- University of Bristol, Faculty of Engineering, School of Civil, Aerospace and Design Engineering, Bristol, United Kingdom of Great Britain – England, Scotland, Wales (ross.woods@bristol.ac.uk)
The science question: how can we use hydrological process knowledge to understand the timing and magnitude of seasonal streamflow in snow-influenced catchments.
What was known: in general, catchments with colder climates have later and larger seasonal streamflow peaks, because more snow tends to accumulate in colder catchments, and it melts later because the time when melt can occur is later in the year in colder climates. Numerical models with fine space and time resolution were able to resolve these phenomena, but there was no theory which directly linked long term climate to seasonal streamflow.
In 2009 I published a very simple deterministic theory of snow pack evolution. I tested it against snow observations at 6 locations in the western USA and it apparently worked well (although I later discovered that I'd been lucky).
In 2015 I used the snowmelt derived from this deterministic theory to predict timing and magnitude of seasonal streamflow. It did poorly, and revealed untested assumptions in my theory. I tried making the theory slightly more complicated by considering within-catchment variation in climate. This did not help.
In 2016 I created a stochastic version of the theory (a weakness identified in 2015), and then also considered the within-catchment variation in climate. It did better at reproducing measured snow storage, but did not help in understanding seasonal streamflow.
My next step will be to consider all forms of liquid water input, i.e. not just snowmelt but also rainfall.
What survived: I will continue to use the stochastic version of the theory as it is clearly an improvement. I will continue to examine whether within-catchment climate variability is important, but it seems unlikely after two negative results. But whether introducing liquid water input will be sufficient, who can say? I will also try to examine in more detail how it is that the finely-resolved numerical models can do an adequate job, but the theory cannot - it is in this gap that the answer probably lies. However the models are very complicated, and it is not easy to get a good understanding of exactly what they are doing, even though we know which equations the are implementing.
How to cite: Woods, R.: Some Perfectly Reasonable Ideas that Didn’t Work: Snow Hydrology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20057, https://doi.org/10.5194/egusphere-egu25-20057, 2025.
