Final Report: Improving Predictions of Water Supply in the Rio Grande under Changing Climate Conditions.
Dates
Publication Date
2020-06-19
Citation
David Gutzler, 2020-06-19, Final Report: Improving Predictions of Water Supply in the Rio Grande under Changing Climate Conditions.: .
Summary
Declining snowpack is one of most easily visible features of a warming climate in mountainous areas of western North America, and the further decline of snowpack is a robust projection from climate models simulating a warmer future climate. Major rivers in western North America are largely fed by snowpack, but the physical relationship between temperature change and snowmelt runoff is complicated, and model projections of future streamflow in western rivers vary widely. The goal of this project was to assess the changing relationship between snowpack and streamflow in the headwaters basin of the Rio Grande, using both observed data and climate model simulations. First, we assessed how well measured snowpack served as a predictor [...]
Summary
Declining snowpack is one of most easily visible features of a warming climate in mountainous areas of western North America, and the further decline of snowpack is a robust projection from climate models simulating a warmer future climate. Major rivers in western North America are largely fed by snowpack, but the physical relationship between temperature change and snowmelt runoff is complicated, and model projections of future streamflow in western rivers vary widely. The goal of this project was to assess the changing relationship between snowpack and streamflow in the headwaters basin of the Rio Grande, using both observed data and climate model simulations.
First, we assessed how well measured snowpack served as a predictor of subsequent runoff season streamflow. We confirmed that snowpack has decreased with time over the past half-century as temperature has risen, and determined that the seasonal predictability of streamflow from observed peak snowpack has also been declining in recent decades, posing a tremendous challenge for management of river flows and annual water supply allocations that depend on seasonal forecasts. We determined that the most important climate variable to add to snowpack, in order to improve streamflow forecasts, is Spring season precipitation.
Second, we applied what we learned from our observational analysis to climate model simulations of future Rio Grande flows. Declining streamflow in snow-fed western rivers is a feature of most 21st Century model projections but the variability among such projections is huge. We sought to constrain this uncertainty by identifying simulations that reproduce historical changes in the snowpack-streamflow relationship. This subset of models generated diminished streamflow, with less variability among simulations, than the comple-ment of simulations that did not reproduce observed changes. This result increases our confidence in the projection of diminished streamflow in a warmer climate.
