Interferência do uso e ocupação do solo na qualidade da água em bacia hidrográfica com disponibilidade hídrica crítica

Abstract

Water demand in agricultural, industrial and urban supply sectors has shown the importance of planning and managing water resources to meet the multiple uses of water in an integrated and optimized way. The use of computational tools allows the management of water resources in a watershed scale to be carried out in an efficient and integrated manner, since it allows the joint modeling of the quality and quantity of water on a daily and / or monthly scale. This master's work aims to evaluate the interference of soil use and occupation in water quality in a watershed with critical water availability. It was studied, specifically, the Ribeirão do Salitre watershed (MG), in which the maximum surface flow granted exceeds the maximum allowed by the current legislation and allocates the pit of a phosphate mine at the head of the main tributary. The water balance and subsequent surface water quality modeling were performed using the computational tool named QUALI-TOOL. The calibration of the water quality model was carried out in a stretch of approximately 8 km in Ribeirão do Salitre, where water quantity and quality were monitored in five points, being three in Ribeirão do Salitre and two in the two main tributaries. The monthly monitoring was accomplished during the dry season (August and September of 2017) and during the rainy season (November and December of 2017). After the water calibration quality model, there were analyzed interference scenarios of land use and occupation in the watershed on the water quality in the Ribeirão Salitre, in a stretch of approximately 38 km up to its drain in the river Quebra Anzol. The estimation of the pollutant load affluent to the watercourse for the six scenarios of land use and occupation was obtained through the computational tool MQUAL. The 1, 2 and 3 scenarios simulated the gradual advance of the mining activity influence, maintaining the proportions of the agriculture and livestock areas to the current values. The 4, 5 and 6 scenarios simulated the influence of the advance of agriculture and livestock to an area of maximum mineral exploitation granted. Based on CONAMA Resolution 357: 2005, for class 2 river, the concentration of the nitrate parameter lied below the maximum allowed in all scenarios, with a maximum value of 0,488 mg / L. The parameter ammoniacal nitrogen presented concentration above the maximum allowed by the resolution only in scenario 6, with a value of 4.33 mg / L, where it was considered 80% of GUIMARAES, T. M. H. Interference of soil use and occupation in water quality in the hydrographic source with critical water availability. Master's Degree Dissertation, Civil Engineering Course, Federal University of Uberlândia, 2018. total area for agriculture. In all scenarios, the parameters BOD, total phosphorus and Escherichia Coli remained above the maximum allowed by the resolution. In the scenario 6, which is the most critical among all of the analyzed, concentrations of BOD, total phosphorus, E. coli presented 11.95 mg / L, 0.55 mg / L, 1.46 × 1011 NMP / 100 mL, respectively. In general, the study depicts the importance of planning and management of water resources in a watershed scale in the preservation of the surface water quality.