When a water right holder refers to their water right they usually call it “my” water. Likewise state water managers frequently refer to “our” water meaning the water that resides within the bound ar ies of New Mexico. Although “my” and “our” carry with them the notion of ownership and control, water does not fit easily into the same prop erty rights concepts we associate with land rights. Land rights have a degree of exclusivity, and water is inherently shared. I have frequently said that if water just stayed in one place it would be easy to manage. But, water doesn’t. It moves through the hydrological cycle being shared by many users over time. This results in a series of water rights, created by both federal and state laws, that can be impacted if changes are made in the way water moves through the cycle. The para meters of each water right are limited by the rules that define the relationships between these water rights (Matthews, 2004). The rules create both horizontal and ver tical forms of shared governance at several scales (Matthews, 1994). How shared governance operates in New Mexico is the subject of this chapter. When water conflicts occur between “neigh bors” horizontal governance mech an isms are used to determine the shared relationships each has with regard to the other and to the water. Jurisdiction in this instance is “sequential” with each neigh bor using water in their turn as it moves through the hydrological cycle. This creates the classic upstream downstream (or down cycle) conflict. The governance mech an isms used may be a treaty between the United States and Mexico, an inter state compact between New Mexico, Colorado and Texas, a Supreme Court de cision equitably apportioning a river, or a statute such as the Clean Water Act which allows a Pueblo’s water quality stand ards to be enforced upstream against a city outside the Pueblo’s boundaries. Vertical governance mech an isms resolves conflicts when water right holders at different scales, including gov ern ment units and private par ties, have jurisdiction or
control over the same water at the same time. These conflicts are “simultaneous” with each inter ested party having some legitimate say in how the water can be used. Sometimes these conflicts can be between two coequal gov ern ment units. This can occur when two state agencies have a role in managing the same water. Probably the most im port ant conflicts occur between: 1. states and the federal gov ern ment and 2. private right holders and the gov ern ment entities that create regu latory rights for the pub lic. Federal water quality stand ards are an example of the first, and statu tory protection of endangered species leading to a potential regu latory “takings” illus trates the second. This chapter is or gan ized around these concepts. At times, such as with regu latory takings, the discussion will go beyond New Mexico’s bound ar ies because the controlling legal authority is found elsewhere. After examining New Mexico’s current ver tical and horizontal relationships the chapter pro jects future concerns and ways to deal with them.