By Marcus Gay, NM WRRI Student Program Coordinator
Ephemeral streams, or arroyos as they are called in New Mexico, flow in direct response to precipitation. In semi-arid climates, flash floods are common in arroyos after a big storm. When the arroyo is flowing, sediment moves from these ephemeral streams into large rivers such as the Rio Grande; however, quantifying sediment influx into large rivers is challenging. Last year, Madeline Richards, under the guidance of her faculty advisor, Dr. Daniel Cadol, was awarded an NM WRRI Student Water Research Grant to study this topic. The title of her project is, Rainfall-Runoff Relationships in the Arroyo de los Pinos, Socorro New Mexico.
Small ephemeral streams in New Mexico are not studied as often as perennial streams because of their erratic nature, and because they are usually located in hard to access deserts. The Arroyo de los Pinos site is cfurrently one of very few study sites collecting data on water discharge, bedload transport, suspended sediment, and other relevant measurements during flash floods in dryland environments. This study site is located close to the confluence of the arroyo and the Rio Grande. Gaining a clearer picture of stream connectivity and rainfall-runoff relationships in this channel will be useful for quantifying flow generation as well as aquifer recharge and transmission loss through the stream bed. These processes affect flow conditions and sediment transport.
To understand stream connectivity and rainfall-runoff relationships, the project required more data on the arroyo’s watershed. To acquire this data, Madeline and her team set up pressure transducers, and rain gauges that collected runoff and rainfall data in the Pinos watershed over the monsoon season. This allowed her to identify when and from where runoff is being generated. This runoff transports sediment and carries it downstream.
The larger project this NM WRRI grant supports is funded by the U.S. Bureau of Reclamation in an effort to better understand the sediment flux from arroyos into main stem rivers like the Rio Grande. Agencies that manage dams, reservoirs, and mainstream channels will benefit from a better understanding of sediment generating mechanisms in ephemeral channels like the Arroyo de los Pinos.
Madeline presented her work on this project at the American Geophysical Union Fall 2019 Conference, and the 64th Annual New Mexico Water Conference.
Madeline is originally from northern California. She received her Bachelor’s in Environmental Geology at the University of California, Santa Cruz (UCSC). At UCSC, she worked in the Geomorphology lab and her research focused on the geomorphology of Santa Cruz Mountain streams. Madeline is now finishing her graduate work in the Earth and Environmental Science Department at New Mexico Tech. Madeline works for the U.S. Army Corps of Engineers in the Hydrology and Hydraulics section, and plans on transitioning to full-time employment after she graduates with a Master of Science in Hydrology.