attributed Soils are potentially powerful indicators of aquatic ecosystem dynamics because of the specific morphological features that develop in wet environments impacting directly on other system characteristics (e.g. water quality, fauna and vegetation) and can be a reflection of the physical processes occurring within the system (e.g. water inflow and water chemistry). Broad categories for soil include peat (organic), mineral (soil) and rock (non-soil). The substrate layer refers to material lying below the soil layer that shows no pedological development. Its source may be from the parent material of the aquatic habitat or from other processes e.g. aeolian deposition. This attribute is often used as a secondary layer that may be useful in classifying various aquatic systems but is not always available or essential. The substrate layer can play a role in determining vegetation communities, water quality and connectivity with groundwater. Where there is more infrequent wetting on, for example, floodplains, the porosity of the soil/substrate layer may be of importance. – Peat (organic) – Mineral (soil) – Sand (non-soil) • Non-porous – Rock (non-soil) Substrate • Clay • Sedimentary (chemical/organic) • Sedimentary (detrital) • Unconsolidated • Volcanic * The use of soils as an attribute for riverine systems is limited due to the lack of soils mapping, and the fact that the surrounding soils do not often match the soils of the riverine system. Edition (summarises more than 70 categories of the more recognisable substrate types e.g. igneous, dolerite, limestone). Refer to ASRIS for access to soils data. In some cases access to soil information at the catchment level is important for providing additional contextual information. Such spatial information is generally available <>. Vegetation/fringing vegetation
As described above, water type has a major impact on both habitat conditions and biota found at a location. It also impacts on many other facets. Within the ANAE, ‘water type’ relates to chemistry and is influenced by the surrounding landscape (geological setting, water balance, quality, type of soils, vegetation and land use) which in turn dictates habitat of the aquatic environment. Water type information can be used to determine the ‘normal’ water chemistry of a waterbody. Metrics and thresholds have been chosen that provide a suitable basis for differentiating and characterising different systems. Whilst these salinity thresholds have been proposed, it is acknowledged that they may not be appropriate for some parts of the Australian landscape. They should be critically evaluated before using, and substituted with more appropriate local levels if necessary. The AETG should be notified of the changes made and their justification, to ensure that future versions of the ANAE reflect the scientific advances in this area. 1. Salinity: • Fresh (<3000 mg/L) • Brackish* (3000–5000 mg/L) • Saline (>5000 mg/L) OR 2. pH** • Acidic (<6) • Neutral (6–8) • Alkaline (>8) *Brackish may not be important for all systems. If so, change saline metric to 3000 mg/L. **pH may change with the changing hydrograph; if so, the ‘normal’ pH should be used. Vegetation mapping layers are one source of remote sensing information that may be used to derive this attribute, as well as other documented ground-based information. Radke (2003, pers. comm.) proposes that more appropriate salinity thresholds are: fresh <1000 mg/L; brackish 1000–3000 mg/L; saline 3000–10000 mg/L; hypersaline > 10,000 mg/L. The calcium carbonate branchpoint occurs at ~1000–1200 mg/L in Australian waters (lac/pal/riverine). This is when calcium carbonate starts to precipitate, and causes a very major change in the ionic composition of water. New aquatic genera emerge at this time (see also Buckney & Tyler 1976). Significant ion pair formation occurs at ~10,000 mg/L, causing another major change in the ionic structure of the water and ecological transition (e.g. emergence of halobionts). Water regime
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: