The real estate deed may say you have water rights, but you need to know how they establish water rights in Cal. In the west water rights are decided by an administrative agency in Cal., or water courts in Colorado. I don't know about other western states, but the legal determination of water rights is quite a process. The deed only says you have a right, but the state's determination through either administrative decision or a court decree tells you what the right is. It will tell how much of that stream flow is yours to use and whether it is a senior or junior right. A junior right can be cut off by rights senior to it in times of drought.
This is no small thing in the west and the complexity of water law here is daunting for most lawyers except for the few who have developed expertise in the field. As the saying goes, "whisky is for drinkin'; water is for fightin'".