Geophysics for groundwater management

Managing what we cannot see

Groundwater supplies a large share of the world's drinking water and irrigation, yet it is among the least observed of our critical resources. Aquifers are mapped from sparse wells and inferred between them. Decisions about extraction, recharge and protection are made on a picture far coarser than the stakes deserve.

The consequences of getting it wrong are severe and slow to reverse: depleted aquifers, subsidence, saltwater intrusion into coastal supplies, and contamination that spreads unseen for years.

Imaging the hidden reservoir

Geophysics is well suited to water because water changes the ground's physical properties so clearly. It conducts electricity differently from dry rock, so electromagnetic and resistivity methods trace the depth, extent and salinity of an aquifer non-invasively. Mapped across a catchment, these surveys reveal the geometry of the resource rather than guessing it from scattered boreholes.

You cannot manage a resource sustainably if your picture of it is a handful of wells and a lot of hope.

Watching it change

Repeated surveys turn a map into monitoring. The movement of the water table, the advance of a saline front, the response of an aquifer to a wet or dry season — all become visible as change between surveys. For a water authority, that is the difference between reacting to a crisis and managing toward sustainability.

Protecting quality, not just quantity

The same methods detect and track contamination. A plume of pollutants alters conductivity and can be imaged and followed without drilling a forest of monitoring wells. As water stress intensifies, the ability to see the resource clearly — its quantity, its quality and how both are changing — moves from useful to essential.