Although the semi-arid region of Brazil appears to be homogeneous due to drought conditions, there is a great deal of variability in climatic elements in the region, so that the definition of homogeneous regions will provide the deployment of measures appropriate for each locality. However, the limited information on climatic parameters in the region makes it difficult to define these regions. This problem can, however, be alleviated by the use of entropy theory. Therefore, this study aimed to investigate the potential of the theory to identify hydrologically homogeneous regions for conditions of the semi-arid region of Brazil. Entropy-based Disorder Index (DI) data were computed, based on monthly precipitation and monthly water balance (precipitationreference evapotranspiration) for 290 gauge stations. For defining homogeneous regions, cluster analysis was utilized, using the data on geographical information about rain gauges (latitude and longitude), annual precipitation, annual water balance, coefficient of skewness, coefficient of kurtosis and DI. The identification of homogeneous regions in the Brazilian semi-arid region was only possible when the grouping of stations was performed, based on DI for precipitation and latitude. Results showed the definition of seven homogeneous regions in the semiarid region of Brazil.
Global population growth drives the increase in demand for water and food. Consequently, there is a build‐up of pressure for land use for agricultural production, creating the necessity of sacrificing areas previously occupied by the native land cover to create production areas. However, globally, the possibilities of agricultural frontier expansion are limited, and agricultural expansion activities conducted without adequate planning can accelerate the erosive processes that decrease the potential land production capability. In an attempt to attenuate environmental imbalances, payment for ecosystem services (PES) programmes have been created, highlighting the possibility of their being applied in the agricultural sector. This study developed a methodology for PES that follows the basic principles of the land use capability classification system proposed by the United States Department of Agriculture. However, the study aimed to make the classification process operational in a way that notes the conditions in which a rural property maintains its production capability without jeopardizing its environmental role. In this way, it is possible to evaluate whether a rural property is suitable to receive PES. To detail the steps for applying the methodology, a case study was conducted on a rural property in the town of Itabira, Minas Gerais State, Brazil.
The current demand for food has been met through the exploitation of natural reserves. Brazil has 26% of its extension occupied by agricultural uses, 62% of which are pastures. Degraded pastures have greater land use intensity than well-managed pastures, leading to greater degradation of the environment. Land use classification systems consider that pastures are well managed, a misconception for the Brazilian reality. Based on this approach, it was aimed to develop a methodology for mapping the intensity of land use by pasture via remote sensing. The method of mapping was developed and validated in basins with different soil and climatic characteristics. Three calibrations were performed based on NDVI values to ascertain the influence on the results, being evaluated from the field campaigns and the kappa and weighted kappa indices. The kappa and weighted kappa indices presented reasonable and moderate agreement, respectively. The results were considered as satisfactory for the three calibrations, evidencing that the degree of degradation of the pastures can be estimated in a simple way by remote sensing. The Limoeiro River Basin has around 46.9% of pastures, at least, heavily degraded and 96.6% with some degree of degradation, which contributes to degradation of the natural resources and reduction of livestock farming and economic potential of the basin.
Regionalization is an important technique for estimating the flow of hydrographic sections with a lack of data. First, it is necessary to identify hydrologically homogeneous regions (HHRs), which are commonly validated via statistical analyses. Because this step is understood to be subjective, studies that contribute to a greater reliability in identifying regions are needed. In this context, the objective was to evaluate the inclusion of a physical analysis of the average regionalized flow rates as an aid to identify HHRs. The groupings were defined on the basis of geographical convenience methods and cluster analysis. For the assessment of regionalized flows, six statistical indices were used with a physical analysis that was performed via a comparison of the runoff coefficient to the spatial distribution of precipitation values. It was concluded that the physical analysis reduced the subjectivity in the identification of HHRs.
Land use capability systems do not present any considerations regarding recharge zones (RZs). To improve conservation planning, the objective of this study was to present a parametrization method for the land use capability of recharge zones (LUC-RZ). RZs were characterized as the upper thirds of the elevations of all slopes with rectilinear, concave and/or convex features in the terrains. The LUC-RZ were parameterized based on the slope of the middle third of the elevations. The proposed methodology was applied to the Doce River basin (DRB) in Brazil, and 27.9% of the total area was characterized as RZs. It was found that 61.9% of the RZs area could be exploited through agricultural and livestock use; however, the usability of most of these areas was conditional on the adoption of rigorous soil and water conservation techniques. The remaining 38.1%, which was equivalent to 10.6% of the DRB, was restricted to native forest cover. Of the 61.9% of RZs area that could be used for agriculture and livestock, 18.2% was occupied by native vegetation. These areas are protected by law and are responsible for several ecosystem services and thus must be preserved. The parameterization of the LUC-RZ was sensitive to pedogeomorphological characteristics. The methodology used for the determination of the recharge zones has a strong theoretical basis and was simple to implement and therefore has great potential for use in multicriteria analyses for determining recharge zones.
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