Modelling liquid water transport in snow under rain-on-snow conditions – considering preferential flow
Rain on snow (ROS) has the potential to generate severe floods. Thus, precisely predicting the effect of an approaching ROS event on runoff formation is very important. Data analyses from past ROS events have shown that a snowpack experiencing ROS can either release runoff immediately or delay it co...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-03-01
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Series: | Hydrology and Earth System Sciences |
Online Access: | http://www.hydrol-earth-syst-sci.net/21/1741/2017/hess-21-1741-2017.pdf |
Summary: | Rain on snow (ROS) has the potential to generate severe floods.
Thus, precisely predicting the effect of an approaching ROS event on runoff
formation is very important. Data analyses from past ROS events have shown
that a snowpack experiencing ROS can either release runoff immediately or
delay it considerably. This delay is a result of refreeze of liquid water and
water transport, which in turn is dependent on snow grain properties but also
on the presence of structures such as ice layers or capillary barriers.
During sprinkling experiments, preferential flow was found to be a process
that critically impacted the timing of snowpack runoff. However, current
one-dimensional operational snowpack models are not capable of addressing
this phenomenon. For this study, the detailed physics-based snowpack model
SNOWPACK is extended with a water transport scheme accounting for
preferential flow. The implemented Richards equation solver is modified using
a dual-domain approach to simulate water transport under preferential flow
conditions. To validate the presented approach, we used an extensive dataset
of over 100 ROS events from several locations in the European Alps,
comprising meteorological and snowpack measurements as well as snow lysimeter
runoff data. The model was tested under a variety of initial snowpack
conditions, including cold, ripe, stratified and homogeneous snow. Results
show that the model accounting for preferential flow demonstrated an improved
overall performance, where in particular the onset of snowpack runoff was
captured better. While the improvements were ambiguous for experiments on
isothermal wet snow, they were pronounced for experiments on cold snowpacks,
where field experiments found preferential flow to be especially prevalent. |
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ISSN: | 1027-5606 1607-7938 |