donor3

 

himg_default_01.jpg

Tech Scientists Study Massive Spring In Rio Grande

SOCORRO, N.M. November 17, 2009 – New Mexico Tech scientists think they’ve found the largest spring yet in the upper Rio Grande, a few miles south of the Colorado border near Ute Mountain.

Peggy Johnson (right), associate director of the Bureau of Geology, watches as staff scientists Stacy Timmons and Louis Gillard collect samples of spring water along the upper reaches of the Rio Grande. Photos by Paul Bauer

 

Dr. Paul Bauer and Peggy Johnson have dubbed it the Lava Tube Spring and say the spring’s crater is 12 feet deep and erupts 6,000 gallons of water a minute, or 13 cubic-feet-per-second into the Rio Grande. Lava Tube is the largest of the 140 springs and seeps the scientists have documented so far in the 80-mile river reach from the Colorado border to the Embudo stream-measuring gage. They estimate that this one spring contributes 10 percent of the total flow of springs and seeps in the stretch.

Surprisingly, the spring is located under the river, rather than on the canyon walls, and generates a continuously dancing plume of gravel in the river. The spring water may flow through an old lava tube in the basalts that cover the Taos Plateau.

Melting snow feeds the Rio Grande and its tributaries in Colorado and New Mexico. Based on calculated water flows at a series of stream gages on the Rio Grande and its tributaries, hydrologists have calculated that springs contribute 130 cubic-feet-per-second of water to the river. That’s enough water to float a kayaker down the rocky river.

“We’re trying to figure out where that 130 cfs is coming from and what the geologic conditions are that control the spring locations,” said Bauer, associate director and principal geologist with the Bureau of Geology at New Mexico Tech. “It’s been known for a long time that there’s accretion – additions to the river from springs and seeps – but no one had tried to figure out where and why.”

Thanks to funding from the Interstate Stream Commission, Taos County and the Healy Foundation, Bauer, Johnson and their colleagues from the Interstate Stream Commission set out three years ago to survey the river looking for springs and studying the source of the additional water.

The Lava Tube Spring has created a 12-foot deep crater and erupts 6,000 gallons per minute.

Student researcher Kristoph Kinzli was given the task of retrieving water samples from the Lava Tube Spring. Above, he attaches a bucket to the top of a 14-foot-long pipe. The force of the spring propelled water four feet above the river level.

 

Bauer had been working on geologic maps of Taos County since the 1980s, while Johnson has been studying the hydrology of the area since about 2000.

“We combined her hydrology skills and my geology skills to begin looking at Taos County,” Bauer said. “Principally, we’ve been trying to understand and assess the interaction between groundwater and the river in the region.”

Bauer, Johnson and other scientists started exploring the Rio Grande Gorge three years ago and documenting the springs and local geology.

“We felt like we were discovering something new and unique,” she said. “This was a special project and we felt privileged to do it. It was a kind of a career highlight for Paul and me.”

Their team first floated over the large Lava Tube Spring in late 2008, but the river was too high to evaluate the spring. They hiked in the next fall at very low water to measure the flow and collect samples.

When they returned, the science team inserted a 14-foot, 1.5-inch-diameter pipe into the spring’s crater to exploit its high pressure. The force of the spring induced artesian flow four feet above the river, so they then could collect water samples from a five-gallon bucket attached to the top of the pipe without risk of contamination from the river water.

“These springs are notable because of the large volume of groundwater feeding the river,” he said. “The springs are important culturally to both native Americans and the people who live in Taos County, but also to anglers, boaters, kayakers, biologists and other river users.”

Until Johnson and Bauer began examining the river, no one had conducted a systematic survey of the upper Rio Grande gorge to find all the springs.

“We went into the project thinking, ‘Oh well, there are 25 springs listed in the literature, maybe we’ll find a few more’,” Bauer said. “Little did we know that we’d find this many more springs in such a diversity of geologic settings.”

The majority of the springs are small and typically seep into the river or trickle down from the banks. However, the seven springs that flow at over 1000 gallons per minute contribute more than half of the total spring accretion. Most of the high-flow springs are located in the least accessible, deepest section of the gorge.

“If you’re kayaking, you look for water moving into the river,” Bauer said. “One of the problems is that the sides of the river and canyon bottom are mantled by these large basalt boulders. Often times, you can’t see water that’s entering the river.”

Some springs trickle out the sides of the canyon walls – in which case the scientists could often hear the spring before they saw it.
The Lava Tube Spring was an anomaly. During periods of low flow, the spring produces a disturbance on the surface of the river, but at higher river levels the spring disappears from view. The spring produces enough water to fill a tanker truck in 90 seconds.

 The survey team located more than 140 springs along 80 miles of river. Many were like this one above, seeping slowly into the river along the bank.

 

Johnson, senior hydrogeologist and associate director at the Bureau, is conducting a basic suite of chemical analyses of the water samples, including ion chemistry, trace element and age dating. The data are starting to come back from the laboratories, but she has not analyzed and interpreted all of it.

We’re trying to track down the source of the spring water,” Johnson said. “We don’t know if it’s coming from Colorado – which the state would be interested in knowing – or if it’s recharging from the distant eastern or western mountain ranges or perhaps from right there on the nearby Taos Plateau.”

They’ve found springs on both sides of the river, but they believe that most of the water is coming from the mountainous watershed to the west.

Another question the Tech scientists aim to answer relates to the age of the water. Johnson is using several different dating methods, including carbon-14, CFC and tritium dating. So far, she’s discovered that some of the water is only 30 to 40 years old, whereas other spring water is many thousands of years old.

They’ve also found areas where old and young groundwater are mixing. “What we’re seeing in the Taos area is quite interesting,” she said. “The age of the water yields valuable clues concerning the hydrologic setting of the plateau.”

It's a dirty job, but someone has to do it. Above, hydrologist Peggy Johnson kayaks down the Rio Grande during the spring 2009 survey. Below, the view from atop the gorge. The survey team made numerous descents and ascents with their survey equipment. Photos by Paul Bauer

 

One of those mixed-water springs is Felsenmeere Spring, which is a series of prolific discharges high on the western side of the gorge. Johnson said Felsenmeere Spring emits young and old water that apparently mixes along a fault zone that dissects the Taos Plateau.

Floating down the Rio Grande might seem like more of a vacation than work, but Johnson and Bauer said these trips tested their endurance and strength. Some stretches of the canyon were too challenging for them to kayak, and other sections were impossible to traverse on foot, but they did ultimately cover nearly all of the 80 miles of the study area.

“I had not done anything like that before,” Johnson said. “Twenty years ago, I would have been able to do this at the drop of a hat, but I had to train for this. It was physically arduous.”

The Rio Grande Gorge is one of the most rugged parts of New Mexico. To collect samples from various springs, Johnson and Bauer made three extended research expeditions with support staff from the Bureau of Geology, and numerous shorter visits. Each time, they made multiple ascents, descents and transects of the gorge.

“The wildlife was incredible; the birds were incredible,” Johnson said. “This area has not been seen by many people – mostly by local residents, anglers, and people who paddle their kayaks through the wild river sections.”

Johnson and Bauer will finish a preliminary report on the springs for the Interstate Stream Commission this winter, but they have enough data to spend another year or two doing in-depth data analysis.

– NMT –

By Thomas Guengerich/New Mexico Tech