Análise do processo chuva-vazão utilizando hidrograma conceitual de Nash em bacias hidrográficas do Sul de Minas Gerais

Abstract

Bearing in mind that population growth, the advance of urbanization and anthropic action in natural environments have led to environmental impacts of different natures and that the waterproofing of these spaces can cause floods and decrease the quality of water, it is increasingly necessary the quantification of the effects generated by these processes. Nash's conceptual hydrograph (1957) is a rainfall-runoff model that considers the watershed as a linear system that is a function of two parameters, namely the number of reservoirs (n) and the rate of decay (k). As a way of evaluating the differences and comparing two different situations, the values of these parameters were calculated for events at two different stations, the Itajubá station on the Sapucaí river and the PCH Ninho da Águia Montante station, located on the Santo Antônio river. These stations are located in neighboring municipalities, and the Santo Antônio river is a tributary of the Sapucaí. For the flow separation, the graphic separation method was used. Of all the events studied, three were discarded due to the fact that they presented abnormal results for the study, and the justification is that there is some disturbance in the measured flow that caused this problem. The average values of n and k for the Itajubá station were 8.63 and 15.81, respectively, while for the PCH Ninho da Águia Montante station these same values were 4.13 and 10.03. The average values of R² were 0.48 and 0.51, respectively, being considered acceptable. There was a good correlation between the n and k parameters for the two stations, being higher in Itajubá. With regard to the peak time (tp), there was a greater correlation between this and the n parameter at the Itajubá station, while the opposite occurred when the correlation between the peak flow (Qp) and the k parameter was analyzed. The data obtained showed that the modeling was efficient and the applicability of the model was satisfactory.