If you're sure it's gophers, there are a TON of links on the web that talk about trapping and catching and even killing gophers. Just make sure that's what you have. So find a friend who knows how to use a Search Engine and let them help you with 'sources'.
In the meantime, I have one link of many for you to start. Gophers. For now, my best to ya and hope this helps.