Influence of land use and occupation on the water quality of a microbasin in the southwestern Amazon

Abstract

Abstract. Water resource management in Brazil is constantly evolving, and greater knowledge about this resource allows better planning and more sustainable uses. In Brazil, the improvement of water resource management faces the difficulty of implementing the instruments of the National Water Resources Policy, such as classification of water bodies. Thus, to help improve the water management instruments in the country's northern region, the objective of the present study was to diagnose the influence of land use and occupation on the water quality of the Igarapé Nazaré microbasin. For this purpose, indirect methods of landscape analysis were applied based on the processing of remote sensing images in a GIS. For the water quality analysis, 10 collection points were selected in the watershed, with samples collected at each one in four periods (high water; HW/LW transition; low water; LW/HW transition). In the collected samples, 14 parameters were analyzed, namely: temperature, pH, electrical conductivity; turbidity; water transparency and depth; dissolved oxygen; chlorophyll a, ammonia, nitrite, nitrate, total phosphorus and dissolved phosphorus; total coliforms and E. coli. The spatial analysis showed that the microbasin has about 84 % anthropized territory, with emphasis on agriculture, and sources of pollution from industries, fish farming and domestic sewage. Parameter analyses showed high values of total phosphorus (0.005–27.55 mg.L−1), total coliforms (4,103–1,09,106 CFU) and E. coli (0–5.8,105 CFU), and low DO concentration (0.0–8.33 mg.L−1), below the official limit established in all periods analyzed The water quality of the Igarapé Nazaré microbasin was found to suffer strong anthropic interference, requiring improvement of the sanitary infrastructure of city of Ji-Paraná, for maintenance of the watershed in class 2.