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Development of Controlled Drainage as a BMP in North Carolina
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0304, .
Authors: R. O. Evans, R. W. Skaggs
Keywords: Controlled Drainage, Water Quality, Best Management Practice
Nonpoint source pollution has been identified by the NC Division of Water Quality as the
primary source of degradation of freshwater rivers and streams in North Carolina. Agriculture is
estimated to account for over 50% of surface water use impairment. North Carolina has
encouraged the agricultural community to address its contribution to nonpoint source water
pollution through voluntary implementation of Best Management Practices (BMPs). This
approach has been supported by financial incentives, technical and educational assistance,
research, and regulatory programs.
Financial incentives are provided through North Carolina's Agriculture Cost Share Program
authorized in 1984. Participating farmers receive 75% of predetermined average costs of
installed best management practices (BMPs) with the remaining 25% paid by farmers directly or
through in-kind contributions. Controlled drainage was designated a Best Management Practice
for soils with improved drainage.
Overall, approximately $137 million state appropriated dollars have been invested in BMPs to
improve water quality since the program was initiated. The Cost Share program is currently
budgeted for $7.1 million in non-reverting, recurring funds annually. Since the first cost share
contracts were issued in 1984, there have been 3,455 water control structures installed affecting
over 120,000 hectares. Controlled drainage has been installed on an additional 50,000 acres of
cropland and 100,000 hectares of forestland from private investments. The water quality benefits
of controlled drainage in North Carolina are estimated at a 1.7 million kilogram reduction in the
amount of N being transported in drainage water from agricultural fields annually.
This paper summarizes events leading to the establishment of controlled drainage as a BMP in
North Carolina and the impact of the practice on water quality since its implementation. Topics
addressed include a chronology of agricultural and environmental issues and concerns; field and
watershed scale research results; Federal and State nonpoint source policy; landowner
involvement; extension and outreach programs; and federal, state and local interaction.