Defining thresholds to protect groundwater-dependent vegetation

Groundwater is widely used for irrigation, urban water supplies and industrial applications. It also provides baseflow to rivers, and sustains groundwater-dependent ecosystems (GDEs), amongst other ecosystem services. Pressures on groundwater are expected to persist with the increasing global population and effects from climate change1. Groundwater extraction can lower the water table, potentially impacting aquatic GDEs, including groundwater-fed springs and rivers and terrestrial GDEs, including groundwater-dependent vegetation. The fact that GDEs are not appropriately considered in water planning is well documented2,3,4. For example, minimizing impacts to GDEs is documented in water use and allocation policies5,6. However, identifying groundwater level thresholds where impacts to GDEs occur and defining and implementing trigger levels that require a management response is challenging2. Straightforward approaches to define trigger levels would help to address this challenge, with impacts to groundwater levels documented using direct observations7, global numerical models8 and inferred changes to storage from the GRACE satellites