University, teaching and researching in the fields of water resources and agrometeorology. Manzione is professor of a graduate level course of Irrigation and Drainage, teaching a groundwater course and supervising master and doctorate students.