What is EGRET
?
Exploration and Graphics for RivEr Trends (EGRET)
EGRET includes statistics and graphics for streamflow history, water quality trends, and the statistical modeling algorithm Weighted Regressions on Time, Discharge, and Season (WRTDS).
A very complete document can be found HERE
Weighted Regressions on Time, Discharge, and Season:
\[ \ln(c)= \beta_0+\beta_1{DecTime}+\beta_2{\ln{Q}}+\beta_3 \sin(2\pi{DecTime})+\beta_4 \cos(2\pi{DecTime})+\epsilon \]