An ecosystem that relies on groundwater for all or a significant portion of its water requirements. GDEs include springs, baseflow-fed streams, wetlands, and phreatophyte vegetation communities that access the water table.
A groundwater-dependent ecosystem (GDE) is an ecological community whose composition, structure, and function are sustained wholly or partially by groundwater. GDEs are broadly classified into three types: aquatic GDEs that depend on the surface expression of groundwater (springs, baseflow-sustained streams, groundwater-fed wetlands and lakes), terrestrial GDEs where plant communities access groundwater via roots extending to the water table (phreatophyte vegetation including riparian forests), and subterranean GDEs that exist within aquifers themselves (stygofauna—organisms adapted to live in groundwater such as cave-dwelling crustaceans and microorganisms). GDEs provide a wide range of ecosystem services including baseflow maintenance during drought, unique biodiversity habitat, water purification, and recreational and cultural values. Groundwater extraction, climate change, and land use modifications that lower water tables or alter recharge threaten GDEs worldwide. In Australia, national water reform legislation explicitly requires that GDEs be identified and their water needs accounted for in groundwater allocation plans. Identifying GDEs requires integrating hydrogeological data (water table depths, groundwater flow paths) with ecological surveys and increasingly, remote sensing indicators such as vegetation greenness anomalies during dry seasons that indicate groundwater access. Protecting GDEs requires setting sustainable extraction limits that maintain water table levels within the tolerance range of dependent ecosystems.