In the Sui Dynasty, this river refers to the Grand Canal.
The original text comes from "Two Nostalgic Poems on the Bianhe River Part 2" by Pi Rixiu, a writer of the Tang Dynasty: This river was the source of death in the Sui Dynasty, and it has been connected to the waves for thousands of miles to this day. If there was no dragon boat incident in the Water Palace, Yu would not have made much merit.
Translation: Everyone says that the construction of the Grand Canal led to the demise of the Sui Dynasty, but travel from north to south still relies on this river. If he had not built dragon boats to indulge in pleasure, Emperor Yang's illustrious achievements could almost be compared to Dayu's flood control.
Creative background:
Pi Rixiu was a poet in the late Tang Dynasty. At that time, the Tang Dynasty had entered a stage of turmoil. It is very difficult for literati to have an official career. Peace and leisure have become their goals in life, and they try not to be disturbed mentally by the outside world. Pi Rixiu is the representative of this kind of escaping mentality and indifference. This gave him more free time to think about history and write realistic epic poems.
During the reign of Emperor Yang of the Sui Dynasty, the people of the counties in Huaibei and Henan were mobilized to dig a grand canal called Tongji Canal. From Luoyang Xiyuan, the Gu and Luo Er Rivers are diverted to the Yellow River, and then enter the Bianshui River through the Yellow River. Then, they follow the old canal route opened by Fu Chai, King of Wu in the Spring and Autumn Period, and divert the Bianshui River into the Si River to reach the Huai River. Therefore, the main trunk of the canal is located in the Bianshui section, which is also called Bianhe River by custom. Emperor Yang of the Sui Dynasty opened the Grand Canal, which consumed a lot of people and material resources.
There are many works in Tang poetry that describe this historical theme, and most of them refer to the Sui Dynasty's death in the Grand Canal. In the era when Pi Rixiu lived, political corruption had already followed the path of the Sui Dynasty. Most people were very slow to learn lessons from history, but the author deliberately reiterated this lesson in the form of poetry.