Técnicas de separação do escoamento em pequena bacia rural

Abstract

The observed flow in a hydrograph is composed by the surface flow, subsurface flow and groundwater flow due to their trajectory and time of detention. The separation of these components is a necessity to understand hydrological processes in watersheds through the use of hydrological and sediment modeling. Some methods have been developed with the aim of automating and simplifying the flow separation process. However, these methods are subjective because they do not represent the actual behavior of water in the soil. Among the flow separators, the separators based on mass balance and the empirical separators stand out. The mass balance methods assume that the different types of flows usually have different chemical characteristics and, by analyzing the composition in the flow of some conservative elements (tracers), their origin can be determined. Among the tracer options, dissolved Silica (DSi) is used for discretization of hydrological components because it is little reactive in the surface runoff. Empirical methods are usually developed based on the hypothetical model calibration with field measurements or simply based on experience. Among the empirical methods, Recursive Digital Filters (RDFs) are used to separate the flow by associating the high-frequency variation of the hydrograph to the surface flow and the low-frequency to the base flow. The parameters of this filter can be calibrated based on observed flow data and tracers. In this work, different methods for flow separation based on FDRs by Lyne and Hollick 1979, Chapman and Maxwell (1996) and Eckhardt (2005) were evaluated, using observed data of dissolved silicon (SiD) for a small basin in southern Brazil. The results showed a good adjustment of the Eckhardt filter to the separation determined with the SiD tracer and also allowed to suggest alternatives for the determination of the parameters in basins without data.