Indicadores hidrológicos para a gestão de recursos hídricos na bacia hidrográfica do Rio Manuel Alves da Natividade, Tocantins

Abstract

The objective of this study was to characterize the hydrological regime of the Manuel Alves da Natividade river watershed, TO, at Fazenda Lobeira gauging station. Therefore, regional hydrological indicators were quantified associated with average flow rates, minimum and maximum, average rainfall in the watershed, annual water balance, in addition to its main morphometric characteristics. It was used digital scenes of the elevation model ASTER in SIG environment, rainfall and fluviometric historical data provided by the Brazilian National Water Agency (ANA). The results showed that the rainfall has a strong concentration in the summer, with 50.4% of the annual rainfall between December, January and February. The extreme hydrological events indicators showed that the average daily flood with a recurrence of 2 years exceeds 7.1 times the average flow, and the event with 100 years recurrence interval, exceeds 2.2 times the average daily flood with a recurrence of 2 years in the watershed. The low flows period is strongly influenced by the long period of drought, which features 5 consecutive months with less than 50 mm of rainfall (May to September). The analysis of hydrologic indicators associated to minimum flows identified a high vulnerability of water resources surface, allowing to conclude that the use of watershed conservation practices and investments in regularization works are essential for an optimization of surface water resources in this watershed.