Trends are provided individually for each parameter and station in a simple table format.
Not all constituents are available for all sites.
STAID = USGS Station ID
PCODE = Parameter code:
P00600 = Total nitrogen (as N)
P00631 = Nitrate (as N)
P00665 = Total phosphorus (as P)
P00671 = Orthophosphorus (as P)
P80154 = Suspended sediment
START_YEAR = First water year of modeling period used to estimate load
END_YEAR = Last water year of modeling period used to estimate load
NYEARS = Length of period over which trend is computed, in years, through 2016
PERIOD = Short-term or Long-term, depending on number of years
lowF = Lower confidence limit (90%) of the estimated change in load, in 10^6 kilograms per year (kg/yr)
estF = Estimate of flow-normalized load change in Trend Period, in 10^6 kilograms per year (kg/yr)
upF = Upper confidence limit (90%) of the estimated change in load, in 10^6 kilograms per year (kg/yr)
FNT_PCT = Total change in flow-normalized load in percent
TrendDir = Trend direction, with 3 categories: No Trend, Degrading, Improving
Likelihood = Likelihood of trend direction, with 4 categories: as Likely as Not (likelihood coef, >0.33 and <0.67), Likely (likelihood coef, >=0.67 and <0.90), Very Likely (likelihood coef, >=0.90 and <0.95), Extremely Likely (likelihood coef, >=0.95 and <=1.0)
Hirsch, R.M., Moyer, D.L., and Archfield, S.A., 2010, Weighted regressions on time, discharge, and season (WRTDS), with an application to Chesapeake Bay river inputs: Journal of the American Water Resources Association, v. 46, no. 5, p. 857-880
Hirsch, R.M. and De Cicco, Laura, 2015, User guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R packages for hydrologic data (version 2.0, February 2015): U.S. Geological Survey Techniques and Methods book 4, chap. A10, 93 p., http://dx.doi.org/10.3133/tm4A10. (accessed May 24, 2016)
Hirsch, R.M., Archfield, S.A., and De Cicco, L.A., 2015, A bootstrap method for estimating uncertainty of water quality trends: Environmental Modelling and Software, v. 73, p. 148-166. http://dx.doi.org/10.1016/j.envsoft.2015.07.017. (accessed May 24, 2016)
Chanat, J.G., Moyer, D.L., Blomquist, J.D., Hyer, K.E., and Langland, M.J., 2016, Application of a weighted regression model for reporting nutrient and sediment concentrations, fluxes, and trends in concentration and flux for the Chesapeake Bay Nontidal Water-Quality Monitoring Network, results through water year 2012: U.S. Geological Survey Scientific Investigations Report 2015-5133, 139 p. http://dx.doi.org/10.3133/sir20155133.
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