Centre for Hydrology Reports

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Global Water Futures Observatories : a solutions oriented network of world class observation sites and laboratories
(2024-03) DeBeer, Chris
Global Water Futures Observatories vision, principles of operation, and Priority Research Support Directions 2023-2029.
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, Alain
The 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.
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, John
The 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.
Climate Change in Canadian Floodplain Mapping Assessments
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2020) Rajulapati, Chandra Rupa; Tesemma, Zelalem; Shook, Kevin; Papalexiou, Simon Michael; Pomeroy, John W.
In the recent decades, precipitation patterns and corresponding streamflow responses in many cold regions catchments have changed considerably due to warming. Understanding historical changes and predicting future responses are of great importance for planning and management of water resources systems. Regional climate simulations using convention- permitting models are helpful in representing the fine-scale cloud and mesoscale processes, which are critical for understanding the physical mechanisms that cause in convective precipitation. From a hydrological perspective, these fine resolution simulations are helpful in understanding the runoff generation mechanisms, particularly for mountainous watersheds, which have high spatial variation in precipitation due to large differences in elevation over small distances. The sister-study of this report, the Bow River Basin Study (BRBS), used a physically based hydrological land surface scheme along with a water management model, coupled with a high resolution convention- permitting atmospheric regional model (Weather Research and Forecasting, WRF) to understand the streamflow generating mechanisms and identify the changes in streamflow responses of the Bow and Elbow River Basins. The coupled model appears to provide a large improvement in predictability, with minimal calibration of parameters and without bias correction of forcing from the atmospheric model. The model4 was able to provide reliable estimates of streamflows, despite the complex topography in the catchment. Using the WRF Pseudo Global Warming (PGW) scenario, estimated future streamflows simulated were then used to develop projected flow exceedance curves. The uncertainty in the simulations is extremely helpful in the risk assessment for downstream flood inundations. However, the uncertainty in streamflows cannot be assessed as the WRF- PGW dataset was only available for a single realization, because of the high computational cost. The research presented in this report focusses instead on using the highly efficient hydrological model developed and verified in BRBS whilst assessing uncertainty using another regional climate model, the CanRCM4, where many realizations are available for different boundary conditions. Since the CanRCM4 simulations have a relatively low resolution, a novel methodology was developed to adjust regional climate model outputs using the WRF-PGW data. An ensemble of 15 CanRCM4 simulations was used to force the Bow River basin model to determine a measure of the uncertainty in the simulated streamflows, and the projected streamflow exceedance probability curves. These curves are extremely useful for risk assessment for downstream flood inundations. Given the importance of understanding how much extreme precipitation will change in urban areas of the basin, where short duration high intensity events cause flash flooding, frequency analysis of these events was carried out for Calgary and Intensity Duration Frequency (IDF) curves were developed. A ready-to-use empirical form of IDF curve has been proposed from this analysis for the City of Calgary. The results from the WRF-PGW modelling indicated that future high flow, low frequency (exceedances less than 10%) streamflow events will decrease compared to those under the current climate condition by 4, 9 and 1.6 m3/s for the Bow River at Banff and Calgary and Elbow River at Sarcee Bridge respectively. The average of the 15 new CanRCM4-WRF-PGW results supports the above result with some greater decreases in streamflow of 9, 16 and 4 m3/s for Bow River at Banff and Calgary and Elbow River at Sarcee Bridge respectively. However, there were some CanRCM4-WRF-PGW realisations that suggested substantial increases in future low frequency streamflow from those indicated by the average CanRCM4- WRF-PGW-drive MESH model. The below average, high frequency (exceedances greater than 30%) future streamflows will increase modestly in all gauging locations by from 1 to 12.5 m3/s. The results of the extreme precipitation analysis at Calgary indicated an increase in future extreme precipitation events of all duration and return periods. On an average an increase of 1.5 times is noted for short return periods (=2, 5), and an increase of 4 times for long return periods (=500, 1000).
