Influência do uso e ocupação do solo na disponibilidade hídrica do Rio Buranhém

Abstract

Considering that the knowledge of the variables that influence water availability help the management and better use of water resources and that the use and occupation of the soil in watersheds is directly and indirectly related to the amount and water quality in water courses, this work sought to verify the influence of the alteration of land use and occupation in the water availability of the Buranhém River, located in IV Region of Planning and Water Management of the state of Bahia. The work was divided into three stages: I. Physiographic characterization of the basin and temporal analysis of the use and occupation of the ground; II. Study of hydrological behavior; and III. Joint analysis of hydrological data and land use and occupation via correlation. All data used were secondary, acquired on official bases, such as the website of the National Water Agency (ANA) and of the MapBiomas project. The rainfall and fluviometric data cover the period of 1972 to 2017, while the land use and occupation refer to the years 1985 to 2017. Deforestation in the region precedes this period, since since 1985 pasture was already the landscape matrix, while the analysis of annual flow and precipitation demonstrated a change in hydrological behavior between the 70's and 80's. Between 1985 and 1991 the loss of native vegetation was significant, being replaced by pasture, which began to be replaced after 2001 by Eucalyptus monoculture and early stage forest vegetation of regeneration. The flows showed that the river is not very perennial, with a strong influence of the annual precipitation, which in turn presents great annual variability. The parameters studied allowed us to infer that the low regularity of flows is aggravated by the high surface runoff to the detriment of soil infiltration and aquifer recharge. At Correlation analyzes showed an inverse relationship between forest vegetation and water flow. Q50 and Q95 permanence, which may be associated with increased water output from the system with the growth of the vegetation, however this would only be confirmed with the calculation of the balance basin water.