Browsing by Author "Pomeroy, John"
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Item Advances in mapping sub-canopy snow depth with unmanned aerial vehicles using structure from motion and lidar techniques(Copernicus Publications on behalf of the European Geosciences Union, 2019) Harder, Phillip; Pomeroy, John; Helgason, Warren D.Vegetation has a tremendous influence on snow processes and snowpack dynamics yet remote sensing techniques to resolve the spatial variability of sub-canopy snow depth are lacking. Unmanned Aerial Vehicles (UAV) have had recent widespread application to capture high resolution information on snow processes and are herein applied to the sub-canopy snow depth challenge. Previous demonstrations of snow depth mapping with UAV Structure from Motion (SfM) and airborne lidar have focussed on non-vegetated surfaces or reported large errors in the presence of vegetation. In contrast, UAV-lidar systems have high-density point clouds, measure returns from a wide range of scan angles, and so have a greater likelihood of successfully sensing the sub-canopy snow depth. The effectiveness of UAV-lidar and UAV-SfM in mapping snow depth in both open and forested terrain was tested in a 2019 field campaign in the Canadian Rockies Hydrological Observatory, Alberta and at Canadian Prairie sites near Saskatoon, Saskatchewan, Canada. Only UAV-lidar could successfully measure the sub-canopy snow surface with reliable sub-canopy point coverage, and consistent error metrics (RMSE <0.17m and bias -0.03m to -0.13m). Relative to UAV-lidar, UAV-SfM did not consistently sense the sub-canopy snow surface, the interpolation needed to account for point cloud gaps introduced interpolation artefacts, and error metrics demonstrate relatively large variability (RMSE <0.33m and bias 0.08 m to -0.14m). With the demonstration of sub-canopy snow depth mapping capabilities a number of early applications are presented to showcase the ability of UAV-lidar to effectively quantify the many multiscale snow processes defining snowpack dynamics in mountain and prairie environments.Item Hydrology and Water Resources of Saskatchewan(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2005) Pomeroy, John; de Boer, Dirk; Martz, Lawrence W.There is little in the natural environment, economy and society of Saskatchewan that is not intimately tied to and sustained by the flow and storage of water. Nowhere else in Canada does the lack or excess of water cause such widespread concern, nor are there many Canadian environments subject to greater seasonal change in precipitation and surface-water storage. Most major landforms of Saskatchewan were created by the deposition and erosion of sediments and rock by water and ice during the glacial and immediate postglacial periods. Saskatchewan’s contemporary hydrology determines the type and location of natural vegetation, soils, agriculture, communities and commerce. However, the scarcity, seasonality and unpredictability of the province’s water resources have proved critical impediments to the productivity of natural ecosystems and to sustainable settlement and economic activity. The hydrology of Saskatchewan is marked by several distinctive characteristics that govern the behaviour of water as a resource in the province (Gray, 1970): i) The extreme variability of precipitation and runoff results in frequent water shortages and excesses with respect to natural and human storage capacities and demand. ii) The seasonality of water supply is manifest in fall and winter by the storage of water as snow, and lake and ground ice, in early spring by rapid snowmelt resulting in most runoff, and in late spring and early summer by much of the annual rainfall. iii) The aridity and gentle topography result in poorly developed, disconnected and sparse drainage systems, and surface runoff that is both infrequent and spatially restricted. iv) The land cover and soils exert an inordinate control on hydrological processes because of small precipitation inputs and limited energy for evaporation and snowmelt. v) The flows in the major rivers of the southern half of the province are largely derived from the foothills and mountains in Alberta. In dry years, arable agriculture can fail over large parts of the province, whilst in wet years, flooding has caused widespread damage to rural and urban infrastructure. Climate change may increase the incidence of both drought and flooding, with earlier spring thaws and increased interannual and interseasonal variability of temperature and precipitation (Covich et al., 1997; Cutforth et al., 1999, Herrington et al., 1997). Changes to the seasonal timing of precipitation can have very severe effects on agriculture and ecosystems; runoff to water bodies and