Patterns and dynamics of river-aquifer exchange with variably-saturated flow using a fully-coupled model

S. Frei, J. H. Fleckenstein, S. J. Kollet, R. M. Maxwell

Research output: Contribution to journalArticlepeer-review

82 Scopus citations

Abstract

The parallel physically-based surface-subsurface model PARFLOW was used to investigate the spatial patterns and temporal dynamics of river-aquifer exchange in a heterogeneous alluvial river-aquifer system with deep water table. Aquifer heterogeneity at two scales was incorporated into the model. The architecture of the alluvial hydrofacies was represented based on conditioned geostatistical indicator simulations. Subscale variability of hydraulic conductivities (K) within hydrofacies bodies was created with a parallel Gaussian simulation. The effects of subscale heterogeneity were investigated in a Monte Carlo framework. Dynamics and patterns of river-aquifer exchange were simulated for a 30-day flow event. Simulation results show the rapid formation of saturated connections between the river channel and the deep water table at preferential flow zones that are characterized by high conductivity hydrofacies. Where the river intersects low conductivity hydrofacies shallow perched saturated zones immediately below the river form, but seepage to the deep water table remains unsaturated and seepage rates are low. Preferential flow zones, although only taking up around 50% of the river channel, account for more than 98% of total seepage. Groundwater recharge is most efficiently realized through these zones. Subscale variability of Ksat slightly increased seepage volumes, but did not change the general seepage patterns (preferential flow zones versus perched zones). Overall it is concluded that typical alluvial heterogeneity (hydrofacies architecture) is an important control of river-aquifer exchange in rivers overlying deep water tables. Simulated patterns and dynamics are in line with field observations and results from previous modeling studies using simpler models. Alluvial heterogeneity results in distinct patterns and dynamics of river-aquifer exchange with implications for groundwater recharge and the management of riparian zones (e.g. river channel-floodplain connectivity via saturated zones).

Original languageEnglish (US)
Pages (from-to)383-393
Number of pages11
JournalJournal of Hydrology
Volume375
Issue number3-4
DOIs
StatePublished - Sep 15 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Water Science and Technology

Keywords

  • Groundwater recharge
  • Heterogeneity
  • PARFLOW
  • Physically-based surface-subsurface model
  • River-aquifer interactions
  • Variably-saturated flow

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