The simple woodchuck solution in rural areas is to shoot the pest with a .22 rifle. In suburban and urban areas where this isn't feasible the woodchuck must be fenced away from the food garden or aggravated enough to leave on his own accord.
The best way of insuring a woodchuck-free garden is to use a fence as suggested above, if that is feasible in your situation. This is even better than shooting them because if you shoot one, more will follow when the various young are chased from their home after reaching the proper age.
You aggravate a woodchuck to leave by using a series of repelling products at two or three week intervals. By insulting his senses – taste, smell, touch, etc. – you help him to decide to seek more agreeable territory. Use a taste repellent for two weeks, then apply an odor repellent, and then three weeks later use the water spritzer device. His life must be made to be miserable.