Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 25, 2001
Publication Date: October 25, 2001
Citation: TOMER, M.D., BURKART, M.R., JAYNES, D.B., JAQUIS, R.J., COLE, K.J., HATFIELD, J.L., DINNES, D.L. FLOW-DURATION CHARACTERIZATION OF WATER AND NITRATE FLUXES FROM A TILE-DRAINED WATERSHED. AMERICAN SOCIETY OF AGRONOMY MEETINGS. 2001. CD-ROM. MADISON, WI. Technical Abstract: In the Midwest, tile drainage is a prevalent feature that has changed the region's hydrology and provides a ready pathway for export of leached nitrate-N. Multi-year data to characterize fluxes of water and nitrate-N from tile-drained watersheds are needed to assess effects of drainage on water quality. Here we summarize tile and streamflow data from Walnut Creek in central Iowa, collected between 1992 and 2000. Two tile mains draining 493 and 863 ha of land were monitored, along with the watershed outlet draining 4744 ha. Row crops occupy nearly 90% of the area. Livestock production is minimal. During nine years of monitoring, total tile flow losses were 1560 mm water and 176 kg NO3-N/ha for the smaller tile, 1710 mm water and 229 kg NO3-N/ha for the larger tile, and 1980 mm water and 182 kg NO3-N/ha for the watershed. Average NO3-N concentrations (flow-weighted) were 11.3 mg/L for the smaller tile, 13.4 mg/L for the larger tile, and 9.2 mg/L at the watershed outlet. Dilution by denitrified groundwater and in-stream processes result in smaller concentrations at the outlet. Of the total mass-flux of water, a large proportion had nitrate-N concentrations greater 10 mg/L; 59% at the smaller tile main, 73% at the larger main, and 39% at the watershed outlet. Results suggest practices to reduce nitrate losses through tiles should be encouraged.