Saymareh dam and hydro-power plant are under construction on Saymareh River in Ravandi anticline, Ilam province. During boring the power tunnel which crosses the anticline, a large volume of water was encountered. This volume of water was not observed in the past. Considering the water quality of springs, water level of dam site piezometers, geological and hydrogeological inspections, isotope analysis, tracing experiments and water balance, it was concluded that the main portion of water is not supplied by the Ravandi anticline. The neighboring Veizenhar, Gavar and Milleh anticlines contribute to providing the main body of water. The most probable paths of water are not cross the dam reservoir and a localized conduit flow is not established in this area. Therefore, water leakage from the reservoir is not expected.