Technically, the only way to correctly answer this question is to read the document itself but the answers pretty simple to answer without it too.
The Nile was the holy grail for the people of ancient Egypt. After all, it provided water to drink, and also water for agriculture. It also provided the Egyptians with many fertile lands that were great for farming. Because of this, they prayed to their gods all the time so that the Nile wouldn't dry out.