If you wish to become an informed Seller or Buyer of Montana Water Rights it is imperative that you understand the basic concepts, laws and processes that determine whether a particular “Water Right” is extremely valuable, or practically worthless (or somewhere in between). Montana observes what is known as the doctrine of “prior appropriation.” This doctrine says that those who first put a specific amount of water to beneficial use in a specific place gets to continue using it “first” when water is scarce.  And that “first right” can be passed on to subsequent holders of that right. This “first in time, first in right” priority dating system ensures that water users whose water right was first put to use (call these the “senior users”) can legally demand that their water needs from a stream or aquifer be fulfilled before the interests of “junior users”. Some senior water rights in Montana go back to the 1860’s. In dry years when water is too scarce to satisfy all water rights, senior users get water and junior users often don’t. So the first basic lesson is that not all water rights are created equal. In a dry year, a 1920 water right for 10 cubic feet/second (cfs) may not provide as much water to the user as an 1875 water right for 2 cfs.