Impact of Urbanization on the Hydrodynamics of a Water Table in a Floodplain with High Potential for Renaturation

摘要

Large river basins influence the development of human populations either by interfering with population growth or by providing a valuable resource that supports population growth. The Paraiba do Sul River catchment (55,400 km(2)) in southeastern Brazil supplies more than 14-million people with water, and is located in a region of Brazil with the highest Gross National Product (GNP). This catchment contains 77 floodplains (2156 km(2)) whose waters are highly regulated, and has a medium urbanization index (18.9%). Fifty-two of these floodplains (67.5%) have characteristics that make them suitable for the implementation of management practices that seek renaturation of the floodplain to ensure the sustainability of regional economic development. The floodplain examined in this study is highly managed and has a great potential for renaturation. We examined variations in groundwater level from the control section (lowest cross-section of the floodplain) to the propagation zone for flooding (9.43 km upstream) from January to December of 2013. The elevation of the water table near the structural control point had less seasonal oscillation than a distant area (p = 0.036). There was also a significant difference in the depth of the water table within the interior of the floodplain (urban area: 3.13 m, non-urban area: 0.49 m, p < 0.001). These results demonstrate that water regulation has been compromised in the study area due to the reduced connection between the river channel and floodplain in the urban region. Thus, land use in this floodplain has interfered with water storage capacity and the connectivity between sub-surface flows. These results suggest that this area is suitable for the implementation of techniques that seek renaturation of the floodplain, so that humans can continue to use this water and so that the effects of climatic changes can be mitigated.