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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