When the wind blows...

The effect of the wind on the levels of Lake Alexandrina.
For the full article see the October Newsletter, page 16

October 1, 2008

The data from Pelican Point wind recording station for Tuesday 30 September, shows that a northerly wind was blowing all day, gradually increasing in strength (5 to 20 knots average). Before midday on Wednesday 1st October, the wind shifted to the west and increased to 30 to 35 kn. and stayed strong for 5 hours before dropping to 10 kn. Direction remained west and turned to the south during Thursday afternoon.

The plot of the water levels, shows Milang increasing from -0.23 m to a max of -0.163 m (130 mm rise) between midday Tuesday to midday Wednesday when the level suddenly drops 400 mm to -0.51 m before returning to close to its mean level of -0.28 m by 5 pm.

The inverse can be seen at Poltalloch, where the level gradually drops to -0.41 m before rapidly rising to -0.12 m at almost the same time as the dip at Milang and then returning to the mean level by the late afternoon.

The level at the Goolwa Barrage gradually rises to a level of +0.1 m (above sea level!) as the wind blows the water to the southern half of the Lake and then drops rapidly on the change of the wind, as the water is pushed east, back along the river past Clayton.

October 5-6, 2008

Later in the week, the wind was gradually increasing south westerly. This pushed the water towards the north east of the Lake, causing water levels at Poltalloch to rise, Milang and Goolwa to drop. The levels returned to neutral when the wind dropped in the evening.

The Excel spreadsheet containing the data for the graphs is here

Where did this data come from?

The data was collected from the DWLBC website at:
data.rivermurray.sa.gov.au (Opens in a new window)

It is map based, so it works best on a fast link.

NOTE: The wind direction recorder is at Pelican Point, on the eastern end of Tauwitcherie Barrage.
It seems to indicate a more easterly wind than is experienced on the Lake. I have allowed for this in assessing the wind direction

An example:

• Click on the link above, and wait for the map to download.
  Its below the data list that you see first.
• Scroll down the page to the map. Use the "outside" slider to move the page. The "inside" one moves the data only.
• Zoom in using the slider on the left.
• Find Goolwa Barrage.
• Point to the blue markers until one shows both EC and level.

• Choose "time series data" from the blue Links. This will open a new window with the data in it.
• Scroll down to the bottom.
• On the left is a box showing Period. Choose "Hourly", "Daily" or "Monthly"
• On the right is a box which says "Export this grid to:" and a selector showing PDF.
• Change this to CSV, and click "Export".

You will then get a file of data which can be opened in Excel or similar.
Not all points have all data and some do not have continuous readings.

Any questions? contact the Secretary!

JY