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- Title
Transience of Riparian Freshwater Lenses.
- Authors
Jazayeri, Amir; Werner, Adrian D.; Irvine, Dylan J.
- Abstract
The current theory for defining the occurrence of riparian lenses (i.e., buoyant, lenticular‐shaped fresh groundwater bodies overlying saline groundwater in riparian zones) is largely based on steady‐state analyses, which neglect the transient dynamics expected in real‐world settings. In this study, the transience of riparian lens movement is investigated for the first time, considering a fully penetrating, gaining river (i.e., the river receives groundwater influxes), and rapid variations in hydraulic boundary conditions. Controlled laboratory experiments and numerical modeling are used to determine the timescales associated with lens movements. Both numerical and experimental timescales show asymmetric behavior in the growth and decline of lenses, whereby growing lenses involve longer timescales than those of shrinking lenses. Inverse relationships between timescales and final hydraulic gradients are observed, such that higher final hydraulic gradients involved shorter timescales. Results also revealed a time lag in the movement of the lens tip (i.e., where the lens and water table intersect) relative to the lens toe (i.e., intersection of the lens with the riverbank). Riparian lenses have near‐identical timescales regardless of whether the river water or aquifer hydraulic head varies, and rather, timescales are more sensitive to the final hydraulic gradient. Application of typical parameter ranges for the River Murray (South Australia) floodplains reveals timescales of years to more than a decade to expand the riparian lens by tens of meters. Insights into riparian lenses transience attained from the current study build on the understanding of transience obtained for other mixed‐convective hydrogeological processes, such as seawater intrusion and retreat. Key Points: Laboratory experiments and numerical modeling of riparian lens transience show growing lenses have longer timescales than shrinking lensesTimescales for lens movements of tens of meters are expected to range from years to more than a decade for field‐scale conditionsThe lens is slower to grow (and shrink) laterally compared to the time required to increase (and decrease) in thickness
- Subjects
RIPARIAN areas; HYDROGEOLOGY; WATER table; TRANSIENTS (Dynamics); FRESH water; GROUNDWATER
- Publication
Water Resources Research, 2022, Vol 58, Issue 5, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2021WR031310