replenishment of groundwater are primarily supplied by spring snowmelt, growth of cereal grains is related to the quantity of rainfall falling between May and early July, maturing and timely harvesting of crops are dependent upon warm dry weather in mid to late summer, and spring runoff is governed by soil moisture reserves in the preceding fall and snowfall the preceding winter (de Jong and Kachanoski, 1987). Saskatchewan’s water resources are vulnerable, as there is little local runoff to the single greatest water resource of the southern prairies, the South Saskatchewan River, which derives overwhelmingly from the Rocky Mountains. Water supplies in the Alberta portion of the South Saskatchewan River system are approaching full apportionment in dry years and the uncertainty imposed by climate change impacts on runoff generation in the mountains makes managing the river increasing difficult. Local water bodies (streams, sloughs, dugouts) are fed by groundwater or small surface drainages, and little runoff is provided by most land surfaces within the ‘topographic catchment’. The effect of soils and vegetation on Saskatchewan hydrology is profound because of the interaction of snow, evaporation and vegetation. In the southern Prairies, water applied from rain or snowmelt to summer-fallowed fields contributes inordinately to runoff, whereas continuously cropped fields, grasses and trees undergo greater infiltration to soils and hence greater evaporation. In the North, evergreen forest canopy and root structures promote infiltration of rainfall or snowmelt to soils and subsequent evaporation. There is much greater runoff and streamflow in boreal forest drainage basins with large cleared areas. This chapter will discuss the key physical aspects of Saskatchewan’s hydrology and water resources, focussing on its drainage basins and the contribution of runoff to streams and lakes within them, its major rivers and their flows, water supply pipelines and river diversions, prairie hydrology, boreal forest hydrology, groundwater and an assessment of the future. Because of its sub-humid, cold region hydrology and low population, water quality concerns in Saskatchewan are primarily related to algal growth in dugouts, and a few cases of contaminated groundwater or immediate downstream effects from sewage outflows, rather than widespread diffuse-source pollution; this chapter will therefore focus on water quantity rather than quality.Item Hydrometeorological, glaciological and geospatial research data from the Peyto Glacier Research Basin in the Canadian Rockies(Copernicus Publications, 2021) Pradhananga, Dhiraj; Pomeroy, John; Aubry-Wake, Caroline; Munro, D. Scott; Shea, Joseph; Demuth, Michael N.; Kirat, Nammy Hang; Menounos, Brian; Mukherjee, KritiThis paper presents hydrometeorological, glaciological and geospatial data from the Peyto Glacier Research Basin (PGRB) in the Canadian Rockies. Peyto Glacier has been of interest to glaciological and hydrological researchers since the 1960s, when it was chosen as one of five glacier basins in Canada for the study of mass and water balance during the International Hydrological Decade (IHD, 1965–1974). Intensive studies of the glacier and observations of the glacier mass balance continued after the IHD, when the initial seasonal meteorological stations were discontinued, then restarted as continuous stations in the late 1980s. The corresponding hydrometric observations were discontinued in 1977 and restarted in 2013. Datasets presented in this paper include high-resolution, co-registered digital elevation models (DEMs) derived from original air photos and lidar surveys; hourly off-glacier meteorological data recorded from 1987 to the present; precipitation data from the nearby Bow Summit weather station; and long-term hydrological and glaciological model forcing datasets derived from bias-corrected reanalysis products. These data are crucial for studying climate change and variability in the basin and understanding the hydrological responses of the basin to both glacier and climate change. The comprehensive dataset for the PGRB is a valuable and exceptionally long-standing testament to the impacts of climate change on the cryosphere in the high-mountain environment. The dataset is publicly available from Federated Research Data Repository at https://doi.org/10.20383/101.0259 (Pradhananga et al., 2020).Item Icefield Breezes: Mesoscale Diurnal Circulation in the Atmospheric Boundary Layer Over an Outlet of the Columbia Icefield, Canadian Rockies(Wiley [Commercial Publisher]; American Geophysical Union [Society Publisher], 2021) Conway, Jonathan; Helgason, Warren D.; Pomeroy, John; sicart, jeanAtmospheric boundary layer (ABL) dynamics over glaciers mediate the response