Quantifying projected changes in runoff variability and flow regimes of the Fraser River Basin, British Columbia
<p>In response to ongoing and future-projected global warming, mid-latitude, nival river basins are expected to transition from a snowmelt-dominated flow regime to a nival–pluvial one with an earlier spring freshet of reduced magnitude. There is, however, a rich variation in responses that dep...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
|
| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/23/811/2019/hess-23-811-2019.pdf |
| Summary: | <p>In response to ongoing and future-projected global warming, mid-latitude,
nival river basins are expected to transition from a snowmelt-dominated flow
regime to a nival–pluvial one with an earlier spring freshet of reduced
magnitude. There is, however, a rich variation in responses that depends on
factors such as the topographic complexity of the basin and the strength of
maritime influences. We illustrate the potential effects of a strong maritime
influence by studying future changes in cold season flow variability in the
Fraser River Basin (FRB) of British Columbia, a large extratropical watershed
extending from the Rocky Mountains to the Pacific Coast. We use a
process-based hydrological model driven by an ensemble of 21 statistically
downscaled simulations from the Coupled Model Intercomparison Project Phase 5
(CMIP5), following the Representative Concentration Pathway 8.5 (RCP 8.5).</p>
<p>Warming under RCP 8.5 leads to reduced winter snowfall, shortening the
average snow accumulation season by about one-third. Despite this, large
increases in cold season rainfall lead to unprecedented cold season peak
flows and increased overall runoff variability in the VIC simulations.
Increased cold season rainfall is shown to be the dominant climatic driver
in the Coast Mountains, contributing 60 % to mean cold season runoff
changes in the 2080s. Cold season runoff at the outlet of the basin
increases by 70 % by the 2080s, and its interannual variability more than
doubles when compared to the 1990s, suggesting substantial challenges for
operational flow forecasting in the region. Furthermore, almost half of the
basin (45 %) transitions from a snow-dominated runoff regime in the 1990s
to a primarily rain-dominated regime in the 2080s, according to a snowmelt
pulse detection algorithm. While these projections are consistent with the
anticipated transition from a nival to a nival–pluvial hydrologic regime,
the marked increase in FRB cold season runoff is likely linked to more
frequent landfalling atmospheric rivers in the region projected in the CMIP5
models, providing insights for other maritime-influenced extratropical
basins.</p> |
|---|---|
| ISSN: | 1027-5606 1607-7938 |