Chaves, L.C.G. Lopes, F.B. Maia, A.R.S. Meireles, A.C.M. Andrade, E.M. de Water quality and anthropogenic impact in the watersheds of service reservoirs in the Brazilian semi-arid region Subjects--Topical Terms: BACIA HIDROGRÁFICAQUALIDADE DA ÁGUAANÁLISE QUÍMICA