Why did the Merrimack Crest Higher than predicted?

Since the NOAA predicted at 53.7 foot crest to the Merrimack River in Lowell today, and the river crested at around 58 feet this afternoon. I was wondering why the NOAA was so off.  For those of you that don’t know the Merrimack is heavily engineered and has been so since the Pawtucket Canal was built in the 1790s.  Levels in the river are controlled by a series of dams.  Including a Dam in Lawrence. 

There is a data point for river height above the Lawrence Dam, in Lowell, and below the Lawrence dam in Haverhill.  I looked at the data found at the USGS waterflow website and found an interesting coincidence.  The water leven in the Merrimack at Lowell was rising very quickly all day yesterday, but at about 1 am the level rose sharper but a 3 am it started to level out.  The changes in the slopes on the graphs are odd looking.  So I decided to look at the Haverhill numbers.  Interestingly at 3 am as the water level in lowell started leveling off the water level in Haverhill below the Lawrence dam started rising rapidly. 

I’m not saying that human or mechanical error in opening the Lawrence water gates too late, was to blame, but it is interesting that the charts seem to show a cause and effect centered around the Lawrence dam. You can see the charts after the jump.

Whas the dam opened too late in Lawrence or was it opened just in time to avert more catastrophic flooding?  Hopefully the media will ask the questions.

About Rob "EaBo Clipper" Eno