Russ, California has a consistant shortage of water. Even though we are in northern California, we are still a semi desert region and only get rain in the winter months. You must have a permit to excavate a pond that will impound water and at this point it is difficult to impossible to get. You can have a natural pond that collects runoff but will still be subject to permits if you wanted to "improve it". The Golden Hills of California are actually dead grass!
Jim