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Alluvia—lower catchment

Infiltration and percolation Fish Surface expression GDEs Mixing of groundwater and surface water Evapotranspiration Infiltration and percolation Terrestrial GDEs Direction of surface water run-off in channel Melaleuca spp Melaleuca spp Melaleuca spp Melaleuca spp Evapotranspiration Eucalypt spp Terrestrial GDEs Melaleuca spp Eucalypt spp Eucalypt spp Melaleuca spp Eucalypt spp Melaleuca spp Melaleuca spp Eucalypt spp Melaleuca spp Casuarina spp Eucalypt spp Casuarina spp Direction of surface water runoff Terrestrial GDEs Eucalypt spp Eucalypt spp Negligible groundwater movement Infiltration and percolation Direction of groundwater movement Palaeochannel Palaeochannel Direction of groundwater movement Palaeochannel Palaeochannel Surface expression GDEs Negligible groundwater movement Direction of groundwater movement Direction of groundwater movement Stygofauna Subterranean GDEs Variable groundwater leakage Direction of groundwater movement Negligible groundwater movement Direction of groundwater movement Moderate to high permeability rock (saturated) Negligible groundwater movement Basement Infiltration and percolation Moderate to high permeability rock (saturated) Permeable rocks Alluvia (saturated) Alluvia (saturated) Alluvia (unsaturated) Alluvia (unsaturated) Colluvia (unsaturated) Eucalypt spp Direction of surface water runoff Direction of surface water runoff Wetland

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Alluvial aquifers are formed from particles such as sand, silt and/or clay deposited by physical processes in river channels or on floodplains. Alluvia can contain one or more unconfined, unconsolidated sedimentary aquifers, where groundwater is stored and transmitted through intergranular voids between gravel and sand particles. These unconsolidated sedimentary aquifers may be layered and/or discontinuous due to the presence of deposits of low permeability silt and clay within the alluvia. Alluvia in lower catchment areas tend to be significantly wider and deeper than alluvia further up-catchment. Alluvia may also contain a number of paleo-channels, remnants of old channels and riverbeds. Paleo-channels may transmit groundwater faster than the surrounding alluvia and may also form perched aquifers under certain conditions. Underlying the alluvia may be an impermeable rock layer which would act as a confining layer separating the unconfined sedimentary aquifer in the alluvia from other groundwater bearing geologies. Flood events provide significant recharge of alluvial aquifers (see Recharge conceptual model).

Unconsolidated sedimentary aquifers in lower catchment alluvial deposits may provide a range of ecosystems with water required to support their plant and animal communities, ecological processes and delivery of ecosystem services.

  • Palustrine (e.g. swamps) and lacustrine (e.g. lakes) wetlands and riverine (e.g. streams and rivers) water bodies on alluvial deposits may depend on the surface expression of groundwater from these unconsolidated sedimentary aquifers.
  • Terrestrial vegetation located on alluvial deposits may depend on the subsurface presence of groundwater in these unconsolidated sedimentary aquifers where groundwater is typically accessed through the capillary zone above the water table.
  • Unconsolidated sedimentary aquifers in alluvial deposits may also support ecosystems within the aquifer itself, which sometimes is indicated by the presence of stygofauna.

Pictorial conceptual model PDF


Last updated: 18 December 2015

This page should be cited as:

Alluvia—lower catchment, WetlandInfo 2013, Queensland Government, Queensland, viewed 11 February 2019, <https://wetlandinfo.des.qld.gov.au/wetlands/ecology/aquatic-ecosystems-natural/groundwater-dependent/alluvia-lower/>.

Queensland Government
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