Wardrobe
As I understand it the body holds onto whatever it senses is in short supply. If it isn't getting enough water it will retain water.

Also, as you lose fat on LC your fat cells will tend to store water in them so that they can retain their shape and stay large. Drinking enough water will help the body signal that there is plenty of water in the system and the fat cells will release the water they hold onto. Water has weight and any retained or stored water will show on the scale even if there is fat loss occurring.