Water

TNFD: FA.A5.0, FA.A5.3

Relevant water quality metrics and thresholds depend on the use of the water and known threats to water quality. Example Tier 1/Tier 2 metrics might include Turbidity, Dissolved Oxygen, Organic and inorganic compounds, Nutrients, Acidity, Salinity/Total Dissolved Solids. Tier 3 could also include additional, more difficult or costly to measure metrics such as concentrations of cyanobacteria, pathogens and parasites, heavy metals and organic contaminants, where appropriate.

See Australian and New Zealand Guidelines for Fresh and Marine Water Quality for information and guidance on how to identify relevant water quality metrics and thresholds or ‘guideline values’ for Australian and New Zealand waters.

See also: Standard Methods for the Examination of Water and Wastewater; UN Environment (2017) A Framework for Freshwater Ecosystem Management (especially Volume 2, Tables 4 and 5 which list example water quality metrics for different freshwater ecosystem types).
Variants of this metric include TNFD Food and agriculture additional disclosure metrics FA.A5.0: “Coastal and freshwater eutrophication; plastic debris density; Chlorophyll-A concentration; In-situ concentration of nitrogen, phosphate and silica.” and FA.A5.3: “Volume (tonnes) of litter in the water column and on the seafloor, including microplastics.”

Plant water use or evapotranspiration is effectively the ‘green’ water footprint for a given geographical area, if it is assumed that all plant water use is production-related (see waterfootprint.org). Otherwise, non-production related evapotranspiration should be deducted from total plant water use to derive the green water footprint.

This measure is a proxy for inputs of sediment to waterways.

TNFD: C2.1, FA.A2.4, FA.A2.5

Where water discharged is of clearly different quality levels (e.g. freshwater vs. polluted), these quantities may be recorded separately. Alternatively, the ‘grey’ water footprint can be calculated, i.e. the amount of fresh water required to assimilate pollutants to meet specific water quality standards (see https://www.waterfootprint.org). Essentially, this involves dividing the pollutant load by the difference between the ambient water quality standard for that pollutant and its natural concentration in the receiving water body (Hoekstra et al., 2011, p. 30).

Variants of this metric include TNFD core disclosure metric C2.1: “Volume of water discharged (m³), split into:

• Total;
• Freshwater; and
• Other.
• Including:
• Concentrations of key pollutants in the wastewater discharged, by type of pollutant, referring to sector-specific guidance for types of pollutants; and
• Temperature of water discharged, where relevant.

Freshwater: (≤1,000 mg/L Total Dissolved Solids). Other: (>1,000 mg/L Total Dissolved Solids). Reference: GRI (2018) GRI 303-4 Water discharge.” and additional disclosure metric A2.0: “Volume of wastewater treated, reused or recycled (m³). Reduction in volume of wastewater relative to baseline as a result of technological or process changes (m³).”; and Food and agriculture additional disclosure metrics FA.A2.4: “Volume of wastewater reused (m³).” and FA.A2.5: “Volume of water discharged (total, freshwater, other) per tonne of crop and/or product dry matter and/or animal protein (m³/tonne).”

TNFD: A3.0, A3.1, A3.2, A3.3, FA.C3.0, FA.A2.6

Water withdrawal and consumption, or consumptive water use, refers to human appropriation of surface water or groundwater, as opposed to human appropriation of evaporative flows of water from a catchment (which is captured under NCMC metric ‘Plant water use’). Consumptive water use includes the extraction of water that is either not recharged, or used beyond its recharge rate (signs of this might include declining groundwater levels or lake/river levels or flow rates), or diverted away from other ecosystem uses (for example, water used for irrigation or stock drinking water). This is broadly equivalent to the concept of the ‘blue’ water footprint (see Water Footprint Network). Consumptive water use can be calculated in absolute quantities of water, and/or multiplied by a water scarcity index (e.g. AWARE) to calculate a water scarcity footprint. Alternatively, measurement of consumptive water use can focus on use of water from water-stressed catchments. Components of consumptive water use (e.g. water extracted, water losses, water used and water returned) may be recorded separately.

Water scarcity or water stress should ideally be calculated using a comprehensive hydrological model with robust data for specific catchments. In the absence of such modelling, an indication of potential water scarcity or water stress in Australian water catchments could be a declining long-term trend in groundwater levels or streamflow. Data on groundwater level trends for Australian aquifers can be obtained from the Bureau of Meteorology Australian Groundwater Insight, and data on streamflow trends for Australian rivers can be obtained from the Bureau of Meteorology Hydrologic Reference Stations.

Variants of this metric include TNFD core disclosure metric C3.0: “Water withdrawal and consumption (m³) from areas of water scarcity, including identification of water source. Water consumption is equal to water withdrawal less water discharge. Reference: GRI (2018) GRI 303-5. Surface water; groundwater; seawater; produced water; third-party water. Reference: GRI (2018) GRI 303-3.”; additional disclosure metrics A3.0: “Total volume of water withdrawal and consumption (m³)”; A3.1: “Volume of water (m³) replenished to the environment through replenishment programmes (split into total and to areas of water scarcity)”; A3.2: “Total volume (m³) or percentage of water (total, freshwater, other) reduced, reused or recycled” and A3.3: “Volume (m³) of water loss mitigated.”; Food and agriculture core disclosure metric FA.C3.0: “Proportion (%) of agricultural products or animal feed produced or sourced from regions with high or extremely high baseline water scarcity.”; and Food and agriculture additional disclosure metric FA.A2.6: “Water Use Efficiency (WUE) calculated as net value added per volume of water use (currency/m³).”