Water Scarcity - Water Depletion

Water Depletion estimates how much of the available freshwater in a river basin is used and not returned to the environment (consumption) by homes, industries, irrigation and livestock.

Overview

Data Type	Modelled data based on a global hydrological model
Source	Brauman et al. (2016)
Spatial Resolution	Spatially explicit to river basins (HydroBASINS level 6)
Temporal Resolution	Based on data for the years 1971-2000. Official updates to be confirmed.
Interpretation	The Water Depletion indicator translates the raw values (%) into a 0-10 score based thresholds established by scientific literature. The categorization also accounts for temporal variation in water depletion such as seasonal or interannual dryness.
Concern Level	Very Low = Score 0 - 2 Low = Score 2 - 4 Moderate = Score 4 - 6 High = Score 6 - 8 Very High = 8 - 10
Framework Relevance	Water Depletion is relevant under CSRD (ESRS E2 and ESRS E3) as well as under TNFD and SBTN.

Detailed Specifications

Explanation

Water Depletion measures the ratio of the consumptive use of surface and ground water to available renewable water. Water consumption refers to the volume of water that is withdrawn through human activity and not returned to the environment because it evaporated or was incorporated into a product. Water consumption estimates within this indicator account for consumption through domestic, industrial, electric, irrigation, and livestock uses. This indicator is based on outputs from the global water resources model WaterGAP3. To account for the seasonal variation in water depletion, the indicator combines average annual water depletion values with values for monthly water depletion, seasonal depletion and depletion levels in dry years.

Transformation & Interpretation

The raw Water Depletion values are expressed as percentages. The following thresholds are used to convert raw values into scores and concern levels analogously to Camargo et al. (2023):

Raw Values (%)	Score	Concern Level
≤ 5% annual depletion	0 - 2	Very Low
5% – 25% annual depletion	2 - 4	Low
5% – 75% annual depletion + >75% monthly depletion in 3 out of 30 years	4 - 6	Moderate
25% – 75% annual depletion + >75% monthly depletion every year	6- 8	High
75% – 100% annual depletion	8- 10	Very High
> 100% annual depletion	10	Very High

Source

The Water Depletion value provided as part of SBTN’s Water Availability Risk layer is sourced from Camargo et al. (2023). The underlying data stems from Brauman et al. (2016).

Date of publication

2023 (2016)

Confidence & Accuracy

Medium (best available at global scale). The Water Depletion indicator is based on a global hydrological model and on past data. The indicator might thus fail to accurately estimate current water depletion levels at the local scale. However, the Water Depletion Indicator is science-based, peer-reviewed and explicitly required for science-based target setting under SBTN.

Relevance for CSRD

CSRD requires companies to identify operational sites situated in areas of water risk, including areas of high-water stress. The Water Depletion indicator is relevant under:

ESRS Article	Disclosure or application requirement
ESRS E2 AR 23 (c)	percentage of emissions of pollutants to water and soil occurring in areas at water risk, including areas of high-water stress
ESRS E3 DR 12 (c)	commitment to reduce material water consumption in areas at water risk
ESRS E3 DR 13	policy for sites located in an area of high-water stress
ESRS E3 DR 19	actions and resources in relation to areas at water risk, including areas of high-water stress
ESRS E3 DR 23 (a)	impacts, risks and opportunities related to areas at water risk, including improvement of the water quality
ESRS E3 DR 23 (c)	reduction targets for water consumption, in areas at water risk, including areas of high water-stress
ESRS E3 DR 28 (b)	total water consumption in m3 in areas at water risk, including areas of high-water stress
ESRS E3 AR 5 (b)	sites located in areas at water risk, including areas of high-water stress
ESRS E3 AR 13 (b)	risks including water quantity (water scarcity, water stress), water quality (...)

CSRD requires companies to consider and describe the data used in their analysis (ESRS E4 AR 27). For convenience, here a description of for the relevant criteria:

ESRS Data Criteria	Comment
(a) methodology, reason for selection, assumptions, limitations & uncertainties	Methodology: Water Depletion is estimated based on a global hydrological model (WaterGAP3). Reason for selection: The indicator has been selected to assess the level of water scarcity. The selected metric is science-based, peer-reviewed, widely used and specifically endorsed by SBTN guidelines. Assumptions: The indicator is model based and incorporates several assumptions detailed in Brauman et al. (2016). Limitations & uncertainties: The Water Depletion indicator is based on a global hydrological model and on past data. The indicator might thus fail to accurately estimate current water depletion levels at the local scale.
(b) scope of metric	The Water Depletion indicator is applied at site level.
(c) biodiversity component of metric	The Water Depletion is an ecosystem-level nature indicator. It assesses ecosystem structure by providing an indicator for the physical state of the ecosystem.
(d) covered geographies	The Water Depletion indicator has global coverage.
(e) integration of ecological thresholds	The Water Depletion indicator relates to the planetary boundaries of freshwater change.
(f) frequency of monitoring, baseline condition and period	The Water Depletion indicator is based on data for the years 1971-2000. Official updates of the indicator remain to be confirmed.
(g) data type (primary, secondary, modelled, expert judgement	The Water Depletion indicator relies on modelled data, based on a global hydrological model (WaterGAP3).

Relevance for TNFD

The Water Depletion indicator is a suitable indicator to estimate water availability under the criteria of Physical Water Risk within TNFD’s LOCATE step.

Relevance for SBTN

The Water Depletion indicator represents one out of three water availability indicators explicitly required to use as a pressure-sensitive State of Nature indicator in SBTN Step1: Assess and Step 2: Interpret & Prioritize.

SBTN Data & Tool Criteria	Evaluation	Comment
Relevance	✅	WD contributes to the pressure-sensitive state of nature metric water availability required by SBTN methodology.
Representative	✅	WD data represents a close fit with the SBTN characterization of the water availability issue and is appropriate to be applied under Step 1 & 2.
Spatial and Temporal Resolution	✅	The WD indicator is provided at the spatial resolution of five-arc-minutes (~10km x 10km at equator). The indicator is based on hydrological modelling for the years 1971-2000.
Stability and Preservation	✅	WD data sets are likely to be maintained and preserved long-term as they are provided by EARTHSTAT and SBTN.
Accessibility	✅	The WD data is readily accessible online.
Interpretability	✅	The WD indicator is sufficiently interpretable and generates an appropriate input for the SBTN methodology.
Coverage	✅	WD covers 15’084 watershed representing 90% of global land area.
Authoritative and Accurate	✅	WD data is science-based, peer-reviewed and explicitly required by SBTN.