The implications of changes in peak SWE timing and magnitude for drought prediction in the Western U.S.
Abstract
Water managers in the western U.S. routinely rely on knowledge of snow water equivalent (SWE) to issue skillful streamflow forecasts, either through model initialization or via statistical forecast. These predictions are particularly important to anticipate and mitigate the impacts of water shortages, i.e. drought. Yet, there is a strong consensus that winter snowpack has decreased in recent decades with decreases likely to continue in the future, raising the question: How will future losses in snowpack impact the utility of SWE as a predictor in seasonal streamflow predictions, particularly during drought. This presentation builds upon previous work using hydrologically downscaled climate projections that showed decreases in snowpack lead to reductions in categorical drought prediction of up to 4.6% and 32.7% by mid- and late-century, with lower-elevation, maritime climates most vulnerable.
Here we investigate the reasons for the decrease in predictive skill and evaluate predictors that could be used along with SWE to improve warm season streamflow forecasts. We focus ona set of representative basins across the western U.S.—a regionwhere snowmelt is often the largest source of seasonal freshwater. Experiments focus on the implications of shifts in the timing and magnitude of peak SWE for seasonal streamflow prediction. Additional experiments evaluate the changes in variability of warm season temperature and precipitation in a similar context. For each experiment, categorical drought forecasts are issued using a multivariate linear predictive model commensurate with operational techniques, where peak SWE is used to predict warm-season streamflow. A discussion into the most sensitive elements of forecast skill is provided in the context of future water supply management where experimental results are compared with projected changes in peak SWE timing, magnitude, and anticipated climate variability.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H14E..07O
- Keywords:
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- 1812 Drought;
- HYDROLOGY;
- 1817 Extreme events;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY