WRTDSplus: Extensions to the WRTDS method.

For some sites and constituents the three dimensions of the Weighted Regressions on Time, Discharge, and Season (WRTDS) model do not capture all the important aspects of water quality variability. For example, in some locations hysteresis or antecedent flow conditions are important influences on water quality concentration and loads. In other places, daily flow is less predictive than the quick flow component of the hydrograph. WRTDSplus helps to calculate trends in these situations.