Yukon River Basin Streamflow Forecasting System
(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2020) Elshamy, Mohamed; Loukili, Youssef; Princz, Daniel; Richard, Dominique; Tesemma, Zelalem; Pomeroy, John W.
The Yukon River Basin is one of the main rivers 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, just across the border in Alaska. Small parts of this catchment are in Alaska. This basin has an area of 288,000 km2, from 58.8 – 65.6°N and 129.2 – 134.1°W. The southern part of the basin is characterized by large glaciers 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, 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 project developed, set up, calibrated, validated, and operationalized a streamflow discharge forecasting system for the Yukon River and several of its tributary rivers within the Yukon Territory. The Yukon River Basin streamflow forecasting system is based around the MESH (Modélisation Environmentale Communautaire - Surface and Hydrology) hydrological land surface model. MESH is a state-of-the-art semi-distributed cold regions hydrological land surface model that models both the vertical exchanges of heat and moisture between the land surface and the atmosphere as well has the horizontal transfer of water to streams that is routed hydrologically to the outlet of the basin. It includes snow, frozen soil and glacier processes as well as the full suite of warm season hydrology. MESH is driven by the Environment and Climate Change Canada GEM weather model and hindcasts are driven by GEM-CaPA which is a data assimilation product that uses local precipitation observations where they exist. The rivers forecasted includes the Yukon River Basin upstream of Eagle, AK and the Porcupine River Basin near the international boundary. MESH provides supplemental high resolution simulations and forecasts for the Klondike, Stewart, Pelly and White Rivers at their mouths. Daily river discharge and water balance forecasts are produced by the system for each river basin. Having MESH run at both 10 km and 5 km resolution provides an assessment of model resolution needed for forecasting and also of model uncertainty in the forecasts. The MESH model was driven by GEM-CaPA for hindcasts and with the GEM ECCC Regional and Global Deterministic Prediction Systems - RDPS and GDPS forecasts for forecasts of 2 and 9 days. The GEM-MESH model showed good to very good predictions in most river basins after calibration and parameter selection, with challenges for the Porcupine and White rivers due to permafrost and wetlands (Porcupine) and to extensive icefields (White) and overall to sparse to non-existent observed precipitation data to assimilate into the CaPA system. The forecast system is capable of providing reliable streamflow predictions and is run with automated scripts on Amazon Web Services. Future development of the forecasting system should focus on the very challenging permafrost hydrology of the Porcupine River Basin, and the glacier hydrology of the White River which drains the largest icefields in North America. The model does not include a river ice component, but one could be added in the future.
Diagnosis of Historical and Future Flow Regimes of the Bow River at Calgary Using a Dynamically Downscaled Climate Model and a Physically Based Land Surface Hydrological Model : Final Report
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2020) Tesemma, Zelalem; Shook, Kevin; Princz, Daniel; Razavi, Saman; Davison, Bruce; Li, Yanping; Pietroniro, Alain; Pomeroy, John W.; wheater, howard
This report assesses the impacts of projected climate change on the hydrology, including the flood frequencies, of the Bow and Elbow Rivers above Calgary, Alberta. It reports on investigations of the effects of projected climate change on the runoff mechanisms for the Bow and Elbow River basins, which are important mountain headwaters in Alberta, Canada. The study developed a methodology and applied a case study for incorporating climate change into flood frequency estimates that can be applied to a variety of river basins across Canada.
The Changing Hydrology of Lhù’ààn Mǟn - Kluane Lake - under Past and Future Climates and Glacial Retreat
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2018) Loukili, Youssef; Pomeroy, John W.
