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research program 3

environmental applications of regolith geoscience

Impact of water level draw-downs on the geochemistry of saline River Murray wetlands

Project Leader : Sebastien Lamontagne, CSIRO Land and Water

Start date and duration: Start : 1 July 2004; Finish : 1 July 2008

Participants : CSIRO Land and Water, Australian National University


Brief project description :

During the last century, many floodplain wetlands in the Murray Basin were converted into disposal basins to store excess irrigation water. From an ephemeral freshwater environment, these wetlands became permanently flooded and saline. These modifications to the hydrology of the wetlands had a profound impact on their biodiversity values, including the loss of riparian red gum and native fish species.

Loveday Wetland (Barmera, SA) was used extensively as a disposal basin from the 1970s to the early 2000s, during which time it became severely degraded. The wetland has been selected as the case study for the rehabilitation of disposal basins in River Murray floodplains. One of the challenges facing managers to rehabilitate disposal basins is how to deal with sulfidic materials present in the sediments. Sulfidic materials were identified at Loveday Wetland during a previous CRC LEME study (Lamontagne et al 2004). Sulfidic materials are known to have potential environmental risks when disturbed (that is, exposed to oxygen), including the generation of noxious smells and acidification. Because rehabilitation of Loveday Wetland will involve changes water level, and possible exposure of sediments to the atmosphere, the risks associated with sulfidic materials are significant.

The aim of the Loveday Drawdown project is to develop knowledge and tools that will enable a safer management of the water level regime in Loveday Basin. This will be done through:

•  reconstruction of historical water, salt and sulfur balances for the wetland between 1970 and 2000 (when the wetland was used as a disposal basin);

•  monitoring of surface water quality to assess impacts of water level variations over two years (May 2005 May 2007);

•  literature review on mechanisms causing noxious smells in sulfide-rich wetlands;

•  estimation of gaseous S losses from the wetland in partnership with the DWLBC Odour control program.

 

Deliverables

In 2007-08, the aim of the project will be to deliver the findings of the study to the end-users, in particular to the managers responsible for the management of saline wetlands in the Lower Murray . The second group of end-users targeted will be the broader scientific community involved in the management of saline wetlands. Delivery will be achieved through a series of targeted output products.

The successful delivery to wetland managers will require some consultation and exchange with the broader scientific community because there is currently a lack of agreement on a few issues related to the management of sulfidic materials. Thus, for the broader scientific community , the proposed outputs are:

•  Host a workshop (Workshop I) for scientists currently involved in sulfidic materials research in the Murray-Darling Basin . The outputs from this workshop will be used in the preparation of the Information Sheet to identify sulfidic materials;

•  Prepare and submit a scientific journal paper on the alkalinity balance of saline Murray wetlands. This work is required to evaluate if Potential Acid Sulfate Soil conditions could develop under a different water regime in wetlands that are currently not at risk of acidification. This work is required because there is a possibility that future management actions to reduce wetland salinity could inadvertently increase the acidification risk;

•  Prepare and publish a CRC LEME Open File Report on the salinity dynamics at Loveday Disposal Basin during the flooding experiment. This work is required to demonstrate that salt dissolution and precipitation (mainly carbonates and gypsum) will play a role in the control of wetland salinity in those Murray wetlands that are currently very saline, such as the floodplain disposal basin.

While these three outputs are primarily aimed at the broader scientific community, they will also be available to wetland managers.

 

For River Murray managers , we plan to summarise the findings of our work by:

•  Publishing an information sheet on how to identify sulfidic materials;

•  Publishing an information sheet on odour-causing gaseous emissions from saline wetlands;

•  Hosting one workshop (Workshop II) where SA wetland managers will be briefed on how to identify sulfidic materials and, when present, the environmental risks that they may pose;

•  A similar presentation will be made in Canberra (Seminar I) targeting the Murray-Darling Basin Commission

 

 

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