Balanço hídrico á superfície da bacia hidrográfica do açude Epitácio Pessoa utilizando informações digitais do terreno.

Abstract

The need for rationalization of the use of water resources, in the semiarid area of the northeast of Brazil, calls for an understanding of the interactions among climate, land use and physiography. Considering the importance of an adequate water resources management, this study examines the impacts of the spatial and temporal rainfall variability, soil depths and vegetal cover on the water balance of a river basin. The catchment upstream of the Epitácio Pessoa reservoir in the state of Paraíba is the nasin chosen for the current study due to its great importance for the city of Campina Grande. Additionally, this study generates a data base of physical characteristics and other data that include information on the topography, tributary lengths, inclination, surface drainage direction, stream order, and total drainage area. The steps involved in the development of this work are: initial data processing, identification of the physical characteristics, vegetal cover estimation, and application of the water balance model. The model is based on the identification and quantification of the hydrological processes in seven different sceneries. In the model, the interception and evapotranspiration are considered as losses. A program codified in FORTRAN, denominated TOPAZ (Topography ParametriZation) and other softwares like Idrisi, Erdas, Surfer and Microdem were utilized in this study. Landsat-TM 5 image, digital elevation data, daily rainfall, evaporation and streamflow data were the main inputs. The results are displayed in digital map form, with the identification major sub-basins. Among the various scenarios tested, the fifth represented best, the surface runoff in the basin upstream of Caraúbas area. For the basin upstream of Poço de Pedras, the sixth was the one that provided the bets results. In general, the model responded well to the variability of the different factors in Epitácio Pessoa river basin, in spite of the large spatial and temporal variability of rainfall. The adjusted model estimated that about 12% of the rainfall is converted in to surface runoff. The Nash coefficient and the coefficient of determination were on the average, 0,89 and 92%, respectively. When compared with the observed flow series at Boqueirão de Cabaceiras between, 1932 –1955 the simulated surface runoff indicated a retardation of the peak and a reduction in volume reflecting the effect of the construction of many new storage dams within the basin that didn´t exist when the flow data were registered..