Background: Canadian Rockies Hydrological Observatory

  • John Pomeroy, Geography and Planning (www)
  • Warren Helgason, Biological and Chemical Engineering (www)
  • Andrew Ireson, SENS (www)
  • Cherie Westbrook, Geography and Planning (www)

Major Goals
The Canadian Rockies Hydrological Observatory (CRHO) aims to improve the understanding of and capacity to predict the changes in water yield from headwater basins where cold climate processes predominate. It will examine the water supply response to climate variability in a range of mountain headwater ecohydrological site types, incorporating the transient responses of both climate forcing and cryospheric and basin hydrological response. Particular attention will be paid to how snowpacks, glaciers, groundwater, wetlands, forests and frozen soils interact and modulate the response of water supply to variability in climate. An important component will be on downscaling climate model products over complex mountain terrain. The project will support improved water resource modelling and management over larger river basins such as the Saskatchewan River Basin by contributing advanced mountain headwater hydrological modelling capability and future flows under downscaled climate scenarios. It will do so by strengthening the hydrological and glaciological science foundation for estimating water resource impacts from future climate scenarios and by testing and improving hydrological models that can be used for current and future water resource assessments. The CRHO will also undertake a focussed effort to communicate scientific findings and new methods useful to governments, communities, and industry and to train and develop the next generation of cold regions hydrologists and glaciologists.

Figure 1: Upper Bow River Basin – showing segments above Kananaskis and the Kananaskis River.

Rationale
Uncertainty in future water flows is one of the great challenges facing western Canada. Water resources in the region are undergoing unprecedented utilization by industrial and agricultural development at a time when climate induced changes are occurring in mountain ecosystems. Both energy and food security are tied to these water resources via hydroelectricity, oilsands development and processing, and irrigation agriculture. There is a moratorium on new water licenses in the South Saskatchewan and Athabasca River basins due to a mismatch between water demand and supply. This mismatch is anticipated to become much more widespread and impact on interprovincial and international transboundary water allocations and our ability to sustainably manage water resources in the Canadian West. Successful water management requires a reduction in the uncertainty of predictions of water supply for this region. Much of the water in western Canada originates from source water areas (hereafter referred to as 'headwaters' or 'headwater basins') in the Rocky Mountains, where cold water processes involving snow, glaciers, wetlands and frozen soils control the storage and delivery of water to river systems. High precipitation, restricted infiltration, storage of frozen water, and rapid seasonal melt provide high runoff efficiencies for these headwaters. Seasonal and interannual storage of water as snow and ice makes estimation of basin runoff in cold regions extremely difficult compared to temperate basins. Climate variability further confounds adequate prediction from basins that contain snow, permafrost and glaciers. Hillslope processes impart important hydrological controls on headwater basins because terrestrial flowpaths control the timing and storage of water flow. Headwater cryospheric and hillslope processes have important ecohydrological interactions with the basin topography, vegetation, and soils. Headwater ecosystems are highly dependent upon hydrological processes associated with snow and ice accumulation and melt, groundwater/lake/wetland exchange, drainage, and runoff generation. Most headwater basins are ungauged, but remain extremely important to infrastructure, ecosystem function, and large scale water resources because of their prevalence and accumulation of flow in river basins. Many headwater basins have been designated national or provincial parks; For example, Rockies headwaters form a UNESCO World Heritage Site that is the largest and one of the most spectacular protected areas in the world.

Engineering design, agricultural and forest land practises, mining, ecosystem management, hydroelectric facilities, water management strategies, and water policy are all predicated on managing risk with respect to ensuring adequate water supply for users and the environment and compensating for expected conditions of water excess and shortage. Traditional water resources management has been based upon observed probabilities of streamflows. This requires not only an extensive and long-serving stream gauge network but also stationarity in the frequency distribution of streamflow over time. Recently it has been fully recognized that streamflow stationarity has never truly existed, that observational networks will remain insufficient to manage water in isolation, and that fluctuations in water supply are tied to climate variability and change. Effective and sustainable management of water resources requires an assessment of how climate and climate variability affect water resources. Headwater basins in cold regions modulate changes in the climate and biosphere through feedbacks which are critical to understand and include in models. By better understanding cold hydrological processes and systems, and better predicting water resources using this understanding, this research can contribute to maintaining ecosystem health under the current stressors of cold regions headwater basins such as climate variability and change, cryospheric change and vegetation change.

Science Questions

  1. How do mountain basin biophysical characteristics affect snow and ice systems to produce hydrological responses to precipitation and energy inputs on time scales from hours to centuries?
  2. Do cold regions mountain hydrological systems enhance or dampen the effects of climate variability on water resources?
  3. Are the Canadian Rocky Mountains a reliable future source of streamflow?

