1 Prairie Hydrology Prairie Hydrology John Pomeroy, Xing Fang, Robert Armstrong, John Pomeroy, Xing Fang, Robert Armstrong, Tom Brown, Kevin Shook Tom Brown, Kevin Shook Centre for Hydrology, Centre for Hydrology, University of Saskatchewan, Saskatoon, Canada University of Saskatchewan, Saskatoon, Canada Climate Change for the Prairies? • Highly variable and harsh climate has limited settlement and development possibilities over the last century. • If weather variability increases, this could degrade the viability of many aspects of ecosystems, human activities and economy • However, moderation of some variability (less cold or dry weather) might open up new possibilities for the Prairies
Transcript
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Prairie HydrologyPrairie Hydrology
John Pomeroy, Xing Fang, Robert Armstrong, John Pomeroy, Xing Fang, Robert Armstrong, Tom Brown, Kevin ShookTom Brown, Kevin Shook
Centre for Hydrology, Centre for Hydrology, University of Saskatchewan, Saskatoon, CanadaUniversity of Saskatchewan, Saskatoon, Canada
Climate Change for the Prairies?• Highly variable and harsh
climate has limited settlement and development possibilities over the last century.
• If weather variability increases, this could degrade the viability of many aspects of ecosystems, human activities and economy
• However, moderation of some variability (less cold or dry weather) might open up new possibilitiesfor the Prairies
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Prairie Climate is Variable and Extreme
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1880 1900 1920 1940 1960 1980 2000 2020
Year
Air Temperature C
April Average Temperature, Saskatoon
Drought 1999-2004
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THE DIRTY THIRTIES
"Saskatchewan,
Saskatchewan, there's
no place like
Saskatchewan; we sit
and gaze across the
plains and wonder why
it never rains…"
These words from the
song Saskatchewan
were written during the
1930s.
Prairie Snow
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Prairie Rain
Fishing Lake Flooding, Spring 2007
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North American Regional PredictionsClimate Difference from 1980-1999 to 2080-2089
A1B – balanced scenario
IPCC 2007
Prairie Hydrology• Major river flow 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.
• Baseflow from groundwater often nonexistent.
• Prairie streams are almost completely ungauged and often altered by dams, drainage, water transfers, etc
*evaporation used here as transpiration + evaporation + sublimation
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Prairie Runoff Generation
Snow Redistribution to Channels
Spring melt and runoff
Water Storage in Wetlands
Dry non-contributing areas to runoff
PRAIRIE HYDROLOGY – Limited
Contributing Areas for Streamflow
Non-contributing areas for streamflow
extensive in Canadian Prairies
Localized hydrology
affected by poor drainage,
storage in small
depressions
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Prairie Hydrology – don’t blink
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01-J
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Streamflow m
3 per second
Average 1975-2006
1995 High Year
2000 Low Year
Smith Creek, Saskatchewan
Modelling Prairie Hydrology
• Need a physical basis to calculate the effects of
changing climate, land use, drainage
• Need to incorporate key prairie hydrology
processes: snow redistribution, frozen soils,
spring runoff, wetland fill and spill, non-
contributing area
• Frustration that hydrological models developed
elsewhere do not have these features
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Cold Regions Hydrological
Modelling Platform: CRHM • Modular – purpose built from C++ modules
• Modules based upon +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 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
First more, then less?• Toyra et al. 2004: median of three most reliable
climate change scenarios suggests increases in annual prairie winter temperature and precipitation from the 1961-1990 average:
– 2050 +2.6 ºC and +11%
– 2080 +4.7 ºC and +15.5%
• Using this scenario in Bad Lake Research Basin (SW Sask) with CRHM results in a 24% rise in 2050 spring runoff, but a 37% drop by 2080, compared to the basin runoff (54 mm) in spring of 1975 (Fang and Pomeroy, 2007).
Climate Change – Winter Snow
Winter Snow Accumulation at Bad Lake, SK
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10
20
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60
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01/1
0/1
974
15/1
0/1
974
29/1
0/1
974
12/1
1/1
974
26/1
1/1
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10/1
2/1
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1/1
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21/0
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2/1
975
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975
18/0
3/1
975
01/0
4/1
975
15/0
4/1
975
29/0
4/1
975
SWE (mm)
Normal SWE (Winter of 1974/75)
SWE (Winter of 2049/50)
SWE (Winter of 2079/80)
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Climate Change – Spring Runoff
Spring Runoff from Creighton Tributary at Bad Lake, SK
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7001/1
0/1
974
15/1
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29/1
0/1
974
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1/1
974
26/1
1/1
974
10/1
2/1
974
24/1
2/1
974
07/0
1/1
975
21/0
1/1
975
04/0
2/1
975
18/0
2/1
975
04/0
3/1
975
18/0
3/1
975
01/0
4/1
975
15/0
4/1
975
29/0
4/1
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Runoff (mm)
Normal Spring Runoff (Spring of 1975)
Spring Runoff (Spring of 2050)
Spring Runoff (Spring of 2080)
Soil Moisture, Evaporation and Runoff
• Should be Easy! If R = 0, then P = E
• Not that easy….. – E = P - ∆S This is when sub-surface coupling becomes critical to the
atmosphere
– Storage is dynamic during dry periods. Decreasing surface area of open water, increased root depths, increased depth to water table
– Seasonality –• most runoff is from snowmelt (snowfall),
• most evaporation is from rainfall + snowmelt
• Precipitation or melt at times of low evaporative energy goes into storage (including soil moisture) or runoff
– Episodic Events – runoff removes water before it can infiltrate and form storage for evaporation.
