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5 August 2009
In a recent report on the health of the Coorong (CLLAMM, 2009), a new model (Digital Elevation Model, DEM) was used by scientists to predict with more accuracy what happens when the water level varies. Together with a hydrodynamic model and a sediment map, they could predict the distribution of key habitats in the region under different intervention strategies, and therefore the distribution of shorebirds and estuarine fish species.
What the levels mean
For the Lower Lakes, it is interesting to us because it shows us the area of soil which would be left dry as water levels recede. It shows whether you would have steep banks, or shallow wading pools, and it tells you whether you’ll have water under your jetty at different AHDs. It also tells scientists a lot about the habitats that will be created or lost at different water levels.
What is 'bathymetry'?
Bathymetry measures the depth of water in oceans or lakes. AHD (Australian Height Datum) levels are given relative to mean sea level, which has an AHD value of 0. Positive values of AHD mean that the water level is above mean sea level (eg at high tide), and negative values mean that the water level is below mean sea level (eg at low tide). A bathymetric map shows the contours of different depths, displayed in our map by different colours
What species would we gain?
Although the CLLAMM (2009) report focuses on the Coorong, the scientists' recommend that a similar investigation be done on the Lower Lakes.
The LakesNeedWater group would like to see an analysis done on what habitats would be created, and what species would inhabit the Lower Lakes should seawater be allowed to flow through the barrages.
Source:
CLLAMM (2009). Water for a Healthy Country, An Ecosystem Assessment Framework to Guide Management of the Coorong. July 31, 2009.
Bathymetry map of Lower Lakes
Click on image to see full-size
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