This water would irrigate cash crops like wheat and cotton up to a hundred miles from a river source.
这些水可以灌溉距离河流源头 100 英里的小麦和棉花等经济作物。
口译与听力自考
Modern exploration of the upper part of the Nile began in about 1837 when Mohammed Ali, the Turkish ruler of Egypt, ordered a search to be made for the river's source.
The source or headwaters of a river or stream is the furthest place in that river or stream from its estuary or confluence with another river, as measured along the course of the river.