Hidden in plain sight: How finding a lake in the Brazilian Pantanal improves understanding of wetland hydrogeomorphology. Issue 2 (19th December 2019)

• Record Type: Journal Article
• Authors: Merino, Eder Renato; Assine, Mario Luis
• Is Part Of: Earth surface processes and landforms. Volume 45:Issue 2(2020)
• Page Start: 440
• Page End: 458
• Publication Date: 2019-12-19
• Subjects: Negro River Interfan System -- time series -- interfan plain -- flooded areas, geomorphological zonation; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4745
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Wetlands are permanently or seasonally flooded areas which support countless species of plants and animals. The Pantanal, in central‐west Brazil is one of the largest freshwater wetlands in the world covering an area of ~150 000 km 2 . The relationships between geomorphology, hydrology, sedimentation, and vegetation cover are critical for understanding how the landscape constrains the dynamics of wetlands. We provide a detailed study of the geomorphology and surface hydrology of the Negro River Interfan System (NRIS), in the southern Pantanal, by applying multiple approaches (i.e. remote sensing analysis, geomorphological zonation and hydrosedimentological surveys). A multitemporal analysis of Landsat imagery produced an inundation frequency map (2000–2011 period) that revealed a permanently flooded area in the central portion of the NRIS. A hidden fluvial lake was previously undetected due to the accumulation of floating mats and floating meadows of macrophytes. The Negro and Aquidauana feeder rivers exhibit remarkable differences in channel planform, water discharge, and sediment load. The Negro River presents a distributary pattern with marginal levees with decreasing elevation as it progrades into the lake and remains as a subaqueous landform conditioning the water flow downstream. The lake outflow to the Paraguay River occurs mainly by sheet flow during flood seasons and through small tributary channels during dry months. The lake's geometry is outlined by east–northeast and west–northwest straight borders, suggesting that the area is tectonically controlled. A cloud‐based worldwide water surface database (1984–2015) revealed frequent channel changes within the NRIS. Recent channel avulsions in the lower course of the Negro River are noteworthy mainly because the former river channel at the confluence with the Paraguay River is no longer connected with the Negro River channel. © 2019 John Wiley & Sons, Ltd. Abstract : A fluvial lake, almost completely hidden by floating macrophytes, is the most striking landform of the Negro River interfan system (NRIS), where the complex geomorphology is coupled with an intricated hydrological and sedimentological regime. Geological structures can be recognized by using vegetation and flood frequency maps indicating that the area is under a Neotectonic regime. Our analysis demonstrates that short‐term climatic variations triggered important changes in the dynamics and morphology of the NRIS.