First-of-its-kind study provides a detailed look at water quality along the Colorado River’s upper basin
INSTAAR faculty fellow Mike Gooseff rows while USGS hydrologist Connor Newman logs a sample of Colorado River water outside Grand Junction, Colo. in October, 2024. All photos by Gabe Allen.
Michael Gooseff and collaborators are gathering the first-ever continuous, long-term water quality sample of the Colorado River's upper basin. INSTAAR senior communication specialist Gabe Allen joined them for three days on the river.
One vessel in particular stood out from the rafts of vacationers and fisherman that floated lazily through Ruby Canyon on a sunny fall day last month. The occupants had swapped the usual fish and tackle for binders, laptops and an assortment of pumps and devices all buckled together with ratchet straps.
Aboard the raft, U.S. Geological Survey groundwater hydrologist bottled river water samples and jotted down notes in a waterproof notebook. Behind him, INSTAAR faculty fellow Michael Gooseff manned the oars and kept a watchful eye on a collection of sensors strung on a pole that extended into the water from the back of the boat.
This is the tenth time Gooseff and his collaborators have rafted this stretch of river since 2018. The goal is to gather the first-ever continuous, long-term water quality sample of the Colorado River's upper basin. In 2023, the USGS awarded Gooseff’s team with funding for biannual surveys through 2026.
Newman pumps river water into sample containers while Gooseff mans the oars.
A new approach
While water quality data is usually limited to discrete monitoring stations posted every few miles along the river bank, Gooseff’s boat-mounted sensors capture data every 40-60 feet. He calls this sampling method “Lagrangian sampling” after the 18th-century mathematician Joseph-Louis Legrange.
“His idea was that you could take the perspective of a moving particle in the world and try to understand how it changed based on its surroundings — as opposed to sitting somewhere and watching the world change around you.” Gooseff explained.
Gooseff’s raft, or “floating sampling platform” as he likes to call it, is equipped to measure pH, temperature, conductivity, turbidity, dissolved oxygen and nitrate. Collectively, these measurements offer a detailed map of the character and contents of Colorado River water as it travels from Rocky Mountain National Park to the canyonlands.
“What we’re trying to do is to figure out, ‘where do we see systematic changes along the river,’” Gooseff explained. “And now we have a higher spatial resolution.”
A map of the Colorado River and a waterproof notebook for logging data lay on a cooler atop the "floating sampling platform." The team collected physical samples of river water every three miles for later analysis.
Pinpointing water quality
The project has already reaped insights. In 2019, . The researchers were able to pinpoint sources of salts, nitrogen, turbidity and temperature fluctuation over time and space.
One particular finding offered important insight to river users. Somewhere around Grand Junction, Colorado, nitrate concentrations in the Colorado River increase. A signal like this is usually the result of agricultural runoff, but water managers weren’t sure exactly where the nitrate was coming from. Was it from the confluence with the Gunnison River, which hosts large farms upstream? Was it from local farms in the Grand Valley?
Gooseff’s data showed that nitrate levels spiked when the Gunnison entered the Colorado and then continued to climb as the river moved through the Grand Valley. The study elucidated, for the first time, how much nitrate was contributed by each source.
Gooseff hopes that findings like these can help water and land managers better solve issues as they arise. The upper basin is especially important because changes in water quality here can compound as the water travels to lower-basin states like California. Nitrate, which can lead to harmful algal blooms in high enough concentrations, is just one example.
“There’s a lot of the Colorado River watershed that has the opportunity to modify water quality before it gets to the end of the basin,” he said.
Newman sits next to the Gasometrix miniREUDI and speculates on potential uses for the device. On this trip, he used the miniREUDI to sense fluctuations in helium. He hopes the data will give the scientists a more precise idea of where groundwater enters the Colorado River.
Understanding groundwater
This year, the floating sampling platform featured a new gadget. Newman brought along a portable mass spectrometer called a that is capable of detecting precise concentrations of noble gases, like helium or argon, in the water.
The miniREUDI was more expensive than everything else in the boat combined, and is one of only two in the U.S., but it was worth it. By tracking helium along the Colorado, Newman can infer where salty groundwater is entering the river.
“The noble gases are an indicator of where there’s old groundwater discharge,” Newman explained. “We essentially look for the helium to show us where there might be influence of salts because the salinity of the Colorado River is one of the primary management concerns for downstream users.”
If the Colorado becomes too salty, it could prevent lower-basin users in California and Mexico from using the water for agriculture, industry or drinking water. Newman’s data will give water managers more information that they can use to map and prevent excess salinity.
Newman, Gooseff and other collaborators outlined their methodology and rationale for using miniREUDI in the boat . They hope to publish more results soon.
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Packing up
As Gooseff’s raft passed through the Black Rocks, a popular swimming, fishing and cliff-jumping spot in Horsethief Canyon, a fisherman waved from a nearby boat.
“You all are with the USGS?” he asked. “I use your data all the time.”
Because Gooseff’s research is funded by the USGS, any papers or datasets that come from it will be freely available to the public. The insights will be invaluable for land and river managers like the Bureau of Land Management. With any luck, they could help especially science-literate fishermen find a new honey hole as well.
By now, the floating sampling platform, oars and camping gear are packed away for the winter. But, it won’t be long before Gooseff heads back up to the Pumphouse Boat Launch to run the river during the high-flow spring season. As much as he relishes long days in the field and nights spent under the moonlight, the quiet months are just as interesting.
“The real reward is stepping back after our samples are analyzed and our data comes together and asking ‘what have we learned,’” he said.
Newman and Gooseff drift into camp at the end of a long day of data collection.
If you have questions about this story, or would like to reach out to INSTAAR for further comment, you can contact Senior Communications Specialist Gabe Allen at gabriel.allen@colorado.edu.