Impacto do Uso de Vazões Naturais em Estudos Hidrológicos

Abstract

A major effort has been dedicated to the reconstitution of natural discharges. The natural discharge is the sum of the consumed discharges and the observed ones. The effect of anthropic actions in the Paracatu basin increased water consumption about 11 times in the last 27 years. This study was undertaken to evaluate the impact of the use of natural discharges to substitute the observed ones in different sections of Paracatu basin. The data of the observed and natural discharges of 21 rivergaging stations from 1976 to 2000 were analyzed. The impact of the use of the natural discharges was estimated to the maximum (Qmax), the medium of long duration (Qmld) and the minimums discharges (Q7,10; Q95 and Q90) by using an index, characterized in this study as ∆ (delta). The correlation between the drainage area of each section and its respective delta was calculated. The delta behavior was analyzed using a graphic, according to the values of the natural discharges. The statistical analysis used the Student t test (α = 5%). The mean value of the ∆ for Qmax, Qmld ,Q90, Q95 and Q7,10 was, respectively, 0.01%, 0.66%, 4.26%, 5.45% and 5.76%. All these deltas were considered significant (α = 5%). The highest values of discharges led to the lowest values of delta. The deltas of the maximum, medium of long duration and minimums discharges were statistically different. The correlation between the drainage area and the delta was not significant. The delta behavior according to the values of the natural discharges followed a potential model with negative declivity at a high R2 (0.9842). For the purpose of hydrologic studies of the Paracatu basin, the use of natural discharges in the case of the maximum and medium of long duration is not a concern, but in the case of the minimums discharges, it is recommended to take some precautions