The goal of this report is to estimate the variability and changes in the lake levels of Kluane Lake over the historical period and into the future climates of the 21st C, with and without the Kaskawulsh Glacier contribution. The study diagnoses the causes of variability of lake levels in the past and evaluates the impact of deglaciation on lake levels in the future in the context of climate change. The methods use a combination of weather data from observations and global climate models to drive a detailed glacio-hydrological prediction model, which calculates streamflows in the Slims River and other inflows to Kluane Lake, lake evaporation and outflows and then the lake level. Historical Kluane Lake levels during the 20th C and future lake levels under global warming projections for the rest of the 21st C were predicted - with and without the Kaskawulsh Glacier contribution to the Slims River. The Canadian glacio-hydrological water prediction model MESH, which couples the Canadian Land Surface Scheme with both surface and subsurface runoff on slopes and river routing, was used to model the hydrology of the Kluane Lake Basin for these predictions. The adjacent gauged Duke River Basin was also included in the model to provide opportunities to evaluate the model performance in this region against gauged streamflows. Model parameterisations of topography, land cover, glacier cover, soil type and runoff directions were made and used to set up the model on various sub-basins flowing into Kluane Lake, including the Slims River Basin. The results drawn from this study are intended to answer important questions posed by Kluane First Nation of Burwash Landing, residents of Destruction Bay and surrounding areas and Yukon Government on the history and the future of Kluane Lake levels. Furthermore, the study will help inform water management and infrastructure design around Kluane Lake, and other environmental and aquatic conservation and adaptation efforts in the region. While the models employed here represent the “state-of-the-art”, there is uncertainty in the predictions. This uncertainty could be reduced in future prediction efforts by resuming Kluane River discharge measurements, which were discontinued in 1994.
Improving and Testing the Prairie Hydrological Model at Smith Creek Research Basin
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2014) Pomeroy, John W.; Shook, Kevin; Fang, Xing; Dumanski, Stacey; Westbrook, Cherie; Brown, Tom
The 2010 Prairie Hydrological Model configuration of the Cold Regions Hydrological Model was developed to include improved snowmelt and evaporation physics and a hysteretic relationship between wetland storage and runoff contributing area. The revised model was used to simulate the snow regimes on and the streamflow runoff from the five sub-basins and main basin of Smith Creek, Saskatchewan for six years (2007-2013) with good performance when compared to field observations. Smith Creek measured streamflows over this period included the highest annual flow volume on record (2011) and high flows from heavy summer rains in 2012. Smith Creek basin has undergone substantial drainage from 1958 when it contained 96 km2 of wetlands covering 24% of the basin area to the existing (2008 measurement) 43 km2 covering 11% of the basin. The Prairie Hydrological Model was run over the 2007-2013 period for various wetland extent scenarios that included the 1958 historical maximum, measured extents in 2000 and 2008, a minimum extent that excluded drainage of conservation lands and an extreme minimum extent involving complete drainage of all wetlands in Smith Creek basin. Overall, Smith Creek total flow volumes over six years increase 55% due to drainage of wetlands from the current (2008) state, and decrease 26% with restoration to the 1958 state. This sensitivity in flow volume to wetland change is crucially important for the water balance of downstream water bodies such as Lake Winnipeg. Whilst the greatest proportional impacts on the peak daily flows are for dry years, substantial impacts on the peak daily discharge of record (2011) from wetland drainage (+78%) or restoration (-32%) are notable and important for infrastructure in and downstream of Smith Creek. For the flood of record (2011), the annual flow volume and the peak daily discharge are estimated to increase from 57,317 to 81,227 dam3 and from 19.5 to 27.5 m3 /s, respectively, due to wetland drainage that has already occurred in Smith Creek. Although Smith Creek is already heavily drained and its streamflows have been impacted, the annual flow volumes and peak daily discharge for the flood of record can still be strongly increased by complete drainage from the 2008 wetland state, rising to 103,669 dam3 and 49 m3 /s respectively. This model simulation exercise shows that wetland drainage can increase annual and peak daily flows substantially, and that notable increases to estimates of the annual volume and peak daily flow of the flood of record have derived from wetland drainage and will proceed with further wetland drainage.
