The watershed of the river Santa Rita includes the towns of Simão and Campinhos, where exists about 150 flour houses. Campinhos is among the largest cassava processing facilities in the region, generating many direct and indirect jobs. Manipueira is a liquid residue originating from the cassava pressing and presents high pollutant potential due to its high amount of glucose and fructose, this potential is 25 times greater than the one from domestic sewer. This work had as objective the evaluation of possible impacts of manipueira release in the water quality of Santa Rita river. For this, the land use map was elaborated and the physiographic characterization developed, besides being performed six campaigns for water samples collection in four sampling points along the river. The obtained results indicated that the watershed is elongated, with low drainage efficiency and it is not prone to flooding. Estimated water quality parameters indicated that organic effluents from Campinhos and Simão impact the values of dissolved oxygen, electrical conductivity, salinity, ammonia, nitrite, nitrate and zinc, suggesting that the water quality of the river Santa Rita is affected by manipueira release. The concentrations of total phosphorus, iron and cooper were superior downstream of the Sewer Treatment Station. The river water was saline in the three sampling points most affected by the release of manipueira.