NWT RESEARCH DATABASE

Regions: Dehcho Region

Tags: physical sciences, permafrost, hydrology, prediction models, permafrost thaw

Objective(s): To improve the understanding, parameterisation and prediction of water flow and storage processes in peatland-dominated, thawing, discontinuous permafrost.

Project Description: This licence has been issued for the scientific research application No.5120. The long-term objective of this research program is to improve the understanding, parameterisation and prediction of water flow and storage processes in peatland-dominated, thawing, discontinuous permafrost. Over the next 5 years, significant progress toward this long term objective will be made through the following short-term objectives: 1: Define the changing spatial distribution of permafrost, wetland and forest cover over the past 70 years from aerial/satellite remote sensing; 2: Conduct field studies to improve the understanding of the a) rates, patterns, controls and causes of permafrost thaw and resulting land-cover changes, and b) water flux and storage processes within peat plateau-bog complexes, runoff from such complexes, conveyance along channel fens, and how such process change with permafrost thaw; 3: Develop a new method to simulate thaw of discontinuous permafrost and the resulting land cover changes; 4: Simulate the major water flux and storage processes controlling runoff from plateau-bog complexes and routing along fens using complementary hydrological models, and improve the models using new knowledge from 2; and, 5: Use the permafrost and hydrological simulations to estimate future quantities of runoff from wetland-dominated basins with discontinuous permafrost under possible scenarios of warming-induced permafrost thaw. This research will inform the development of new parameterisations and numerical descriptions of permafrost thaw, land cover changes, and water flow and storage processes. The research team will develop new knowledge on the rates, patterns, controls and causes of local permafrost change needed for simulation and improved prediction (S. Wright). The team will identify the processes driving permafrost thaw, thresholds and feedbacks that may alter thaw rates and patterns, and insights into trajectories of thaw-induced land cover change. Mass and energy flux data collected at Scotty Creek since 1999 from permafrost, transitional and permafrost-free land covers will be examined to identify causal linkages between site characteristics and thaw rates, and improve conceptual and numerical models of permafrost thaw. This research will provide new knowledge on the interactions among climatological, hydrological and permafrost systems, and how they vary among sites with contrasting bio-physical characteristics. Changes in site characteristics over time, and spatial variations of such characteristics among different sites, will isolate the drivers of change and identify thresholds leading to state changes in land covers in response to thaw. The team will then measure seasonal ground thaw and document and characterise the occurrence of talik. The rate of snowmelt and active layer thaw, and the occurrence and thickness of talik will be documented for contrasting biophysical sites from point measurements at representative transects. These will begin at the time of maximum snow water equivalent (SWE). As snow disappears, SWE measurements at 1-m intervals will be superseded by measurements of depth to the FT, and of near surface (0-10 cm) soil moisture. The same transects will be used at end of winter (mid-March) to determine depth of refreeze using an ice auger at selected points along each transect. From the measured thaw and re-freeze depths, the active layer and talik thicknesses for each point will be derived. Taliks will be identified as connected or isolated, and their growth and connectivity will be monitored annually. The team will examine the major runoff and storage processes of the plateaus and wetlands and how they change with permafrost thaw (I. Thomson/S. Wright). Overland flow will be measured continuously at gauging stations near the outlets of selected bog cascades. A rating curve will be developed for each station from continuous stage (pressure transducer) and discrete discharge (v-notch weir) measurements. The sub-surface runoff rate, (m day-1) of the ephemeral channels connecting the bogs of each gauged cascade, will be computed using the Dupuit-Forchheimer assumptions, with the saturated hydraulic conductivity (K) estimated as a function of depth. The thickness and depth of the saturated layer will be derived from water table (WT) measurements along the channels. WT depth will be measured and recorded every 30 minutes at both ends of each transect continuously to estimate the hydraulic gradient. Over-winter flow through the connected taliks identified and monitored and will be quantified using passive flux metres installed in August, 2020. The team will examine the wetlands previously identified to have transitioned to a hydrologically-connected state. For each identified wetland, the time since onset of hydrological connection will be defined, and the present vegetation and micro-topography will be characterised and compared with reference wetlands that are still isolated. High-resolution digital elevation models (DEMs) will be generated for each identified wetland from Lidar or optical data and used to quantify wetland surface roughness, areas occupied by hummock and inter-hummock zones, hummock sizes and densities, and tortuosity of inter-hummock pathways. The DEMs will be used with WT data to examine 1) if water moves preferentially through interhummock zones, 2) if hummocks obstruct flow causing water to follow tortuous flowpaths, and 3) if hummocks retard wetland runoff by abstracting water during high flows, then releasing it during low flows. At Scotty Creek, archived WT data collected since 1999 will also be used to quantify changes to the average annual water storage of wetlands, including isolated wetlands and those that developed connections prior to or since 1999. The team will quantify changes in precipitation and stream flow for the areas of reconstructed permafrost loss using hydrometric records (I. Thomson). Seasonal and annual runoff ratios will be computed for all Primary and Secondary basins to characterise their present runoff response for a range of antecedent moisture conditions. The magnitude of the observed increase in discharge since the mid-1990s will be quantified and the relative contributions of 1) source area expansion and 2) water released from wetlands that became hydrologically-connected, will be quantified. Other possible contributions to increasing discharge, including groundwater and changes in precipitation patterns, will be evaluated. Drive-point piezometers ranging in depth from 1 m (surface peat) to 4 m (glacial deposit) were installed in cascade bogs at Scotty in August, 2021. Preliminary measurements suggest that the upstream bogs of cascades recharge ground water systems while bogs at lower elevations (i.e. downstream) receive groundwater, although the source of groundwater input is not yet known. The team will examine key basin-scale flow routing processes at Scotty Creek to improve conceptual and numerical models of governing processes for use at all Nodes (S. Wright). New gauging stations will be installed along the main drainage courses of the channel fens at the Primary basins to collect data for testing several roughness-based routing algorithms (e.g. Manning equation). The research team continue to liaise with the Lidlii Kue and Jean-Marie First Nations. Annual reports to the Aurora Research Institute, and publications will be sent to the communities each year. The Principal Investigator also visits as many of the band offices and government agencies when in the Fort Simpson region. Dissemination and outreach is enhanced through the 10-year (2010- 2020) Partnership Agreement between Laurier and the GNWT. Recently the Partnership appointed a community Liaison to facilitate two-way communication with communities. Examples of direct community engagement include: Dehcho K’Ehodi: Scotty researchers participate in Dehcho K’Ehodi Regional gatherings so that the Scotty Creek Research Station is available and prepared to assist with helping to train the Dehcho Guardians. This is an opportunity to update Dehcho communities on research/training/engagement activities of the SCRS. Scotty Creek Field Course: The research team will host a one-week field course at the SCRS in February of March of each year for high school environmental science students (grades 10-12) from the Dehcho Region. Scotty researchers collaborate with the Dehcho Guardians to monitor permafrost conditions along the Enbridge pipeline (Line 21). This involved training of Guardians for permafrost monitoring (May, 2018), and collaboration with Guardians on permafrost monitoring of the pipeline (May - Aug., 2019), and geophysical measurements along the pipeline (Sept., 2019) in collaboration with Guardian teams. We continue to collaborate with Guardians with on-going monitoring of Line 21 and other areas of concern to the Dehcho. Scotty researchers in collaboration with the DFN co-proposed the Dehcho collaborative on permafrost (DCoP), a three-year programme designed to improve the capacity of the Dehcho to manage permafrost thaw. The fieldwork for this study will be conducted from March 1, 2022 to September 01, 2022.