Jiajing said:

The ancients called the Yangtze River a river and the Yellow River a river. The water in the Yangtze River is clear, and the water in the Yellow River is turbid. The Yangtze River is flowing, and the Yellow River is also flowing. An old proverb goes: When a saint comes out, the Yellow River becomes clear. But when will the Yellow River be cleared? The water of the Yangtze River irrigates the fields in several provinces on both sides of the river, and the water of the Yellow River also irrigates the fields on both sides of the provinces. It can only be used because the water is clear, and it can only be used not because the water is turbid. This has been true since ancient times. Hai Rui doesn't understand this truth. In his memorial, he advised me to only use the Yangtze River instead of the Yellow River. Is that okay with me? On the contrary, once the Yellow River overflows, it needs to be controlled. This is why I deposed Yan Song and killed Yan Shifan. On the other hand, once the Yangtze River floods, I will also control it. This is why I deposed Yang Tinghe and Xia Yan, and killed Yang Jisheng, Shen Lian and others.

In this passage, Jiajing compared Yan Song and other treacherous ministers to the Yellow River, and compared the clear streams to the Yangtze River. Using the Yellow River's turbid water but nourishing the people on both sides to demonstrate the necessity of appointing Yan Song and others was an imperial trick. Or sophistry

The following answer

Based on historical facts, this passage is more like a portrayal of the Jiajing Emperor’s mind. Although Jiajing did not go to court for decades, he was still a great hero in the writings of historians. The reason was that he was an emperor who had a mastery of power, which made his subordinates hesitate and fear him. Yan Song was also an unparalleled masochist. Crazy, it’s amazing that when you meet an emperor like Jiajing, they can practice Tai Chi with each other for nearly twenty years.

According to Jiajing's usual method, when promoting a person to serve as the first assistant, he must arrange a person after him. Once the former becomes more powerful, he will be defeated by the latter to ensure that power will not be lost to a specific person. The control lies with him, the emperor. Therefore, he dismissed Xia Yan, Yang Tinghe, and even Yan Song out of this consideration.

Therefore, the metaphor of rivers in dramas can actually be seen as a balance of power~