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C:\Program Files\CRHM\Examples\badlakeflow7475jp.prj
Characterising the Surface Hydrology of Prairie Droughts
John Pomeroy, Kevin Shook, Robert Armstrong, Xing FangCentre for Hydrology
University of SaskatchewanSaskatoon, Sask
www.usask.ca/hydrology
Prairie Hydrology Major river flow (SSR, NSR) is primarily from mountain
runoff, but prairie runoff supplies smaller rivers, streams, wetlands, and lakes
Prairie Runoff forms in internally drained (closed) basins that are locally
important but non-contributing to river systems that drain the prairies, OR
drains directly to small prairie rivers (Battle, Souris, Assiniboine) >80% of runoff during snowmelt period
Redistribution of snow to wetlands and stream channels in winter is critical to formation of runoff contributing area
Drainage of small streams and wetlands ceases completely in summer when actual evaporation* consumes most available water.
Prairie streams are almost completely ungauged and often altered by dams, drainage, water transfers, etc
*evaporation used here as transpiration + evaporation + sublimation
Non-Contributing Areas to Streamflow a Prairie Characteristic
Prairie Runoff GenerationSnow Redistribution to Channels
Spring melt and runoff
Water Storage in Wetlands
Dry non-contributing areas to runoff
Prairie Hydrology – don’t blink
0
5
10
15
20
25
01-Jan
31-Jan
02-Mar
01-Apr
01-May
31-May
30-Jun
30-Jul
29-Aug
28-Sep
28-Oct
27-Nov
27-Dec
Str
eam
flow
m3
per
seco
nd
Average 1975-2006
1995 High Year
2000 Low Year
Smith Creek, Saskatchewan
Drainage area ~ 450 km2
No baseflow from groundwater
Hydrological drought can be viewed as the absence of prairie runoff……
Sparse Prairie Streamflow Network Suitable for Drought Analysis
Burn et al., 2008 Inadequate coverage to characterise prairie runoff
How to Characterise Hydrological Drought for the Prairies?
River flows well gauged, but subject to abstraction, storage and do not reflect Prairie hydrological conditions.
Streamflow network is more representative but is sparse, and subject to changes in land use (drainage), abstraction, storage.
Existing indices considered inappropriate. Possibility to model prairie runoff generation and
related hydrological processes to create a hydrological drought “surface” for the Prairies using atmospheric data.
Cold Regions Hydrological Modelling Platform: CRHM
Modular – purpose built from modules Modules physically based algorithms derived from +45
years of prairie hydrology research at Univ of Saskatchewan
Hydrological Response Unit (HRU) basis – natural landscape units with horizontal interaction, ponds, no need for stream
HRUs assumed internally uniform, basis for coupled energy and mass balance
HRUs connected aerodynamically for blowing snow and via dynamic drainage networks for streamflow
Incorporate wetlands directly in drainage system
CRHM Module Development
Data interpolation from station or grid to HRUs
Infiltration into soils (frozen and unfrozen)
Snowmelt (prairie & forest) Radiation – level, slopes Evapotranspiration Snow transport Interception (snow & rain) Sublimation (dynamic & static) Soil moisture balance Wetland water balance Sub-surface runoff Routing (hillslope & channel)
DATA ASSIMILATION
SPATIAL PARAMETERS
Basin and HRU parameters are set. (area, latitude, elevation, ground slope, aspect)
PROCESSES
CRHM Drought Hydrology Simulation Model the effects of local drought meteorology on the
hydrology of ”representative”, first-order prairie basins Create “virtual” basin models, which can be applied to
gridded datasets Allows comparison of basin response to drought
conditions and to normal variability Requires high resolution driving data over entire Prairies
for normal (1961-1990), non-drought (1962-1987) and drought periods (1999-2004) Snowfall, rainfall Incoming shortwave radiation, cloudiness or sunshine hours Temperature Humidity Wind speed
Modelling Objectives
To Demonstrate the: differences between drought and non-drought
hydrological cycling at the surface, evolution of hydrological drought over time and
space Calculated Variables as ratios to non-drought
conditions (~Hydrological Drought Indices~) Snow Accumulation peak SWE, duration Spring Runoff total, duration Actual ET/PET growing season
CRHM – Prairie Hydrological Model Configuration
Flow Chart in Cold Regions Hydrological Modelling
Platform (CRHM)
CRHM Tests Creighton
Tributary of Bad Lake-well drained semi-arid
St. Denis National Wildlife Area-internally drained sub-humid
CRHM HRU Configurations
Fallow Stubble
Grass Coulee
Stream
Creighton Tributary, Bad Lake
Cultivated
Wooded Wetland
Pond
Wetland 109, St Denis
Well Drained Poorly Drained
Creighton Tributary Water Balance 1974-75
-500
-400
-300
-200
-100
0
100
200
300
400
500
Fallow Stubble Coulee Basin
mm
wat
er e
qu
ival
ent
Snowfall
Rainfall
Runoff
Sublimation
Drifting Snow
Evaporation
30% Summer Fallow55% Stubble15% Grassland Coulee Fallow Stubble
Coulee
Snowmelt Runoff for Creighton Tributary
No calibration
Snow Accumulation at Wetland 109, St Denis
CRHM Hydrological Indices Surfaces
Snowcover duration Peak SWE Spring discharge amount Streamflow duration AET/PET