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Climate and Drought

Groundwater Laws

Click the Fluent Water Facts below to learn more about Colorado’s groundwater and the challenges it poses.

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Early Colorado Water Law: Focus on Streams

Colorado’s semi-arid climate was a challenge to early American settlers. Growing crops required extensive irrigation networks. Settlers mostly drew their water from streams and rivers. When Colorado became a state, water law was established under the doctrine of prior appropriation, allowing the holders of senior (older) rights to draw water before the holders of junior (newer) rights in times of shortage.

At this time, groundwater use was minimal in most areas. Wells were generally shallow and hand-dug. Windmills pumped limited quantities of groundwater for livestock and homesteads. Throughout the decades, use of groundwater increased, but it was not until the 1950s that new technology, population growth, and drought would combine to push the state’s first set of extensive groundwater regulations into place.

Pressure from Below

Surface rights holders in the South Platte and Arkansas river basins became concerned that wells were pumping water that depleted streams, leaving senior surface rights unfulfilled. Since this groundwater pumping was not administered, as surface water was, senior surface rights holders had little recourse. In response, statutes and court decisions in the 1950s and 1960s required the State Engineer to administer tributary groundwater under the doctrine of prior appropriation.

Regulating Non-Tributary Groundwater

In 1957, the Colorado General Assembly created the Colorado Ground Water Commission for the purpose of examining and possibly regulating critical groundwater areas.

The Commission established eight “designated groundwater” basins in eastern Colorado. Under natural conditions, these basins do not recharge or supplement to any significant degree continuously flowing surface streams. Since these designated groundwater basins do not deplete water from surface streams, they are not administered by the prior appropriation doctrine. They are regulated by the Ground Water Commission, which uses a modified appropriation system to allocate designated water outside of the Denver Basin on a permit-by-permit basis. In the Denver Basin, designated groundwater is allocated to the owners of the overlying land.

Making Non-Renewable Water Last: The 100 Year Rule

In 1973, Senate Bill 213 established how water pumped from deep and potentially non-renewable aquifers should be managed. This bill also set criteria for the State Engineer to follow when issuing well permits in these bedrock aquifers. This established the 100-year pumping rule. Landowners who want to pump groundwater must first receive estimates of how much groundwater can be pumped from that source. Landowners may withdraw water at the rate of 1% of the aquifer resource under their property per year. In theory, this would ensure that the groundwater would last 100 years. In practice, however, there is no such guarantee. Estimates of the amount of water in an aquifer are not precise, so the supply could last more or less than 100 years.

Groundwater Rules for the Denver Basin

In 1985, the General Assembly passed Senate Bill 5, which specifically addresses groundwater in the Denver Basin. Much of this water is considered non-renewable. Since most of this groundwater is non-tributary, pumping it should have little effect on the holders of surface water rights. The Senate recognized, however, that some hydrologic connection may be evidenced over very long time periods. They ruled that not all the water withdrawn from the non-tributary Denver Basin aquifers could be consumed; 2% had to be replaced. Most of this provision is met by return flows from outdoor watering or other sources.

The legislature also recognized that some of the deep Denver Basin aquifers were not completely separated from overlying streams, and were not actually non-tributary. These aquifers received the confusing designation “not-nontributary.” Areas along the South Platte River and Denver streams, including Monument Creek and Cherry Creek, are considered not-nontributary. Users of not-nontributary water must return at least 4% of the water they pump to the surface stream.

WEco Climate Resources

Guide to Colorado Climate Change presents a range of contemporary climate change information written by experts. Take a look.

Water 101 Sheets are one-page references available for download and distribution. Explore the basics of drought, and wildfire or read various water conservation tips through a series of fact sheets. Interested in additional resources? Find them herefact_sheetsClimate Workshop
Participants tour the National Ice Core Lab, hear how researchers study climate and what that means locally. Learn more.

Connecting the Drops Radio

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