Groundwater-surface water connectivity

Groundwater-surface water connectivity refers to the direction and magnitude of flow between water resources located above and below ground. Factors such as topography, geology and climate can change the direction and magnitude of these flows. Assessing groundwater-surface water interactions is complex and difficult. However, a range of tools are available to assess the level of connectivity and understand the processes which control the movement of water from surface to sub-surface storages.

Increasing demand for water and a decline in the availability of surface water has seen significant growth in groundwater extraction in Australia in recent years. Independent management of groundwater and surface water means that there is a risk of allocating the same water twice. Discharge of fresh groundwater into a stream is critical for surface water users and aquatic ecosystems during the low-flow period. Pumping from an aquifer near a river can dramatically change the amount of this baseflow to the stream. In contrast, if the groundwater is salty or contaminated, increased groundwater discharge can have a negative effect on surface water quality. Understanding the extent of groundwater-surface water connectivity is crucial for the sustainable management of the overall water resource.

The interaction between surface water features and aquifers can take place in different ways and in different settings. Along the length of its course, a river may receive groundwater from its aquifer, lose water to it, or either depending on the season.

A stream reach, lake or wetland can either be:

• Gaining Stream - receiving inflow of groundwater
• Losing Stream - losing water to the groundwater system by leakage to the aquifer.