Abstract
The natural vulnerability characterization provides fundamental support for identification of areas more susceptible from the hydrology point of view, assuring the maintenance of water resource features. In this context, this study aimed to characterize the natural vulnerability of water resources based on long-term streamflows, base flow and aquifers’ susceptibility to contamination, for Formoso River basin, located in southwestern Tocantins. For that, subdivision by level 5 Ottobasins and discharge and precipitation data sets, both available from the “Brazilian National Water Agency”, and the geological map developed by “Tocantins State Bureau of Planning” (SEPLAN) were used. The final natural vulnerability of water resources presented degrees varying from low to very high. Areas with lower vulnerability were observed in the basin headwaters, mainly due to the greatest both long-term (SYqlt) and 90% of the exceedance (SY90%) specific discharges. “High” vulnerability were identified in most of the middle basin course while “Very High” vulnerability in the lower basin course given by lower SYqlt and SY90% and by the occurrence of the alluvial aquifers which present high natural susceptibility to contamination. Key words: Natural resources, hydrology, watershed management.
Highlights
One of the greatest contemporary environmental concerns is the preservation of water resources given the numerous human activities potentially harmful to this feature, since the demand for them has increased exponentially in the last decade
Among several aspects related to water resources, there is the concern to ensure the maintenance of its availability and quality
This study aims to determine the natural vulnerability of water resources taking the surface and subsurface runoff, and aquifer susceptibility to contamination as a reference, for the Tocantins portion of the Formoso River basin
Summary
One of the greatest contemporary environmental concerns is the preservation of water resources given the numerous human activities potentially harmful to this feature, since the demand for them has increased exponentially in the last decade. Agricultural and livestock are the human economic activities that spatially have greater demand for landing, Changing significantly the landscape These activities are based on the alteration of the natural ecosystems, and they have redefined the land use in large scales throughout the last three Centuries (Ramankutty and Foley, 1999). According to Bartholomé and Belward (2005) almost 16% of the planet’s surface is occupied by tillage. These activities have been important sources of water pollution mainly if they are developed based on inadequate soil conservation practices (Zhang et al, 2009; Orzepowski et al, 2014), affecting the water quality by soil erosion that carries
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