Groundwater-surface water connectivity
Although it is not always apparent, surface water in many rivers, dams, lakes and wetlands is connected to underground water resources in aquifers. There are several different examples of these connections:
- groundwater can contribute to base flows in streams when it is discharged from aquifers.
- surface water can recharge groundwater resources when it seeps down into aquifers.
- extraction bores can affect surface water stream flows, even if they are tens of kilometres away from the stream.
This connectivity means that issues such as over-extraction, environmental flows and river salinity could impact on the water quantity and quality in both ground and surface water systems.
"The Commission considers that unless and until it can be demonstrated otherwise, surface water and groundwater resources should be assumed to be connected, and water planning and management of the resources should be conjunctive. This is the reverse of the current situation."- Biennial Assessment 2009 - |
Managing connected systems
Traditionally groundwater and surface water have been managed separately in Australia. This has led to the same water being recorded twice - once in the groundwater management plan, and again in the surface water management plan. This has contributed to the overallocation of water resources.
Another difficulty in managing connected systems is that it takes some time for the effects of taking water from one system to be apparent in the other. While the impacts of groundwater extraction on stream flows can be virtually instantaneous in some systems, in others the impacts may take decades.
There's now concern that groundwater extractions over the past decades will result in reduced surface stream flows in some areas, although how much the flows will be reduced and how long this will take to occur is not clear.
An area of particular concern is the Murray-Darling Basin, where groundwater extractions have increased dramatically following the 1997 cap on surface water diversions.
Groundwater-surface water connectivity and water reform
Groundwater and surface water resources are intimately linked. Although we are still unclear as to the extent of these interconnections, they have important implications for management of both ground and surface water resources. It is critical that we build the knowledge and capacity needed to jointly manage these resources.
The National Water Initiative recognises the connectivity between surface and groundwater resources and requires connected systems to be managed as a single resource.
In its 2009 Biennial Assessment of progress against the National Water Initiative, the Commission found that although good progress is being made, more work is needed to complete the identification and integrated management of connected surface water and groundwater resources across Australia.
To mitigate the risks to the water resource, the Commission considers that unless and until it can be demonstrated otherwise, surface water and groundwater resources should be assumed to be connected, and water planning and management of the resources should be conjunctive. This is the reverse of the current situation.
Addressing groundwater quality issues
The National Groundwater Assessment Initiative under the Groundwater Action Plan provides for investment in managing risks to groundwater quality.