New SNOTEL stations to improve streamflow forecasts

A location north of Creede, somewhere near Lost Lake around La Jara Creek, a site in the Trinchera area. Those are some of the general areas in the San Luis Valley where new SNOTEL stations, or automated snow monitoring stations, could show up under the Rio Grande Snow Measurement Enhancement Project being developed by water conservancy districts.

San Luis Valley Water Conservancy District Manager Heather Dutton is helping spearhead the project and has an outline for four new full SNOTEL stations and three SNO-Lite stations. 

Establishing seven new sites would deliver more data from critical high-elevation areas to improve snow-depth readings and better forecast corresponding spring runoff into the creeks that feed the Upper Rio Grande Basin.

“We’re definitely going to build some sites, it’s just getting them dialed in,” Dutton said this week in an interview with Alamosa Citizen.

What’s at stake 

Warmer seasonal temperatures, less snow occurrence, drier snow, and higher winds over the past two decades have created challenging conditions to forecast streamflows on the Upper Rio Grande.

Accurate forecasting, which relies on the accumulation of data from existing National Resource Conservation Service (NRCS) SNOTEL stations, matters particularly to Colorado’s management of the Rio Grande Compact with New Mexico and Texas. Better streamflow forecasting would also aid managers with the Rio Grande Water Conservation District and local irrigators in their management of groundwater well pumping and annual replacement plans.

“The goal of the project is to add more clarity, more data to on the ground sites so we can improve streamflow forecasting,” Dutton said. 

The San Luis Valley Water Conservancy District initially received a $45,000 grant from the Colorado Water Plan to assist with establishing a series of SNO-Lite sites. But after showing conceptually that there were big data holes with the existing SNOTEL locations, the project evolved to include the four full stations to help with the NRCS model.

The cost is pegged at $293,000 for the seven sites, with funding coming from the San Luis Valley Water Conservancy District, the Colorado Water Conservancy District, Trinchera Ranch, and potentially from the Rio Grande Water Conservation District.

The additional SNOTEL sites will nearly double the current number of sites in the San Luis Valley, said Craig Cotten, division engineer for the state Division of Water Resources.

“This is really going to be a help for us,” he said.

The current SNOTEL sites, he said, are good for the location that they’re in. “But if you get a couple of miles away, it could be a totally different amount of snow and elevation as well.”

Why it matters

Data from SNOTEL sites is transmitted in near real time every hour to gauging stations to help water managers predict spring and summer streamflows. The gauging station at Del Norte, for instance, is essential to helping the state determine how much water from the Rio Grande is available to be delivered downstream into New Mexico.

The weight of the snow, which determines how much water is in the snow that has fallen, is the data a full SNOTEL site transmits. A SNO-lite site doesn’t have a similar snow pillow to weigh, and instead estimates the amount of water in snow.

In addition to improving streamflow forecasting, more SNOTEL sites means better soil moisture data, which is critical to assessing drought conditions and estimates of crop yields.

Historically, water managers could make safe assumptions on streamflows based on the readings from SNOTEL stations located in similar elevations. But those forecasts are no longer holding up as a result of the changing ecological environment in the San Luis Valley, Dutton said.

“What it comes down to, is the stream yield based on snow production is not tracking the way it used to,” she said.

The water conservancy districts, Alamosa County and the Rio Grande Water Conservation District contributed to a new Doppler weather radar at the Alamosa Regional Airport two years ago to help improve San Luis Valley weather forecasts.

The addition of SNOTEL stations is another step to get more data. They’ll be located in historically high snow-producing areas and where there currently is a need for more data, like the elevations north of Creede and in the southern end of the Valley.

“We want to make sure (a location) gets enough snow that is useful,” Dutton said.

The conservancy districts will spend the winter modeling the project and then conduct on-site analyses coming out of winter going into spring. The goal is to add two full SNOTEL sites both in 2023 and 2024, and the three SNO-Lite stations in 2023.