Development of a Snowmelt Runoff Model for the Lower Smoky River
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2013) Pomeroy, John W.; Shook, Kevin; Fang, Xing; Brown, Tom; Marsh, Christopher
The Smoky River tributary of the Peace River has an ungauged (in real-time) basin area of 23,769 km2, corresponding to 46% of its basin area of 51,839 km2 . The purpose of this study was to develop a model to simulate the daily spring ungauged flows of the Smoky River and its main tributary, the Little Smoky River for recent periods using measured meteorological data and forecast periods using the outputs of a numerical weather forecast model. A physically-based model of the ungauged local flows contributing to the Smoky River at Watino and the Little Smoky River at Guy, the Lower Smoky River Model (LSRM), was developed using the CRHM platform. The model was deployed to 26 ungauged sub-basins, from which discharges were routed and accumulated to produce the ungauged discharges at Guy and Watino. The LSRM modelled discharge was evaluated to estimate the discharge of the Smoky River and Little Smoky River in an operational setting with measured meteorological observations. Results from this comparison were very good with a high degree of hydrograph predictability, small bias in flow estimation, and very good prediction of peak daily discharge and excellent prediction of the timing of peak daily discharge. The results were somewhat better for the Smoky River than for the Little Smoky River, showing the effect of increasing basin size in compensating for inadequate precipitation observation density and/or errors in model structure or parameterization. The model has not yet been tested in an operational setting during a spring snowmelt event and its full capabilities and usefulness cannot be assessed until it has been tested in such a setting.
Informing the Vermilion River Watershed Plan through Application of the Cold Regions Hydrological Model Platform
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2012) Pomeroy, John W.; Fang, Xing; Shook, Kevin; Westbrook, Cherie; Brown, Tom
The Vermilion River Basin has been identified as one of most altered basins in the North Saskatchewan River Basin by the North Saskatchewan Watershed Alliance. Of all the basin altering activities, wetland drainage is thought to be the most important one in impacting watershed hydrology. The Cold Regions Hydrological Model (CRHM) has had recent developments that make it particularly appropriate to evaluate the impacts of Canadian Prairie wetlands on hydrology. In light of the importance of wetlands in the Vermilion River Basin and the capability of CRHM, this study had five objectives: 1) Setup CRHM for the Vermilion River Basin and conduct preliminary tests using local meteorological data. 2) Develop an improved wetland module that incorporates the dynamics of drained wetland complexes in the physically based, modular Prairie Hydrological Model of CRHM. 3) Refine CRHM results using advances in the improved wetland module, additional parameter data and other adjustments as necessary. 4) Demonstrate scenarios/sensitivity of landscape components such as wetlands and uplands to support planning decisions and make recommendations for land and watershed management. 5) Apply CRHM results to fortify recommendations and support decision making during initial plan implementation. The objectives were addressed with the following methodology. Existing data on precipitation, hydrometeorology, wetland characteristics, stage and extent, drainage pattern and land cover in the Vermilion River Basin were compiled. The existing CRHM Prairie Hydrological Model formulation was set up on the basin and test runs conducted and compared to streamflow hydrographs over multiple years. Then, improvements to the Prairie Hydrological Model formulation of CRHM were made so that CRHM could simulate sequences of many wetlands of varying sizes. The improved model was evaluated through hydrological simulation and quantitative analysis of streamflow and then used in sensitivity analysis of the effect of changing wetland drainage/restoration on streamflow for the Vermilion River. The model was then used to evaluate wetland manipulation and climate scenarios to fortify recommendations, explore options and support decision making for the implementation of the Vermilion watershed plan. The streamflow response of the Vermilion River Basin at its mouth was found to be dominated by channel hydraulics and the control structures in the lower basin and so it is influenced by wetlands only to the extent that the management regime of these control structures is affected by upstream hydrological behaviour of the tributaries with respect to volume and timing of streamflow inputs to the structures. Changes in the upper basin streamflows are more likely to be controlled by changes in the basin hydrological processes rather than in-stream water management and/or channel modifications and therefore the upper basin streamflows are more likely to show the effects of the manipulation of wetland storage.
