The role of soil moisture memory in spring runoff predictability in Western US river basins
Abstract
The release of accumulated winter snow and soil moisture storage as spring runoff provides critical water supply in the Western US. However, shifts in climate regime will affect the timing and magnitude of both snow and soil moisture storage, with implications for our ability to forecast seasonal runoff. Here, we define the evolution and role of antecedent winter soil moisture in predicting springtime runoff in 71 natural (unmanaged) headwater catchments across the Western US, and assess how climatic and physiographic conditions control this relationship. We also conduct a companion analysis of spatially distributed hydrologic conditions for snow-dominant 1/16th degree latitude-longitude grid cells over the entire western U.S. domain. Over a modeled period of record from 1920 to 2019, we calculate the predictability between November 1 soil moisture and total spring runoff (expressed as the Pearson correlation coefficient and coefficient of prediction) for each of the 71 basins, and assess the patterns in these predictability metrics across basins with different climate regimes, winter soil moisture variations, and winter temperature. We also conduct a synthetic experiment with a +2 °C temperature scenario to evaluate potential future impacts on the predictability metrics. The basin and spatially distributed assessments show that - (i) fall soil moisture and spring runoff are positively correlated at most locations; (ii) this correlation decreases as winter soil moisture and average winter temperature increase; (iii) the correlation is stronger in snow-dominated catchments than rain-dominated catchments. The synthetic scenario shows that the predictability of spring runoff from fall soil moisture is significantly eroded in catchments with mixed climate regimes (i.e., basins with winter average temperature around 00C in the current climate) by temperature warming.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H54G..07V
- Keywords:
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- 1833 Hydroclimatology;
- HYDROLOGY;
- 1840 Hydrometeorology;
- HYDROLOGY;
- 1843 Land/atmosphere interactions;
- HYDROLOGY;
- 1866 Soil moisture;
- HYDROLOGY