of glacier mass balance to large-scale climate forcing. Despite this, very few ABL observations are available over mountain glaciers in complex terrain. An intensive field campaign was conducted in June 2015 at the Athabasca Glacier outlet of Columbia Icefield in the Canadian Rockies. Observations of wind and temperature profiles with novel kite and radio-acoustic sounding systems showed a well-defined mesoscale circulation developed between the glacier and snow-free valley in fair weather. The typical vertical ABL structure above the glacier differed from that expected for “glacier winds”; strong daytime down-glacier winds extended through the lowest 200 m with no up-valley return flow aloft. This structure suggests external forcing at mesoscale scales or greater and is provisionally termed an “icefield breeze.” A wind speed maximum near the surface, characteristic of a “glacier wind,” was only observed during nighttime and one afternoon. Lapse rates of air temperature down the glacier centerline show the interaction of down-glacier cooling driven by sensible heat loss into the ice, entrainment and periodic disruption and warming. Down-glacier cooling was weaker in “icefield breeze” conditions, while in “glacier wind” conditions, stronger down-glacier cooling enabled large increases in near-surface temperature on the lower glacier during periods of surface boundary layer (SBL) disruption. These results raise several questions, including the impact of Columbia Icefield on the ABL and melt of Athabasca Glacier. Future work should use these observations as a testbed for modeling spatio-temporal variations in the ABL and SBL within complex glaciated terrain.Item Prairie Hydrological Model Study Final Report(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2010) Pomeroy, John; Fang, Xing; Westbrook, Cherie; Minke, Adam; Guo, Xulin; Brown, TomThis report describes the development of the Prairie Hydrological Model (PHM), a model that is suitable for hydrological process simulations in the prairie pothole region of Western Canada. The model considers all major prairie hydrological cycle, wetland storage, and runoff generation mechanisms and is capable of addressing the influences of changing land use, wetland drainage and climate variability. The purpose of this report is to describe the model, examine the performance of the model, and to demonstrate the model as a predictive tool for prairie hydrology. This purpose is achieved by using the model to analyze the impacts of wetland drainage and restoration as well as changes in surrounding upland land use on downstream hydrology. This focus on wetland drainage impacts required the development and testing of a new volume-area-depth (v-a-h) method for estimating wetland volume in the prairie pothole region. The method was incorporated into the PHM and improved the model’s ability to estimate wetland volume. The Cold Regions Hydrological Model platform (CRHM) is a computational toolbox developed by the University of Saskatchewan to set up and run physically based, flexible, object oriented hydrological models. CRHM was used to create the PHM for Smith Creek Research Basin (~400 km2 ), Saskatchewan. Two types of PHM runs were performed to estimate the basin hydrology. The non-LiDAR (Light Detection and Ranging) runs used a photogrammetric based DEM (digital elevation model) to estimate drainage area and hydrograph calibration to determine maximum depressional storage. The LiDAR runs used a fine-scale LiDAR derived DEM to determine drainage area and maximum depressional storage; use of LiDAR information meant that calibration was not required to set any parameter value. In both cases all non-topographic parameters were determined from basin observations, remote sensing and field surveys. Both LiDAR and non-LiDAR model predictions of winter snow accumulation were very similar and compared quite well with the distributed snow survey results. The simulations were able to effectively capture the natural sequence of snow redistribution and relocate snow from ‘source’ areas (e.g. fallow and stubble fields) to ‘sink’ or ‘drift’ areas (e.g. tall vegetated wetland area and deeply incised channels). This is a vital process in controlling the water balance of prairie basins as most water in wetlands and prairie river channels is the result of redistribution of snow by wind and subsequent snowmelt runoff. Soil moisture status is an important factor in determining the spring surface runoff and in controlling agricultural productivity. Unfrozen soil moisture content at a point during melt was adequately simulated from both modelling approaches. Both modelling approaches were capable of matching the spring streamflow hydrographs with good accuracy; the non-LiDAR