Cold, Colder, Coldest

Has anyone else noticed that for the past two months Duluth city tap water doesn’t seem as cold as it used to? I mean, it’s cold, it’s just not the same level of… coldness it has been in the past. Is this a result of the Flizzard, the amazingly long streak of hot days, a combination, neither?



about 12 years ago

I too have noticed this and assumed the same.


about 12 years ago

I assume it's because we've been having an especially warm summer. Tap water is always significantly warmer in the summer then it is in the winter. In the depths of winter, full strength cold tap water can be too cold, or darn near. This summer, the water never gets cold enough for my liking.


about 12 years ago

After 4 years in Texas where summer cold water tap temperatures approach body temperatures, I cannot complain about the cold tap here.  My bet is that the temperature difference is in the pipes and the heat on land. The water offshore where the city draws from is pretty consistent, with only slight temperature variations.


about 12 years ago

We get our water from Lake Superior, and the lake currently is having one of it's warmest years on record (if not THE).

Yes, the flizzard has a lot to do with it, but so does the heat.


about 12 years ago

Not 100% sure, but I think the water comes from wells at the bottom of the lake, not from a direct intake pipe.  Either way, this water is likely much cooler than the surface water.  

I've noticed warmer tap water in the summer in years past and think it is more from the land warming up.


about 12 years ago

Well that does play a part, to be sure.

But generally the earth absorbs more heat from the sun than it does from the ambient air temperature. So it being hotter than normal does not play as large a part in affecting the ground temps, as the sun's radiation is rather constant regardless of the air temp. 

Anyhow, per this .PDF from our water quality assessment "The source water supply for the City of Duluth is a surface water source: Lake Superior"

Duluth 2010 Drinking Water Quality Report

Lake Superior has been warmer than normal in recent years as well due to the lack of ice.


about 12 years ago

In winter the ground can freeze (32degF) to a depth of around 4 feet around here.  Water pipes are usually located below this frost line, but the temperature around water pipes most certainly drops as well.  If we take summertime ground temperature to be 55degF (like in a typical cellar), there's about a 20degF swing from winter to summer.  

"In the City of Duluth, the Water Treatment Plant draws water from Lake Superior, several miles east of the Lester River from a depth of about 55 m (180 ft)"  The buoy featured in the recent PDD post indicates a temperature of 5degC (41degF)at 40m depth.  "This one is roughly 10 miles northeast of Duluth, about a mile offshore of the McQuade Harbor."

The temperature change in the ground from winter to summer is about 20degF, and if we assume conditions at the buoy and the intake pipe are similar,the change in the lake water at depth is likely about 10degF from winter to summer.  Which change is more important at the tap? I don't know.


about 12 years ago

Berv beat me to it. We chose the McQuade Harbor site to be close to the Duluth Water Intake- water at depth appears to be pretty uniformly 5C- in the winter it can cool off to roughly 1C at that site, so not a huge swing there. If I had to guess, I'd say that most of the difference has to do with soil temp, as Berv guessed as well. 

You can see the whole record of water temperature here.


about 12 years ago

From the Large Lakes Observatory at UMD:
 University Minnesota Duluth to measure flood's effects on Lake Superior

Technology usually used in oceans will be planted in Lake Superior this week by University of Minnesota Duluth researchers. Two "moored proofing platforms" will be placed on the bottom of the lake for year-round data collection, something that hasn't been done before because of the difficulty of going out onto the lake for data during the winter, said Jay Austin, a researcher with UMD's Large Lakes Observatory. Out on the Blue Heron on Monday, researchers shared their plans for the platforms and some of their studies of effects from the June 20 flood with lawmakers, University of Minnesota President Eric Kaler, UMD Chancellor Lynn Black and Regent David McMillan of Duluth.

Pioneer Press: 
University of Minnesota Duluth: Lake Superior data devices installed

Duluth News Tribune: 
UMD to measure flood's effects on Lake Superior 
Photo Gallery: Aboard the R/V Blue Heron

Crew Members Show off Research Ship to Minn. Leaders 

Robot divers to report on Lake Superior's depths

Sacramento Bee
 UMD to install data devices beneath Lake Superior

After flood turned Lake Superior color of Tang, Duluth researchers plan in-depth study

Northland's NewsCenter 
UMD Large Lakes Observatory Plants Robot-like Innovation in Lake Superior

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