Estimativa de vazão com dados escassos: novas hipóteses para o método silveira

Abstract

The estimates of low flow in ungauged basins with data lacking represent in Brazil an urgent technical demand as a result of the environmental licensing and water rights. These processes are requirements of our legislation at federal and state level. The reference flows presented in the Brazilian laws are related to minimum and medium flow into our rivers and streams. The reference flows must keep the integrity to environmental sustainability. On the other hand, Brazil with its continental dimensions has no runoff network that meets the needs of traditional hydrological studies. In 1997 was proposed a methodological strategy was proposed, in which this study aims to maximize its use through new application cases. A network of 12 basins was structured to support the studies because there are not monitoring data. The goal is to establish a protocol using the proposed method based on the interpretation and recognition of major factors of rainfall-runoff process. The river depletion is the key concept that supports a water balance applied to estimate the minimum flows in basins with data lacking by using three flow measurements in the fluvial section of interest. In this process it is used a mathematical model of two parameters, one parameter related to water balance, Cinf, and another to the river depletion, the Ksub. From the network of 12 basins with runoff continuous monitoring, it is obtained a technical database with 600 simulations that supported the assessment expansion of its applicability for up to 1000 km² basins. As outcome a protocol is achieved for implementing the method associated to an acceptance interval of Cinf from 0.1 to 0.6; the effective characterization of river depletion during flow measurement campaign; the definition of a previous rainy period with limited of total precipitated in 14 days prior to flow measurement campaign; the possibility of using the method in basins until 1000 km² since a representation of at least two rain gauges is considered to support the water balance. Finally, it is evaluated the possibility of the method application for both fractured aquifers as sedimentary aquifers in small basins.