Drainage water management for water quality protection

l and drainage has been central to the development of North America since colonial times, with the first organized drainage efforts occurring as early as the 1600s (Evans et al. 1996). Drainage has been encouraged to improve public highways, reduce public health risks, promote increased crop yield and reduced yield variability, reduce surface runoff and erosion, and increase land value. Agricultural drainage includes artificial subsurface drainage and surface drainage. Most agricultural producers improve the drainage on their land for better trafficability, to enhance field conditions, to facilitate timely planting and harvesting operations, and to help decrease crop damage from saturated soil and standing water during the growing season. Agricultural drainage improvement also decreases year-to-year variability in crop yield, ensuring consistent production. Increasingly, agricultural drainage is being targeted as a conduit for pollution, particularly nutrient pollution (Needelman et al. 2007). Considerable resistance exists in some regions to the expansion of drainage systems despite their importance to food production, with up to 50% of the cropland in some states under artificial drainage. However, because drainage ditches and subsurface drainage systems convert diffuse flows from the landscape into concentrated flows, they also provide opportunities for precision conservation, the targeting of specific practices to improve downstream water quality (Delgado and Berry 2008). Drainage water management has emerged with the objective of balancing production and conservation goals. To be effective, drainage water management strategies must account for the many facets of today’s farming systems. Neither one practice alone constitutes drainage water management nor does one strategy fit all systems. The export of agricultural drainage water and associated pollutants to surface water can be managed and controlled, to an extent, using a combination of infield, edge-of-field, and off-site practices. With all practices, their applicability and performance depends upon the context (physiography, management systems, and pollutants of concern) in which they are to be implemented. We seek to highlight major areas within drainage water management that show promise from the standpoint of water quality protection, emphasizing the array of options, established and nascent. What follows are eight components of drainage water management where land managers can positively impact water quality. Our intent is not to prescribe a strict set of practices, but rather to showcase areas within drainage water management that provide opportunities for water quality protection and enhancement.