Because the calm water surface is equivalent to a plane mirror, the reflection of the trees on the shore in the lake is formed by the plane mirror image, that is, the reflection of light;
The image formed by the plane mirror is upright. Virtual images of equal size; it is known that the distance between the bird and the water is 10m, then the image of the bird in the lake is also 10m, so the distance between the image and it is 10m+10m=20m;
Clear The bottomed Lijiang River looks shallower than it actually is because light enters the human eye from the water through the air, so it is a virtual image formed by the refraction of light.
So the answer is: reflection; 20; refraction.