Source: \Dropbox\web\raspberry_pi\temperature_analysis\

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Water Temperature Measurements - River Dart 2021-05-18

Sample Measurements

A down-and-back kayak trip, in two kayaks, was made along the River Dart starting from Stoke Gabriel, turning round at Sugary Cove (near Dartmouth Castle), and retuning to Stoke Gabriel, with a break at Warfleet Cove.

The trip was undertaken close to Neap Tides.

      Trip Timings
LabelTimeHeight
  A     12:40 UTC     leave Stoke Gabriel  
  B     12:51 UTC     temperature spike near East Cornworthy  
  C     13:08UTC     temperature spike Gurrow Point  
  D     13:53 UTC     temperature spike at Lower Kilngate  
  E     14:36 UTC     turn at Sugary Cove  
  F     14:48 UTC     arrive Warfleet Cove  
  -     15:16 UTC     Low Tide Dartmouth  
  G     16:08 UTC     leave Warfleet Cove  
  H     16:14 UTC     minor temperature spike above Lower Kilngate  
  I     17:17 UTC     temperature spike at Gurrow Point  
  J     17:50 UTC     arrive Stoke Gabriel  




Time Series

Temperature measurements were made from two kayaks. Both made measurements down stream but one failed part way through the return trip.

The graph below shows a time series of temperature measurements (vertical axis) from one of the kayaks covering the whole period of the trip (horizontal axis). The measurements include a time (F-G) when the kayak was out of the water at Warfleet Cove.

The water temperature was mostly in the range 11.7-12.3°C but with a number of temperature spikes.

    Click image below for full size graph





Mapping

By combining these temperature-time measurements with position-time information from a GPS the location of each temperature measurement can be determined. These values can then be plotted on an interactive map.

In the maps below measurements from both kayaks/sensors are presented as colour coded circles with whites and greens being cold, and reds and purples being warm. By clicking on a circle the actual measurements can be examined. One set of maps shows the measurements made travelling downstream, and the other set upstream.


      non-interactive map



Discussion

There are a number of 'spikes' in the measurements taken in the water. The larger of the spikes in the graph above were labelled. Given the time of each spike it is possible to locate the high values on the maps above. Below we show the satellite images in the region of each spike.

The highest water temperatures measured were obtained in the shallow creek leading to Stoke Gabriel. Temperatures in the water adjacent to the pontoons reached 15.19°C (compared to 11.7-12.3°C in the free river.

All the other temperature spikes observed were measured close to shore adjacent to mud flats.

The temperature spikes measured when travelling downstream with the outgoing tide were more pronounced than those observed when returning.

Spikes A & J - Start & Finish at Stoke Gabriel Creek




Spike B 12:51:10 13.25°C

This temperature spike occured after we had paddled across the choppy estuary towards the mud flats near East Cornworthy.




Spike C 13:07:40 14.40°C

This temperature spike was adjacent to the extensive mud flat at Gurrow Point abve Dittisham.




Spike D 13:53:20 13.81°C

This spike occured adjacent to mud flats above Lower Kilngate.