Land cover change and climate change effects on streamflow in puget sound basin washington
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Land Cover Change and Climate Change Effects on Streamflow in Puget Sound Basin, Washington. Lan Cuo 1 , Dennis Lettenmaier 1 , Marina Alberti 2 , Jeffrey Richey 3 1 : Department of Civil and Environmental Engineering, University of Washington

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Land Cover Change and Climate Change Effects on Streamflow in Puget Sound Basin, Washington

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Land cover change and climate change effects on streamflow in puget sound basin washington

Land Cover Change and Climate Change Effects on Streamflow in Puget Sound Basin, Washington

Lan Cuo1, Dennis Lettenmaier1, Marina Alberti2, Jeffrey Richey3

1: Department of Civil and Environmental Engineering, University of Washington

2: Department of Urban Design and Planning, University of Washington

3: Department of Chemical Oceanography, University of Washington

March 1, 2007

Climate Impact Group

University of Washington


Land cover change and climate change effects on streamflow in puget sound basin washington

  • Background

    Early settlement started in the mid 1800s in the Puget Sound Basin.

    Population has increased by 17 times since 1900.

    70% of Washington state population lives in the Puget Sound Basin.

    Land cover change is mainly caused by logging and urbanization.

    Temperature is changing in the Puget Sound.

  • Objectives

    How does land cover change affect streamflow in the Puget Sound Basin?

    How does temperature change affect streamflow in the Puget Sound Basin?


Methodology

Methodology

  • Study Area - Puget Sound Basin

  • Bounded by the Cascade

    and Olympic Mountains

  • Area: 30,807 sqr.km

  • Maritime climate, annual precipitation 600 mm - 3000 mm, October – April

  • Land cover: 82% vegetation

    7% urban

    11% other


Methodology1

Methodology

  • Generate 1/16th degree gridded forcing data and land cover maps for the study area.

  • Calibrate hydrology model.

  • Study land cover change effects by removing the long term trend in temperature.

  • Study temperature change effects using temperature regime detrended 1915, temperature regime detrended 2002, and historical temperature regime.


Methodology2

Methodology

  • Interception

  • Evapotranspiration

  • Snow accumulation and melt

  • Energy and radiation balance

  • Saturation excess and infiltration excess runoff

  • Unsaturated soil water movement

  • Ground water recharge and discharge

  • Model: Distributed Hydrology Soil Vegetation Model


Forcing data basin averaged historical annual precipitation

Forcing Data –Basin Averaged Historical Annual Precipitation

Eastern Puget

Sound Basins

Mean annual Prcp:

1200 mm – 2500 mm


Forcing data basin averaged historical annual precipitation1

Forcing Data –Basin Averaged Historical Annual Precipitation

Western Puget

Sound Basins

Mean annual prcp:

1600 mm – 3000 mm


Land cover change and climate change effects on streamflow in puget sound basin washington

Forcing Data –Basin Averaged Historical Annual Tmin

Eastern Puget

Sound Basins

Mean annual Tmin:

-0.5 – 4.5 C


Forcing data basin averaged historical annual tmin

Forcing Data –Basin Averaged Historical Annual Tmin

Western Puget

Sound Basins

Mean annual Tmin:

-1.8 – 2.5 C


Forcing data basin averaged historical annual tmax

Forcing Data – Basin Averaged Historical Annual Tmax

Eastern Puget

Sound Basins

Mean annual Tmax:

10 – 15 C


Forcing data basin average historical annual tmax

Forcing Data – Basin Average Historical Annual Tmax

Western Puget

Sound Basins

Mean annual Tmax:

9 – 13 C


Land cover change and climate change effects on streamflow in puget sound basin washington

Data: 2002 Land Cover Map (Alberti et al., 2004)


Land cover change and climate change effects on streamflow in puget sound basin washington

Data: Reconstructed 1883 land cover

  • Source:

