CONVERSION OF FOREST TO URBAN LAND COVER:
INFLUENCES ON DRINKING WATER QUALITY AND
WILLINGNESS TO ACCEPT PAYMENTS FOR WATER
QUALITY SERVICES
Lauren D. Behnke, School of Forestry, Auburn University
Dr. Graeme Lockaby, School of Forestry, Auburn University
Dr. David Laband, Department of Economics, Georgia Tech University
Marlon Cook, Groundwater Assessment Program, Geologic Survey of Alabama
Project Description

Objectives
 Determine
the effects of land use change in aquifer
recharge zones on groundwater chemistry
 Identify
the terms and conditions under which private,
non-industrial landowners within aquifer recharge
zone would be willing to participate in a program
that would pay them to retain and/or expand the
amount of forest cover on their property.
Background

Aquifers
Source of drinking water
 Infiltration in recharge
zones replenish aquifer


Anthropogenic changes

Land-use change
Increased forest loss
 Increased urbanization


Impacts on aquifer supply
Increased pollutants
 Little known about effects

http://imnh.isu.edu/digitalatlas/hydr/concepts/gwater
/imgs/6comp.jpg
Forecasted change in the proportion of counties in urban land use
(www.rsr.fs.usda.gov/futures/)
Projection of population change (change in people per square-mile)
(www.rsr.fs.usda.gov/futures/)
Water Quality Approach



Water quality data from
Utilities Board of the City
of Trussville, AL from 19922008
8 wells were sampled
(differed among samplings)
Analyzed water chemistry
http://ga.water.usgs.gov/edu/pictures/artesiansmall.jpg
Water Quality Approach



Recharge zones were delineated by Marlon Cook
of the AL Geologic Survey
AGS provided land use/land cover data
Regression analyses were used to relate changes in
impervious cover across time to water quality data
Aquifer Recharge Zone – Trussville, AL
Trussville Water Quality Assessment
Percent land use/land cover data
Type
1992
1997
2000
2006
2008
0.57
1.04
0.76
1.03
1.08
Vegetation
78.03
75.41
73.02
71.18
64.11
Impervious
21.40
23.55
26.22
27.79
34.81
Water
Results of regression analyses for water
quality indices and % impervious surface
Water variables
Nitrogen as nitrate
R-square
0.5829
Pr>F
0.0458*
Sodium
0.4016
0.0916
pH
0.3795
0.1039
Total alkalinity
0.5213
0.0431*
Calcium
0.0058
0.8578
Chloride
0.2477
0.2094
Magnesium
0.0177
0.7537
Total Dissolved Solids
0.0369
0.6486
Turbidity
0.2676
0.2344
*significant at the 0.05 level
The relationship between percent impervious surface in the
recharge zone and N-NO3 in Trussville, AL well water
0.8
r2=0.5829
0.7
Nitrate (mg/L)
0.6
0.5
0.4
0.3
0.2
0.1
20
22
24
26
28
30
% Impervious surface
Actual nitrate
Predicted
32
34
36
The relationship between percent impervious surface in the
recharge zone and alkalinity in Trussville, AL well water
Water Quality Results


Increasing N-NO3 and declining alkalinity as impervious
surface increased from 1992 to 2008
Elevated N-NO3 is generally considered to be an indicator of
water quality degradation although the levels observed in the
Trussville wells (0.7 mg/L) do not approach the US EPA
allowable limit for drinking water
Water Quality Results


These data suggest the chemistry of the water supply for of
Trussville, AL is undergoing changes due to increased
urbanization within the recharge zone
Sources of N-NO3 include lawn fertilizers, sewer and septic
systems, animal waste, and atmospheric deposition from
anthropogenic sources
Economic Analysis


Identify terms and conditions under which private,
non-industrial landowners would participate in a
program that pays them to retain and/or expand
the amount of forest cover on their property
Mailed 204 surveys to individual owners of 10+
acres in Jefferson and St. Clair counties
 24
returned
Economic Analysis
Method of Acquisition
Years of Ownership
Economic Analysis
Number of Tracts Owned
Total Acreage Owned
Willingness to accept payment to retain forested acreage
and acceptable annual payment after 1 year
After 1 year
Willingness to accept payment to retain forested acreage
and acceptable annual payment after 3 and 5 years
After 3 years
After 5 years
Cash versus tax credit as payment
Key Findings

Water Quality Findings
 Levels
of nitrate were below EPA critical limits; but a
significant, positive relationship was found between
increasing development and rising levels of nitrate in wells
http://www.charlottewilderness.org/img/Photos/Dry-Mesic%20Oak-Hickory%20Forest.jpg
Economic Findings

Landowners were willing to participate in a
program:
 to
retain forest cover for pay
 program of a short duration
 relatively low payment amounts

As the desired contracting period lengthens,
landowners react by:
 unwilling
to participate under existing payments
 require higher annual, per-acre compensation

No preference between cash or a tax credit
Acknowledgements




Alabama Association of RC&D Councils, Inc.
Auburn University’s Center for Forest Sustainability
Utilities Board of the City of Trussville, AL
Alabama Geologic Survey
Questions?
http://eeekeverywhere.files.wordpress.com/2011/05/img_1967.jpg