Nitrogen (N), phosphorus (P), and total suspended solids (TSS) loads, in Hampton Roads, Virginia stormwater conveyance systems have been calculated using monitoring data from 12 intensively monitored watersheds for the period from water year (October - September) 2016 through 2020. Nutrient and TSS loads were computed using a surrogate (multiple-linear regression) approach with lab analyzed N, P, and TSS samples as the response variable and basic water-quality parameters (e.g. turbidity, specific conductance, water temperature), streamflow, a baseflow separation Boolean term, and time and seasonal terms as predictor (surrogate) variables. Load results represent the mass of N, P, and TSS exported from each of the Hampton Roads watersheds. Coefficients are provided for each unique station-constituent model. Loads are provided for the following constituents: TSS, total N, total P, nitrate plus nitrite, total Kjeldahl N, total organic N, and orthophosphate. Streamflow is an important driver of water-quality conditions; therefore, datasets are provided describing stream flashiness as well as a suite of event-based metrics, which include stormflow volume, peak flow, lag to peak, storm event duration, time to peak, runoff ratio, and rise rate. Streamflows are driven by precipitation patterns; therefore, rainfall data collected at 10 Hampton Roads Sanitation District (HRSD) gages are also provided. These data were used to evaluate rainfall patterns during the study period as well as compute the lag to peak and runoff ratio metrics for each storm event. This data release contains six comma-delimited (.csv) files and one zip file with corresponding data dictionary files (.csv). HRSD.Rain.csv contains 15-minute interval rainfall data collected at 10 precipitation gages operated by the HRSD. HR_Loads_CalibrationData.csv contains all data used in the calibration of surrogate regression models for the computation of N, P, and TSS loads. HR_Loads_SurrogateData.csv contains 5-minute interval measurements of streamflow, water-quality parameters, and a Boolean baseflow separation identifier “BASE.” These data were used to compute 5-minute interval measurements of N, P, and TSS loads using surrogate regression models, which were calibrated with the data provided in HR_Loads_CalibrationData.csv. Model_Coefficients.csv contains the coefficients for each station-constituent specific model. Storm_Events.csv contains an identification number and mean timestamp for each storm extracted using the methods described in Porter, 2022, and seven metrics describing the hydrograph. RBI.csv contains an average Richards-Baker Flashiness (RBI) index score for 41 streamgaging stations operated by the United States Geological Survey: Virginia and West Virginia Water Science Center. UV_Loads.zip contains 12 identically formatted data tables with 5-minute unit value predictions of N, P, and TSS loads from the beginning of water year (October 1 - September 30) 2016 through 2020 at 12 stormwater monitoring stations in the Hampton Roads region of Virginia. For each file entity and attributes are described in data.dictionary.csv that shares the same name. The data dictionary file "UV_Loads_Data.dictionary..csv" applies to all .csv files in the UV_Loads.zip. A README text file is also attached, which contains descriptions of each data table and supplementary information.

Nitrogen (N), phosphorus (P), and suspended-sediment (SS) loads, in Fairfax County, Virginia streams have been calculated using monitoring data from five intensively monitored watersheds for the period from water year (October - September) 2008-2017. Nutrient and suspended-sediment loads were computed using a surrogate (multiple-linear regression) approach with lab analyzed N, P, and SS samples as the response variable and basic water-quality parameters (e.g. turbidity, specific conductance, pH, water temperature), streamflow, and time and seasonal terms that could be measured continuously as predictor (surrogate) variables. The load results represent the total mass of N, P, and SS that was exported from each of the Fairfax County watersheds. Trends in N, P, SS concentrations, as well as basic water-quality parameters including turbidity, water temperature, dissolved oxygen, specific conductance, and pH have been calculated using both non-flow-normalized and flow-normalized Seasonal Kendall tests at 14 monitoring stations in Fairfax County, Virginia for the period beginning April 2008 and ending March 2018. Flow-normalized trends were used to integrate out the effect of annual streamflow variability on concentration (or unit value). Streamflow is an important driver of water-quality conditions; therefore, several datasets are provided describing a suite of annual streamflow metrics: streamflow volume/yield, flashiness, peak stage, baseflow index, stormflow index, and runoff ratio. Depending on the metric, data are provided from the 5 intensively monitored Fairfax County, VA watersheds, the entire 20-station Fairfax County monitoring network (5 intensively monitored + 15 trend only monitoring stations), and/or 3 reference stations that are part of the USGS Chesapeake Bay Non-Tidal Network (USGS Station IDs 01646000, 01654000, 01658500). Streamflow analyses were conducted on data collected in water years 2008-2017 for all Fairfax County monitoring stations as well as station ID 01658500, 1948-2017 for station ID 01654000, and 1946-2017 for 01646000. Benthic macroinvertebrate data were collected annually (waters years 2008 - 2017) by Fairfax County staff from each of the 20 monitoring stations. These data were used to explore trends in 20 biological metrics; the data used to calculate these trends are provided.

Nitrogen (N), phosphorus (P), and suspended-sediment (SS) loads, in Fairfax County, Virginia streams have been calculated using monitoring data from five intensively monitored watersheds for the period from water year (October - September) 2008-2017. Nutrient and suspended-sediment loads were computed using a surrogate (multiple-linear regression) approach with lab analyzed N, P, and SS samples as the response variable and basic water-quality parameters (e.g. turbidity, specific conductance, pH, water temperature), streamflow, and time and seasonal terms that could be measured continuously as predictor (surrogate) variables. The load results represent the total mass of N, P, and SS that was exported from each of the Fairfax County watersheds. Trends in N, P, SS concentrations, as well as basic water-quality parameters including turbidity, water temperature, dissolved oxygen, specific conductance, and pH have been calculated using both non-flow-normalized and flow-normalized Seasonal Kendall tests at 14 monitoring stations in Fairfax County, Virginia for the period beginning April 2008 and ending March 2018. Flow-normalized trends were used to integrate out the effect of annual streamflow variability on concentration (or unit value). Streamflow is an important driver of water-quality conditions; therefore, several datasets are provided describing a suite of annual streamflow metrics: streamflow volume/yield, flashiness, peak stage, baseflow index, stormflow index, and runoff ratio. Depending on the metric, data are provided from the 5 intensively monitored Fairfax County, VA watersheds, the entire 20-station Fairfax County monitoring network (5 intensively monitored + 15 trend only monitoring stations), and/or 3 reference stations that are part of the USGS Chesapeake Bay Non-Tidal Network (USGS Station IDs 01646000, 01654000, 01658500). Streamflow analyses were conducted on data collected in water years 2008-2017 for all Fairfax County monitoring stations as well as station ID 01658500, 1948-2017 for station ID 01654000, and 1946-2017 for 01646000. Benthic macroinvertebrate data were collected annually (waters years 2008 - 2017) by Fairfax County staff from each of the 20 monitoring stations. These data were used to explore trends in 20 biological metrics; the data used to calculate these trends are provided.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2019. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2019. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2019. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2019. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2017. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2017. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring Network (RIM) stations for the period 1985 through 2018. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the RIM watersheds.