 The land in the province is in the Greater Nan Basin, which is part of the Chao Phraya Watershed.The province includes land within both of the greater Nan basin's sub-basins, i.e., the Nan Basin and Yom Basin.The provincial capital of Phitsanulok is sometimes called "Song Kwae", the "city of two rivers", an ancient name dating to a time centuries ago when the Nan and Khwae Noi Rivers met near the city.