1. Others can't use royal things.
Ancient classes were clearly divided, so how could royal things be used? The royal family is also very particular about using things, such as their own hunting places, their own vacation places and so on. These things are not for civilians. So according to the class, this place was requisitioned by the royal family, and it will be the royal water in the future. Of course, it is impossible for the Qing royal family to give it to others. And Ganlong especially likes the water in this place. At that time, there was a measurement method, which said that the water in Yuquan Mountain was lighter than that in other places under a unified volume, so the density was relatively small. At that time, people thought that the lighter the water, the better.
2. I am afraid that others will pollute the water source.
I think it is reasonable for the royal family to be afraid of others polluting the water source. After all, everyone will be curious about royal places, and they will visit them. If the water source is polluted, there won't be such good water for the royal family to drink, so of course they should protect this place and provide them with good water for Yuquan Mountain.
I'm worried that the water source of Yuquan Mountain will dry up.
I think ancient people are idolized as we are now, especially where the emperor has been. We must see what the emperor likes. The emperor likes the water in Yuquan Mountain so much, I think people will take a look at the freshness and try why the emperor likes it so much. Later, everyone found that the water was so good that they all used it. It may not be very durable. Therefore, in order to protect the interests of the royal family, the emperor will not let others use it, but can only use it for his own home.