The Sao Francisco River is a main river that flows through seven states. In Pernambuco, the Pajeu River is the largest tributary and it flows into the Itaparica reservoir. The Brazilian semi-arid region suffers from a great shortage of water and the federal government has implemented two water transposition axes of the Sao Francisco Rivers to minimize this problem. The objective of this study was to evaluate the influence of the Pajeu River on the water quality of the Itaparica reservoir, where the catchment point of the East Transposition axis is located. The water quality data refer to the period from January / 2011 to September / 2014, totaling four collections in the dry period and four in the rainy period. A Principal Component Analysis (PCA) was developed between the monitored points, where the first two main components explained 52.6% of the total variability. For the most significant parameters, bloxplot graphs were elaborated and the data analyzed. Although the flow of the Pajeu River is not high, with its characteristics of greater electrical conductivity, BOD, COD and nitrate, the contribution of its waters to the Itaparica reservoir tends to contribute negatively to the water quality of the East axis.