Water quality of Coqueiro stream watershed, northwest of Sao Paulo State

Human activities need environmental resources for their survival and the different kinds of water use produces a countless pressure on water resources. The Water Quality Index (WQI) is a tool applied to the study and assessment of water quality. The objective of this study was evaluate spatial and temporal water quality based on the calculation of WQI and provide information for the management of water resources. The watershed of the Coqueiro stream is located in the north western part of the State of Sao Paulo, with an area of 190 km(2); along the main river five sampling points were distributed for water collecting, from March 2009 to December 2010. The turbidity values, total solids, total nitrogen, total phosphorus influenced the calculation of WQI. Differences in temperature values at points analyzed were significant between the dry and rainy season. The turbidity values, total solids, dissolved oxygen and BDO5 showed no significant difference between the dry and rainy season. The variables pH, total nitrogen and total phosphorus showed a significant difference only in some sampling points.