Wildfire effects on water quantity and quality

Kevin D. Bladonbladonk@oregonstate.edu

Department of Forest Engineering, Resources, and Management

April 23, 2019Oregon Wildfire Response Council

Salem, OR

Convergence of Threats

Bladon et al. ES&T 2014; Robinne et al. Forests 2016; Robinne et al. Sci. Total Environ. 2018

• global wildfire water exposure index (GWWEI)• framework to define the potential for wildfires to

adversely affect water resources important for downstream ecosystems and human water needs

~65-70

Fire effects on annual streamflow

Hallema et al., Nature Communications, 2018

• Main factors driving post-fire streamflow:

• post-fire climate, burn severity, area burned

• ↑ streamflow if > 20% catchment burned

• No change in streamflow after prescribed fire

Wagenbrenner et al., International Journal of Wildland Fire, 2019

Longevity of effects of fire on streamflow

• Review of post-fire hydrology research in Mediterranean climates

• 13 of 30 recovered within 5 yrs

• 17 of 30 no evidence of recovery 5+ yrs after fire

Post-fire response can influence streamflow

• 1 burned catchment 37 % above predicted from pre-fire 35–41 yrs post-

• 2 catchments salvage logged, aerially seeded, fertilized = recovered

Niemeyer et al., Hydro. Proc., In Review

Miller et al. 2011 Int. J. Wildland Fire

Water quality: Predicted post-fire erosion rates

• W. Oregon post-fire erosion rates:

• 50–500 Mg ha-1 year-1

(18–184 tons acre-1 year-1)

Sediment after wildfire and post-fire land management

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Sed

imen

t co

ncen

tratio

n (m

g l-1

)

1

10

100ReferenceBurned Salvaged

Year

11x

9x 9x

4x

11x5x

1x

4x

28x

20x

37x

11x

20x

4x5x

2x

16x

1x

2x

Silins et al. 2011 Catena; Emelko et al. 2016 Global Change Biology

Site

Turb

idity

(NTU

)

0.01

0.1

1

10

100

1000

Shively Creek (Reference) Stouts Creek (Burned)

Turbidity

• Shively (Reference): mean 0.3 +/- 0.02 NTU • Stouts (Burned): mean 43.5 +/- 1.4 NTU

Burned

Unburned

Nutrients and Aquatic Ecology

Bladon et al. 2008 CJFR; Emelko et al. 2016 Global Change Biology; Rhoades et al. 2018 Catena

2004 2005 2006 2007 2008 2009 2010 2011 2012 20130

25

50

75

100

125

8x

7x

4x

9x

9x4x 4x

3x

12x

5x

9x

3x7x

5x 6x

2x

6x

1.2x

2x

Pho

spho

rus

(g

l-1)

Reference

Burned Salvaged

DOC Exceedance Curves

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

DO

C (m

g l-1

)

0.1

1

10

UnburnedBurnedSalvage logged

20

Proportion of time DOC or turbidity is greater than or equal to value on ordinate

Unburned BurnedBurned &

salvage logged

Bladon et al., ES&T, 2014

Take Home Messages

• How are we doing? • Don’t know… we lack research (and knowledge) on post-fire and post-

fire management effects on water quantity and quality in OR• Web of Science search (keywords: fire, water, Oregon) = 6 studies

Preparedness and Response

• Mitigation of wildfire effects on drinking water supplies:• Assessment of wildfire risks to drinking water supplies • Strategic fuel management for protection of source water supplies• Drinking water supplier preparedness (i.e., anticipate range of effects,

enhanced infrastructure, identifying alternate sources, knowledge mobilization, operator training)