Comparison of Algorithms and Parameterisations for Infiltration into Organic-Covered Permafrost Soils

Infiltration into frozen and unfrozen soils is critical in hydrology, controlling active layer soil water dynamics and influencing runoff. Few Land Surface Models (LSMs) and Hydrological Models (HMs) have been developed, adapted or tested for frozen conditions and permafrost soils. Considering the vast geographical area influenced by freeze/thaw processes and permafrost, and the rapid environmental change observed worldwide in these regions, a need exists to improve models to better represent their hydrology. In this study, various infiltration algorithms and parameterisation methods, which are commonly employed in current LSMs and HMs were tested against detailed measurements at three sites in Canada’s discontinuous permafrost region with organic soil depths ranging from 0.02 to 3 m. Field data from two consecutive years were used to calibrate and evaluate the infiltration algorithms and parameterisations. Important conclusions include: (1) the single most important factor that controls the infiltration at permafrost sites is ground thaw depth, (2) differences among the simulated infiltration by different algorithms and parameterisations were only found when the ground was frozen or during the initial fast thawing stages, but not after ground thaw reaches a critical depth of 15 to 30 cm, (3) despite similarities in simulated total infiltration after ground thaw reaches the critical depth, the choice of algorithm influenced the distribution of water among the soil layers, and (4) the ice impedance factor for hydraulic conductivity, which is commonly used in LSMs and HMs, may not be necessary once the water potential driven frozen soil parameterisation is employed. Results from this work provide guidelines that can be directly implemented in LSMs and HMs to improve their application in organic covered permafrost soils

The Changing Hydrology of Lhù’ààn Mǟn - Kluane Lake - under Past and Future Climates and Glacial Retreat

Prepared for Government of Yukon, Yukon Community Services, Infrastructure Branch, Whitehorse, Yukon.Non-Peer ReviewedThe 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

Review of Lake Diefenbaker Operations 2010-2011 : Centre for Hydrology Final Report to the Saskatchewan Watershed Authority

Saskatchewan Watershed AuthorityNon-Peer ReviewedAnalysis 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

Simulating cold regions hydrological processes using a modular model in the west of China

SummaryThe Cold Regions Hydrological Model platform (CRHM), a flexible object-oriented modeling system, was devised to simulate cold regions hydrological processes and predict streamflow by its capability to compile cold regions process modules into purpose-built models. In this study, the cold regions hydrological processes of two basins in western China were evaluated using CRHM models: Binggou basin, a high alpine basin where runoff is mainly caused by snowmelt, and Zuomaokong basin, a steppe basin where the runoff is strongly affected by soil freezing/thawing. The flexibility and modular structure of CRHM permitted model structural intercomparison and process falsification within the same model framework to evaluate the importance of snow energy balance, blowing snow and frozen soil infiltration processes to successful modeling in the cold regions of western China. Snow accumulation and ablation processes were evaluated at Binggou basin by testing and comparing similar models that contained different levels of complexity of snow redistribution and ablation modules. The comparison of simulated snow water equivalent with observations shows that the snow accumulation/ablation processes were simulated much better using an uncalibrated, physically based energy balance snowmelt model rather than with a calibrated temperature index snowmelt model. Simulated seasonal snow sublimation loss was 138mm water equivalent in the alpine region of Binggou basin, which accounts for 47 % of 291mm water equivalent of snowfall, and half of this sublimation loss is attributed to 70mm water equivalent of sublimation from blowing snow particles. Further comparison of simulated results through falsification of different snow processes reveals that estimating blowing snow transport processes and sublimation loss is vital for accurate snowmelt runoff calculations in this region. The model structure with the energy balance snowmelt and blowing snow components performed well in reproducing the measured streamflow using minimal calibration, with R2 of 0.83 and NSE of 0.76. The influence of frozen soil and its thaw on runoff generation was investigated at Zuomaokong basin by comparing streamflow simulated by similar CRHM models with and without an infiltration to frozen soil algorithm. The comparison of simulated streamflow with observation shows that the model which included an algorithm describing frozen soil infiltration simulated the main runoff events for the spring thawing period better than that which used an unfrozen infiltration routine, with R2 of 0.87 and NSE of 0.79. Overall, the test results for the two basins show that hydrological models that use appropriate cold regions algorithms and a flexible spatial structure can predict cold regions hydrological processes and streamflow with minimal calibration and can even perform better than more heavily calibrated models in this region. Given that CRHM and most of its algorithms were developed in western Canada, this is encouraging for predicting hydrology in ungauged cold region basins around the world

Modelling Snow Water Conservation on the Canadian Prairies

Prepared for John Kort and Gary Bank, Agriculture and Agri-Food Canada.Non-Peer ReviewedSnowcover 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

High-Resolution Large-Eddy Simulations of Flow in the Complex Terrain of the Canadian Rockies

Canada First Research Excellence Fund's Global Water Futures Programme, the Natural Sciences and Engineering Research Council of Canada, Alberta Innovates, the Canada Foundation for Innovation, and the NSERC CREATE program in Water SecurityPeer ReviewedImproving 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

Hydrology and Water Resources of Saskatchewan

© Centre for Hydrology, 117 Science Place University of Saskatchewan, Saskatoon, Saskatchewan February 2005There 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

Sensitivity of Snowmelt Hydrology on Mountain Slopes to Forest Cover Disturbance

Alberta Sustainable Resource Development, IP3 Network, NSERC Discovery Grants and Research Tool Instrument Grants and the University of Calgary Biogeoscience Institute.Non-Peer ReviewedMarmot 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

Radiative Transfer Modeling of a Coniferous Canopy Characterized by Airborne Remote Sensing

Solar radiation beneath a forest canopy can have large spatial variations, but this is frequently neglected in radiative transfer models for large-scale applications. To explicitly model spatial variations in subcanopy radiation, maps of canopy structure are required. Aerial photography and airborne laser scanning are used to map tree locations, heights, and crown diameters for a lodgepole pine forest in Colorado as inputs to a spatially explicit radiative transfer model. Statistics of subcanopy radiation simulated by the model are compared with measurements from radiometer arrays, and scaling of spatial statistics with temporal averaging and array size is discussed. Efficient parameterizations for spatial averages and standard deviations of subcanopy radiation are developed using parameters that can be obtained from the model or hemispherical photography