  • Department of Interior, Density of Forests-Washington Territory, 1883

  • 2. Historical records of Puget Sound county population development


Results model calibration

Results: Model Calibration


Results model calibration1

Results:Model Calibration


Results monthly statistics of calibrated and measured streamflow

Results: Monthly Statistics of Calibrated and Measured Streamflow


Results land cover change effects seasonal flow

Results: Land Cover Change Effects: Seasonal Flow

Eastern Puget

Sound Basins


Results land cover change effects seasonal flow1

Results: Land Cover Change Effects: Seasonal Flow

Western Puget Sound Basins


Results land cover change effects seasonal flow2

Results: Land Cover Change Effects: Seasonal Flow

71% urbanization

Urbanization Affected Gages

64% urbanization

31% urbanization


Land cover change and climate change effects on streamflow in puget sound basin washington

Results: Mean Annual Streamflow


Results daily peak flow

Results: Daily Peak Flow

Eastern Puget

Sound Basins

Controlled Basin


Results daily peak flow1

Results: Daily Peak Flow

Western Puget Sound Basins


Results daily peak flow2

Results: Daily Peak Flow

71% urbanization

Urbanization Affected Gages

64% urbanization

31% urbanization


Mann kendall trend analysis on measurement and model residuals for upland gages

Mann-Kendall Trend Analysis on Measurement and Model Residuals for Upland Gages

Annual Maximum Daily Peak Flow (AMDPF)

  • No significant trend was found in monthly and annual streamflow at the above gages.

  • Although model simulation shows increase trend in AMDPF and annual streamflow for upland basins, the trend might not be statistically significant.


Temperature change effects seasonal flow

Temperature Change Effects: Seasonal Flow

Eastern Puget Sound Basins


Temperature change effects seasonal flow1

Temperature Change Effects: Seasonal Flow

Western Puget Sound Basins

Warmer T regime

Detrended 1915

Colder T regime

Detrended 2002


Temperature change effects seasonal flow2

Temperature Change Effects: Seasonal Flow

71% urbanization

Urbanization Affected Gages

64% urbanization

31% urbanization


Land cover change and climate change effects on streamflow in puget sound basin washington

Potential problems in summer

DJF: winter months, JJA: summer months


Temperature change effects mean annual flow change

Temperature Change Effects: Mean Annual Flow Change


Temperature change effects daily peak flow

Temperature Change Effects: Daily Peak Flow

Eastern Puget Sound Basins


Temperature change effects daily peak flow1

Temperature Change Effects: Daily Peak Flow

Western Puget Sound Basins


Temperature change effects daily peak flow2

Temperature Change Effects: Daily Peak Flow

71% urbanization

Urbanization Affected Gages

64% urbanization

31% urbanization


Land cover change and climate change effects on streamflow in puget sound basin washington

Mann-Kendall Trends of Raw Measurement: Combination of Climate Change Effects and Land Cover Change Effects

For upland basins, land cover is not a dominant effect in changing streamflow.


Pacific decadal oscillation pdo

Pacific Decadal Oscillation (PDO)

  • Positive phase (+): warmer and dryer climate

  • Negative phase (-): colder and wetter climate

  • In upland basins, PDO perhaps play a more important role than land cover change effects.


Conclusions

Conclusions

  • In upland basins, fall, winter and spring streamflows are higher under current land cover condition because of lower ET. Summer streamflow is lower in 2002 scenario because of less water storage in the basin.

  • On average, mean annual streamflows are slightly higher under current land cover condition which might not be statistically significant in upland basins.

  • Peak flows are affected by the combination of ET and infiltration excess runoff. Peak flows tend to be higher under current land cover condition for most basins.

  • Chances of getting peak flows are higher under current land cover condition.


Conclusions1

Conclusions

  • Temperature change mainly affects upland basins where snow occurs. Temperature change mainly affects seasonal distribution of streamflow. Warmer temperature regime tends to generate higher winter flow but lower summer flow due to less snow occurrence, early snow melt and less basin snow storage.

  • Simulation shows that land cover change might be more important than climate change in affecting the streamflow in lowland urbanizing basins.

  • Trend study in upland gauged stations shows that land cover change is not the dominant factor that influences streamflows in the upland basins.

  • Regional climate system such as PDO perhaps plays a more important role in affecting streamflow in the upland basins.


Thank you

Thank You !


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