Review of Lake Diefenbaker Operations 2010-2011 : Centre for Hydrology Final Report to the Saskatchewan Watershed Authority
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2012) Pomeroy, John W.; Kevin Shook
Analysis of the Lake Diefenbaker operation and hydrometeorological events of 2010-2011 suggests that minimum reservoir levels have been rising over time and were particularly high in the winter and spring of 2010-2011 resulting in a greater risk of high outflow events if predicted inflows were not accurate. Rules and policies for operating Gardiner Dam based on verified information and priority of operations to minimize cumulative risk were not in place to optimize dam operations after several mid winter events restricted outflows from the dam. Unfortunately inflows were underpredicted in 2011 due to underestimation of upstream snowpacks, inability to quantify ungauged inflows from prairie runoff, inadequate available information on upstream and local meteorological conditions, and reliance on statistical forecast procedures based on previous climate conditions. The impact of outflows on downstream areas was difficult to quantify because of an underestimation of outflows from the Coteau Creek hydroelectric station at Gardiner Dam and the lack of sufficient hydrometric stations downstream. Whilst water supply goals for the reservoir were met in the period, and downstream flood extent was cut in half; the acreage duration of flooding between Moon Lake and Saskatoon was not reduced by dam operation and the annual peak flow downstream on the Saskatchewan River was not reduced by dam operation. The overall evaluation of SWA operation of Lake Diefenbaker in light of the operational objectives understood at the time is that SWA forecasting staff did a superb job with the limited tools and resources, complex operating system and unspecified operating rules available to them.
Wetland Drainage Effects on Prairie Water Quality : Final Report
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2011) Westbrook, Cherie; Brunet, Nathalie; Philllips, Iain; Davies, John-Mark
This report describes factors influencing the spatial variation in wetland water quality and how drainage of wetlands affects downstream receiving waters in terms of their water quality and biotic health. The specific objectives of this work were to: 1) characterize the spatial and temporal variation in water quality of prairie potholes after snowmelt; 2) quantify solute export along a newly constructed wetland drainage ditch; 3) characterize solute export from drained pothole wetlands; 4) determine the extent to which stream water quality is influenced by wetland drainage; 5) contribute to the understanding of how wetland drainage affects ecosystem health. The research was conducted at the Smith Creek watershed, southeastern Saskatchewan, where there has been controversy over recent renewed efforts to drain wetlands to increase agricultural production.
Sensitivity of Snowmelt Hydrology on Mountain Slopes to Forest Cover Disturbance
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2011) Pomeroy, John W.; Fang, Xing; Ellis, Chad; Guan, May
Marmot Creek Research Basin was the subject of intense studies of snowmelt, water balance and streamflow generation in order to generate a five year database of precipitation inputs, snowpack dynamics and streamflow that could be used in hydrological model testing. A physically based hydrological model of the basin was constructed using the Cold Regions Hydrological Model and tested over four years of simulation. The model was found to accurately simulate snowpacks in forested and cleared landscapes and the timing and quantity of streamflow over the basin. The model was manipulated to simulate the impacts of forest disturbance on basin snow dynamics, snowmelt, streamflow and groundwater recharge. A total of 40 forest disturbance scenarios were compared to the current land use over the four simulation years. Disturbance scenarios ranged from the impact of pine beetle kill of lodgepole pine to clearing of north or south facing slopes, forest fire and salvage logging impacts. Pine beetle impacts were small in all cases with increases in snowmelt of less than 10% and of streamflow and groundwater recharge of less than 2%. This is due to only 15% of the basin area being covered with lodgepole pine and this pine being at lower elevations which received much lower snowfall and rainfall than did higher elevations and so generated much less streamflow and groundwater recharge. Forest disturbance due to fire and clearing affected much large areas of the basin and higher elevations and were generally more than twice as effective in increasing snowmelt or streamflow. For complete forest cover removal with salvage logging a 45% increase in snowmelt was simulated, however this only translated into a 5% increase in spring and summer streamflow and a 7% increase in groundwater recharge. Forest fire with retention of standing burned trunks was the most effect forest cover treatment for increasing streamflow (up to 8%) due to minimizing both sublimation of winter snow and summer evaporation rates. Peak daily streamflow discharges responded more strongly to forest cover decrease than did seasonal streamflow with increases of over 20% in peak streamflow with removal of forest cover. It is suggested that the dysynchronization of snowmelt timing with forest cover removal resulted in an ineffective translation of changes in snowmelt quantity to streamflow. This resulted in a complementary increase in groundwater recharge as well as streamflow as forest cover was reduced. Presumably, a basin with differing soil characteristics, groundwater regime or topographic orientation would provide a differing hydrological response to forest cover change and the sensitivity of these changes to basin characterisation needs further examination.
