That is not a safe way to lose weight .Even if you hardly move around everyday, you are still alive and your body functions, you see, talk, breathe etc and your body requires energy to do that. Your body needs energy from certain foods to function and water cannot give you that. You need to try and stop that before your body develops a mechanism where you can absorb proper nutrients.
While water is excellent for detoxification, digestion, excretion, water has no calorific value. Think about it as a medium for other body fluids and nutrients to move around. The safest way to lose weight is to eat the right food in moderation and exercise regularly. Do this and prevent yourself from developing illnesses as a result of starvation.