To what extent do long-duration high-volume dam releases influence river–aquifer interactions? A case study in New South Wales, Australia [长期大容量水坝放水对河流-含水层相互作用的影响能到什么程度?澳大利亚新南威尔士州的一个研究实例] [Dans quelle mesure les lâchers de barrages de longue durée et gros volume influencent-ils les interactions nappe–rivière? Une étude de cas en Nouvelle-Galles du Sud, Australie] [Até que ponto as descargas de longa duração e grande volume de barragens influenciam as interações rio–aquífero? Um estudo de caso na Nova Gales do Sul, Austrália] [En qué medida los vertidos de larga duración y alto volumen de los diques influyen en la interacción río–acuífero? Un estudio de caso en Nueva Gales del Sur, Australia]

Long-duration high-volume dam releases are unique anthropogenic events with no naturally occurring equivalents. The impact from such dam releases on a downstream Quaternary alluvial aquifer in New South Wales, Australia, is assessed. It is observed that long-duration (>26 days), high-volume dam releases (>8,000 ML/day average) result in significant variations in river–aquifer interactions. These variations include a flux from the river to the aquifer up to 6.3 m3/day per metre of bank (at distances of up to 330 m from the river bank), increased extent and volume of recharge/bank storage, and a long-term (>100 days) reversal of river–aquifer fluxes. In contrast, during lower-volume events (<2,000 ML/day average) the flux was directed from the aquifer to the river at rates of up to 1.6 m3/day per metre of bank. A groundwater-head prediction model was constructed and river–aquifer fluxes were calculated; however, predicted fluxes from this method showed poor correlation to fluxes calculated using actual groundwater heads. Long-duration high-volume dam releases have the potential to skew estimates of long-term aquifer resources and detrimentally alter the chemical and physical properties of phreatic aquifers flanking the river. The findings have ramifications for improved integrated management of dam systems and downstream aquifers. © 2014, Springer-Verlag Berlin Heidelberg.