In the scene where the baboon shows Simba his reflection, he's looking into some sort of water hole; most likely a river. However, after Mufasa shows up in the clouds, Simba runs towards him through an open field. What happened to the water?
Wasn't the water a pond? It was surrounded by reeds. There was also a sort of lake type of thing that Simba was staring into before Rafiki came and sang his annoying song.
It was a pond. Simba leans down to look into the water, because he is sitting on the edge of the bank. You see him turn his head to the side when he looks up at the clouds, indicating that he would easily be able to run along side the bank.