Background:
Pond-based aquaculture is a significant industry in Queensland that offers real environmental, economic and social beneifts.
Aquaculture containment structures may include intake reservoirs, supply channels, production ponds, discharge channels and water treatment ponds.
Usually, aquaculture is undertaken in earthen ponds 1–2 metres (m) in depth formed by a combination of cut and fill earthworks, However, the state government and the aquaculture industry acknowledge that there are inherent risks in storing water in aquaculture containment structures, that all earthen ponds have the capacity to leak, and that this can affect groundwater or adjacent environments.
Water stored in aquaculture ponds is often characterised by biological and chemical properties that differ from those in natural surface or groundwater.
Poor design, construction and maintenance of aquaculture containment structures may result in vertical or horizontal flow into soil and groundwater, or embankment failure. This may cause:
- localised increases in the groundwater level
- impacts on groundwater quality (salinity or nutrients)
- waterlogging
- vegetation dieback.
(See Figure 1.)
In addition, storing large volumes of water above the watertable may result in ‘mounding’ of the watertable in proximity to the farm. This mounding may not necessarily indicate excessive leakage, but may be due to complex interaction between hydrostatic pressure and hydraulic resistance in the aquifer.
These factors need to be considered in the overall context of ecologically sustainable development. To this end, the state government and the aquaculture industry are committed to minimising the risk of environmental harm, and have worked in partnership to develop these guidelines.
Purpose:
Regulatory agencies and individual landholders have spent much time addressing concerns about the impacts of unsatisfactory performance of containment structures on adjacent properties and groundwater aquifers.
Historically, construction standards for aquaculture ponds have been determined on a case-by-case basis and have not been consistently applied across Queensland.
When complaints are lodged about the impacts of unsatisfactory aquaculture containment structures, it may take significant time and money to investigate and identify the causes, and remediate adjacent properties or groundwater.
Through the multi-agency Aquaculture Inter-Departmental Committee, the Queensland Government identified the need for a consistent approach to the construction and maintenance of aquaculture containment structures.
These guidelines provide technical guidance to aquaculturalists, contractors, consultants, project managers and regulators involved in the construction or assessment of aquaculture facilities.
Also, they include information to assist aquaculturalists undertake environmental monitoring to verify that containment structures are performing appropriately and the potential for environmental harm is minimised.
Scope:
These guidelines refer to the design, construction and maintenance of low height (<4 m wall height) aquaculture containment structures to minimise the potential for environmental harm from unsatisfactory performance.
In applying these guidelines, other factors need to be considered, such as access to water, flooding, separation distances to adjacent residences and disease management.
These factors are critical to the successful planning and operation of aquaculture facilities. While these issues are not covered by these guidelines, it is strongly recommended that aquaculturalists attend whole-of-government meetings as early as possible to ensure that they identify significant issues.
Where the location and size of a containment structure is such that its failure might threaten human life, the structure is likely to be a referable dam under the Water Act 2000. In that case additional dam safety requirements will almost certainly apply.
For up-to-date information on the requirements for referable dams, contact your regional Department of Natural Resources and Water office.
The information in these guidelines is based on established engineering principles; however, the recommended methods may be revised from time to time, as new ones are developed. Where standards or other guidelines are referred to, consult the current version of the document.
Proposals involving alternative materials or methods may be appropriate where the recommended approach is equivalent to or exceeds the recommendations in these guidelines.
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