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/

Trends in nutrient fluxes and streamflow for selected tributaries in the Lake Erie watershed were calculated using monitoring data at 10 locations. Trends in flow-normalized nutrient fluxes were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). Site information and streamflow and water-quality records are contained in 3 zipped files named as follows: INFO (site information), Daily (daily streamflow records), and Sample (water-quality records). The INFO, Daily (flow), and Sample files contain the input data, by water-quality parameter and by site as .csv files, used to run trend analyses. These files were generated by the R (version 3.1.2) software package called EGRET - Exploration and Graphics for River Trends (version 2.5.1) (Hirsch and DeCicco, 2015), and can be used directly as input to run graphical procedures and WRTDS trend analyses using EGRET R software. The .csv files are identified according to water-quality parameter (TP, SRP, TN, NO23, and TKN) and site reference number (e.g. TPfiles.1.INFO.csv, SRPfiles.1.INFO.csv, TPfiles.2.INFO.csv, etc.). Water-quality parameter abbreviations and site reference numbers are defined in the file "Site-summary_table.csv" on the landing page, where there is also a site-location map ("Site_map.pdf"). Parameter information details, including abbreviation definitions, appear in the abstract on the Landing Page. SRP data records were available at only 6 of the 10 trend sites, which are identified in the file "site-summary_table.csv" (see landing page) as monitored by the organization NCWQR (National Center for Water Quality Research). The SRP sites are: RAIS, MAUW, SAND, HONE, ROCK, and CUYA. The model-input dataset is presented in 3 parts: 1. INFO.zip (site information) 2. Daily.zip (daily streamflow records) 3. Sample.zip (water-quality records) Reference: Hirsch, R.M., and De Cicco, L.A., 2015 (revised). User Guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R Packages for Hydrologic Data, Version 2.0, U.S. Geological Survey Techniques Methods, 4-A10. U.S. Geological Survey, Reston, VA., 93 p. (at: http://dx.doi.org/10.3133/tm4A10).

Trends in nutrient fluxes and streamflow for selected tributaries in the Lake Erie watershed were calculated using monitoring data at 10 locations. Trends in flow-normalized nutrient fluxes were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). Site information and streamflow and water-quality records are contained in 3 zipped files named as follows: INFO (site information), Daily (daily streamflow records), and Sample (water-quality records). The INFO, Daily (flow), and Sample files contain the input data, by water-quality parameter and by site as .csv files, used to run trend analyses. These files were generated by the R (version 3.1.2) software package called EGRET - Exploration and Graphics for River Trends (version 2.5.1) (Hirsch and DeCicco, 2015), and can be used directly as input to run graphical procedures and WRTDS trend analyses using EGRET R software. The .csv files are identified according to water-quality parameter (TP, SRP, TN, NO23, and TKN) and site reference number (e.g. TPfiles.1.INFO.csv, SRPfiles.1.INFO.csv, TPfiles.2.INFO.csv, etc.). Water-quality parameter abbreviations and site reference numbers are defined in the file "Site-summary_table.csv" on the landing page, where there is also a site-location map ("Site_map.pdf"). Parameter information details, including abbreviation definitions, appear in the abstract on the Landing Page. SRP data records were available at only 6 of the 10 trend sites, which are identified in the file "site-summary_table.csv" (see landing page) as monitored by the organization NCWQR (National Center for Water Quality Research). The SRP sites are: RAIS, MAUW, SAND, HONE, ROCK, and CUYA. The model-input dataset is presented in 3 parts: 1. INFO.zip (site information) 2. Daily.zip (daily streamflow records) 3. Sample.zip (water-quality records) Reference: Hirsch, R.M., and De Cicco, L.A., 2015 (revised). User Guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R Packages for Hydrologic Data, Version 2.0, U.S. Geological Survey Techniques Methods, 4-A10. U.S. Geological Survey, Reston, VA., 93 p. (at: http://dx.doi.org/10.3133/tm4A10).

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/

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/

Data provided in this release support the findings in Choquette et al. (2019), utilizing methods for evaluating water-quality and daily-streamflow trends described also in Hirsch and DeCicco (2015 and 2018a) and Hirsch (2018). The trend results and model-input data focus on 10 locations in the Lake Erie watershed that have long-term (20 or more years) water-quality and streamflow monitoring records. The trend results include the years 1987 through 2016 or specified sub-periods during this time frame. The model-input data records spanned the time period 1974 through 2016 although record lengths varied by site, data type, and trend analysis. The water-quality records were provided by the National Center for Water Quality Research (NCWQR; Heidelberg University, Tiffin, Ohio) and the Indiana Department of Environmental Management (IDEM), and streamflow records were provided by the U.S. Geological Survey (USGS). The 10 water-quality trend sites were identified using abbreviated names of the nearby USGS streamgage that provided streamflow data for determining nutrient fluxes at these sites (see Site_map.pdf and Site-summary_table.csv). Trends in flow-normalized nutrient fluxes were determined using the method Weighted Regression on Time, Discharge, and Season (WRTDS) method (Hirsch and DeCicco, 2015, 2018a, and 2018b) and streamflow (discharge) trends were determined using the graphical-statistical method of Quantile-Kendall plots (Hirsch, 2018). The nutrient trend analyses focus on the parameters total phosphorus (TP, as P), soluble reactive phosphorus (SRP, as P), total nitrogen (TN, as N), nitrate plus nitrite (NO23, as N) filtered at NCWQR sites or unfiltered at IDEM sites, and total Kjeldahl nitrogen (TKN, as N). TN was calculated as TKN plus NO23. SRP was monitored at only 6 of the 10 trend sites. Additional information on field and laboratory methods appears in Choquette et al. (2019). The dataset is presented in two parts: 1. Nutrient and Streamflow Model-Input Data 2. Nutrient and 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., 2015 (revised). User Guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R Packages for Hydrologic Data, Version 2.0, U.S. Geological Survey Techniques Methods, 4-A10. U.S. Geological Survey, Reston, VA., 93 p. (at: http://dx.doi.org/10.3133/tm4A10). Hirsch, R.M., and De Cicco, L.A., 2018a, Guide to EGRET 3.0 Enhancements: at https://cran.r-project.org/web/packages/EGRET/vignettes/Enhancements.html. Hirsch, R.M., and De Cicco, L.A., 2018b, EGRET release 3.0, and EGRETci release 2.0, at: https://cran.r-project.org/ .

