Riparian laws determine who may possess or use water as it flows or touches various properties. In the United States, riparian laws are generally followed in the eastern states. The states on the West Coast follow a doctrine known as "prior appropriation."

Under the riparian doctrine, the water from watercourses belongs to those who own the land bordering the water. Riparian rights attach to all contiguous tracts as long as one of them borders the water in question. Riparian owners are only allowed to use this water in connection with the riparian parcel.

What Are “Natural Flow” and “Reasonable Use”?

There are two theories that guide the riparian ownership doctrine. The following are the basic guidelines that make up these competing theories of water use: 

  • Natural Flow Theory: Under this theory, a riparian owner’s use resulting in a material decrease of the water’s quantity, quality, or velocity can be stopped. Each riparian owner is entitled to have the water in the stream maintained in its natural state, not diminished in quantity or quality.
  • Reasonable Use Theory: Under this theory (which is the most common one), all riparian owners share the right of reasonable use of the water. This means that no owner’s use can be stopped unless it substantially interferes with the use of other riparian owners. The reasonableness of a use can be determined by evaluating the:
    • Changes to the flow of the water
    • Purpose of the use
    • Resulting pollution
    • Extent of use
    • Where the water is going

What’s the Difference between “Natural Use” and “Artificial Use”?

When assessing the fairness of water allocation, courts also look closely to the nature of the water use. There are two basic uses of water, Natural Use and Artificial Use: 

  • Natural Use: Natural uses are those arising out of a necessity of life, such as water needed for drinking, watering of domestic animals, or for general household uses
  • Artificial Use: Artificial uses are those that do not minister directly to the necessities of life upon the land. Such uses are primarily for the purpose of improvement, trade or profit

Should I Contact a Property Attorney?

Water law is very complex and often controversial. If you are in a riparian state and are involved in a dispute over the use of a watercourse, the advice of a real property attorney can be extremely helpful in resolving your legal matter. A property lawyer can explain how the laws of your state affect your rights and can represent you in court.