Centre for Hydrology

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https://hdl.handle.net/10388/14587

The Centre for Hydrology provides a focus and catalyst for hydrological research at the University of Saskatchewan. The Centre is an interdisciplinary University research cluster designed to bring together and coordinate academic, graduate student, postdoctoral and allied government research staff for research, training and outreach on hydrological issues of local and global importance and to coordinate the University presence in hydrology. It focusses on advancing the theory and practice of hydrology as a physical environmental science, and emphasizes research and training related to improving descriptions and explanations of the natural and human factors which control the quantity and quality of water resources. This mission is carried on from the former Division of Hydrology (1962-2001) which conducted and coordinated some of the earliest Canadian hydrology research. The Centre contributes to the Global Institute for Water Security and the Global Water Futures programme.

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High-Resolution Large-Eddy Simulations of Flow in the Complex Terrain of the Canadian Rockies
(Earth and Space Science, 10/25/2023) Rohanizadegan, Mina; Petrone, Richard; Pomeroy, John W.; Kosovic, Branko; Muñoz-Esparza, Domingo; Helgason, Warren
Improving the calculation of land-atmosphere fluxes of heat and water vapor in mountain terrain requires better resolution of thermally driven diurnal winds (i.e., valley, slope winds) due to differential heating by terrain and radiative fluxes. In this study, the Weather Research and Forecasting model is used to simulate flow in large-eddy simulation (LES) mode over the complex terrain of the Fortress Mountain and Marmot Creek research basins, Kananaskis Valley, Canadian Rockies, Alberta in mid-summer. The model was used to examine the temporal and spatial evolution of local winds and near-surface boundary layer processes with variability in topography and elevation. Numerically resolving complex terrain wind flow effects require smaller grid cell size. However, the use of terrain-following coordinates in most numerical weather prediction models results in large numerical errors when flow over steep terrain is simulated. These errors propagate through the domain and can result in numerical instability. To avoid this issue when simulating flow over steep terrain a local smoothing approach was used, where smoothing is applied only where slope exceeds some predetermined threshold. LES results from local smoothing were compared with a mesoscale model and LES with global smoothing. Simulations are evaluated using sounding data and meteorological stations. The differences in flow patterns and reversals in two mountain basins suggest that valley geometry and volume is relevant to the break up of inversion layers, removal of cold-air pools, and strength of thermally driven winds.
Modelling the regional sensitivity of snowmelt, soil moisture, and streamflow generation to climate over the Canadian Prairies using a basin classification approach
(Hydrology and Earth System Sciences, 10/9/2023) He, Zhihua; Shook, Kevin; Spence, Christopher; Pomeroy, John W.; Whitfield, Colin
This study evaluated the effects of climate perturbations on snowmelt, soil moisture, and streamflow generation in small Canadian Prairies basins using a modelling approach based on classification of basin biophysical characteristics. Seven basin classes that encompass the entirety of the Prairies Ecozone in Canada were determined by cluster analysis of these characteristics. Individual semi-distributed virtual basin (VB) models representing these classes were parameterized in the Cold Regions Hydrological Model (CRHM) platform, which includes modules for snowmelt and sublimation, soil freezing and thawing, actual evapotranspiration (ET), soil moisture dynamics, groundwater recharge, and depressional storage dynamics including fill and spill runoff generation and variable connected areas. Precipitation (P) and temperature (T) perturbation scenarios covering the range of climate model predictions for the 21st century were used to evaluate climate sensitivity of hydrological processes in individual land cover and basin types across the Prairies Ecozone. Results indicated that snow accumulation in wetlands had a greater sensitivity to P and T than that in croplands and grasslands in all basin types. Wetland soil moisture was also more sensitive to T than the cropland and grassland soil moisture. Jointly influenced by land cover distribution and local climate, basin-average snow accumulation was more sensitive to T in the drier and grassland-characterized basins than in the wetter basins dominated by cropland, whilst basin-average soil moisture was most sensitive to T and P perturbations in basins typified by pothole depressions and broad river valleys. Annual streamflow had the greatest sensitivities to T and P in the dry and poorly connected Interior Grasslands (See Fig. 1) basins but the smallest in the wet and well-connected Southern Manitoba basins. The ability of P to compensate for warming-induced reductions in snow accumulation and streamflow was much higher in the wetter and cropland-dominated basins than in the drier and grassland-characterized basins, whilst decreases in cropland soil moisture induced by the maximum expected warming of 6 ∘C could be fully offset by a P increase of 11 % in all basins. These results can be used to (1) identify locations which had the largest hydrological sensitivities to changing climate and (2) diagnose underlying processes responsible for hydrological responses to expected climate change. Variations of hydrological sensitivity in land cover and basin types suggest that different water management and adaptation methods are needed to address enhanced water stress due to expected climate change in different regions of the Prairies Ecozone
Snowcover : accumulation, relocation, and management
(National Hydrology Research Institute, 1995) Pomeroy, John; Gray, Donald M.
Much of Canada's water supply is derived from snow. In most parts of the country, the annual spring freshet plays a key role in sustaining our aquatic ecosystems, while for semi-arid, boreal, alpine and arctic regions, snow is an important source of fresh water. In the context of sustainable development, i.e., the balanced management of natural resources to achieve a long-term, reasonable level of economic well-being while maintaining environmental values, snow plays a vital part. On the Canadian Prairies, for instance, snow management practices now often go hand-in-hand with no-tillage practices in the ongoing effort to sustain agricultural production over the long term. As another example, research conducted under the Canadian Model Forest Programme has highlighted the important role of snow in sustainable forestry management practices. Snow can be considered as a physical resource, a raw material possessing properties that contribute to the production of food, fibre and other beneficial products for human use and enjoyment. As with the sun, the soil, the air and the rain, the natural behaviour of snow can be studied, understood and ultimately managed. In a country such as Canada, a better understanding of snow processes will make a significant contribution to hydrological science. This scientific report on snowcover accumulation, relocation and management is a necessary step on the road to sustainable development. The dedication of the authors in preparing this comprehensive report that will be widely used by engineers, agriculture and forestry practitioners, scientists and university students is gratefully acknowledged.