approach performed slightly better than the LiDAR approach because the streamflow hydrograph was calibrated, whereas no calibration was involved in the LiDAR simulation. However, the LiDAR approach to simulation shows promise for application to ungauged basins or to changing basins and demonstrates that prairie hydrology can be simulated based on our current understanding of physical principles and good basin data that provides “real” parameters. The approach uses a ii LiDAR DEM, SPOT 5 satellite images and involved automated basin parameters delineation techniques and a new wetland depth-area-volume calculation. The new wetland depth-area-volume calculation used a LiDAR-derived DEM to estimate maximum depressional storage, a substantial improvement over estimates generated from simpler area-volume methods. This was likely due to the inclusion of information on depression morphology when calculating volume. Further, the process to retrieve the coefficients from a LiDAR DEM was automated and wetland storage was estimated at a broad spatial scale. A GIS model was created that can automatically extract the elevation and area data necessary for use in the new depth-area-volume method. Using the Prairie Hydrological Model, PHM, a series of scenarios on changing land use and wetland and drainage conditions was created from 2007-08 meteorological data. The scenario simulations were used to calculate cumulative spring basin discharge, total winter snow accumulation, blowing snow transport and sublimation, cumulative infiltration, and spring surface depression storage status. From these simulations, spring streamflow volumes decreased by 2% with complete conversion to agriculture and by 79% with complete restoration of wetlands; conversely it increased by 41% with complete conversion to forest cover and by 117% with complete wetland drainage. The greatest sensitivity was to further drainage of wetlands which substantially increased streamflow. Additional sensitivity analysis of scenarios on basin streamflow using historical (29-year periods: 1965-82 and 1993-2005) meteorology and initial conditions and current land use was carried out. Results showed that the effects of land use change and wetland drainage alteration on cumulative basin spring discharge volume and peak daily spring discharge were highly variable from year to year and depended on the flow condition. For both forest conversion and agricultural conversion and wetland drainage scenarios increased the long-term average peak discharge from current conditions, whereas wetland restoration reduced it. Forest conversion, agricultural conversion and wetland drainage scenarios increased the long-term average spring discharge volume by 1%, 19%, and 36% respectively; whilst the wetland restoration scenario reduced volumes by 45%. Several recommendations were made regarding the modelling challenges faced by this study and value of local meteorological data collection and using a LiDAR generated DEM for Prairie hydrological modelling purposes. It is recommended that similar studies be conducted in other geographic areas of the prairies where climate, soils, wetland configuration and drainage may produce differing results.Item Sensitivity of extreme streamflow to wetland drainage and restoration in the Canadian Prairies(2023) He, Zhihua; Shook, Kevin; Spence, Christopher; Pomeroy, John; Whitfield, ColinItem Simulation of the impact of future changes in climate on the hydrology of Bow River headwater basins in the Canadian Rockies(Journal of Hydrology, 2023) Fang, Xing; Pomeroy, JohnItem Snow Surveys and Hydrometeorology Data Collection in 2009 Winter Field Season at Smith Creek Basin(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2009) Pomeroy, John; Westbrook, Cherie; Fang, Xing; Minke, Adam; Guo, XulinThis report describes the data collection being conducted in 2009 winter field season at Smith Creek Basin. The data collection consists of two components: snow surveys and hydrometeorology. The following sections explain the procedures of collecting these data and how a comparison to the data from last winter field season.Item Storms and Precipitation Across the continental Divide Experiment (SPADE)(American Meteorological Society (AMS), 2022) Thériault, Julie M.; Leroux, Nicolas; Stewart, Ronald; Bertoncini, André; Déry, Stephen J.; Pomeroy, John; Thompson, Hadleigh; Smith, Hilary; Mariani, Zen; Desroches-Lapointe, Aurélie; Mitchell, Selina; Almonte, JurisThe Canadian Rockies are a triple-continental divide, whose high mountains are drained by major snow-fed and rain-fed rivers flowing to the Pacific, Atlantic, and Arctic Oceans. The objective of the April–June 2019 Storms and Precipitation Across the continental Divide Experiment (SPADE) was to