Suggest improvements for the highlighted problem areas:
Liyao told Lu that she should explain how the Yangtze River can be both a lake and a dam. At Lake Poyanghu during the winter, the river comprises small streams on a broad lake bed. In the summer, high waters fill the reservoir and curb the inflow of tributaries like a dam.
Liyao also described how she tried to visit a friend which had called for help from the other side of the lake. It was summer and they always warn you about the high waters. While rowing across Lake Poyanghu, Liyao became exhausted and decided, with great regret, to return home. It was too far across.