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 UniversityDr. Graeme Lockaby, School of Forestry, Auburn University Dr. David Laband, Department of Economics, Georgia Tech UniversityMarlon 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

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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 1992-2008

8 wells were sampled (differed among samplings)

Analyzed water chemistry

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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

Percent land use/land cover dataType 1992 1997 2000 2006 2008Water 0.57 1.04 0.76 1.03 1.08Vegetation

78.03 75.41 73.02 71.18 64.11

Impervious

21.40 23.55 26.22 27.79 34.81

Trussville Water Quality Assessment

Results of regression analyses for water quality indices and % impervious surface

Water variables R-square Pr>FNitrogen as nitrate 0.5829 0.0458*Sodium 0.4016 0.0916pH 0.3795 0.1039Total alkalinity 0.5213 0.0431*Calcium 0.0058 0.8578Chloride 0.2477 0.2094Magnesium 0.0177 0.7537Total Dissolved Solids 0.0369 0.6486Turbidity 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

% Impervious surface

20 22 24 26 28 30 32 34 36

Nitr

ate

(mg/

L)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Actual nitratePredicted

r2=0.5829

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

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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?

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