Cherie Westbrook, John Pomeroy, Xing Fang, Kevin Shook, Tom Brown, Xulin Guo, Adam Minke, Nicole Seitz, Nathalie Brunet

Centre for Hydrology (www.usask.ca/hydrology)cherie.westbrook@usask.ca

• First – what is distinctive about our hydrology?

• Second – examine available approaches and technical options

• Third – recognize we have a unique hydrography and hydrology. Then, do it right.

• Fourth – recognize prairie hydrology rapidly changes and adapt

Interflow

Runoff

SnowfallSublimation

Blowing SnowEvaporation

Evapo-transpirationRainfall

Snowmelt

Infiltration Frozen Ground

Saturated Porous Media Flow

Bergeron Process

Ice

Wetland storage

Snow redistribution to channels

Spring melt and runoff

Water storage in wetlands

Dry non-contributing areas to runoff

Wetland 1

Wetland 2

sill

Lack of groundwater connections in this landscape – heavy tills

The ‘fill and spill’ hypothesis

Smith Creek Watershed, Spring 2011(courtesy of DUC)

Lack of inventory of wetland extent and loss in the Canadian Prairies

1958 2009

Smith Creek, SaskatchewanDrainage area ~ 450 km2

No baseflow from groundwater (?)

Hydrological drought can be viewed as the absence of prairie runoff……

• The Hydrological Cycle is manifested with strong regional variations around the world.

• Hydrologists have created a vast number of models (assumptions) to describe some aspects of this cycle.

• It is generally not necessary or likely that one hydrological model approach is applicable to all environments, scales or predictive interest

• Physically-based models attempt to describe reality faithfully (but do not completely succeed)

• Hydrological models predict most successfully in catchments near where they were derived

• Logical selection and design of model strategy, structure and their inherent assumptions are governed by local problems and local hydrology – this is not just parameter selection.

• Frustration with adding process algorithms to existing hydrological models that do not have cold regions features

• Frustration with trying to fit inappropriate structure of existing models to basins – all water does not drain to the stream!

• Frustration with inability to fit gridded or other conceptual spatial representations to reality – water flows in drainage basins, not grid cells.

• Frustration with models that only focus on streamflow response to precipitation – soil moisture or wetland storage level are equally interesting to some.

• Frustration with attempts to teach modelling to young hydrologists using older computer languages, no user interface, limited documentation of models - Fortran belongs in a museum.

• Frustration with the lack of a graphical system to evaluate model inputs and outputs

• Need a physical basis to calculate the effects of changing climate, land use, wetland drainage

• Need to incorporate key prairie hydrology processes: snow redistribution, frozen soils, spring runoff, wetland fill and spill, non-contributing areas

• Frustration that hydrological models developed elsewhere do not have these features and fail in this environment

• Streamflow calibration does not provide information on basin non-contributing areas and is not suitable for change analysis

• Modular – purpose built from C++ modules

• Modules based upon +45 years of prairie hydrology research at Univ. of Saskatchewan

• No provision for calibration or optimization, parameters set by knowledge

• Hydrological Response Unit (HRU)

• HRUs assumed to represent one response type, basis for coupled energy and mass balance

• HRUs connected aerodynamically for blowing snow and via dynamic drainage networks for streamflow

• Incorporate wetlands directly using fill and spill algorithm

• Data from multiple sites• Interpolation to the HRUs

• Infiltration into soils (frozen and unfrozen)• Snowmelt (open & forest)• Radiation – level, slopes• Wind speed variation – complex topo• Evapotranspiration• Blowing snow transport• Interception (snow & rain)• Sublimation (dynamic & static)• Soil moisture balance• Pond/depression storage• Surface runoff• Sub-surface runoff• Routing (hillslope & channel)

DATA ASSIMILATION

SPATIAL PARAMETERS

PROCESSES

• Basin and HRU parameters are set (area, latitude, elevation, ground slope, aspect)

• A HRU is a spatial unit in the basin that has 3 groups of attributes

• biophysical structure - soils, vegetation, drainage, slope, elevation, area (determine from GIS, maps)

• hydrological state – snow water equivalent, snow internal energy, intercepted snow load, soil moisture, depressionalstorage, lake storage, water table (track using model)

• hydrological flux - snow transport, sublimation, evaporation, melt discharge, infiltration, drainage, runoff. Fluxes are determined using fluxes from adjacent HRU and so depend on location in a flow sequence.

• HRUs need not be spatially continuous but must have some approx. geographical location or location in a hydrological flow sequence

Sequential HRU –landscape connectivity

Grouped HRU or Tile –must drain to stream

HRU 1

HRU 2

HRU 3

OUTFLOW

Ifpond

Snowmelt Rainfall

Snowmelt Infiltration

Rainfall Infiltration

Recharge Zone

Soil Column

Evapotranspiration

SubsurfaceDischarge

Groundwater GroundwaterDischarge

Ifsoil column

is full

Yes

No

No Yes

Saturated OverlandFlow = 0

SaturatedOverland

Flow

Ifdepression

NoRunoff

YesRunoff to

Depression

Depression

Evaporation

GroundwaterGroundwaterDischarge

SubsurfaceDischarge

Ifdepression

is full

NoNo fill-and-spill

Yesfill-and-spill

Snowmelt Rainfall

Snowmelt Infiltration

Rainfall Infiltration

Wetland Pond

Evaporation

Groundwater

Ifpond is full

No fill-and-spill

No

Yesfill-and-spill

SubsurfaceDischarge

GroundwaterDischarge

Surface Runoff

• Calculated depression storage using simplified pond volume-depth-area method (see Minke et al. 2010, Wetlands)

Original 10-m LiDAR DEM Filled depressionless10-m LiDAR DEM

‘Cut-fill’ output

Note, blowing snow aerodynamic routing from smooth to rough land covers

Amongst HRU in a Representative Basin

Amongst Representative Basins

(for details see Fang et al. 2010, HESS)

Rapidly changing climate, adaptive human management, etc.

May 10, 2011

May 11, 2011after 35 mm of rain

Stream in central part of Smith Creek Research

Watershed

Groundwater contributions to streamflow after series of

very wet years?

Spring 2011Spring 2005courtesy of Don Werle

Smith Creek Watershed(Spring 2011)

• Newly established beaver bounties in SK (2011) and MB (2012)

Lot of process field work has been done at various sites• Stream water quality• Water quality of wetland drainage (see Brunet and Westbrook 2012, AEE)• Water quality along fill and spill sequences

• How to best incorporate water quality into CHRM?

• Appropriate models must be selected for Canadian Prairie hydrological conditions

• This has meant a +40 year research programme at the University of Saskatchewan

• The resulting CHRM model platform has key components of prairie hydrology → some more are needed

• Applications in wetland dominated basins are leading to information to guide management practices

• Prairie Habitat Joint Venture Committee• Saskatchewan Watershed Authority• Manitoba Water Stewardship• Ducks Unlimited Canada• Agriculture and Agri‐food Canada, PFRA• Saskatchewan Ministry of Agriculture• Environment Canada (WSC, PPWB)• Smith Creek Watershed Association and landowners• NSERC• DRI, IP3, CRC, Univ. of Saskatchewan