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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.