Ecohydrological methods for characterizing groundwater dependence of terrestrial ecosystems to support sustainable water resources management: A review

A strategic plan for groundwater use must integrate ecological, social, and economic dimensions. This is essential to maintain a sustainable balance between human demands and the ecological water requirements (EWRs) of groundwater-dependent ecosystems (GDEs). Given limited groundwater resources and a changing climate, effective groundwater management is crucial for ensuring the health and long-term stability of these systems. The European Water Framework Directive makes this clear by stating that groundwater-dependent ecosystems, intrinsically linked to groundwater regimes, must not be significantly affected by human changes in groundwater quantity, quality, or ecological functioning. Phreatophytes are critical elements of groundwater-dependent terrestrial ecosystems (GDTEs). They are particularly sensitive to groundwater level fluctuations intensified by climate change and extreme events such as droughts. Understanding their response to declining groundwater levels is crucial for sustainable management and ecological resilience. This paper reviews legal and policy frameworks and current multidisciplinary scientific approaches for incorporating groundwater-dependent terrestrial ecosystems into strategic groundwater planning. It evaluates methods for assessing ecosystem dependence on groundwater, estimating abstraction thresholds or critical groundwater levels, and addressing related uncertainties. Analytical and field-based techniques for determining environmental water requirements have seen little evolution in recent years, but significant advances have occurred in modelling and remote sensing, supported by targeted field validation. These findings form the basis of a proposed framework for integrating groundwater-dependent terrestrial ecosystems into groundwater management. The framework emphasizes preliminary assessments of groundwater dependence and availability, with SWOT analysis aiding the selection of the most appropriate approach.