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.
A Review of Canadian Prairie Hydrology: Principles, Modelling and Response to Land Use and Drainage Change
(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2007) Fang, Xing; Minke, Adam; Pomeroy, John; Brown, Tom; Westbrook, Cherie; Guo, Xulin; Guangul, Seifu
This report reviews research on the hydrological cycle, runoff generation, hydrological modelling and the influence of changes to land cover and wetlands on the same for the Canadian Prairies. The purpose of this report is to identify and examine the major processes that are responsible for prairie hydrology as well as the impacts of land cover change such as wetland drainage on water storage and on the streamflow hydrograph. The objective of this report is to propose hydrological modelling techniques; these techniques can contribute to the development of a predictive tool in the form of a prairie hydrological model. It is intent to utilize such a hydrological model to evaluate the impacts of wetland drainage and restoration as well as changes in the surrounding upland land use on downstream hydrology. Hydrology in the Canadian Prairie region is complex and highly varied. Only one third of annual precipitation occurs over the winter and the surface snow water equivalent distribution is highly heterogeneous due to wind redistribution of snow during blowing snow storms. Blowing snow can transport and sublimate as much as 75% of annual snowfall from open prairie fields. The formation of drifts from windblown snow lengthens the spring runoff season and modulates the peak spring flows. The frozen state of mineral soils results in rapid snowmelt runoff in the springtime, which produces 80% or more of annual local runoff. The prairie region is characterized by glacially-formed depressions; these depressions fill with water to form pothole sloughs and wetlands and are very important to prairie hydrology due to their surface storage capacity. A fill-and-spill runoff mechanism is identifiable in prairie basins that are dominated by these surface depressions where flow does not commence until all storage in the depressions is filled. This results in an episodic and rapid increase in contributing area during peak runoff events. However outside of these events much of the prairie landscape is non-contributing to streamflow and even in the most extreme runoff events, some prairie basins are internally drained and never contribute to streamflow. This fill and spill phenomenon is in contrast to forms of hydrological storage found in temperate regions in which the flow rate is proportional to storage. Because of depressional storage and poorly and internally drained basins, most surface runoff in the prairie region does not contribute to the major river systems. Hydrological processes in the prairie region are sensitive to the land cover and climate change. Wetlands can be completely dried out when surrounded by native grassland rather than agricultural fields. Droughts are frequent on the Canadian Prairies. Lower precipitation and higher air temperature are the common characteristics of droughts; surface snowmelt runoff is largely suppressed and can even completely cease when warmer (e.g. 5 ºC increase of temperature) or drier (e.g. 50% decrease of precipitation) conditions develop. The Cold Regions Hydrological Model platform (CRHM) is a “state-of-the-art” physically-based hydrological model designed for the prairie region. CRHM is based on a modular, object-oriented structure in which component modules represent basin descriptions, observations, or physically-based algorithms for calculating hydrological processes. Preliminary tests show reasonable performance of CRHM in simulating the water balance and streamflow hydrograph for prairie regions. The model also shows capabilities to simulate impact of land use change and climate change on hydrological processes and streamflow. Further work in CHRM will be development of surface storage and surface routing models that are suitable for modelling hydrology in the prairie wetland region.
Prairie Hydrological Model Study Progress Report, April 2008
(Centre for Hydrology, University Saskatchewan, Saskatoon, Saskatchewan, 2008) Pomeroy, John; Westbrook, Cherie; Fang, Xing; Minke, Adam; Guo, Xulin
This report is an update on the progress made over the first 12 months of the Prairie Hydrological Model Study and corresponds to Milestone #3. In summary, we have characterized the 2007-2008 Hydrological Year for modeling by installing weather, soil moisture, rainfall and pond level recording stations, observing summer evaporation, fall freeze-up and winter snowpack development to the start of melt. We have also made progress on wetland and basin characterization using remote sensing and other spatial information, and begun analysis of hydrometeorological data.
Saskatchewan’s Natural Capital in a Changing Climate : An Assessment of Impacts and Adaptation
(Prairie Adaptation Research Collaborative, 2009) Sauchyn, Dave; Henderson, Norm; Barrow, Elaine; Wheaton, Elaine; Fang, Xing; Johnston, Mark; Pomeroy, John W.; Thorpe, Jeff; Williams, B
Climate change impacts in Saskatchewan are already evident and will become increasing significant over time. This report draws on the expertise of top climate change researchers and a large body of previous work to create a state-of-knowledge synthesis of key biophysical impacts and adaptation options specific to Saskatchewan. The focus is Saskatchewan’s ecosystems and water resources and the sectors of our economy, agriculture, and forestry, which are most dependent on these natural resources. The purpose of this report is to 1) document the expected impacts of climate change on Saskatchewan’s natural resources and dependent industries, and 2) outline options for adaptation of resource management practices, policies and infrastructure to minimize the risks associated with the impacts of climate change and to take advantage of opportunities provided by a warming climate.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

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