Evaluation of Variation in Nitrate Concentration Levels in the Raccoon River Watershed in Iowa
- Sampath Jayasinghe *a,
- David Millerb and
- Jerry L. Hatfieldc
- a Research Analyst, Decision Innovation Solutions, 3315 109th St., Suite B, Urbandale, IA 50322
b Director of Research and Commodity Services, Iowa Farm Bureau Federation, 5400 West, Des Moines, IA 50266
c Director, USDA–ARS, The Laboratory for Agriculture and the Environment, Ames, IA 50011. Assigned to Associate Editor Ali Sadeghi
The Raccoon River Watershed in Iowa has received considerable attention in the recent past due to frequent detections of nitrate concentrations above the federal drinking water standard. This paper econometrically investigates the determinants of variation of nitrate concentrations in the Raccoon River. The analysis relies on a generalized autoregressive conditional heteroscedastic process to model the serial dependence of volatility of the monthly nitrate concentrations in the Raccoon River. Monthly nitrate concentration data from Des Moines Water Works at Van Meter from 1992 to 2008 are used in the study. We found no statistically significant increasing trend in nitrate concentrations over the study period. There are substantial intra-annual variations in nitrate concentrations, and we noted a very strong seasonal pattern. Variations in rainfall and temperature contribute more to the monthly variation in nitrate concentration than do the changes in nitrogen application rates.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2012. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.