NMT Student Using NM WRRI Funding to Study Sediment Flow in Arroyos
by Thom Guengerich, NM Tech Office of Communications and Marketing
New Mexico Tech doctoral student Kyle Stark is putting his NM WRRI grant to good use. He is conducting a multi-year study of sediment transport in an ephemeral arroyo near Socorro.
Stark, along with his advisors and other funding agencies, constructed a monitoring station on the Arroyo de los Piños, which is a seasonal tributary to the Rio Grande. That arroyo only runs a few times each year, but the flow can provide significant sediment transport into the river.
The Rio Grande is a crucial part of life in the southwest United States. Constant maintenance along these rivers is required to ensure that the adjacent communities have consistent access to water, to prevent avulsions and the development of sediment plugs, to manage reservoir infilling, and to maintain aquatic habitat for life in the Rio Grande.
One source of uncertainty in managing these rivers is the sediment incoming from arroyos and other dry river channels. Flowing water in these channels is rare, but sediment production can be high when they do flow.
“The Rio Grande is connected to the surrounding landscape via these ephemeral channels,” Stark said. “We are trying to improve our models to help manage the rivers in these arid environments.”
Stark’s NM WRRI funding helped him fund a student worker during the 2018 monsoon season and the installation of additional instrumentation. NM WRRI funding allowed Stark to install an instrument to measure water velocity at in large flows. Prior to that, his only way to measure water speed was to wade out into the stream. “This new method is not nearly as dangerous,” he said.
The Arroyo de los Piños system was designed and constructed to be a premier sediment monitoring station. Funded by the U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers, Stark’s array of sensors incorporates peer-reviewed methods of monitoring water and sediment with novel approaches that are new to the arid Southwest. The goal is to better understand the mechanisms that transport water and sediment down these dry riverbeds into their mainstem counterparts. Armed with these unique datasets, river managers at the local, state, and federal level will be better prepared for a changing Rio Grande. Researchers can study other dry channels in desert regions all over the world with technologies developed on the Piños. As these mainstem rivers become more managed, communities can better prepare for changes that happen along them.
The Bureau of Reclamation engineered and built the station that has three key features:
- Stabilized banks using rip-rap in Gabion baskets;
- Automated instruments that measure sediment and upload it to the cloud; and
- An array of instruments that were deployed to be passive and not interfere with flow.
The heart of the monitoring station is a Reid-type slot sampler system with three pit samplers, which are chambers below the river bed that capture rocks, gravel, and sand as a flood rolls, slides, or bounces them down the channel.
Stark, along with his advisors Dr. Dan Cadol of NMT and Dr. Jonathan Laronne of Ben-Gurion University of the Negev in Israel, have added an array of other sensors.
Stark is collecting data from these five “surrogate sensors”:
- Impact pipe microphones, which record the sound of sediment hitting the pipe
- Plate microphones that also record impacts
- A vertical pipe microphone that records different modes of bed load transport
- Two pairs of hydrophones that record the sound-scape of the bed load and turbulence in the water
- Seismometers that measure the vibrations caused by bed load and turbulence
Stark said that for every flood, the array collects 22,000 data points. The real key is finding which instrument works best in these sandy, flash-flood-dominated channels. He said that parsing out the signals is the challenge. “My Ph.D. primarily will be based on data from the pipe sensors and plate sensors.”
“What’s novel about this site is that we are using six different ‘surrogate’ methods to measure sediment transport,” Stark said. “This combination of methods has not been tested anywhere in the U.S. in tandem. We are trying to find out which instruments work best for these ephemeral tributaries. We hope to find answers so that in the future, rather than deploying a huge set of instruments, we can calibrate a smaller array of sensors to do it more efficiently.”