Water law is the field of law dealing with the ownership, control, and use of water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 as a resource. It is most closely related to property law

Property law

Property law is the area of law that governs the various forms of ownership in real property and in personal property, within the common law legal system. In the civil law system, there is a division between movable and immovable property...

, but has also become influenced by environmental law

Environmental law

Environmental law is a complex and interlocking body of treaties, conventions, statutes, regulations, and common law that operates to regulate the interaction of humanity and the natural environment, toward the purpose of reducing the impacts of human activity...

. Because water is vital to living things and to a variety of economic activities, laws attempting to govern it have far-reaching effects.
The history of man's relation to water illustrates varied approaches to the management of water resources.