Paper No. J05105 of the Journal of the American Water Resources Association (JAWRA).
Model Based Nitrate TMDLs for Two Agricultural Watersheds of Southeastern Minnesota1
Article first published online: 12 FEB 2007
© 2007 American Water Resources Association. No claim to original U.S. government works
JAWRA Journal of the American Water Resources Association
Volume 43, Issue 1, pages 254–263, February 2007
How to Cite
Gowda, P. H., Dalzell, B. J. and Mulla, D. J. (2007), Model Based Nitrate TMDLs for Two Agricultural Watersheds of Southeastern Minnesota. JAWRA Journal of the American Water Resources Association, 43: 254–263. doi: 10.1111/j.1752-1688.2007.00020.x
- Issue published online: 12 FEB 2007
- Article first published online: 12 FEB 2007
- Received July 23, 2005; accepted March 28, 2006.
- nonpoint source pollution;
- tile drainage;
- ADAPT model;
Abstract: In this study, a set of nitrogen reduction strategies were modeled to evaluate the feasibility of improving water quality to meet total maximum daily loads (TMDLs) in two agricultural watersheds. For this purpose, a spatial-process model was calibrated and used to predict monthly nitrate losses (1994-96) from Sand and Bevens Creek watersheds located in south-central Minnesota. Statistical comparison of predicted and observed flow and nitrate losses gave r2 coefficients of 0.75 and 0.70 for Sand Creek watershed and 0.72 and 0.67 for Bevens Creek watershed, respectively. Modeled alternative agricultural management scenarios included: six different N application rates over three application timings and three different percentages of crop land with subsurface drainage. Predicted annual nitrate losses were then compared with nitrate TMDLs assuming a 30% reduction in observed nitrate losses is required. Reductions of about 33 (8.6 to 5.8 kg/ha) and 35% (23 to 15 kg/ha) in existing annual nitrate losses are possible for Sand and Bevens Creek watersheds, respectively, by switching the timing of fertilizer application from fall to spring. Trends towards increases in tile-drained crop land imply that attaining nitrate TMDLs in future may require other alternative management practices in addition to fertilizer management such as partial conversion of crop land to pasture.