PATRICK SEJKORANOVEMBER 17 , 2009

GIS IN WATER RESOURCES

Yellowstone Fires and Their Hydrologic Effects

Yellowstone National Park 1988 Fires

1988 driest summer on record

7 major fires burned June-September 1988

3,215 km2 (36% of park) burned 485 km2 on August 20

alone!Fires extinguished in

September by rain/snow

Objectives

Did fires augment surface water runoff regimes in Yellowstone?

Hypothesis: Evapotranspiration and infiltration rates decrease in burned areas1, increasing runoff

Evaluate using runoff ratio:

Is runoff ratio post-fires higher than pre-fires?

1. Robichaud 2000

GIS DATAPark outline and Digital Elevation Map (DEM)

NHD Flowlines and USGS Gage Sites

Burn Type Raster

Compare runoff ratios between heavily burned and unaffected (control) watersheds

Before Fire After Fire

Firehole River

Boundary Creek

Firehole River(burned/experimental watershed)Baseflow 7.37 m3/s

724 km2 watershed (obtained with ArcHydro Terrain Preprocessing)

288 km NHD flowline

Drainage Density of 0.40/km

4th order stream at gage

Janua

ry

March May Jul

y

Septe

mber

Novem

ber

02468

10121416

Mean flow

Flow

(m

3/se

c)

Boundary Creek(unburned/control watershed)Baseflow 1.94 m3/s

224 km2 watershed

151 km NHD flowline

Drainage Density of 0.68/km

3rd order stream at gage

Janua

ry

March May Jul

y

Septe

mber

Novem

ber

012345678

Mean f...

Flow

(m

3/se

c)

4% 4% 1% 1

% 0%

90%

Canopy burnMixed burnNonforested burnUndifferentiated burnWaterUnburned

21%

14%

1%1%

0%

63%

Firehole River Boundary Creek

Precipitation Data Find similar precipitation events before and after 1988 fires

Obtain data from National Climactic Data Center

Interpolate rainfall across park via Spline

Pre-1988 Precipitation Event Spline raster can be used to estimate rainfall across watersheds

Zonal Statistics Tool in Spatial Analyst

July 10, 1987

July 11, 1987

September 18, 1989

0.6 cm

1.6 cm

1.6 cm

0.5 cm

1.7 cm

1.6 cmAv

erag

e Pr

ecip

itatio

n Ac

ross

Wat

ersh

eds

1.9

2

2.1

2.2

2.3

2.4

Dis

char

ge

(m3/

sec)

1.8

1.9

2

2.1

2.2

2.3

2.4

Dis

char

ge

(m3/

sec)

Boundary Creek

Pre-

Fire

Post

-Fir

eStorm Event Flow Conditions

9/9/19899/14/1989

9/19/19899/24/1989

6.8

7.3

7.8

8.3

8.8

Dis

char

ge (

m3/

s)

7/2/19877/7/1987

7/12/19877/17/1987

6.8

7.3

7.8

8.3

8.8

Dis

char

ge (

m3/

s)

Firehole River

Runoff Ratios

Boundary CreekPre-Fire RR = 1.1%Post Fire RR = 0.9%

Firehole RiverPre-Fire RR = 1.1%Post Fire RR = 0.9%

Runoff Ratio Example Calculation (Boundary Creek 9/18/1989)

These Runoff Ratios aren’t very different!

Conclusions

Runoff Ratios before and after fire are indistinguishable in burned watershed

An event’s runoff ratio same for both watershed

Suggests other factors besides landcover may influence runoff regimes Antecedent dry period, storm intensity, etc.?

Future Work

Evaluate other storm events using same methodology NEXRAD precipitation data for recent events

Similar effects for snow melt?

Questions?

Firehole River Boundary Creek

Lodgepole Pine, post disturbance

1%

Lodgepole Pine, climax

9%

Nonforested14%

Lodgepole Pine, suc-cessional

37%Engelmann

Spruce & Sub-alpine Fir, climax

2%

Douglas Fir, climax

2%

Pygmy Lodgepole

Pine36%

Lodgepole Pine, climax

25%

Nonforested5%

Lodgepole Pine, suc-cessional

66%

Engelmann Spruce & Subalpine Fir, climax

2%Pygmy Lodgepole Pine

1%

Lodgepole Pine, climax20%

Nonforested6%

Lodgepole Pine, post disturbance

38%

Lodgepole Pine, successional

34%

Engelmann Spruce & Subalpine Fir, climax

1%Pygmy Lodgepole Pine

1%

Firehole River Boundary Creek

Lodgepole Pine, post disturbance

1%

Lodgepole Pine, climax

9%

Nonforested14%

Lodgepole Pine, suc-cessional

37%Engelmann

Spruce & Sub-alpine Fir, climax

2%

Douglas Fir, climax

2%

Pygmy Lodgepole

Pine36%