International water law deals with managing water resources that pass through multiple sovereign states and territories. The majority of international water laws are developed through international custom. These customs are sometimes codified by international organizations, principally the United Nations.
Nations also commonly enter into agreements with each other to handle transboundary or shared water resources. International tribunals are often responsible for hearing and adjudicating disputes that arise over these agreements. Major areas of litigation include transboundary waterway regulation, environmental protection and water quality, acceptable uses of water and waterways, and distribution of resources.
International Watercourses: According to Art. II of the U.N. Convention on the Law of the Non-navigational Uses of International Watercourses:
"(a) "Watercourse" means a system of surface waters and groundwaters constituting by virtue of their physical relationship a unitary whole and normally flowing into a common terminus;
(b) "International watercourse" means a watercourse, parts of which are situated in different States."
Transboundary Waters: Water resources that cross national boundaries or may be accessed and used by two or more sovereign states or territories. Examples include rivers, lakes, or groundwater.