A Conceptual Model for Anticipating the Impact of Landscape Evolution on Groundwater Recharge in Degrading Permafrost Environments

• Published in: Geophysical research letters 2020-06, Vol.47 (11), p.n/a
• Main Authors: Young, N. L., Lemieux, J.‐M., Delottier, H., Fortier, R., Fortier, P.
• Format: Article
• Language: English
• Subjects: chronosequence; Degradation; Ecological effects; Evolution; Groundwater; Groundwater data; Groundwater recharge; Groundwater table; hydrogeology; Land cover; Landscape; Lichens; Melting; Meltwater; Permafrost; Permafrost thaws; recharge; Shrubs; Snow; Soil; Soil degradation; Soil moisture; Soil water; Soils; Thawing; Thaws; Tundra; Vegetation; Water levels; Water table; water table fluctuation
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL087695

Temperatures in the arctic and subarctic are rising at more than twice the rate of the global average, driving the accelerated thawing of permafrost across the region. The impacts of permafrost degradation have been studied in the discontinuous permafrost zone at Umiujaq, in northern Quebec, Canada, for over 30 years, but the effects of changing land cover on groundwater recharge are not well understood. The water table fluctuation method was used to compute groundwater recharge using 4 years of water level data and soil moisture readings from five field sites characteristic of different stages of permafrost degradation and vegetation invasion. Results indicate that as vegetation grows taller, groundwater recharge increases, likely due to increased snow thickness. Results were then combined with a preexisting conceptual model that describes the evolution from tundra to shrubland and forests to create a new model for describing how groundwater recharge is affected by landscape evolution. Plain language summary Thawing permafrost (ground that is below 0°C for at least 2 years) allows for vegetation to grow in areas where growth was not previously possible. This paper examines how different types of vegetation affect the ability of water to infiltrate the soil and flow toward the water table, a process called groundwater recharge. Using field data from five typical types of vegetation in the discontinuous permafrost zone in northern Quebec, Canada, we estimated how much groundwater recharge occurred under these different types of vegetation: tundra/permafrost mound, lichens and herbs, lichens and low shrubs, medium shrubs, and trees. Based on the results, as the plants grow larger, more groundwater recharge is possible. This increase in recharge occurs because taller plants trap more snow in winter, resulting in the production of more meltwater in spring. We then combine our results with the findings from another study in the same area, which stated that the five types of land cover represent a model for how the landscape will change as the permafrost thaws. Our new combined model allows for the estimation of how groundwater recharge will change as a result of permafrost thaw and ecological change. Key Points Increased landcover height appears positively correlated with increased recharge As land cover increases in height, the date of the first recharge event in a given hydrologic year moves later into the summer Increased recharge is driven by greater snow t