Timing and Mechanisms of Fluvial Responses to Rapid Land Use Changes in the Surrounding Highlands of the Pantanal Wetland (Brazil): The Case of Taquari River

Since the 1970s, the intensification of anthropogenic activities in the surrounding plateau has caused changes in surface processes that directly influence the fluvial dynamics of the Pantanal. As a consequence of these changes, the intensification of avulsion processes and increases in the magnitude of floods in the lowlands is observed, causing severe environmental and socioeconomic damage. Therefore, considering the ecological importance of the Pantanal and the changes that the basin has been suffering, there is a need to understand past and current conditions on fluvial behavior and how anthropogenic impacts on the plateaus have affected the lowlands. Here we propose to evaluate the response of the Taquari River to the human effects on its upper course in the last 50 years. Our approach uses satellite images to estimate suspended sediment concentration and quantify morphological changes in the channel. The results obtained demonstrate that the impacts resulting from deforestation in the plateau interfere with the water discharge and sediment load along the river course. With the increase in cultivation and pasture and suppression of natural vegetation, there was an increase in production and sediment transport (soil erosion) in the basin, altering the river's dynamic, structure, and functioning. Thus, the response of water discharge and suspended sediments was rapid and synchronous with land use changes. However, the river bar response time was slower, with the most significant increase in bars occurring around 10–20 years after the peak of deforestation rates. Changes in channel width and migration rates were insignificant, suggesting that these parameters have greater resilience or longer response time. The information obtained here provides new data to predict anthropogenic effects on the river system and support plans for conservation.