Specific Objectives

  1. Improve the understanding and description of the governing cold regions hydrological factors for mountain water supply through intensive process studies in representative headwater research sites.
  2. Develop an improved cold regions hydrology model based upon improved numerical descriptions of processes and enhanced basin representation.
  3. Use new scientific information and improved models to predict headwaters water resource sustainability in light of climate change and variability. Specifically:
    1. downscale current meteorology and future climate scenarios to drive cold regions hydrology in light of concurrent ecohydrological dynamics,
    2. predict hydrological cycling and quantify uncertainty in these calculations in ungauged mountain basins.
    3. improve the coupling of the groundwater system to the surface-atmosphere system

Methodology

  1. Sustain and enhance point and areal observations of hydrological and cryospheric processes in the Upper Bow River Basin (Kananaskis and upstream Bow). These will serve as outdoor laboratories or testbeds to improve and to test models. Smaller research basins will be located in headwater regions representative of a range of mountain environments (dry Front Range, high snowfall, glaciated). Research basins will have stream gauges and a network of meteorological stations. The nested design will permit scaling up from small basins to the larger Upper Bow River Basin.
     
  2. Conduct focussed field campaigns in research basins to answer specific process questions and to collect information to evaluate model performance and to suggest model improvements
     
  3. Use dynamical distributed modelling and statistical (e.g. multi-fractal) methods to downscale from regional climate model grid scales to basin scales and to upscale from point observations to hydrological model and climate model grid scales. Apply this for hydrological impact prediction using future climate scenarios.
     
  4. Develop assessments of the uncertainty in hydrological predictions using ensemble predictions from hydrological models so that users can manage water risks using information from model outcomes based on time series that extend far beyond the observational record.
     
  5. Use explicit modular model development strategies to rapidly incorporate new algorithms and structures (e.g. glacier module, groundwater module, mountain wetland, hillslope hydrology module) into a purpose-built predictive model, the Cold Regions Hydrological Model (CRHM) which has been specifically developed as a “community model” to incorporate the findings of numerous researchers (Pomeroy et al., 2007).
     
  6. Use a two-way nested modelling strategy employing the European Union's 'Open Modelling Interface' (OpenMI) standards to move information between large and small scales. Models will be coupled as necessary for integrated predictions of water resources and climate using Environment Canada’s Modélisation Environmentale Communautaire (MEC) system to support the development of MESH model for larger scale application.
     
  7. Manage hydrological and glaciological data using an advanced data management system developed in the IP3 Network for storage, organisation, access, and visualisation of hydrological information.
     
  8. Conduct synthesis studies on cross cutting issues like extreme climate variability impacts on water supply, influence of changing vegetation on hydrology, and evidence for thresholding behaviour in coupled hydrological and cryospheric systems under change
     
  9. Hold workshops that bring private and public water resource professionals together with network scientists and students to address key issues in improving the scientific basis for water resources management. This will be accomplished by organizing workshops and conferences that promote the sharing of new techniques, research outcomes and advanced syntheses of emerging knowledge and by translating knowledge from technical forms into concepts that can be readily applied in support of policy development and sustainable water management.

Themes
This Project will be organized around two Themes to

  1. advance development and integration of information on how hydrological and cryospheric processes interact to form streamflow
     
  2. develop and run hydrological models to produce water resource predictions for past and future climates.

Theme 1 – Cold Regions Mountain Hydrology
This theme includes advances in the understanding and description of cold regions hydrological and cryospheric processes and basin response for their more accurate inclusion in models. Mountain research basins will be used for field observations of snow, glaciers, frozen/unfrozen soil, evapotranspiration and groundwater processes and linkages to vegetation such as forest structure or alpine shrubs. Specific advances are anticipated to develop from focused research on

  1. Runoff over and infiltration into frozen hillslopes. Frozen soil infiltration research has focused on level sites. In mountains the primary runoff generation zones are on hillslopes where the partitioning of snowmelt and rain water into infiltration and runoff are poorly understood. Process studies will examine whether assumptions from level sites are valid on hillslopes and will develop new conceptual and mathematical models of hillslope infiltration and water movement under frozen soils.
     
  2. Wetland storage and hydrology. Mountain valley wetlands have complex hyporheic interactions that regulate streamflow and water storage, particularly for low flow periods.
     