determine the atmospheric processes producing precipitation on the eastern and western sides of the Canadian Rockies during springtime, a period when upslope events of variable phase dominate precipitation on the eastern slopes. To do so, three observing sites across the divide were instrumented with advanced meteorological sensors. During the 13 observed events, the western side recorded only 25% of the eastern side’s precipitation accumulation, rainfall occurred rather than snowfall, and skies were mainly clear. Moisture sources and amounts varied markedly between events. An atmospheric river landfall in California led to moisture flowing persistently northward and producing the longest duration of precipitation on both sides of the divide. Moisture from the continental interior always produced precipitation on the eastern side but only in specific conditions on the western side. Mainly slow-falling ice crystals, sometimes rimed, formed at higher elevations on the eastern side (>3 km MSL), were lifted, and subsequently drifted westward over the divide during nonconvective storms to produce rain at the surface on the western side. Overall, precipitation generally crossed the divide in the Canadian Rockies during specific spring-storm atmospheric conditions although amounts at the surface varied with elevation, condensate type, and local and large-scale flow fields.Item Towards a coherent flood forecasting framework for Canada: Local to global implications(Chartered Institution of Water and Environmental Management and John Wiley & Sons Ltd., 2023) Arnal, Louise; Pietroniro, Alain; Pomeroy, John; Fortin, Vincent; Casson, David; Stadnyk, Tricia; Rokaya, Prabin; Durnford, Dorothy; Friesenhan, Evan; Clark, Martyn P.Operational flood forecasting in Canada is a provincial responsibility that is carried out by several entities across the country. However, the increasing costs and impacts of floods require better and nationally coordinated flood prediction systems. A more coherent flood forecasting framework for Canada can enable implementing advanced prediction capabilities across the different entities with responsibility for flood forecasting. Recently, the Canadian meteorological and hydrological services were tasked to develop a national flow guidance system. Alongside this initiative, the Global Water Futures program has been advancing cold regions process understanding, hydrological modeling, and forecasting. A community of practice was established for industry, academia, and decision-makers to share viewpoints on hydrological challenges. Taken together, these initiatives are paving the way towards a national flood forecasting framework. In this article, forecasting challenges are identified (with a focus on cold regions), and recommendations are made to promote the creation of this framework. These include the need for cooperation, well-defined governance, and better knowledge mobilization. Opportunities and challenges posed by the increasing data availability globally are also highlighted. Advances in each of these areas are positioning Canada as a major contributor to the international operational flood forecasting landscape. This article highlights a route towards the deployment of capacities across large geographical domains.Item Using ground-based thermal imagery to estimate debris thickness over glacial ice: fieldwork considerations to improve the effectiveness(Cambridge University Press, 2022) Aubry-Wake, Caroline; Lamontagne-Hallé, Pierrick; Baraër, Michel; McKenzie, Jeffrey; Pomeroy, JohnDebris-covered glaciers are an important component of the mountain cryosphere and influence the hydrological contribution of glacierized basins to downstream rivers. This study examines the potential to make estimates of debris thickness, a critical variable to calculate the sub-debris melt, using ground-based thermal infrared radiometry (TIR) images. Over four days in August 2019, aground-based, time-lapse TIR digital imaging radiometer recorded sequential thermal imagery of a debris-covered region of Peyto Glacier, Canadian Rockies, in conjunction with 44 manual excavations of debris thickness ranging from 10 to 110 cm, and concurrent meteorological observations. Inferring the correlation between measured debris thickness and TIR surface temperature as a base, the effectiveness of linear and exponential regression models for debris thickness estimation from surface temperature was explored. Optimal model performance (R2 of 0.7, RMSE of10.3 cm) was obtained with a linear model applied to measurements taken on clear nights just before sunrise, but strong model performances were also obtained under complete cloud cover during daytime or nighttime with an exponential model. This work presents insights