Clay County Drainage Site: Field Scale Drainage Research in the Minnesota Red River Valley.

Northwestern Minnesota’s Red River Valley is experiencing an unprecedented increase in subsurface drainage tile installation. In this region of silty clay loam soils, drainage tile is installed to remove excess soil water to facilitate earlier agricultural fieldwork and improved soil conditions for enhanced crop growth. The impact of subsurface drainage on water quality and quantity in the Red River Valley remained largely unstudied until 2010, when the Minnesota Department of Agriculture established a 155 acre field-scale research project in Clay County, to monitor environmental impacts of surface and subsurface drainage from agricultural fields in the Red River Valley. The instrumentation and layout of the site offers an opportunity to address a number of critical water related issues in the valley, which is Minnesota’s flattest and driest region. The site includes one surface and six subsurface drainage plots, each monitored using automated samplers collecting hydrologic, nutrient and sediment characteristics. Five site data years are available, initial results estimate 61% of subsurface drainage has occurred between May and June. Annual mean flow weighted nitrate concentrations in subsurface drainage ranged from 3.7 mg/l to 23.7 mg/l, with highest concentrations in June and July. Annual mean flow weighted total phosphorus concentrations ranged from 0.04 mg/l to 0.08 mg/l. Long term (>10 years) water quality and quantity data from these plots will enhance our ability to gain a system understanding of the hydrologic effects of subsurface drainage in the Red River Valley’s agricultural landscape. Data collected at this site will inform local conservation professionals, crop advisers and policy makers on the impacts of subsurface drainage and contribute to discussions involving producers and landowners.