Interesting stream flow record this week

My favorite USGS hydrograph is the East Branch of the Pemi in Lincoln, which for the past three to four days (14th-17th) shows an interesting 12-hour lag or so in peak discharge following maximum daytime solar melting of the snowpack higher in the drainage basin (there has not been any rainfall to mask the diurnal variation and most of the daytime sky this week has been sunny according to weather data archives at nearby sites, such as Plymouth State). You can also pick up the same diurnal lag for the 10th and 11th, but then the lag is lost as the overall discharge dropped in response to the temperature drop and cloudiness on the 12th and 13th. So, in sum, the hydrograph records a shorter time-scale diurnal response superposed on longer-scale trends related to changes in air masses over the area.

The connection to this site is that some times we need to deal with stream crossings in our search for VftT. Rememer what happened to Chris McCandless in his fatal Alaska adventure.

http://waterdata.usgs.gov/nwis/uv/?site_no=01074520&PARAmeter_cd=00065,00060,00062,72020

Counter intuitive to learn that the best time to cross would be mid-day and the worst to be midnight. Not an issue unless you're a regular headlamp hiker.

One could also envision an unwelcome surprize if you make camp in the wrong spot.

John H Swanson said:

Counter intuitive to learn that the best time to cross would be mid-day and the worst to be midnight. Not an issue unless you're a regular headlamp hiker.

One could also envision an unwelcome surprize if you make camp in the wrong spot.

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Indeed, that is what caught by eye in the EB hydrograph this week, as in most cases one waits until the early morning hours to cross meltwater streams in the alpine and arctic, say 4 to 8 in the morning. But, the response times of those braided streams to solar radiation is much faster than the EB, apparently.

But, of course, we do not camp within 200 ft of streams in the Whites, right?

210 feet from the stream but if I'm only 2-4" higher....

cross in the early Am & cross back before they go up to their midnight highs

John H Swanson said:

Counter intuitive to learn that the best time to cross would be mid-day and the worst to be midnight.

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Note that it depends on where in the drainage basin you are:
* The small brooks near the head of the drainage area often peak late afternoon/evening and are probably falling well before midnight as much of the day's meltwater is long gone
* As noted, Lincoln Woods which is several miles downstream lags until midnight
* If you were to look at Plymouth the peak might actually be the next day, you could verify this if you could find a very warm day followed by a cold day with no precip

RoySwkr said:

Note that it depends on where in the drainage basin you are:
* The small brooks near the head of the drainage area often peak late afternoon/evening and are probably falling well before midnight as much of the day's meltwater is long gone
* As noted, Lincoln Woods which is several miles downstream lags until midnight
* If you were to look at Plymouth the peak might actually be the next day, you could verify this if you could find a very warm day followed by a cold day with no precip

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Agreed. But I have a question....

Is the stream guage down in the town of Lincoln, near where the East Branch flows into the Pemi, or is it up by Lincoln Woods? I always assumed it was in the town, and that would definitely help to explain why there is such a lag time.

http://nh.water.usgs.gov/Publications/annual97/01074520.htm

THis site describes the guage is downstream from Pollard Brook, so that's close to the center of Lincoln. I can see how it would take awhile for the streams to reach max near here, especially since the temperatures are only warm for a few hours in the upper elevations this time of year. We do have flashy streams, but I don't think they are as extreme as ones up in Canada and Alaska.

grouseking

RoySwkr said:

Note that it depends on where in the drainage basin you are:
* The small brooks near the head of the drainage area often peak late afternoon/evening and are probably falling well before midnight as much of the day's meltwater is long gone
* As noted, Lincoln Woods which is several miles downstream lags until midnight
* If you were to look at Plymouth the peak might actually be the next day, you could verify this if you could find a very warm day followed by a cold day with no precip

Click to expand...

Exactly. In fact, you can see the continued lag downstream at the Woodstock and Plymouth hydrographs for the same time periods.

http://waterdata.usgs.gov/nwis/uv?01075000

http://waterdata.usgs.gov/nwis/uv?01076500

Dr. Dasypodidae said:

Exactly. In fact, you can see the continued lag downstream at the Woodstock and Plymouth hydrographs for the same time periods.

http://waterdata.usgs.gov/nwis/uv?01075000

http://waterdata.usgs.gov/nwis/uv?01076500

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Interesting that the hydrograph at Plymouth appears to be dampened compared to those from Woodstock and Lincoln. Possibly due to scaling? or influence from being impacted by watersheds farther south less under influence of diurnal temp fluctuations. Sorry my geekiness is showing.

Hey Dr D. did you summit Moriah today?

Jazzbo said:

Interesting that the hydrograph at Plymouth appears to be dampened compared to those from Woodstock and Lincoln. Possibly due to scaling? or influence from being impacted by watersheds farther south less under influence of diurnal temp fluctuations. Sorry my geekiness is showing.

Hey Dr D. did you summit Moriah today?

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I agree entirely on your take with the hydrographs, as well as Roy's and Grouseking's. Yes on Moriah; I will post something on the Events thread.

Jazzbo said:

Interesting that the hydrograph at Plymouth appears to be dampened compared to those from Woodstock and Lincoln. Possibly due to scaling? or influence from being impacted by watersheds farther south less under influence of diurnal temp fluctuations. Sorry my geekiness is showing.

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Yeah, like anything in statistics the fluctuations seem to cancel out.

If you read a hydrology text, you can get very intense rainfall over small areas but over larger areas the average will be less. If you look at the shape of a watershed, some points are closer to the gauge than others so the peak flows from all points won't arrive at the same time - what you see as damping.

A Federal hydrologist explained how those catchment basins often placed near shopping centers to reduce peak flows and let the water out gradually may reduce the peak flow at their outlet but may actually increase peak flows somewhere downstream, if by retarding water from the shopping center they cause its water to arrive downstream later and at the same time as a peak from farther away.