Groundwater is the reserve of water that is located beneath the earth’s surface in pores and crevices of rocks and soil. These areas vary in size and volume throughout Victoria and are known as aquifers.

Compared to surface water, Victoria's use of groundwater is relatively small and amounts to approximately 15% of surface water use. Aquifers do not align with surface water catchments, and some aquifers are interconnected to surface water resources across several basins.

An important part of the water cycle, groundwater is slow-moving, and often provides the basis for groundwater-dependant ecosystems which includes streams and wetlands. It is also important for some terrestrial vegetation that relies on groundwater sources for water supply.

Groundwater also supports a significant amount of agricultural activity, provides urban supplies to a number of towns across Victoria, including Geelong and is an essential source of domestic and stock supply. Like surface water, groundwater is allocated for commercial and irrigation purposes under strict licensing arrangements under the Water Act 1989.

Groundwater and surface water are interdependent and are affected by drought and climate change. In Victoria, eleven years of below average rainfall has not only reduced water levels in dams and streams, it has also reduced the water levels in groundwater systems. Recharge of these systems is slow and can take a great many years.

DSE’s Groundwater and Licensing Branch is responsible for monitoring and caring for groundwater in Victoria.