The flow of the Colorado River has decreased by approximately 20 percent over the past century, according to the U.S. Geological Survey. This continued decline is alarming considering that the river provides water to around 40 million people and supplies major reservoirs such as Lake Powell and Lake Mead.

Both reservoirs have experienced significant drops in water levels in recent years, with Lake Mead currently sitting at just over 30 percent full and facing the possibility of reaching dead pool levels in the near future.

A hydrologist at the University of Colorado has raised concerns about potential misestimates of the Colorado River water flow, suggesting that a study from the 1910s may have been disregarded by experts.

Shemin Ge, a hydrogeologist at the university, presented her findings at the American Geophysical Union (AGU) meeting, highlighting the impact of a decision made in 1922 on the current Colorado River crisis.

In 1922, the Colorado River Commission, consisting of seven individuals, made a decision to divide the water of the Colorado River between the Upper Basin (Colorado, New Mexico, Wyoming, and Utah) and the Lower Basin (Arizona, California, and Nevada).

However, this decision was based on an assumption that the Colorado River had 16.4 acre-feet of water flowing through the Lees Ferry area of Arizona each year, without taking into account an alternative estimate from 1916.

Hydrologist Eugene Clyde La Rue's estimate in 1916 stated that the Colorado River actually discharged only 15 million acre-feet of water in the same area.

Unfortunately, this estimate was overlooked by the commission, leading to potential misestimations of the river's water flow. Shemin Ge expressed her intrigue at how such important work from the past was ignored, whether intentionally or out of ignorance, and emphasized the need to learn from history to improve water management practices.

Ge has highlighted publicly her concern that La Rue's method of collecting data on the river by personally measuring its depth and flow rate through extensive hiking across the region. This "low tech" but "elegant" approach is still taught in geology courses today.

In contrast, the Colorado River Commission's estimate was based on data gathered from just one site, potentially leading to an overestimation of the water flow.

Currently, experts believe that the Colorado River's water flow is around 13 million acre-feet per year, a number that could further decrease due to drought and excessive water consumption in surrounding areas. Ge expressed concern that the Colorado River Compact, which governs water allocations, still relies on the larger estimate of water flow.

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In a press release, it noted that the seven states within the Colorado River Compact are working to revise agreements and guidelines by 2026.

Ge emphasized the need to prioritize understanding the actual water availability in the Colorado River, stating that discussions should focus on the quantity of water rather than solely on droughts, infrastructure, and water conservation.

While a wet winter in 2023 provided some relief and allowed the Colorado River and its reservoirs to replenish slightly, the ongoing megadrought in the southwest remains a significant concern.