Actually, Gu Yihan had already considered Gu Nuo'er's proposal to build a waterway five years ago.
However, at that time, he was busy fighting wars and creating massacres everywhere. He didn't have the energy to spare to build a waterway.
The further they went, the more difficult it was without the waterway.
The slow exchange of supplies between the north and south had greatly affected the development of the country.
After Gu Yihan's thought through and tidied up Gu Nuo'er's proposal overnight, he gathered his trusted officials to discuss this matter in the imperial study the next day.
Constructing waterways was a big deal. Although the people could suffer losses, the outcome it brought was good. Moreover, it could benefit future generations for hundreds of years or even longer!
When Gu Yihan explained to the officials, he was in high spirits.