Modelling Snow Water Conservation on the Canadian Prairies
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, 2011) Pomeroy, John W.; Fang, Xing; Williams, Brad
Snowcover accumulation has tremendous impacts on Canadian Prairie hydrology and agriculture (Pomeroy and Gray, 1995; Fang and Pomeroy, 2007). Wind redistribution of snow or blowing snow is frequent in the Prairies and controls the accumulation of snowcover. Blowing snow transport is normally accompanied by in-transit sublimation (Dyunin, 1959; Schmidt, 1972; Pomeroy, 1989). Blowing snow transport and sublimation result in losses to exposed snowcovers from erosion of from 30% to 75% of annual snowfall in prairie and steppe environments (Tabler, 1975; Pomeroy et al., 1993). The disposition of this eroded snow to either sublimation or transport and subsequent deposition is important to surface water budgets. Transported snow is available for snowmelt, while that sublimated is returned to the atmosphere. Blowing snow fetch, or the downwind distance of uniform terrain that permits snow transport, determines the disposition between sublimation and transport, longer fetches promoting greater sublimation per unit area (Tabler, 1975; Pomeroy and Gray, 1995). Calculation of blowing snow fluxes (erosion, transport, sublimation) for a uniform area, using the presumption of horizontal steady state flow (Pomeroy, 1989), does not provide sufficient information to calculate the snow cover mass balance over larger areas where flow at many points in the landscape will deviate significantly from steady state conditions. A comprehensive model of blowing snow was assembled by Pomeroy and Li (2000) and tested extensively in the Prairie and Arctic environments where it was shown to accurately predict snow accumulation. Subsequent tests by Fang and Pomeroy (2009) show that the model can accurately predict snow accumulation in a wide range of prairie to partly wooded environments. This project compares field measurements of snow distribution, associated with shelterbelts at various spacings, to modeled results of snow redistribution by wind. Virtual shelterbelt configurations modeled with real climate data examine the likely impacts of shelterbelt systems on snow water conservation over multi-year time periods including drought and snowy years.
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, Tom
This 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.
Wolf Creek Cold Regions Model Set-up, Parameterisation and Modelling Summary
(Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan and State Hydrological Institute, Saint Petersburg, Russia, 2010) Pomeroy, John W.; Semenova, Olga M.; Fang, Xing; Vinogradov, Yuri B.; Ellis, Chad; Vinogradova, Tatyana A.; MacDonald, Matt; Fisher, Elena E.; Dornes, Pablo; Lebedeva, Ludmila; Brown, Tom
Wolf Creek Research Basin is in the Upper Yukon River Basin near Whitehorse, Yukon and is representative of headwaters in the northern Coast Mountains. It was established in 1993 to better develop northern hydrological models, and related hydrological process, ecosystem and climate science. Yukon Environment maintains Wolf Creek hydrometeorological and hydrometric stations and conducts regular snow surveys in the basin. A number of hydrological models have been tested on Wolf Creek and all have had great difficulty in simulating the cold regions hydrological processes that dominate its streamflow response to snowmelt and rainfall events. Developments in understanding hydrological processes and their interaction with terrestrial ecosystems and climate at Wolf Creek have lead to the development of the Cold Regions Hydrological Model (CRHM) by a consortium of scientists led by the University of Saskatchewan and Environment Canada. CRHM comprehensively incorporates the blowing snow, intercepted snow, sublimation, melt energetics, infiltration to frozen soils, organic terrain runoff and other cold regions hydrological phenomenon and discretizes the catchment on a hydrological response unit basis for applying water and energy balance calculations. The model is intended for prediction of ungauged basins with parameter selection from physically measurable properties of the river basin or regional transference of calibrated values. In Russia, a long tradition of cold regions hydrological research has led to the development of the Hydrograph model by the State Hydrological Institute, St. Petersburg. The Hydrograph model contains several promising innovations regarding the formation and routing of runoff, discretizes the basin using hydrological response units and addresses some (but not all) cold regions hydrological processes. Hydrograph parameter selection is made from both physically measured properties and those that are calibrated, but the calibrations can be easily regionalized. Test simulations of runoff processes using CRHM and Hydrograph for Wolf Creek Research Basin was undertaken using data archives that had been assembled and cleaned up in a related project by the University of Saskatchewan. The test simulations are a demonstration of model capabilities and a way to gain familiarity with the basin, its characteristics and data and to better compare model features. Data available included a GIS database of basin characteristics (topography and vegetation distribution) and the hydrometeorological and hydrometric observational dataset from Yukon Environment. The sub-surface hydrology presented a formidable unknown in parameterising the model. Hydrograph performed well in initial simulations of the basin hydrograph for multi-year runs. Several issues with observational data quality created substantial uncertainty in evaluating the model runs.
