Manejo da Mata Ciliar e Eutrofização de Reservatórios do Semiárido Nordestino

Abstract

The semi-arid region comprises about 70% of the Northeast and a small portion of the Southeast of Brazil, the Caatinga biome being the most predominant, consisting of plant species characterized by leaf fall (deciduous) and its regeneration capacity. The vegetation is quite heterogeneous, composed of a mosaic of shrubs and areas of dry season forest, presenting great physiognomic and floristic variation, constituted mainly by vegetation of woody and herbaceous species, small, branched and usually endowed with thorns and deciduous. The mean annual precipitation varies between 240 and 1,500 mm, concentrated in four months of the year and average temperatures varying between 26 and 28 ° C. Few studies quantify changes in water quality as a result of increasing or decreasing riparian forests. The removal of riparian forests influences the water quality of water bodies, according to the results of several surveys. Some studies cite the efficiency of the riparian forest in relation to the capacity to retain and assimilate the nutrients transported by the surface runoff. The riparian forests are forests of close contact with the water bodies and their degradation exposes the soil and, thus, facilitates the transport of sediments and nutrients and can cause changes in the water quality of the water bodies. Therefore, studying the riparian forests, as a means of protecting water resources, is of fundamental importance for the semi-arid region. The main objective of this work is to evaluate the relationship between the management of the Caatinga riparian forests, the sediment and nutrient exports, and the eutrophication process in the semi - arid Northeastern dams. The characterization of the study area was carried out in the Marengo Açude ciliary forest, located in the 25th of May settlement, located in the limits of three municipalities: Madalena, Boa Viagem and Quixeramobim. Then the areas of the riparian forest plots were defined and installed. Four plots (managements) were installed: two plots with preserved riparian forests with two different lengths (100x3m² and 30x3m²); a plot with thinned riparian forests (100x3m² and 30x3m²) and another plot without riparian forest (100x3m² and 30x3m²). For the simulation of the artificial rains a rain simulator with irrigation structure was set up, which pumped water from the Marengo dam and structure with motor pump, sprinklers, all PVC and water boxes. Simulations were carried out to separate the period of the first rains and the rainy season. The simulations lasted an hour. The results were evaluated with respect to the quantity and quality of sediments, the quantity and the quality of the superficial flows, evaluating some physical-chemical parameters.