You must check the legality. Many places will not allow you to draw water from a river. If you find that it is legal, you should think through all of the related costs, including upkeep of the pipeline, pump, dealing with the rise and fall of the river, and replacing the intake when a flood takes the old one out. Also, do you own the property between the river and your home? If not, you have a right-of-way problem. You should keep in mind that this water will have weed seeds in it that will reseed your lawn regularly. You may find the free or cheap water isn't so free or cheap after all.