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An up and down trip, in two kayaks, was made along the Dart Estuary starting from Stoke Gabriel and turning round in Totnes.
The trip was undertaken on a Neap Tide with a Tidal Coefficient of 41 (i.e. its height was 41% of the mean height of all Dartmouth Spring Tides).
The wind was a slight northerly.
| Time | Height |
|---|---|
| 05:01 UTC | Low Tide Totnes |
| 09:10 UTC | leave Stoke Gabriel |
| 11:02 UTC | High Tide Totnes |
| 11:16 UTC | arrive Steamer Quay, Totnes |
| 12:04 UTC | leave Steamer Quay, Totnes |
| 13:36 UTC | arrive Stoke Gabriel |
| 17:38 UTC | Low Tide Totnes |
The red bars in the graph below show the timing of the two sections of the trip. The upstream section was with the weak incoming tide and the second downstream section was with the outgoing tide.
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The light northerly wind and the limited tidal assistance meant that the upstream leg was somewhat slower than the downstream one.
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Temperature measurements were made from both kayaks. As both followed similar courses the temperatures were very similar.
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On the upstream leg the water temperature was relatively steady between 9°C and 10°C. There were minor dips at 09:30 and 09:40 and small peaks at around 10:08 and 10:14.
Going downstream the temperature increased from 9°C to 11°C, with a large peak at 12:50 and a smaller one at 13:35.
Using the links below you can zoom and pan the map - clicking on a coloured circle shows the actual temperature measurement at that point.
The temperature dips at 09:30 and 09:40 occurred on the shallow mud banks adjacent to Stoke and Ashprington Points.
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The temperature rises at 10:08 and 10:14 also occurred on shallow mud banks - in this case alongside Sharpham Vineyard. It is not clear why some mud banks are associated with temperature rises and others with falls.
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Going downstream (with the falling tide) the temperature showed a large peak at 12:50 this was also alongside Sharpham Vineyard.
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The broad temperature peak around 13:35 was associated with entering the approach to Stoke Gabriel.
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Measurements of salinity were estimated at 10 second intervals using an electrical conductivity probe. The conductivity measurements were temperature corrected and converted to salinity values.
Sea water has a salinity of around 33 ppt (parts per thousand). The salinity near Stoke Gabreil (nearer to the sea) was around 22-24 ppt. Moving upstream the salinity fell to close to zero near Totnes.
This is to be expected with fresh water descending the Dart, and the river being much narrower near Totnes.
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Using the link below you can view the salinity data on an interactive map - and by clicking on a coloured circle show the actual salinity at that point.
At a number of points the salinity on the upstream leg was higher than on the downstream one.
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Measurements of turbidity (cloudiness) were taken using a probe which detects light scattered at right angles to a beam of IR light. This reports the frequency output of a photo detector. Higher frequencies indicate higher turbidity.
Subjectively the water appeared to be cloudier over the shallow mud flats.
The baseline (lowest) values of turbidity ranged from around 8 Hz near Totnes to 9 Hz near Stoke Gabriel.
Using the link below you can view the turbidity data on an interactive map - and by clicking on a coloured circle show the actual turbidity at that point.
The map below shows the location of some of the largest turbidity values - in the muddy shallows adjacent to Sharpham Vinyard.
This, and other points, appear to confirm the subjective observation that the cloudiest areas are associated with shallow water over mud flats.
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