Index Value Plot

http://waterwatch.usgs.gov/index.php?id=real&sid=w__plot&r=nc

Index value plots are graphical depictions of a line according to data through a an equation. This plot is a time series plot of the stream flow of North Caroline.  The graph shows data since July 2, 1999 and is measured by wet, normal, and dry according to the average stream flow index. You can see that from 2001-2003 it was dry, then changed to wet from 2003-2007, then dipped back to dry for around three years and then stayed in the normal range.