• Problem: Inability to reliably model the basins of the Upper Assiniboine River and other prairie basins where variable contributing area, wetlands, nonsaturatedevaporation, frozen soils, snow redistribution and snowmelt play a major role in hydrology.
• Objectives– Develop a Prairie Hydrological Model computer program that
can simulate the response of streams, wetlands, and soil moisture to weather inputs for various basin types.
– Evaluate the model performance in Smith Creek by comparing to observations of streamflow, wetland extent, and snowpack.
– Use the Prairie Hydrological Model to estimate the sensitivity of streamflow, wetland water storage, and soil moisture to changes in drainage and land use.
Instrumentation of Smith Creek
Hydrometeorological Station
11 dual rain gauges
7 wetland level recorders
Completed
Summer 2007
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Main Hydrometeorological StationTemperature, humidity, wind
speed, shortwave radiation,
longwave radiation, soil
moisture, soil temperature
soil heat flux, snow depth,
rainfall, snowfall
Telemetry of Hydrometeorological Data
to Website – community accessTelemetry to U of Sask website
http://www.usask.ca/hydrology
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Snow and Wetland Surveys
Streamflow over Time
Smith Creek Annual Streamflow
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5000000
10000000
15000000
20000000
25000000
30000000
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Annual Streamflow (m
3)
Top 4 years for streamflow since 1995
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Peak Flow over Time
Maximum Daily Discharge of Smith Creek during 1975-2006
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Maxim
um Daily Discharge (m
3/s)
Top 6 peak daily flows since 1995
Changing Climate?Mean Annual Air Temperature at Yorkton
y = 0.0239x + 1.4259
R2 = 0.0404
-1
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Mean Annual Temperature (°C
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Annua l R a in fa ll an d Snow fa ll a t Yo rk to n
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1977
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1981
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Rainf a ll (mm)
Snow f a ll (mm)
Warming but high variability
No trend in
rainfall and snowfall
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Drainage of Wetlands?
Drainage of Wetlands?
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Modelling Approach
Smith Creek Basin CharacteristicsDrainage Network Spot Image
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CRHM – Prairie Hydrological Model Configuration
Flow Chart in Cold Regions
Hydrological Model Platform
(CRHM)
HRU Configuration for Smith Creek
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Parameterisation
without Calibration:
LiDAR DEM to Calculate
Depression Storage
Derivation of Wetland Depressions
for Basin
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SCR-9
SCR-8LR-5
LT-2/SCR-4
SCR-9
SCR-8LR-5
LT-2/SCR-4
SCR-9SCR-9
SCR-8SCR-8LR-5LR-5
LT-2/SCR-4LT-2/SCR-4
Remote Sensing Supervised Classification
CRHM Tests Smith Creek – No CalibrationObse rved SWE vs Simulated SWE at Smith Creek Sub-basin 1
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100
150
200
250
300
7-Feb 18-Feb 29-Feb 11-Mar 22-Mar 2-Apr 13-Apr
2008
Snow Accumulation
(mm SWE)
Fallow Obs. SWE Fallow Sim. SWE
Channel Obs. SWE Channel Sim. SWE
Wetland Obs. SWE Wetland Sim. SWE
Volumetric Soil Moisture at Smith Creek during Spring Snowmelt
Pe riod
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22-Mar 31-Mar 9-Apr 18-Apr 27-Apr 6-May
2008
Volumetric Soil
Moisture
Observed
Simulated
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Runoff Prediction:
No LiDAR & Calibration = old basin
LiDAR & No Calibration = new basin
Smith Creek Discharge with LiDAR Uncalibrated and
No LiDAR Calibrated Parameters
Conclusions
• Possible to model Prairie hydrology without calibration using physically based landscape scale simulations.
• Prairies are expected to become warmer and wetter with an initial increase in spring runoff followed by a substantial decrease in spring runoff generation later in the 21st Century.
• Drought sensitivity is extreme which will lead to magnification of drought-wet cycles in streamflow responses.
• Drainage is increasing streamflow and peak flow in wet and normal years
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