192 km between Saravane and Champassak; the Nam Selanong in Savannakhet runs for 115 km; the Nam Kading of Borikhamsay province is 103 km long; the Nam Khanh runs for 90 km between Huaphanh and Luang Prabang.
In Xieng Khouang, Luang Prabang and Sayaboury provinces, annual rainfall is 100-150 millimetres; in Vientiane and Savannakhet 150-200 millimetres of rainfalls every year.