Source: \Dropbox\web\raspberry_pi\temperature_analysis\

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Water Temperature Measurements - River Torridge 2021-05-07

Sample Measurements

An up-and-back kayak trip, in two kayaks, was made along the River Torridge start from Appledore and turning around at Halfpenny Bridge.

The trip was undertaken close to Neap Tides. We left Appledore at mid-tide and paddled with the tide up-stream. We waited near Halfpenny Bridge for High Water then followed the out-going tide back to Appledore.

For most of the trip the river is estuarine with large mud and sandbanks.

  Appledore Tide Times: 2021-05-07
  Low     09:32 UTC     0.94 m  
  High     15:14 UTC     5.79 m  
  Low     21:47 UTC     0.94 m  

Time Series

The graph below shows a time series of temperature measurements (vertical axis) covering the period of the trip (horizontal axis). The measurements include times when the kayak was out of the water.

Measurements from the blue kayak are shown in blue and from the orange kayak in red. The raw measurements from the orange temperature sensor were 0.32°C warmer than those from the blue sensor, this amount has been subtracted from the values displayed. This discrepency is within the accuracy expected from DS18B20 sensors (±0.5°C).

    Click image below for full size graph

      Features in Graph
  A     13:21 UTC     leave Appledore  
  B     14:6 UTC     warm water temperatures  
  -     15:14 UTC     High Water Appledore  
  C     15:20 UTC     turn around at Halfpenny Bridge  
  D-E     15:41 - 16:06 UTC     stop for coffee  
  F     16:30 UTC     warm water temperatures  
  G     17:34 UTC     arrive Appledore  


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 are presented as colour coded circles with greens being cold and reds and purples being warm. By clicking on a circle the actual measurements can be examined. One map shows the measurements made travelling upstream, and the other downstream.


The following graph shows the data collected while the sensor was in the water.

The sea surface temperature (SST) at Padstow measured by NOAA satellites was 15.8°C. It is assumed that this is the temperature just off the coast.

The measurements show the water temperature increasing from about 16°C to nearly 21°C above Wadebridge. Presumably the water in the River Camel and the streams feeding it were somewhat warmer than the sea temperature.

Interestingly there are a number of 'spikes' in the measurements taken in the water. The larger of the spikes in the graph were labelled and their time and height above neighbouring values estimated.

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. Note that the satellite images were taken when the tide was at a different level from that encountered on 17 July.


Spikes b, s and t

These spikes all occured adjacent to the sewage works just south of Porthilly Cove.

Spike i

This spike occured adjacent to the sewage works just south of Wadebridge.

Spikes e and f

These spikes occured alongside streams feeding into the estuary.