Drought Wetland Monitoring

To achieve evaporative water savings as part of the State’s broader drought response to protect domestic water supply, temporary disconnection from the main river channel of 6 permanently connected wetlands has occurred. These are:

• Murbko South (annual evaporation 1947 ML)
• Ross Lagoon (annual evaporation 649 ML)
• Jaeschke Lagoon (annual evaporation 349 ML)
• Lake Bonney (annual evaporation 28147 ML)
• Yatco Lagoon (annual evaporation 5161 ML)
• Nelwart Swamp (annual evaporation 316 ML)
• Total (annual evaporation 36,569 ML)

The Board has contracted the Murray-Darling Freshwater Research Centre, based in Mildura to undertake monitoring of the effects of the temporary closures.

The following parameters are being monitored:

• Surface Water Level – Six weekly (fortnightly in Lake Bonney)
• Water Quality (Surface water, electrical conductivity (EC), pH, turbidity,
• temperature and dissolved oxygen)  - Six weekly (EC fortnightly in Lake Bonney)
• Groundwater levels and EC - Six weekly
• Blue-green algae (Lake Bonney only) - Fortnightly over summer, Monthly over winter
• Fish - Six monthly
• Vegetation (Understorey and aquatic vegetation) - Six monthly
• Tree health, Photopoints - Six weekly

Results

• Since Lake Bonney was closed in late September 2007 the SA MDB NRM Board has set up a monitoring program so that informed decisions can be made regarding the management of the Lake and the minimisation of any risks that may be involved in the closure.
• Data and analysis of the monitoring program will be posted on the SA MDB NRM Board - Drought website regularly as the results are received.

• Murray Darling Freshwater Research Centre (MD FRC) is undertaking the monitoring of most parameters, with SA MDB NRM Board and Berri Barmera Local Action Planning Association complementing this by taking weekly salinity samples and regular water level data.

Five sites within Lake Bonney are monitored weekly, four within the Lake (LKB SW 02 – LKB SW 05) and one within Lock Luna near the closure bank (LKB SW 01).

As can be expected, since the closure a gradual rise in salinity has been detected, probably due to lack of exchange with the river and evapo-transpiration.

Historical records of salinity show that there has been a general steady rise in salinity towards 9000 EC within the Lake since the late 1990’s. This is probably due to the lack of high River flows and flooding over the past 10 years.

Surface Water Levels

Predictions have been made for the drop in surface water levels under two scenarios: average climate conditions and extreme dry conditions.  Actual drop in Lake Bonney water level has been less than was predicted.

Blue Green Algae

Blue-green Algae levels  are being monitored at three sites within the Lake; fortnightly during summer and monthly during winter. Samples are analysed through the MD FRC and results are sent to the Department of Health to determine whether there are any risks or concerns for public health and safety.

• 9/11/07 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 23/11/07 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 6/12/07 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 19/12/07 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 03/01/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 17/01/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 01/02/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 14/02/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 25/02/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 12/03/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 26/03/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.
• 10/04/08 - The results do not represent a problem. The algae detected are small non-toxic species that do not represent a health risk.

Results

site code	eastings	northings	Site	location description
LKB SW 01	446948	6215655	Napper's Bridge - Loch Luna	western side of Napper's Bridge (Loch Luna side of structure)
LKB SW 02	447030	6215640	Napper's Bridge - Lake Bonney	eastern side of Napper's Bridge (Lake Bonney side of structure)
LKB SW 03	447242	6215990	North edge pumps	northern side of Lake, take gravel road to Lake edge, site near ramp and pumps, (not that far east of Napper's Bridge)
LKB SW 04	450365	6215275	Greenwood Park	eastern side of Lake, stop just north of Greenwood Park buildings and walk to lake. SW site is in front of pump sheds
LKB SW 05	450242	6210124	jetty	southern side of Lake, sample taken from lower landing of jetty

• Salinity
• Water Levels