The Basic Systems of Surface Water Allocation
Authors: Dellapenna Joseph W. 
Published: October 2020

From earliest times, at least in arid and semi-arid regions, law has been used to allocate water to particular users, at particular locations, and for particular uses, as well as to regulate the uses of water. In the early 21st century, such laws are found everywhere in the world. While the details of such systems of water law are specific to each culture, these systems, in general terms, conform to one of three basic patterns, or to some combination thereof. The three patterns can be understood as a system of common property, a system of private property, or a system of public property. In a common property system, each person is free to use water as he or she chooses so long as the person has lawful access to the water source and does not unreasonably interfere with other lawful users. Such systems were common in humid regions where generally there was enough water available for all uses, but these break down when demand begins to outstrip supply frequently. Private property systems, more common in arid and semi-arid regions, where water is generally not available to meet all demand on the water sources, is a system that allocates specific amounts of water from an identified water source, for a particular water use at a particular location, and with a definite priority relative to other uses. The problem with such private property systems is their rigidity, with transfers of existing water allocations to new uses or new locations proving difficult in practice. In Australia, the specified claim on a water source is defined not as a quantity, but as a percentage of the available flow. Despite the praise heaped upon this system, it has proven difficult to implement without heavy government intervention, benefiting only large irrigators without adequately addressing the public values that water sources must serve. In part, the problems arise because cheating is easier in the absence of clear volumetric entitlements. The public property systems, which has roots dating back centuries but is largely an artifact of the 20th century, treats water as subject to active public management, whether through collaborative decision-making by stakeholders (a situation that is also sometimes called “common property” but is actually very different from the concept of common property used here), or through governmental institutions. Public property systems seek to avoid the deficiencies of the other two systems (particularly by avoiding the incessant conflicts characteristic of common property systems as demand approaches supply and the rigidity characteristics of actual private property systems), but at the cost of introducing bureaucratized decision making. In the late 20th century, many stakeholders, governments, and international institutions turned to market systems—usually linked to a revived or new private property system—as the supposed optimum means to allocate and re-allocate water to particular uses, users, and locations. Before the late 20th century, markets were rare and small, but institutions like the World Bank set about to make them the primary mechanism for water allocation. Markets, however, proved difficult to implement, at least without transferring wealth from relatively poor users to more prosperous users, and therefore produced a backlash in the form of support for a human right to water that would trump the private property claims central to water markets. The protection of public values, such as ecological or navigational flows, also proved difficult to maintain in the face of the demands of the marketplace. Each of these systems has proven useful in particular settings, but none of them can be universally applied.