Finding a suitable water supply at the proposed building site should come before any other actions. A good quality ground water source is generally the most economical source of water.
Whether drawing from a surface or ground source, maximum usage without a permit to take water is 379,000 L/day for livestock watering, and an additional 50,000 L/day for non-animal consumption uses.
According to an OMAFRA specialist, only a handful of livestock producers in the province would come close to this limit, however if you estimate that you will be over this requirement then you will need a permit from the ministry of environment and must have a full hydrogeological survey completed. Famers who exceed the 379,000 L/day maximum and who are on the boundary of a drainage basin, (i.e. their farms drain into two different great lakes) will have to abide by the International Great Lakes Charter. Despite these exceptions, a livestock producer may still be required to obtain a permit if you are impacting neighboring wells or the nearby environment. This is because existing water users in Ontario take precedent over new or proposed uses. This means that if your well is already established and a new water taking activity in the area affects you, the issue can be reported to the Ministry of The Environment by calling the Spills Action Centre 1-866-663-8477