Ecohydrology in Permafrost Systems: The Impact of Watershed Heterogeneity on Stream Flow Dynamics and Hydrologic Pathways

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The overall objective of this study is to quantify the relative roles of vegetation water use and soil water storage dynamics associated with permafrost presence/absence in determining the water flow pathways, mechanisms, timing and magnitudes in the sub-Arctic boreal forest ecosystem. This ecosystem is located in the zone of discontinuous permafrost and has two primary ecosystem types: permafrost free, deciduous dominated and permafrost affected, coniferous dominated. This study will integrate climatic, ecologic, thermal, and hydrologic processes through an intense field study program using hydrologic modeling. The field site comprises three catchments that represent a gradient of varying permafrost extent and ecosystem-type composition at the Caribou Poker Creeks Research Watershed (CPCRW) Long Term Ecological Research (LTER) site. In addition to stream flow observations, measurements of plant water use, soil moisture, seasonal soil thaw, and meteorologic variables will be collected along a north-facing (permafrost affected) coniferous dominated ecosystem to a south-facing (permafrost free) deciduous dominated ecosystem. Data from the field study will be used to develop and parameterize a vegetation water use model, which in turn will be integrated into a hybrid hydrologic model. Development of this semi-distributed, process-based hybrid hydrologic model will simulate the major hydrologic processes of the boreal forest ecosystem, emphasizing the water storage and release mechanisms. The boreal forest is a critical source of Alaska?s freshwater. This study will contribute to improved understanding and prediction of freshwater availability that will be affected by changes in permafrost and ecosystem distributions in the boreal forest. This study will also advance the field of ecohydrology, which is relatively under-explored in northern systems. The sub-Arctic environment will be the first in the Arctic to experience most of the current or expected climate-associated changes. Such changes have the potential to shift the magnitude and timing of freshwater delivery to the Arctic Ocean which is anticipated to lead to changes in sea-ice formation, thermohaline circulation, and ultimately the climate system from local to global scales. Outreach is an important aspect of this study. Teachers from local K-12 schools will participate in training workshops focused on the boreal forest ecosystem that will be conducted in conjunction with the Global Learning and Observations to Benefit the Environment program (GLOBE) program at the University of Alaska Fairbanks. Prior experience shows that the approach that will be used in this project is an effective means to integrate the natural science of the region into local classrooms.