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Colorado's public lands are faced with new challenges but water and land management depend on working together. Read about the relationship between water and land in Colorado and how Coloradans are converging to restore Colorado's public lands in the Spring 2018 issue of Headwaters magazine.

Browse articles and find a flipbook of the magazine here.

Connecting the Drops

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Water Education Colorado

1938 Rio Grande Compact Meters Water to Thirsty Basin

Traveling 1,885 miles through Colorado, New Mexico, Texas and five Mexican states, the Rio Grande's history is marked by conflict and debate as countries and states fought for what they believed to be their fair share of the river.

In 1906, treaty negotiations between the U.S. and Mexico established how much Rio Grande water Mexico would receive. But the states of Colorado, New Mexico and Texas still had no formal agreement on how to divide the waters among them. When farmers in Colorado's San Luis Valley sought to increase diversions of the river to bring more acreage into production, New Mexico and Texas quickly voiced their opposition. They feared such diversions would compromise the Rio Grande Project, a U.S. Bureau of Reclamation system which supplies agricultural irrigation water to those two states.

Although the 1922 Colorado River Compact served as a good model for interstate cooperation, such optimism did not translate into the Rio Grande Basin. Continued opposition from New Mexico and Texas derailed any attempts to come to an agreement. With the prospect of costly litigation at hand, in 1929 the three states eventually decided on a temporary compact which established a commission to resolve disputes. It wasn't until December 18, 1938 that a formal compact was signed by the water commissioners of each state.

The 1938 Rio Grande Compact sought to establish an equitable division of the Rio Grande's water above Ft. Quitman, Texas. Based on data collected at gauging stations from 1928-1938, a sliding scale for water deliveries was established and outlined in the compact's provisions.

Today, Colorado must deliver different percentages of the total amount of water recorded in the Conejos and Rio Grande rivers and their tributaries, minus 10,000 acre-feet, to the Colorado-New Mexico state line. The compact's sliding-scale dictates what portion of the total flow is delivered. New Mexico's deliveries are also dictated by a similar sliding-scale.

To help Colorado meet its compact delivery requirements, the Closed Basin Project was completed in 1993. This network of 170 wells draws water from the shallow aquifers of the ‘Closed Basin’ which is part of the unique hydrogeologic structure of the San Luis Valley. Scientists think that no water flows out of the Closed Basin and the basin is not hydrologically connected to the Rio Grande River. Large confined and unconfined aquifers in the basin store water—the majority of which is pumped for agricultural irrigation. Wells from the Closed Basin Project pump water across that hydrologic divide and into the Rio Grande to help meet Colorado's compact obligations.
However, to receive credit for water pumped from these wells, Colorado must deliver water that meets certain guidelines for its salt content. This provision protects downriver users from the low quality water naturally found in these aquifers. The water that infiltrates the aquifers carries heavy loads of salts and other solids left behind by eons of evaporation. Colorado must mix the low quality aquifer water with higher quality water from agricultural return flows and precipitation runoff to ensure that it meets the compact standards.

Salinity is not the only challenge facing the Closed Basin Project. Project planners questioned whether continual pumping of the aquifers would compromise the surrounding wetlands. Ralph Curtis, recently retired general manager of the Rio Grande Water Conservation District in Alamosa recalls that ‘an Environmental Impact Statement was done and it was anticipated that, yes, the wetlands would be impacted.’ To mitigate potential damages to the wetlands within the project area, 5,300 acre-feet of water from the Closed Basin was allocated to two specific wetlands outside the project boundaries. The Alamosa National Wildlife Refuge receives 4,500 acre-feet while the Blanca Wildlife Habitat Area receives 800 acre-feet.

The Rio Grande Compact also requires an annual review of water deliveries from all three states. If Colorado and New Mexico are below or above their delivery requirements, they must adjust how much water will be stored in their reservoirs in the coming year. In January of each year, New Mexico or Texas compact commissioners may demand that reservoir storage (for all reservoirs built after 1929) be sufficient to cover any shortfalls on behalf of Colorado or New Mexico.

Such shortfalls plagued Colorado in the 1950s and 1960s when it failed to meet its compact obligations. By 1967, Colorado had a delivery debt of 940,000 acre-feet and New Mexico and Texas reacted by suing Colorado in the U.S. Supreme Court. Colorado responded by agreeing to immediately curtail its use of water from the Conejos and Rio

Grande rivers. Since 1968, Colorado has never failed to deliver its required water allotments to the other states.
At the same time, however, these cutbacks complicated matters in Colorado. Although the compact outlines two separate delivery schedules for the Conejos and the Rio Grande, the two rivers had been historically operated as though they were one river.

Over time, the state engineer worked with water users along these two rivers to devise a scheme by which surface diversions could be limited, ensuring that flows leaving the state met the compact's provisions. Through a lengthy, tumultuous period of negotiations and law suits, operating criteria were finally enforced by the Colorado Supreme Court in 1983 which upheld the two river management system outlined in the original compact.

Every five years, the Rio Grande Compact Commission convenes to review and amend the compact as necessary with any changes approved by the state legislatures and Congress. Changes have been very limited. In 1948, the Commission agreed to discontinue use of a few gauging stations in New Mexico while altering New Mexico's water delivery schedules. And although the three states have faced their share of challenges in dividing the Rio Grande's water since this resolution, no other amendments have been made to the original 1938 compact.

Compared to other rivers governed by multi-state, multi-nation compacts, the conflicts facing the Rio Grande are relatively few. David Robbins, attorney for the Rio Grande Water Conservation District, attributes that in part to the structure of the compact. ‘Because the compact has specific schedules of delivery for both Colorado and New Mexico, with provision for shortfalls and over delivery, it is pretty easy to operate,’ he says. This format has allowed water managers to better adapt to the Rio Grande's variable flows while ensuring that water rights are met.

Yet, as water demands increase from growing cities up and down the Rio Grande, not to forget recreational needs and shifting environmental priorities, the Rio Grande compact will surely be put to additional tests.

The current Rio Grande Compact Commissioners are:

Harold ‘Hal’ Simpson (CO)
John D'Antonio (NM)
Joe Harmon (TX)
Bill Ruth (Federal Representative)
The state engineer acts as the compact commissioner for Colorado and New Mexico while a Governor appointee represents Texas. A federal representative is appointed by the President of the United States and serves as Chairman of the Commission.

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