Map of Acaraú River water quality by the use of WQI and GIS

Abstract

This study was conducted to assess the spatial and temporal variability of water quality from the Acaraú river Basin, Ceará, Brazil. We used a Water Quality Index (WQI) with support of a Geographic Information System (GIS). Water quality parameters were sampled in February, July, November/2003 and March/2004. Surface water samples were collected at 13 sampling points in the Acaraú basin and analyzed for dissolved oxygen, biochemical oxygen demand, pH, phosphate, nitrate, fecal coliforms, turbidity and suspended solids. A vulnerability map of the Acaraú basin water quality was produced. The lowest values of WQI were obtained in the region near the Sobral city and downward the Groairas city. Sewage from the later city are disposed in the Groairas River. The Acaraú basin water was classified as regular to good. The lowest values of WQI was 60.79 and the highest was 80.28. There was no significant difference (α = 0,01) in the temporal WQI values from rainy and dry seasons.