There’s a good chance you’ve heard about the Colorado River compact because it's been in the news a lot. But compacts also govern rivers in southeastern Colorado. The agreements help guide how water is shared across state lines. Decrees and treaties also affect our waterways.
The Arkansas River flows nearly 1,500 miles from the mountains near Leadville, through southeastern Colorado, into Kansas and Oklahoma, eventually meeting the Mississippi River.
At nearly 1,900 miles long, the Rio Grande River flows out of the San Juan Mountains through the San Luis Valley into New Mexico and then on to Texas.
Both rivers are critical resources providing water for homes, farms, industry and recreation. As growth and drought strain water resources, interstate agreements affecting these waterways take on more significance.
Colorado is part of nine river compacts including ones that cover the Arkansas and the Rio Grande
Colorado is a headwaters state, which means that some major rivers start here and flow out over state lines. The Supreme Court has ruled states can’t suck up every drop of river water, so water gets divided up by contracts between states.
A Colorado-based water attorney once described compacts to KRCC as "a strange creature made from state and federal law" because they have to be approved by each individual state and by Congress.
Each compact has its own specific terms as to how water is allocated.
When it comes to the Arkansas River, how did the compact between Colorado and Kansas come about?
Legal disputes between the two states–mostly Kansas suing Colorado–over the river started in the early 1900s. By the late 1940s, they formed a compact.
Essentially it says Colorado gets to keep using water rights it had in 1948, but no more. This means that development can keep happening in southeastern Colorado and other changes in water distribution can occur. But Kansas has a right to the same amount of water flow it would have gotten in 1948. Colorado has a compact with Kansas, but not with the other states, which have agreements with each other.
Water levels go up and down. How does the water get divided up during dry years?
Colorado’s obligation per the compact isn't a specific number and it's complicated, as a lot of water law is. It involves 10-year rolling averages. That means if there’s a year when extra water is delivered to Kansas, Colorado gets credit. When not enough water makes it to Kansas, those are debits for Colorado. Each year the official number crunchers take the amounts for each new year and replace the figures from ten years prior.
A compact did not solve all the disputes between Kansas and Colorado
The lawsuits continued for a while after the compact was put in place. Notably in 1985 Kansas sued Colorado in a case that lasted decades and went to the Supreme Court. Part of it was over Colorado’s management of reservoirs in Pueblo and Trinidad. That decision went against Kansas. But the Sunflower State won a decision saying wells in southeastern Colorado were depleting the water flow.
It's worth keeping in mind that the Arkansas River basin is big and includes tributaries like Fountain Creek and the Purgatoire River. So to meet its obligations, Colorado came up with rules governing groundwater and irrigation in the basin.
Colorado has to abide by two compacts in the San Luis Valley
The Rio Grande compact was signed in 1938, but Colorado flouted it until a lawsuit in the late 1960s forced the state to get with the program. There’s been more conflict since then and ongoing court cases - especially between New Mexico and Texas. Mexico also relies on the river and controls some tributaries, so there’s an international treaty for the Rio Grande too.
As for the second compact, a tributary south of the town of San Luis called Costilla Creek meanders across the Colorado and New Mexico state line before joining the Rio Grande. It’s governed by its own compact and interstate commission.
How does Colorado manage water in the Rio Grande River basin?
Like with the Arkansas, Colorado needs to send a percentage of the river's water downstream. In the Rio Grande it is a sliding amount based on how much water is flowing in the river in any given year. The mountain snowpack directly affects this calculation and that’s been depleted by ongoing drought among other issues.
These legal agreements for both the Arkansas River and the Rio Grande from decades ago have a big effect on life today
Demand and climate change are stretching our rivers thin. Developers and water utilities in Aurora, Douglas County and elsewhere own or are looking at buying water rights in southeastern Colorado.
San Luis Valley farmers are scrambling to deal with the effects of drought on both the Rio Grande and their groundwater aquifer. In the Arkansas basin, there are efforts to prevent the water from going out of the basin to support growth in the Denver metro area. But there are some innovative projects too to try to increase conservation.
- Southern Colorado property owners are starting to receive notices of illegal ponds. Here's why hundreds of them may need to go
- Declines in Upper Rio Grande River Basin have San Luis Valley water users worried and taking action
- The Colorado Springs Utilities Board opposes Aurora's recent purchase of water rights in Otero County
- Many people on the Front Range depend on water from the Denver Basin. But the underground supply isn't infinite
