Alluvial deposits are sediments composed of gravel, sand, silt or clay deposited in river channels or on floodplains. They occur in most regions of Australia and are a major resource for irrigation, town, stock and domestic uses. About 20 per cent of all bores in Australia are in alluvial systems and they account for 60 per cent of Australia’s groundwater extraction.
Alluvial aquifers are generally shallower than sedimentary and fractured rock aquifers and water levels often fluctuate due to varying recharge and pumping rates. Due to their shallow and unconfined nature, alluvial aquifers are susceptible to contamination and pollution.