Confinement An unconfined aquifer, or • Unconfined (often superficial): aquifer, receives recharge from • Depth to water table: the land surface directly above. – shallow (0–20 m) Ecological conditions in unconfined – Deep (> 20 m) aquifers are responsive to rainfall • Confined and land use. A confined aquifer is overlain by a low permeability layer, • Semi-confined so it does not receive direct recharge and is less responsive to surface conditions. Water in a confined aquifer is under pressure. A aquifer is overlain by a lens of lower permeability material, such as a clay lens in an unconfined aquifer composed of gravel and sand. Dominant porosity (aquifer type) Porosity is the percentage of rock or Primary porosity dominant (porous consolidated and unconsolidated soil that is void of material. Primary aquifer) porosity consists of the spaces Secondary porosity dominant (fractured rock aquifer) between grains in consolidated or Tertiary porosity dominant (conduit-type aquifer [includes Karstic]) unconsolidated aquifers. Secondary porosity is the void caused by fractures. Fractures may be enlarged by solution or other processes, creating large voids or conduits. This is termed tertiary porosity. Porosity determines available habitat and affects the rate of water flow. Water Type Water type has a major impact on • Saline > 3,000 mg/L both habitat conditions and biota • Fresh: < 3,000 mg/L found at a location. It also impacts pH:
Confinement An unconfined aquifer, or aquifer, receives recharge from the land surface directly above. Ecological conditions in unconfined aquifers are responsive to rainfall and land use. A confined aquifer is overlain by a low permeability layer, so it does not receive direct recharge and is less responsive to surface conditions. Water in a confined aquifer is under pressure. A aquifer is overlain by a lens of lower permeability material, such as a clay lens in an unconfined aquifer composed of gravel and sand. • Unconfined (often superficial): • Depth to water table: – shallow (0–20 m) – Deep (> 20 m) • Confined • Semi-confined Dominant porosity (aquifer type) Porosity is the percentage of rock or soil that is void of material. Primary porosity consists of the spaces between grains in consolidated or unconsolidated aquifers. Secondary porosity is the void caused by fractures. Fractures may be enlarged by solution or other processes, creating large voids or conduits. This is termed tertiary porosity. Porosity determines available habitat and affects the rate of water flow. Primary porosity dominant (porous consolidated and unconsolidated aquifer) Secondary porosity dominant (fractured rock aquifer) Tertiary porosity dominant (conduit-type aquifer [includes Karstic]) Water Type Water type has a major impact on both habitat conditions and biota found at a location. It also impacts • Saline > 3,000 mg/L • Fresh: < 3,000 mg/L pH:
ae-toolkit-module-2-anae-classification.docx