Dec. 20, 2024

Northern Water Teams Predict Streamflows Using Variety of Snow, Environmental Data

Once the first snowflake sticks to the ground, the Water Resources team at Northern Water is busy monitoring regional snow data on both the East and West slopes to predict streamflows for the coming year. Snowpack is the most-significant indicator of future streamflows, but other factors include late season precipitation, soil moisture, wildfires and air temperature. 

Water Resources Specialist Emily Carbone said streamflow forecasts are vital to key operational decisions that Northern Water staff and the Board of Directors make annually. Perhaps the most vital decision is setting the quota, which quantifies the amount of Colorado-Big Thompson Project water the Board makes available to allottees each year. An initial quota is set Nov. 1 of each year to supply winter water delivery accounts, with a supplemental quota set in April for the start of the irrigation season. Northern Water also sends forecasts to its allottees to plan for the upcoming water year.

Water Resources uses a combination of complex physical and statistical models to create forecasts. They also qualitatively compare data and forecasts from external agencies such as the Natural Resources Conservation Service (NRCS) and the U.S. Bureau of Reclamation to make the most-accurate predictions.   

Colorado River headwaters in Rocky Mountain National Park in early June
The headwaters of the Colorado River are shown here during runoff in spring 2024.

Northern Water remains on the forefront by updating its models and using cutting-edge technologies such as Airborne Snow Observatories (ASO), which calculates snow depth from flights over surface watersheds. The data from those flights is used to measure the snow-water equivalent, or how much water is stored in the snow.

According to Carbone, forecasting has become more difficult due to increased variability from factors such as climate change and wildfires, however Water Resources has maintained an average forecast error of only 15 percent. For real-time data, live snowpack reports and additional resources are available on our website, and Water Resources releases monthly forecasts based on this data from February through May.