Data provided in this release support the findings in Choquette et al. (2019), utilizing methods for evaluating water-quality and daily-streamflow trends described also in Hirsch and DeCicco (2015 and 2018a) and Hirsch (2018). The trend results and model-input data focus on 10 locations in the Lake Erie watershed that have long-term (20 or more years) water-quality and streamflow monitoring records. The trend results include the years 1987 through 2016 or specified sub-periods during this time frame. The model-input data records spanned the time period 1974 through 2016 although record lengths varied by site, data type, and trend analysis. The water-quality records were provided by the National Center for Water Quality Research (NCWQR; Heidelberg University, Tiffin, Ohio) and the Indiana Department of Environmental Management (IDEM), and streamflow records were provided by the U.S. Geological Survey (USGS). The 10 water-quality trend sites were identified using abbreviated names of the nearby USGS streamgage that provided streamflow data for determining nutrient fluxes at these sites (see Site_map.pdf and Site-summary_table.csv). Trends in flow-normalized nutrient fluxes were determined using the method Weighted Regression on Time, Discharge, and Season (WRTDS) method (Hirsch and DeCicco, 2015, 2018a, and 2018b) and streamflow (discharge) trends were determined using the graphical-statistical method of Quantile-Kendall plots (Hirsch, 2018). The nutrient trend analyses focus on the parameters total phosphorus (TP, as P), soluble reactive phosphorus (SRP, as P), total nitrogen (TN, as N), nitrate plus nitrite (NO23, as N) filtered at NCWQR sites or unfiltered at IDEM sites, and total Kjeldahl nitrogen (TKN, as N). TN was calculated as TKN plus NO23. SRP was monitored at only 6 of the 10 trend sites. Additional information on field and laboratory methods appears in Choquette et al. (2019). The dataset is presented in two parts: 1. Nutrient and Streamflow Model-Input Data 2. Nutrient and 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., 2015 (revised). User Guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R Packages for Hydrologic Data, Version 2.0, U.S. Geological Survey Techniques Methods, 4-A10. U.S. Geological Survey, Reston, VA., 93 p. (at: http://dx.doi.org/10.3133/tm4A10). Hirsch, R.M., and De Cicco, L.A., 2018a, Guide to EGRET 3.0 Enhancements: at https://cran.r-project.org/web/packages/EGRET/vignettes/Enhancements.html. Hirsch, R.M., and De Cicco, L.A., 2018b, EGRET release 3.0, and EGRETci release 2.0, at: https://cran.r-project.org/ .

This Child Item contains (1) a table of trends in eight annual streamflow statistics for the time periods 1940-1969, 1970-1999, and 2000-2018, and (2) a .zip file of plots of the eight statistical trends for the three time periods. The annual streamflow statistics and their trends were computed by Climate Year (CY) for 1-,7- and 30-day minima and by Water Year (WY) for 1-,7- and 30-day maxima, median and mean. Streamgages from the original dataset (n = 409) were excluded from one or more time periods of analysis because of extensive data gaps that would interrupt trend lines; therefore, streamgages were indexed into the earliest possible time period relative to their installation date (for example, a streamgage with an operating start year of 1958 would be included in the analysis for the time periods 1970-1999 and 2000-2018), which resulted in different sample sizes for each period: 1940-1969 (n = 90), 1970-1999 (n = 167), and 2000-2018 (n = 243). Similarly, multiple streamgages were wholly excluded because of frequent discontinuities in the daily mean streamflow used to derive the annual mean streamflow through all three time periods.

This Child Item contains (1) a table of trends in eight annual streamflow statistics for the time periods 1940-1969, 1970-1999, and 2000-2018, and (2) a .zip file of plots of the eight statistical trends for the three time periods. The annual streamflow statistics and their trends were computed by Climate Year (CY) for 1-,7- and 30-day minima and by Water Year (WY) for 1-,7- and 30-day maxima, median and mean. Streamgages from the original dataset (n = 409) were excluded from one or more time periods of analysis because of extensive data gaps that would interrupt trend lines; therefore, streamgages were indexed into the earliest possible time period relative to their installation date (for example, a streamgage with an operating start year of 1958 would be included in the analysis for the time periods 1970-1999 and 2000-2018), which resulted in different sample sizes for each period: 1940-1969 (n = 90), 1970-1999 (n = 167), and 2000-2018 (n = 243). Similarly, multiple streamgages were wholly excluded because of frequent discontinuities in the daily mean streamflow used to derive the annual mean streamflow through all three time periods.

This dataset utilized available water-quality data from the Mississippi Department of Environmental Quality and streamflow from the U.S. Geological Survey to estimate total nitrogen and total phosphorus loads and changes in loads from water years 2008 through 2018. Nutrient loads and changes in loads were estimated at 22 state ambient water-quality network sites, and were estimated using LOADEST regression models, Beale-Ratio Estimator, or WRTDS (Weighted Regression on Time, Discharge, and Season). The method selected is based on the evaluation of the flux-bias statistic and use of multiple graphical tools through EGRET to identify and characterize issues with particular models for each given dataset and is included in this data release.