Process-based simulations of percolation from various landfill final
covers in a cold climate
Abstract
Accurate estimation of percolation is crucial for assessing landfill
final cover effectiveness, designing leachate collection/treatment
systems, and many other applications, such as in agriculture. Despite
the importance, percolation is seldom measured due to the high cost and
maintenance of lysimeters, underlining the need for skillful simulation.
Process-based numerical models, despite requiring validation and
numerous parameters, present an alternative for percolation simulation,
though few studies have assessed their performance. This study compares
percolation measured from three fully instrumented large-scale
experimental plots to simulate percolation using a new version of the
Soil Vegetation and Snow (SVS) land-surface model with an active
soil-freezing module. Previous research indicates numerical model
performance may significantly vary based on soil-related parameter
values. To account for input data and parameter uncertainty, we use an
ensemble simulation strategy incorporating random perturbations. The
results suggest that SVS can accurately capture the seasonal patterns of
percolation, including significant events during snowmelts in spring and
fall, with little to no percolation in winter and summer. The continuous
ranked probability skill score values for the three plots are 0.13,
-0.13, and 0.33. SVS simulates near-surface soil temperature dynamics
effectively ( R 2 values 0.97-0.98) but underestimates temperature and
has limitations in simulating soil temperature in snow-free situations
in the cold season. It also overestimates soil freezing duration,
revealing discrepancies in the onset and end of freezing periods
compared to observed data. This study highlights the potential of land
surface models for the simulation of percolation, with potential
applications in the design of systems such as leachate collection and
treatment. While the SVS model already provides an interesting outlook,
further research is needed to address its limitations in simulating soil
temperature dynamics during soil freezing periods.