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, Xulin
This 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.
Impacts of Climate Change on Saskatchewan’s Water Resources
(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2009) Pomeroy, John; Fang, Xing; Williams, Brandon
The purposes of this report are two-fold, i) documenting the expected impacts of climate change on Saskatchewan's water resources, ii) outlining the options for adaptation of water resource management practices, policies and infrastructure to minimize the risk associated with the impacts of climate change. Prairie province hydrology is dominated by cold regions processes so that snowmelt is the primary hydrological event of the year for both the major rivers that derive from the Rocky Mountains and small streams and rivers that arise in Saskatchewan. Climate change impacts on water resources are therefore focussed on changes to snow accumulation, snowmelt and infiltration to frozen soils. Climate change scenarios suggest generally warmer and wetter winters for Saskatchewan. Large scale hydrological models that take these scenarios into account suggest changes in the annual streamflow of the South Saskatchewan River ranging from an 8% increase to a 22% decrease, with an 8.5% decrease being an average prediction. Small scale hydrological models for prairie streams suggest a 24% increase in spring runoff by 2050 followed by a 37% decrease by 2080 is possible as the winter snowcover becomes discontinuous. Both model results suggest that there is not a dramatic drying of the prairies to be anticipated under climate change and that in some cases streamflow will increase for certain scenarios and under moderate degrees of climate change. For the major rivers draining from Alberta into Saskatchewan, more efficient water use for irrigation or a reduction in irrigated acreage in Alberta could compensate for the reduced water availability, which is due mainly to reduced mountain snowmelt. Current minimum tillage and continuous cropping systems are resilient for most climate changes to agricultural water resources. Initially there will be increases in prairie runoff but as climate change progresses later in the 21st C there will be dramatic drops in runoff and the flow of small streams to wetlands and depressions and to small prairie rivers. Infrastructure will have difficulty keeping up with this level of change unless agricultural land management is used to compensate for changes in hydrology. New crop varieties and tillage methods which are able to leave some water for runoff to natural ecosystems will need to be devised. Drainage of wetlands may have to be reversed to limit high spring streamflows and wetland/lake levels. Integrated basin management of the South Saskatchewan River across both Alberta and Saskatchewan and for smaller watersheds in Saskatchewan is the preferred adaptation method for dealing with these uncertainties. Integrated basin management plans with apportionment powers, enforceable land use controls and agricultural management incentives will need to be 2 implemented to deal with rapid changes and increased uncertainties in water management designs. In all cases the uncertainties in the model outputs and driving hydrometeorological data for current simulations make recommending adaptation measures very difficult as the range of predictions is from a decrease to an increase in available streamflow compared to current estimates. It is imperative that the scientific basis of these hydrological models be improved so that there is reduced uncertainty in model predictions. The current climate and water resources available in the headwater basins are themselves uncertain and need to be better quantified to permit more reliable comparisons of future climate and water resource predictions with the current situation.
