The headwaters of the Buyuk Menderes Nehri river are supplied by springs during the dry season, any rainfall moving directly underground. The springs are supplemented by surface flows during periods of heavy rainfall in the winter months when the ephemeral drainage channels become active. The resurgences are of two types. (a) Those fed by percolation waters from a very fractured and often thinly bedded area of limestone. (b) The one at Isikli fed by the surface river sinking gradually into its bed, plus water stored in alluvial floodplains and transmitted to the resurgence by a well-fractured aquifer in which a master conduit may have developed.