(2) Reading by the Water: The author faces the river, which is the time when the water is rushing. This is like the author's future career, which will be smooth sailing. Secondly, when the author reads Clouds in Beijing, "reading by the river" can show the author's desire to do something. Third, the author faces the great rivers with great momentum, which shows the broad mind of the author being reused.
As for "reading in the cabin" or "reading under the lamp", the place is completely different and the scenery you see is different. The cabin is narrow, brightly lit and the environment is cold, which is completely unsuitable for the author's happy mood at this time.