into the use of surface temperature and TIR observations to estimate debris thickness and gain knowledge of the state of debris-covered glacial ice and its potential hydrological contribution.Item WDPM: the Wetland DEM Ponding Model(Open Journals, 2021) Shook, Kevin R.; Spiteri, Raymond; Pomeroy, John; Liu, Tonghe; Sharomi, OluwaseunThe hydrography of the Canadian Prairies and adjacent northern US Great Plains is unusual in that the landscape is flat and recently formed due to the effects of pleistocene glaciation and a semi-arid climate since holocene deglaciation. Therefore, there has not been sufficient energy, time, or runoff water to carve typical dendritic surface water drainage networks in many locations. In these regions, runoff is often detented and sometimes stored by the millions of depressions (known locally as “potholes” or “sloughs”) that cover the landscape. Conventional hydrological models are unable to simulate the spatial distribution of ponded water in prairie basins dominated by depressional storage. When the depressions are filled, the detented water may overflow to another depression, through a process known as “fill and spill” (Spence & Woo, 2003). Therefore, the fraction of a depression-dominated prairie basin that contributes flow to the outlet changes dynamically with the state of water storage within the basin. The WDPM simulates the spatial distribution of ponded water, as it is added, removed or drained, and can be used to calculate the changing connected/contributing fraction of a prairie basin.Item Windmapper: An Efficient Wind Downscaling Method for Hydrological Models(Wiley Online Library, 2023) Marsh, Christopher; Vionnet, Vincent; Pomeroy, JohnEstimates of near-surface wind speed and direction are key meteorological components for predicting many surface hydrometeorological processes that influence critical aspects of hydrological and biological systems. However, observations of near-surface wind are typically spatially sparse. The use of these sparse wind fields to force distributed models, such as hydrological models, is greatly complicated in complex terrain, such as mountain headwaters basins. In these regions, wind flows are heavily impacted by overlapping influences of terrain at different scales. This can have a great impact on calculations of evapotranspiration, snowmelt, and blowing snow transport and sublimation. The use of high-resolution atmospheric models allows for numerical weather prediction (NWP) model outputs to be dynamically downscaled. However, the computation burden for large spatial extents and long periods of time often precludes their use. Here, a wind-library approach is presented to aid in downscaling NWP outputs and terrain-correcting spatially interpolated observations. This approach preserves important spatial characteristics of the flow field at a fraction of the computational costs of even the simplest high-resolution atmospheric models. This approach improves on previous implementations by: scaling to large spatial extents O(1M km2); approximating lee-side effects; and fully automating the creation of the wind library. Overall, this approach was shown to have a third quartile RMSE 𝐴𝐴of 1.8 m ⋅ s−1 and a third quartile RMSE of 58.2° versus a standalone diagnostic windflow model. The wind velocity estimates versus observations were better than existing empirical terrain-based estimates and computational savings were approximately 100-fold versus the diagnostic model.Item Yukon River Basin Streamflow Forecasting System - Advancing, Calibrating, Demonstrating Snow Assimilation and Estimating Ungauged Basin Flow: The Vector-Based MESH Model of the Yukon River Basin(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2023) Elshamy, Mohamed; Pomeroy, John; Pietroniro, AlainThe Yukon River Basin the second largest river in the Arctic region of North America and is shared between Canada and the US. The Canadian part covers almost half of the Yukon Territory in addition to a small portion of the province of British Columbia, while the US part falls totally within the state of Alaska. This study is concerned with Canadian part of the Yukon River with its outlet at Eagle, Alaska - just downstream of the international boundary (288,000 km2). The southern part of the Yukon River basin is characterized by extensive icefields and snowfields at high elevations (up to 4700 m above sea level) with steep slopes, and thus generates considerable runoff. There are also mountain ranges on the eastern and northern boundaries of the basin, while the western areas are milder in slope and partially forested. Snow redistribution by wind, snowmelt, glacier melt and frozen soil processes in winter and spring along with summertime rainfall-runoff and