Alluvial aquifers with dams with limited or no sustained surface water discharge

Alluvial aquifers are formed from particles such as gravel, sand, silt and/or clay deposited by fluvial processes in river channels or on floodplains. These deposits store and transmit water to varying degrees through inter-granular voids. These aquifers may have structures, such as dams, that modify the flow of surface water and groundwater. Where dams restrict the discharge of surface water, there is less recharge of downstream alluvial aquifers from channels reducing their saturation over time. This can also occur in dry or drought conditions. Both stream and alluvial aquifers may then be recharged from other adjacent aquifers (e.g. permeable rock aquifers).

• Palustrine (e.g. swamps), lacustrine (e.g. lakes) and riverine (e.g. streams and rivers) wetlands on alluvial aquifers below or down-gradient of a dam may depend on the surface expression of groundwater from these underlying alluvial aquifers.
• Terrestrial vegetation on alluvial aquifers down-gradient of a dam may depend on the subsurface presence of groundwater, typically accessed through the capillary zone above the water table.

Pictorial conceptual model PDF