Estabelecimento de metodologia para a conservação e recuperação de pequenas bacias hidrográficas do semiárido.

Abstract

In tropical regions, such as the Brazilian semiarid region, the reduction of forest areas by extracting firewood, subsistence agriculture and livestock, associated with spatial and temporal variability of the climatic and hydrological regimes, have significantly contributed to environmental degradation of extensive areas. Research in experimental basins have shown the role of vegetation on erosion reduction as a major factor for the conservation of small rural basins, but generally do not consider the relationship between human society and the environment. This thesis has as its main research problem the conservation and/or environmental remediation of small rural watersheds in the semiarid region of Brazil. The hypothesis that guides the work is that a methodology that considers future scenarios of land use and occupation and the communities’ relationships with the environment will result in a greater possibility of implementation of conservation strategies. The objective of this work is to propose a methodology for the selection of strategies for conservation and/or restoration of small watersheds, from a water resources viewpoint through environmental modeling, considering the social acceptability of these strategies by rural communities that occupy the basins. The methodology emphasizes the need for environmental characterization considering climatic, hydrological, political, economic and social aspects, to support a realistic and feasible conservation planning, considering the farmers’ needs. It advocates the use of interviews and meetings with farmers and environmental simulation models as methodological tools. Models can help in locating critical areas and provide tools for identifying potential strategies to reduce erosion at different spatial scales. The methodology was applied in a small watershed in semiarid region of the State of Paraíba. Candidate strategies for the conservation and restoration of the basin were identified through meetings with focus groups of farmers. The SWAT hydrological model was used to estimate sediment production and runoff. Four scenarios of land use and occupation were simulated using climate data for the period 1998-2012. The scenarios were selected according to the opinions of farmers, having been contemplated strategies with greater social acceptability. Society involvement in the discussions and negotiations helps to incorporate environmental, cultural and social aspects in the planning process. Simulation results show an estimate of annual sediment yield at the current scenario of the use and occupation of land exceeding 1.7 to 2.7 times the tolerance limits established for soil loss worldwide, but the restoration strategies can reduce almost totally the annual sediment yield and increase water production in the basin up to 55.0%. An advantage of the proposed methodology is that through a list of socioeconomic and environmental indicators, the community can actively participate in the field research, becoming an integral part of natural resource management.