Assessing the effects of groundwater extraction on coastal groundwater-dependent ecosystems using satellite imagery

Terrestrial vegetation that depends on the subsurface presence of water can be severely affected by groundwater extraction. We analysed Landsat imagery to assess the ecological risk posed by groundwater pumping to native vegetation on the Tomago Sandbeds, a coastal sand mass in northern New South Wales. The effect of extraction on each major vegetation community was assessed by comparing rates of evapotranspiration between extraction zones and matched areas outside the influence of extraction. We found a significant long-term change in evapotranspiration close to groundwater extraction points within most forest, woodland and scrub communities, including those not currently regarded as being wholly dependent on groundwater. We therefore suggest that management of groundwater-dependent ecosystems should not be based on degree of dependence but instead on their sensitivity to groundwater management regimes. Our approach can provide policy makers with information needed to evaluate and adjust groundwater management within groundwater-dependent ecosystems.