At first...At last

[joham]

At first...At last is often used in telling stories. But can the phrases be used in a context like the following (explaining how the Mekong River runs into the sea)? Is it because this paragraph is in a personalized style? Thank you in advance.

At first the river is small and the water is clear and cold. Then it begins to move quickly. It becomes rapids as it passes through deep valleys, travelling across western Yunnan Province. Sometimes the river becomes a waterfall and enters wide valleys. We were both surprised to learn that half of the river is in China. After it leaves China and the high altitude,the Mekong becomes wide，brown and warm. As it enters Southeast Asia, its pace slows. It makes wide bends or meanders through low valleys to the plains where rice grows. At last, the river delta enters the sea.

[5jj]

At first...At last is often used in telling stories.

Where did you get that idea?

But can the phrases be used in a context like the following (explaining how the Mekong River runs into the sea)? Is it because this paragraph is in a personalized style? Thank you in advance.

At first the river is small and the water is clear and cold. Then it begins to move quickly. It becomes rapids as it passes through deep valleys, travelling across western Yunnan Province. Sometimes the river becomes a waterfall and enters wide valleys. We were both surprised to learn that half of the river is in China. After it leaves China and the high altitude,the Mekong becomes wide，brown and warm. As it enters Southeast Asia, its pace slows. It makes wide bends or meanders through low valleys to the plains where rice grows. At last, the river delta enters the sea.

It's fine there.

[Rover_KE]

It's fine there, as 5jj confirmed.

More natural, though would be 'Finally, the river flows into the sea' (I have a feeling that the delta stays where it is; the water enters the sea).

Rover