ABSTRACT
347Groundwater and surface water are hydraulically connected in some regions of the world. This type of groundwater system is called a tributary aquifer and can affect flows of adjacent streams. Colorado state law requires all water users—of both surface and tributary groundwater—to follow a strict water-right priority system of “first in time, first in right.” This Doctrine of Prior Appropriation, adopted in Colorado in 1876, is rigidly followed today. Since 2003, thousands of tributary groundwater irrigation wells have been curtailed from pumping (legally shut off) due to the negative impacts of pumping depletions that reduce stream flow. Surface and tributary groundwater use conflicts are inevitable in locations where rigid water-allocation systems are followed. Nobel Prize winner Elinor Ostrom points out that common-pool resource management requires collective-choice arrangements if resource users—in this case, surface water and groundwater users—are to develop a stable management plan.
