Yesterday I drove up along the Rio Grande south of Taos, NM and saw a river full of exposed rocks and islands. Rafters struggled down the river through the shallow clear water. Odd that the river is so low in the middle of our rainy season when the mountains have been receiving rain. Why would the Rio Grande be running so low?
It would be nice to imagine that the river is running according to rainfall, old snowpack and springs in the beautiful mountains. Yet while we fish, raft and watch the Rio Grande and understand it to be a five-million-year-old river, for many people the Rio is plumbing, a source of water for agriculture and cities. The people who take water out of the river have control over the fate of people who enjoy it, and they impact the wildlife that depends on the river, be they fish, otters, cottonwood trees or small insects.
For northern New Mexicans, the river fluctuates wildly because of the farms in the San Luis Valley, just north of Taos and the Colorado border. This vast, high attitude valley is the highest of the riff basins in the Rio Grande Valley and its extensive farms use a lot of Rio Grande water. Back in the 1880s, these farms were using almost all the Rio Grande water when eastern corporations built a system of big canals to divert the Rio Grande into the San Luis Valley. Potato and alfalfa farms expanded to absorb the water from the canals while the small farmers in New Mexico saw their fields dry up.
The San Luis Valley spreads out to the east of the San Juan Mountains of Southwest Colorado. This huge, high mountain range pulls snow out of the Pacific storms and creates a haven for summer rain clouds that soak its high valleys and peaks in heavy rain during the summer. The San Juan Mountains source the San Juan, Animas, La Plata, Deloris and Rio Grande Rivers. Only the Rio Grande flows on the east side of the Continental Divide while the others boost the Colorado River as it works its way through the southwest deserts toward the Gulf of California. Seventy five percent of the Rio Grande’s flow comes from Colorado mountains snowpack.
The San Luis Valley farmers may have imagined they could have all the water they wanted just because they had the technology to divert the water, and because they were at the top of the watershed. But the outcry from downstream users, many of whom were Hispano farmers who had been using water for hundreds of years, forced the federal government to intervene and establish a system for establishing water rights. Mexico needed its share too.
In 1902, the federal government passed the Reclamation Act which gave the government the power to build dams and regulate interstate rivers. But ultimately, control of water rights fell to the states. And each state had to consider other state demands when it set water rights for individual users. This proved to be a source of major conflict over many decades.
The Hispano farmers in New Mexico had never established formal water rights for their ditch systems (called acequias) and they used only small amounts of water in the big picture of the river. An acequia in the southern San Luis Valley, called the San Luis People’s Ditch, diverted water off the Rio Culebra and established the first water right in Colorado. The acequias in New Mexico were much older, dating to the 1700s though Pueblo people created irrigation ditches in prehistoric times. In any case, these old uses, by law, took precedent over the corporate farms of the San Luis Valley and the Rio Grande Valley in southern New Mexico. These big farms use 75% of the river’s water.
Ultimately the federal and state governments established a framework for setting out water rights on the Rio Grande. With the climate warming and drying, the river is producing less water than in centuries past and water rights on paper may not have actual water in the river to fulfill them. Over time this problem will get worse.
Past compacts and water rights on both the Colorado River and the Rio Grande are fast losing their relevance in the age of climate change. Federal and state regulators on both river systems are struggling to grapple with the implications of the permanent loss of water in these rivers.
According to Bureau of Reclamation’s West-Wide Climate Risk Assessment, the Rio Grande’s flow will continue to decline over the next few decades. They expect the Colorado stretch of the Rio Grande to fall by 25% in the next 75 years while the New Mexico portion of the river could decline by 35%. These declines are driven by less precipitation, faster melting snows, increased evaporation, and damaged watersheds that yield less water because of tree death, destroyed grass cover by livestock, and more demand on the water supply from farmers.
Standing by the Rio Grande near Pilar, I remember rafting the river in 2023 when high snowfall in the southern Rockies brought high water to the river in the spring. I remember the feeling when our raft flipped in the big waves. This seems like a distant memory today looking at the river hiding among rocks and sneaking past gravel islands in the hot afternoon sun. We know that high water years don’t make up for the larger trend toward less precipitation.
Tom Ribe
