genrally the water and electric is not on the same trench btw and i dont know where you from at all so i cant say too much but in state of wisconsin the water supply useally buried at least 3feet [1 meter] or deeper to advoid the frost but check your area i am sure they have somekind of codes what it can allow and what dont allow it at all,, so i suggest to check the ahj inspectors see what they have for guideline for it and the uiltes have their own regulations too so best bet is check both ways.
merci , marc
ps the natural gas is keep min of 3 feet away from power line and phone/ catv lines can use the same trench for electric so check it around there..
