Water leak detection - long drive way
I don't know of any special water finding tools.

"0.8 tons" is an odd way of measuring water, but that's about 200 gallons per day. Not exactly a lot for a normal household. How exactly have you arrived at that number? According to the USGS typical consumption is around 100 gallons per day per person. 200 gallons is about what you would get if you left a garden hose running for half an hour. If there were a leak in your water service line I am not sure you would notice.

Finding the leak may be tough. A leaking fixture (e.g. a constantly running toilet) could easily leak that much water. If you have access to the water meter you could shut off the water at the entrance to the house and see if it continues to spin... that would tell you if the leak is inside the house or in the yard.