USE AND OCCUPATION OF SOIL AND WATER QUALITY IN THE RIVER BASIN URUPÁ, RONDÔNIA
Water quality index. Index of trophic status. Eutrophication.
The main productive processes of the State of Rondônia have undergone a modernization, with rise and evidence of some economic activities, which represent risks to the environment by the potential polluter. To do so, the management of these activities should consider the river basin as the territorial planning unit, because the impacts of land use and occupation directly reflect the quality of the water in its rivers. However, there is no platform that concentrates information on these activities and their integrated planning at the municipal, state and federal levels, and the main management tool, ZSEE-RO, is out of date, and there is a lack of studies on the limnological characteristics of surface waters, which makes it impossible to correlate the impacts of the activities with the environmental dynamics of the basins and prevents the adoption of control measures, putting at risk the sustainability of these systems. In this context, the objective was to evaluate the water quality of the Urupá river and the relation as the use and occupation of the soil in its basin, central region of Rondônia. To do so, from May / 2018 to April / 2019, six collections (bimonthly) were carried out at 10 sampling points on the Urupá river, from the source to the mouth of the Mirante da Serra municipalities (P1, P2, P3 and P4 ), Urupá (P5, P6 and P7) and Ji-Paraná (P8, P9 and P10), with analyzes of dissolved oxygen parameters, temperature, pH, turbidity, biochemical oxygen, nitrate, total phosphorus (PT) chlorophyll a, with determination of the Water Quality Index (IQA) and Index of Trophic Status (EIT) in the dry season (May to October) and rains (November to April). The evaluation of the use and occupation was done through geoprocessing tools and the statistical evaluation contemplated a descriptive and multivariate analysis of principal component analysis. Along the longitudinal profile of the river, IQA of regular class predominated, with contrast in the dry for the bad and good
classes, in P5 and P10, respectively. The EIT revealed potential eutrophication for the presence of PT in the stretches that comprised from P2 to P10, in both periods. Although in the river there is a predominance of regular quality, a reference to CONAMA Resolution No. 357/2005 and evidences the capacity of self-purification, the poor quality of P4 to P5 during the dry season indicates that the deterioration of water occurs due to sources of pollution punctual, by the presence of residues and / or effluents from activities inherent to the urban
area, agroindustries and agricultural activities in the drainage area, together with soil susceptibility. To that end, the potential risk of intermediate eutrophication calls for the adoption of measures to coordinate the activities compatible with the basin's support capacity, in the face of a scenario of climatic changes that can aggravate water quality and compromise multiple uses is intended.