evapotranspiration processes are thus key to the simulation of streamflow in the basin. This supplement shows further development of a vector-based MESH setup for the Canadian portion of the Yukon River Basin down to Eagle, Alaska. For operational forecasting, MESH is driven by the Environment and Climate Change Canada Global Multiscale Model (GEM) weather model forecasts with precipitation replaced with the Canadian Precipitation Analysis (CaPA) which assimilates local precipitation observations where they exist, collectively referred to as GEM-CaPA. Additionally, the newly developed Regional Deterministic Reforecast System v2.1 (RDRS v2.1) forcing has been extended to span the period 1980-2018 enabling long-term assessments of hydrology. The revised vector-based model was calibrated for operational use based on the GEM-CaPA forcing dataset, and for performing historical simulations based on the RDRS v2.1 forcing dataset, using the period 2004-2011 in both cases. Performance was compared to the previously generated grid-based MESH model whose development was documented in Centre for Hydrology Report #16. A long-term historical simulation was then performed using RDRS v2.1 from which streamflow exceedance return periods for 15 important stations were calculated and presented in this supplement. Calibration has generally improved the performance of the vector-based setup compared to the previous simulations presented in supplement #1 of report #16. Parameter sets are slightly different when the model is calibrated to RDRS v2.1 compared to GEM-CaPA due to differences between the two datasets. A pilot study of the potential benefits of snow data assimilation into the existing MESH forecast system was conducted using historical data and the gridded MESH product that is used operationally by Yukon Environment. This test showed benefits to assimilating surface snowpack observations into MESH to correct winter precipitation. Outputs with assimilation showed improved snowpack simulations and improved streamflow forecasts.Item Yukon River Basin Streamflow Forecasting System - Vector-Based MESH Model Setup for Yukon River Basin(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2022) Aygun, Okan; Elshamy, Mohamed; Pietroniro, Alain; Pomeroy, JohnThe Yukon River Basin the second largest river in the Arctic region of North America and is shared between Canada and the US. The Canadian part covers almost half of the Yukon Territory in addition to a small portion of the province of British Columbia, while the US part falls totally within the state of Alaska. This study is concerned with Canadian part of the Yukon River with its outlet at Eagle, Alaska - just downstream of the international boundary (288,000 km2). The southern part of the Yukon River basin is characterized by extensive icefields and snowfields at high elevations (up to 4700 m above sea level) with steep slopes, and thus generates considerable runoff. There are also mountain ranges on the eastern and northern boundaries of the basin, while the western areas are milder in slope and partially forested. Snow redistribution by wind, snowmelt, glacier melt and frozen soil processes in winter and spring along with summertime rainfall-runoff and evapotranspiration processes are thus key to the simulation of streamflow in the basin. This supplement shows the development of a vector-based MESH setup for the Canadian portion of the Yukon River Basin at Eagle. Without additional calibration, the vector-based model performance was compared to the previously generated grid-based MESH model whose development was documented in Centre for Hydrology Report #16. MESH was driven by the Environment and Climate Change Canada Global Multiscale Model (GEM) weather model forecasts with precipitation replaced with the Canadian Precipitation Analysis (CaPA) which assimilates local precipitation observations where they exist, collectively referred to as GEM-CaPA. Additionally, the models were run, without additional calibration using the newly developed Regional Deterministic Reforecast System v2 (RDRS v2) forcing. RDRS v2 forcing is being extended as a hindcast by ECCC to approx. 1980 and so will permit 40 year runs of MESH from which streamflow exceedance return periods can be calculated. Model performance was slightly inferior for the vector-based setup compared to the original grid-based one. This may be due to the full calibration applied to the grid-based model and parameter transfer to the vector-based model without recalibration. Model performance also deteriorated when the RDRS v2 was used as forcing data, as the model was originally calibrated to GEM-CaPA. It is expected that model performance will improve once it is fully calibrated using the RDRS v2 forcing data.