Qualidade da água e regime hidrológico em sub-bacias hidrográficas dos rios Capivari e Mortes

Abstract

Water is essential for supply the society, food production and for the life general way. For food production, much of the water has been lost via evapotranspiration and overland flow due to its inadequate use in the irrigation systems. Deep changes in the environment are associated with natural and anthropogenic activities. The aim of this study was to evaluate the Water Quality Index (IQA), Trophic State Index (IET), Specific Yield and Sediment Discharge in the Capivari River (GD1) and Mortes River (GD2) basins. Three sampling points were sampled in both GD1 (P - I at the Ingaí – Minduri River, P - II at Capivari River and P - III in Ingaí – Luminarias River) and GD2 (P - IV at Mortes River, P - V at Peixe River and P - VI at Tabuões Creek). The monitoring covered the period between April/2015 and February/2016, summing eight samples per river, with the exception of P - V in which seven samples were taken. The parameters evaluated were: hydrogen potential (pH), biochemical oxygen demand (BOD), dissolved oxygen (DO), coliform thermotolerant, turbidity, total solids, phosphate (PO3-4), phosphorus (P), nitrate (NO3-), temperature, aluminum bromide, copper, hexavalent chromium, iron, manganese, nickel and zinc. With these data sets, it was calculated the specific yield discharge, solid discharge suspended, IET and the IQA following the IGAM proposals. Water quality parameters obtained was compared to the maximum allowed values according to COPAM Normative Resolution CERH 01/2008 for the classes 1 and 2 (heavy metals and water quality, respectively). The results obtained by the specific discharge yield showed differences in the two hydrological regions (GD1 and GD2). There was a greater aquifer recharge in GD1 than GD2, demonstrated by the baseflow behavior. On the other hand, solid discharge suspended ion showed a satisfactory result in four sampling points, with intense rainfall events generating large amounts of sediment. Similar to the other two points of sampling, the high rainfall amounts did not provoke large amounts of sediment and, in addition, the last sample point was quite silted. Heavy metals were greater than those reference values that are permitted mainly due to improper launch domestic sewage, industrial and mineral, the local mineralogy, precipitation and the contact of the livestock actives with the river banks. The water quality parameters had their values greater than the permitted due to high amounts of CT, turbidity, ST, P and also the NO3- because of both diffuse and point pollution close to the respective sample points. All sampling points for IQA were classified as “bad”, because they are associated with livestock activities contact, mining, dumps of domestic and industrial sewage effluents.