Saturday, September 17, 2016

Drought Streamflow

OCTOBER 1 UPDATE: after two inches of rain in the last two days, Salisbury Brook has risen dramatically!  (Two photos at the very bottom of the post.)  I am astonished: since you seldom see surface runoff--except on pavement--I assumed nearly all the rain would sink into the soil and begin the long process of restoring soil moisture.  

I expect two inches might penetrate half a foot or so into dry soil on level ground, reaching most plant roots.

Instead, a good deal of rain has almost directly entered this brook (or others, or the sewers)The bad news: by running off rather than sinking in, most of this water will be lost from the system.  And eastern Massachusetts is still about 10 inches below normal rainfall for the year.

Original post of September 17:
A news report a couple of weeks ago said the Ipswich River in the northeast part of Mass was at its lowest level since records began, back in the 1930s.  Meanwhile, the Boston Globe yesterday reported that half of Massachusetts is now in extreme drought (an official designation--the second worst possible), and rainfall in the Boston area is 9.5 inches below normal for the year, and 18.5 inches below normal since January, 2015.  

I have been taking photos of a bit of Salisbury Brook here in Brockton every so often this year.  Here are photos early and late in the year.  

 February 2

late February

March 11

By chance, I took no photos for more than three months, not having planned a complete chronicle.

 July 29

 August 5

August 13

 August 29

 Sept 3

  September 17

Water still trickles among stones it once splashed over, but the flow is only perceptible if you stop and look awhile.
Of course, there is regular seasonal variation in streamflow, but around here it shouldn't be too extreme: rainfall is typically pretty even throughout.  Here is a climate diagram for nearby Taunton to contrast with the current drought.  Climate diagrams* show average monthly rainfall (thicker line, millimeter scale on right) and temperature (thinner line, Celsius temperatures on left) throughout the year (tic marks at bottom).  The scales are made to line up so that when the two lines cross ("temperature higher than rainfall"), water evaporates more quickly than it is replaced by rain--producing dry conditions.  As you can see, that rarely happens around here--even though rainfall dips in summer.

*Climate Diagram World Atlas

 Late morning, Saturday, October 1, after 2 inches of rain in two days.


  1. I had no idea?! The drought conditions are pretty stark in your photos. Your update shows how little I & most folks know about how recharge happens. We see rain & think - hurray all is hoid (or maybe I should start building an ark).