You need to get all of the deeds and contracts for sale and have a real estate attorney review them asap.Generally, if a certain right or easement is not retained via contract or deed, then the buyer looses certain rights after the sale of the property... which would include water rights.  However, if there is language in one of the documents, then he may still have certain rights.  His rights will depend on how they are worded.  Thus, the reason that all of the documents regarding the sale needs to be reviewed by an attorney.