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Project Title: NitrogenTrends in Minnesota Streams
Project Number: NQ00ANH
Project Chief: Dave Lorenz
Project Start Date: 2011
Project End Date: 2011
Cooperator: Minnesota Pollution Control Agency

Scope: In response to a directive by the Minnesota Legislature to establish water quality standards for nitrate-nitrogen and total nitrogen the Minnesota Pollution Control Agency (MPCA) is leading an effort to develop nitrate water-quality standards for surface waters based on aquatic life toxicity. As part of this effort, the USGS is working with the MPCA to characterize nitrogen loading in watersheds throughout Minnesota to provide a foundation for developing and evaluating nitrogen reduction strategies.

Objectives: Nitrate is a major component of total nitrogen, along with ammonium and organic nitrogen. This study will characterize nitrogen loading and trends to Minnesota's surface waters to help provide a scientific foundation of information that will be used to develop and evaluate nitrogen reduction strategies.

Methodology:

1. Use an existing SPAtially Referenced Regression On Watersheds (SPARROW) model to address watershed nutrient loads, nitrogen source identification, and estimate load reductions from reducing sources.
2. Describe existing stream concentrations thought out the state by using simple summary statistics of recently collected data, since January 1, 2000.
3. Long-term trend analysis of selected Minnesota Milestone sites using the QWTREND model.
4. Short-terrm trend analysis of selected Minnesota Milestone and other sites using seasonal Kendall.

Communications Plan: Maps and table will be provided to the MPCA as available and as needed for internal communication with the MPCA. A Scientific Investigations Report will be prepared to present the results from methods 2 through 4. A journal article, funded by other sources will present the tools required for method 1.

Progress for FY11: The SPARROW modeling was completed. Data and results were provided to the cooperator. Simple summary statistics of annual, and seasonal concentrations of total nitrogen, nitrate plus nitrite, ammonia, and Kjeldahl nitrogren were completed and a summary was and maps were provided to the MPCA.

Statement of Work for FY12: Temporal trend analyses will be conducted on seasonally and flow-adjusted concentrations for all stations chosen for trends analysis. This will employ the QWTREND model or a comparable model for the long term nitrate trends assessment. The MPCA will provide in-kind services for part of the task. Short-term (17 year) nitrate plus nitrite trends will be determined and mapped for approximately 48 sites around the state. This trend analysis will concentrate on monotonic, linear, or quadratic time trends for the 17 year period using the Seasonal Kendall method.