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2006: How Voluntary Environmental Programs Affect Water Quality

Jay Abolofia (Economics) University of Washington

Agriculture contributes excess nutrients, pesticides, sediment, heavy metals, and toxic substances to our waters. Under the Chesapeake Bay Agreement the agricultural sector is to play a significant role in helping the region remove the Bay from the EPA's impaired waters list by 2010. Virginia's agricultural best management practices (BMPs) cost-share program is one of the state's primary tools to help meet this goal. The program's goal is to install BMPs on agricultural fields that will yield the greatest increases in overall water quality per dollar spent of cost-share. My research specifically focused on The Colonial Soil and Water Conservation District's BMP cost-share program and its effectiveness in reducing agricultural non-point source pollution. Using GIS software, I spatially examined the district's environmental field conditions that affect water quality and contrasted those environmental conditions with the spatial patterns of cost-share BMP implementation. These environmental field attributes included soil types and their water quality characteristics (permeability, drainage, and slope), proximity to nearest water body and impaired stream, and field acreage. With these data I determined whether cost-share BMP installation outcomes reflected the program's water quality goals. I ran a probit regression model that modeled a field's probability of having an installed BMP. Because the outcome was binary, the model's dependent variable took the value of 0 if a BMP was not installed or 1 if a BMP was installed. To explain the probability of this binary outcome, we assigned the environmental field attributes as the model's explanatory variables. Model results were then able to tell us how each field attribute probabilistically explained participation in the program. When running the model we found that fields with a greater acreage or those closer to lakes or coastline had higher probabilities of having a BMP. We also found that fields with soil types of poor permeability or drainage or those with higher slopes were less likely to have an installed BMP. Given these results, we were able to better understand the program's effectiveness and to offer the district insight for enhancing water quality in the future.

For additional documentation Jay Abolofia provided 2 PowerPoint Presentations provided here in PDF form.

One for the Colonial Soil and Water Conservation District entitled "The Virginia Agricultural BMPs Cost-Share Program"

A second for the REU program entitled "How Voluntary Environmental Programs Affect Water Quality".