Prairie Hydrological Model Study Progress Report, December 2008
(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2009) Pomeroy, John; Westbrook, Cherie; Fang, Xing; Brown, Tom; Minke, Adam; Guo, Xulin
This report is an update on progress made to the middle of December 2008, corresponding to “Milestone Month 20”. According to our study plan, at this milestone “we will have completed a wetland module and with evaluation on Smith Creek Research Basin and archival data available at the Centre for Hydrology (Objective 3, 4)”. More specifically, Objectives 3 and 4 are stated as: • Objective 3: A physically based, hydrological response unit-based hydrological model, (the Prairie Hydrological Model), will be developed that is suitable for multiple season simulation of the hydrology of the Canadian Prairie environment. The model will be capable of predicting water balance, soil moisture, snow cover, actual evaporation and streamflow on a daily time-step with minimal calibration of model parameters from streamflow records. The model will contain a wetland module that includes assigned variable drainage rates from the wetland. The intended basins would drain to a stream or internally drained lake/wetland, with basin size to be greater than ~1 km2 and less than ~250 km2. • Objective 4: The Prairie Hydrological Model will be evaluated at Smith Creek through hydrological simulation and quantitative analysis of multi-objective criteria, including streamflow and wetland extent. Whilst calibration will be minimised and limited to non-physical aspects of the model, certain parameters will be optimised from these comparisons. For streamflow, both annual and peak flows are parameters of interest. For wetlands, seasonal extent is the parameter of interest. Outlined below are the research activities regarding these two objectives, beginning with a description of the model created with the Cold Regions Hydrological Modelling Platform (CRHM), the CRHM-Prairie Hydrological Model, or CRHM-PHM, followed by a description of the addition of the wetland module, and concluding with preliminary results from CRHM-PHM evaluations at Smith Creek.
Progress Report: Land Use and Wetland Drainage Effects on Prairie Water Quality Study
(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2009) Westbrook, Cherie; Brunet, Nathalie N.
This report is an update on progress made to the end of December 2008. According to our study plan, we should have completed one summer worth of data collection and made progress in laboratory analytical work. Outlined in the report are data collection methods and progress to date made on our research objective of “determining changes in water quality of streams and impacts to ecosystem function associated with wetland drainage”. Considerable progress toward the research objective was achieved during the reporting period, and overall, the project is on schedule. Smith Creek was broken down into its tributaries (North Fork, South Fork and Thingvalla). Water samples at the outlet and tributaries of Smith Creek were taken on 35 occasions during the spring, summer and fall. Chemical analysis of these samples is 70% complete. The wetland for the drainage experiment was selected and instrumented with an electronic water level recorder and precipitation gauge. A bathymetry survey of the wetland was carried out and used to compute the volume of water stored in the wetland at different water levels. Water chemistry for the wetland was analyzed 29 times during the spring, summer and fall. Preliminary results show concentrations of DOC increased over the spring and early part of the summer as the wetland evaporated. Concentrations then fell to post-snowmelt values during the unusually wet late summer period. The wetland was drained this fall ahead of schedule due to the needs of the landowner. Once drained, the wetland lost 42% of its volume within 22 hours. Preliminary findings were that the drain was a source of TP during the first 2.5 hours and then transitioned to a sink. The Benthic Entomology (BENT Lab) of the Saskatchewan Watershed Authority (SWA) provided a preliminary assessment of the biotic health in the Smith Creek watershed. Sampling was conducted in spring 2008, and the progress of this assessment is as follows: a) Four sites were sampled in the watershed; b) 83% of all samples have been processed and identified; c) to date, a total of 9,669 individuals have been identified, representing 80 taxa; and d) of the samples processed, they are characterized primarily by pollution-tolerant fly larvae, and fast growing non-insect taxa typical of seasonal prairie streams. SWA is now preparing plans for additional assessment in 2009, and further evaluation of 2008 results using a reference condition approach and test site analysis in order to obtain robust measures of ecosystem health in the Smith Creek watershed.

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