Estudo qualitativo e quantitativo da água do rio Cuiabá na seção hidrométrica do Porto

Abstract

This study presents a qualitative and quantitative analysis of the water in the Cuiaba River at the Hydrometric Station of Porto, which was installed in 1933 between the cities of Cuiaba and Varzea Grande in the state of Mato Grosso. In the twelve field campaigns put into practice from December 2011 to February 2013, related to this study, the flow was measured and sediment collected. In six of those campaigns, three in the dry season and three in the rainy one, samples of water were collected too. A hydrometric vane was used in the flow measuring; in the collection of suspended sediment and water samples it was used a sampler USDH-59 and a Rock-Island sampler to collect sediment in the bed of the river. The method of Equal Width Increment was adopted to collect suspended sediment; the bottom sediment and water samples were collected at 1/6, 1/2 and 5/6 of the total width of the river. The estimated Total Solid Discharge was calculated using the simplified method of Colby. In this study the results of liquid and solid discharge were associated to the aspects of water quality, according to Item I of Article 3 of General Guidelines for Action Federal Law No. 9433 of January 8, 1997. A rating curve was created with the flow measures, which was compared to another one provided for the same hydrometric station by the National Agency of Water – ANA. The concentration of suspended sediment, together with the water flow, produced a rating curve of concentration which was compared to concentration data from other studies, beyond being used to calculate the total solid discharge – TSD. A rating curve of solid discharge related with water flow was also created and compared to another studies about the Cuiaba River. To analyze water quality, the CONAMA Resolution 357/2005 and the Water Quality Index – WQI – adopted by the state of Mato Grosso were used. The results of flow proved a direct relation to the dry and rainy seasons and showed clearly the regularization of the flow due to the Manso Reservoir (also called APM Manso). The results of solid discharge were also closely related to the seasons, beyond indicating an human influence in its production. In the results about water quality, some parameters are in disagreement with the CONAMA Resolution 357/2005, specially total phosphorus, Escherichia coli, dissolved oxygen and turbidity. As for the Water Quality Index, the study section got grade 60 which is considered by the index as AVERAGE. This study is concluded also observing that solid discharge, flow and water quality are closely related and should not be dissociated.