sentences:  The rivers of Sungei Changi, Sungei Selarang, Sungei Loyang, Sungei Tampines and Sungei Api-Api, from east to west on mainland Singapore are tributaries into the harbour.The Sungei Serangoon and Sungei Punggol are no longer tributaries into the harbour after they have been dammed to create their respective reservoirs.The rivers of Sungei Tiga, Sungei Jelutong, Sungei Puaka and Sungei Teris from east to west on Pulau Ubin are also tributaries into the harbour.