Abstract. In many Mediterranean mountain regions, the seasonal
snowpack is an essential yet poorly known water resource. Here, we examine,
for the first time, the spatial distribution and evolution of the snow water
equivalent (SWE) during three snow seasons (2013–2016) in the coastal
mountains of Lebanon. We run SnowModel (Liston and Elder, 2006a), a
spatially distributed, process-based snow model, at 100 m resolution forced
by new automatic weather station (AWS) data in three snow-dominated basins
of Mount Lebanon. We evaluate a recent upgrade of the liquid water
percolation scheme in SnowModel, which was introduced to improve the
simulation of the SWE and runoff in warm maritime
regions. The model is evaluated against continuous snow depth and snow
albedo observations at the AWS, manual SWE measurements, and MODIS snow
cover area between 1200 and 3000 m a.s.l. The results show that the new
percolation scheme yields better performance, especially in terms of SWE but
also in snow depth and snow cover area. Over the simulation period between
2013 and 2016, the maximum snow mass was reached between December and March.
Peak mean SWE (above 1200 m a.s.l.) changed significantly from year to year
in the three study catchments, with values ranging between 73 and 286 mm w.e. (RMSE between 160 and 260 mm w.e.). We suggest that the major sources of
uncertainty in simulating the SWE, in this warm Mediterranean climate, can
be attributed to forcing error but also to our limited understanding of the
separation between rain and snow at lower-elevations, the transient snowmelt events during the accumulation season, and the high variability of snow
depth patterns at the subpixel scale due to the wind-driven blown-snow
redistribution into karstic features and sinkholes. Yet, the use of a
process-based snow model with minimal requirements for parameter estimation
provides a basis to simulate snow mass SWE in nonmonitored catchments and
characterize the contribution of snowmelt to the karstic groundwater
recharge in Lebanon. While this research focused on three basins in the
Mount Lebanon, it serves as a case study to highlight the importance of wet
snow processes to estimate SWE in Mediterranean mountain regions.