A proposed water quality index: the case of Trussu River, Ceará, Brazil

Abstract

This study was carried out to assess water quality in the Trussu River valley by indexing numerically the potential pollution. This study was done in the part of the valley where is located several farms with livestock activities and some villages. Thirteen physico-chemical variables in water were measured in nine collected samples taken from stations located along 24 km of the Trussu River. Water samples were took out every month from sept./2002 to mar./2004. The physico-chemical variables were: pH, EC, Na+, Ca+2, Mg+2, K+, Cl-, HCO3-, PO4-2, NH+4, NO3-, SO4-2 and SAR. Results showed up that the worst water quality index (WQI) occurred during the dry season, while the best one was registered in the end of rainfall season. Sampling stations 6 and 7 presented the lower WQIs to surface water due to chloride and nitrate. They were suitable to human consume with an annual average over to eighty. To shallow well, sampling stations 8 and 9 registered the lowest WQIs and they were inapt to human consume. These results can be explained by a bigger demographic concentration close to stations and the lack of sewer in the region.