SNOW AND HYDROLOGIC PROCESSES IN THE INTERMOUNTAIN WEST
Location: Watershed Management Research
Title: Comparison of algorithms and parameterisations for infiltration into organic-covered permafrost soils
Submitted to: Hydrology and Earth System Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2010
Publication Date: May 11, 2010
Citation: Zhang, Y., S.K. Carey, W.L. Quinton, J.R. Janowicz, J.W. Pomeroy, and G.N. Flerchinger. 2010. Comparison of Algorithms and Parameterisations for Infiltration into Organic-Covered Permafrost Soils. Hydrology and Earth System Sciences, 14:729-750.
Interpretive Summary: Vast areas worldwide are influenced by freeze/thaw processes and permafrost, but few hydrological models have been developed or tested for infiltration under frozen soil conditions. Various approaches for predicting rainfall and snowmelt into frozen soil were implemented into the Simultaneous Heat and Water (SHAW) model and tested against detailed field measurements at three sites in Canada. The study concluded that the single most important factor in predicting infiltration was properly simulating the depth of ground thaw; the approach for simulating infiltration was important only when the ground was frozen or in the early stages of thawing stages. Results from this work provide guidelines and can be directly implemented in hydrologic and land surface models to improve their application in frozen soil infiltration, runoff and erosion.
Infiltration into frozen and unfrozen soils is critical in hydrology, controlling active layer soil water dynamics and influencing runoff. Few Land Surface Models (LSMs) and Hydrological Models (HMs) have been developed, adapted or tested for frozen conditions and permafrost soils. Considering the vast geographical area influenced by freeze/thaw processes and permafrost, and the rapid environmental change observed worldwide in these regions, a need exists to improve models to better represent their hydrology.
In this study, various infiltration algorithms and parameterisation methods, which are commonly employed in current LSMs and HMs were tested against detailed measurements at three sites in Canada’s discontinuous permafrost region with organic soil depths ranging from 0.02 to 3 m. Field data from two consecutive years were used to calibrate and evaluate the infiltration algorithms and parameterisations. Important conclusions include: (1) the single most important factor that controls the infiltration at permafrost sites is ground thaw depth, (2) differences among the simulated infiltration by different algorithms and parameterisations were only found when the ground was frozen or during the initial fast thawing stages, but not after ground thaw reaches a critical depth of 15 to 30 cm, (3) despite similarities in simulated total infiltration after ground thaw reaches the critical depth, the choice of algorithm influenced the distribution of water among the soil layers, and (4) the ice impedance factor for hydraulic conductivity, which is commonly used in LSMs and HMs, may not be necessary once the water potential driven frozen soil parameterization is employed. Results from this work provide guidelines and can be directly implemented in LSMs and HMs to improve their application in organic covered permafrost soils.