The objective of this study was to evaluate the physical and chemical variability of the water in Sitios Novos, a reservoir in semiarid Northeastern Brazil, comparing samples collected in areas of intensive tilapia farming to samples from areas not directly impacted by aquaculture, in both the dry and the rainy season. Between October 2010 and July 2011, data were collected on temperature, conductivity, pH, turbidity, salinity, chlorophyll α, dissolved oxygen, oxygen demand, total phosphorus and total nitrogen levels in the water column using a multiparametric probe at four different sampling locations. Physical and chemical differences between the four locations were evaluated with the Kruskal-Wallis test and Dunn's post test, while the t test, followed by Welch...s correction, was used to compare samples collected in different seasons. No influence of intensive aquaculture was detected when comparing sampling locations near fish farms to locations not directly impacted by aquaculture. However, the sampling locations differed significantly with regard to conductivity, pH, turbidity and chlorophyll α levels.