Fault-controlled springs: A review

Springs sustain groundwater-dependent ecosystems and provide freshwater for human use. Springs often occur because faults modify groundwater flow pathways leading to discharge from aquifers with sufficiently high pressure. This study reviews the key characteristics and physical processes, field investigation techniques, modelling approaches and management strategies for fault-controlled spring systems. Field investigation techniques suitable for quantifying spring discharge and fault characteristics are often restricted by high values of spring ecosystems, requiring mainly non-invasive techniques. Numerical models of fault-controlled spring systems can be divided into local-scale, process-based models that allow the damage zone and fault core to be distinguished, and regional-scale models that usually adopt highly simplified representations of both the fault and the spring. Water resources management relating to fault-controlled spring systems often involves ad hoc applications of trigger levels, even though more sophisticated management strategies are available. Major gaps in the understanding of fault-controlled spring systems create substantial risks of degradation from human activities, arising from limited data and process understanding, and simplified representations in models. Thus, further studies are needed to improve the understanding of hydrogeological processes, including through detailed field studies, physics-based modelling, and by quantifying the effects of groundwater withdrawals on spring discharge.