NMT Ph.D. Candidate Studies Upper Rio Grande Runoff Processes, Dec. 14, 2007

Marty Frisbee

by George Zamora

SOCORRO, N.M., Dec. 14, 2007 – New Mexico Tech doctoral candidate Marty D. Frisbee can often be found hiking the high elevations of the northern San Luis Valley in south-central Colorado, not in hopes of taking in more of the beautiful scenery, but in trying to better understand the runoff and recharge processes of the Upper Rio Grande.

Frisbee’s research study of a portion of the headwaters of the Rio Grande, titled “Runoff Processes and the Evolution of Water Chemistry in the Saguache Creek Watershed of the Upper Rio Grande,” is funded in large part by the New Mexico Water Resources Research Institute (WRRI).

“So far, during the first two years of this study, we’re beginning to see some very interesting temporal and spatial trends in the stream, spring, and groundwater chemistry of our field samples,” Frisbee says. “After analyzing water samples collected from 32 spring and stream sampling locations ranging from the headwaters to the lower reaches of this particular subcatchment, we’re finding that stream chemistry appears to be heavily dependent upon groundwater contributions. Also, some interesting trends in chemistry emerge as the sampling scale changes within the watershed.

“Not a lot is known about the nature of deep groundwater flow within a mountain block, and, consequently, not much is know about deep groundwater contributions to streamflow in these settings, but what we’re finding is that these contributions from the fractured bedrock may be significant,” he adds.

Furthermore, Frisbee’s initial findings about the water chemistry of streams in the high reaches of the San Luis Valley, which is being done in conjunction with his faculty and research advisor, New Mexico Tech hydrology professor Fred Phillips, is likely directly applicable to watersheds found in geologically similar mountain ranges, such as the Cascades and Sierra Nevadas.

“The results of this study will aid in understanding the partitioning of water and also will help develop better distributed models that simulate and predict mountain front recharge and flow and transport at high-elevation catchments,” Frisbee says. “Also, the information we gain on water residence times, flow paths, and runoff mechanisms in headwater systems of the Rio Grande can be applied to larger-scale climate change models of the region.”

Frisbee and his research colleagues at New Mexico Tech have used much of the WRRI funding made available for this particular study to purchase and install equipment to continuously monitor and data-log the chemistry at a long-term monitoring site located in the lower reach of the stream. Other lab equipment was purchased to measure the chemical composition of samples which are collected along a longitudinal transect of Saguache Creek.

A typical set of field measurements includes conductivity, pH, temperature, TDS, and various chemical components naturally present in the water, such as chloride, sodium and calcium.

“It takes at least three or four days to retrieve the collected data from all the monitoring stations and gauge the flow at each site situated throughout this watershed during each sampling trip,” Frisbee says. “And then after that, there’s a good deal of lab work involved to identify and evaluate these deep groundwater contributions to streamflow. . . . Nevertheless, my research at New Mexico Tech has introduced me to some beautiful places, which is a fringe benefit of studying hydrology.”