ALLOCATION AND ADMINISTRATION OF GROUDWATER IN COLORADO

All water in Colorado is a public resource known as “water of the state.” Surface and tributary groundwater is allocated to users based on prior appropriation (first in time first in right). Deep groundwater is administered differently. The Colorado Ground Water Commission allocates “designated ground water” pursuant to a modified prior appropriation doctrine. Nontributary ground water and Denver Basin groundwater are allocated to the overlying landowner. Tributary groundwater is hydrologically connected to a river and is often called shallow groundwater. Under Colorado Law, the use of all subsurface water hydraulically connected to a surface stream, the pumping of which would have a measurable effect on the surface stream within one hundred years, is subject to the doctrine of prior appropriation. The State Engineer issues or denies well permits for appropriations of tributary water, and the Water Court of the Water Division for that hydrological basin reviews and issues a decree setting the priority of the water right. Coloradans rely heavily on pumping of deep groundwater for a variety of municipal, agricultural, industrial, and other uses. Deep groundwater refers to aquifers geologically confined such that they have no measurable connection to surface waters. Tributary groundwater is recharged from precipitation and seasonal runoff. Deep groundwater is not readily replenished. Groundwater pumping at a rate in excess of annual recharge creates what is called a mining condition. Unless the rate of pumping is regulated, mining will ultimately lower groundwater levels to a depth where water can no longer be withdrawn economically. In Colorado, deep groundwater is divided by statute into three categories: (1) designated (2) nontributary, and (3) Denver Basin groundwater. Denver Basin groundwater refers to deep groundwater within the Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers. There are two types of Denver Basin groundwater, not nontributary and nontributary. Both are allocated to overlying landowners like nontributary water, at a rate of 1 percent per year assuming a 100-year life of the aquifer.