  3. Groundwater storage-discharge. Groundwater in unconfined aquifers in glacial moraines plays a crucial role in the magnitude and timing of discharge from alpine glacial headwater catchments. Groundwater levels at Marmot creek in the Canadian Rockies have been monitored since the 1960s along with stream discharge, and there is a clear but poorly understood relationship between the two. Groundwater and streamflow peak at the same time, indicating that both are primarily feed by snowmelt. However, after the intermittent stream has stopped flowing, groundwater levels continue to decline for a number of months, suggesting that the groundwater continues to discharge downstream of the stream gauge. We will explore relationships between recharge, storage and discharge using field observations and physically based models. We will seek to capture the essential behaviour of the groundwater flow regime in simplified model, consistent with the HRU approach, which can be implemented within CRHM.
     
  4. Turbulent transfer to and sublimation from snow. Sublimation of snow is a vastly important process in the Canadian Rockies, however existing turbulent transfer schemes have been found to be inadequate in mountain environments and require reformulation to account for advected turbulence and non-steady state conditions. Detailed atmospheric sounding and eddy flux measurements will be used to propose improved turbulent transfer schemes and parameterisations for models and will better quantify sublimation losses from the mountain water balance.
     
  5. Spatial variability of snowmelt runoff contributing area. Whereas mountain snow redistribution and melt processes are now well understood – how these processes interact to form particular contributing areas at the basin scale in complex mountain terrain is less well understood. Particular interest will be in the treeline zone, snow avalanche deposits and small forest clearings as major contributing areas for streamflow generation.
     
  6. Glacier hydrology. Storage and discharge of water from glaciers follows reservoirs on the ice surface and under the ice. Parameterisations of existing understanding of glacier hydrology will be developed and tested for inclusion in mountain hydrological models to better quantify the contributions of glacier snowmelt and ice wastage on runoff generation.
     
  7. Climate variability and mountain hydrology. Precipitation phase and amount and hydrological process dynamics change with climate. Long term observations will be used to determine the sensitivity of cold regions mountain catchments to cycling associated with oceanic climate signals, temperature/humidity change, and changes in the amount and timing of precipitation. The approach will be from detailed studies of precipitation phase and the processes of snow redistribution, sublimation and melt, infiltration to frozen soils, evapotranspiration and runoff generation.

Theme 2 – Hydrological Prediction
Numerous studies have used hydrological models to project the hydrological consequences of future climate scenarios generated by climate models. Of these, some studies have modified future land cover conditions such as vegetation to reflect the effects of climate change. Most of these models have had poor, non-physical snow, glacier and frozen soil hydrology representations (eg temperature index melt routines). Modelling the coupled influence of both climatic and cryospheric change on headwater basin hydrology is highly complex. The few studies to incorporate routines for modelling glacier hydrology directly into a conceptual catchment model have been based on scaling relationships, and thus may not properly represent the timing and rate of glacier response.

Hydrological models have poorly represented cold regions processes such as frozen soil infiltration, snow redistribution and melt, glacier runoff and the influence of mountain topography on these processes. Existing models such as CRHM, and MEC - Surface Hydrology (MESH) and others will be evaluated and validated for a range of cold regions headwater research basins. The models will be tested and adapted in research basins with glaciers, snow and/or permafrost for the period of contemporary record.

The CRHO will aid in prediction by adding key new stations and new types of measurements. Further development and employment of acoustic SWE sounding will be accomplished and the SAS2 acoustic snow sounder will be deployed at CRHO stations. Reductions in predictive uncertainty by adding new stations will be quantified.

Hydrological models will be used for water resource prediction and driven by station and NARR data for contemporary water resource assessment compared to current water resource measurements and also applications to ungauged basins, and downscaled climate model information products for future water resource assessments. Climate scenarios information will be obtained from the Pacific Climate Impacts Consortium (PCIC) Regional Analysis Tool and products from the European Union ENSEMBLES project (ENSEMBLE based predictions of climate changes and their impacts) will also be evaluated. A wide range of scenarios from many climate models will be assessed as part of the uncertainty analysis. In all assessments scaling atmospheric and surface variable and parameters from observation to prediction scale or between prediction scales is fundamental to driving the models. For hydrological model precipitation and its phase (snow, rain) is an extremely important component that scales with great difficulty as its variability exhibits not only seasonal but also decadal and multidecadal variability, and further climate change influences are expected. Analysis of precipitation intensity, area, duration and new physical analysis of the phase of precipitation will permit more reliable hydrological predictions from information on climate variability. Similar statistical analysis of mountain thermal and wind structure will develop statistics that can be used to downscale atmospheric model outputs for hydrological calculations. Model structure with be modified with scale to preserve greater physical realism for parameters and to carefully identify and stay within the limits of scale inherent to various hydrological process algorithms. All data will be archived with the GIWS system.






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