This data set includes WRTDS nutrient flux trend results and the values of daily streamflow trend results displayed in the Quantile-Kendall plots. For 1995-2015 nutrient trends, the method of generalized flow normalization (FNG) was used which explicitly addresses non-stationary streamflow conditions. For 2005-2015 nutrient trends, the WRTDS trend analyses used the method of stationary flow normalization (FNS) because streamflow nonstationarity is difficult to assess over this shorter duration time frame. The 1995-2015 annual nutrient trends were determined for all five nutrient parameters (TP, SRP, TN, NO23, TKN), and monthly trends were evaluated only for SRP. The 2005-2015 annual nutrient trends were determined for the three parameters TP, SRP, and TN. For the water-quality parameter SRP, monitoring data and trend results were available for 6 of the 10 trend sites. Daily streamflow trends were evaluated for the time-period 1987-2016 at 9 of the study sites, applied as climatic years (years which start April 1 and end March 31) for a period of 29 climatic years (1988 – 2016). Details on the WRTDS method of generalized flow normalization appear in Hirsch and De Cicco (2018) and in Choquette et al. (2019). Details on the Quantile-Kendall plots and their construction appears in Hirsch (2018) and in Appendix A of Choquette et al. (2019). Details regarding interpretations of these trend results and the watershed characteristics upstream of these sites appear in Choquette et al. (2019).
The results dataset is presented in 5 parts: 1. AnnualNutrientTrends_1995-2015.csv (WRTDS nutrient flux trend results) 2. MonthlySRPTrends_1995-2015.csv (SRP monthly flux trend results for 6 sites) 3. AnnualNutrientTrends_2005-2015.csv (WRTDS nutrient flux trend results) 4. DailyFlowTrends_1987-2016.zip (Annual streamflow trend results, by site, presented in the Quantile-Kendall plots) 5. Quantile-Kendall-plots.pdf (plots showing 1988-2016 streamflow trend results) References: Choquette, A.F., Hirsch, R.M., Murphy, J.C., Johnson, L.T., and Confesor, R.B. Jr., 2019, Tracking changes in nutrient delivery to western Lake Erie: approaches to compensate for variability and trends in streamflow: J. of Great Lakes Research, v. 45, no. 1, p. 21-39, https://doi.org/10.1016/j.jglr.2018.11.012. Hirsch, R.M., 2018, Daily streamflow trend analysis: U.S. Geological Survey Office of Water Information Blog, 38 p., at: https://owi.usgs.gov/blog/Quantile-Kendall/. Hirsch, R.M., and De Cicco, L.A., 2018, EGRET release 3.0, and EGRETci release 2.0, at: https://cran.r-project.org/