Surficial hydrogeological materials show the distribution of sediment deposited in glacially influenced environments. Most drinkable groundwater resources in Canada occur in shallow surficial-sediment aquifers. Surface sediments, such as gravel, sand, silt and clay, or mixed sediments, are an important control on vegetation patterns and surface-water recharge to aquifers. In addition, areas with significant thicknesses of sand and gravel-large moraines and buried valleys-often host prolific aquifers.