Water Pollution - Coastal Eutrophication Potential

Coastal Eutrophication Potential (CEP) estimates the risk of excess nitrogen and phosphorus in rivers leading to coastal eutrophication. Eutrophication causes harmful algal blooms and ecological imbalances.

Overview

Data Type	Data based on global model of nutrient exports by rivers
Source	World Resource Institute
Spatial Resolution	Spatially explicit to river basins (HydroBASINS level 6)
Temporal Resolution	Based on hydrological modelling representing baseline values for the year 2000. Official updates to be confirmed.
Interpretation	The raw CEP indicator is expressed in kilograms of carbon per square kilometer of river basin area per day. The raw values are categorized into a 0-10 score based on thresholds established by scientific literature.
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	CEP is relevant under CSRD (ESRS E2 and ESRS E3) as well as under TNFD and SBTN.

Detailed Specifications

Explanation

Eutrophication occurs when there is an excessive input of nutrients, particularly nitrogen and phosphorus, into water systems. This nutrient overload can lead to harmful algal blooms. The heightened algal growth and its decomposition can deplete oxygen levels in the water, resulting in ecological imbalances and potentially harming other aquatic life. The amounts and ratios of nitrogen (N), phosphorus (P), and silica (Si) determine the types of algae that grow and affect how severe and fast eutrophication happens. The indicator of coastal eutrophication potential (CEP) measures how excess N and P in rivers (relative to Si) can trigger eutrophication in coastal waters, with higher values indicating more favorable conditions for harmful algal growth and eutrophication. The underlying nutrient data is based on the Global NEWS 2 model (Mayorga et al. 2010).

Transformation & Interpretation

The raw CEP indicator is expressed in kilograms of carbon (from algae biomass) per square kilometer of river basin area per day [kg C-equivalent/km2/day]. A negative value indicates that Si is present in excess over N and P and thus suggests the absence of eutrophication. A positive value indicates an excess of N and P suggesting suitable conditions for the growth of harmful algae. The following thresholds are used to convert raw values into scores and concern levels:

Raw Values (Risk)	Score	Concern Level
≤ -5	0 - 2	Very Low
-5 - 0	2 - 4	Low
0 - 1	4 - 6	Moderate
1 - 5	6 - 8	High
> 5	8 - 10	Very High

Source

The CEP value provided as part of SBTN’s Water Pollution layer is sourced from Camargo et al. (2023). The underlying data stems from Hofste et al. (2019).

Date of publication

2023 (2019)

Confidence & Accuracy

Medium (best available at global scale). The CEP indicator is based on a global hydrological model and tailored to large-scale comparison of coastal eutrophication potential levels. The indicator might occasionally fail to accurately estimate water quality at the local scale. Furthermore eutrophication potential in freshwater is not reflected in the indicator due to lack of global data. Nevertheless, the CEP 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, incl. areas of high-water stress. The Coastal Eutrophication Potentia 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 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 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: Coastal Eutrophication Potential (CEP) is estimated based on a global model of nutrient exports by rivers. Reason for selection: The indicator has been selected to assess the level of water pollution. 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 Hofste et al. (2019). Limitations & uncertainties: The CEP indicator is based on a global hydrological model and tailored to large-scale comparison of coastal eutrophication potential levels. The indicator might occasionally fail to accurately estimate water quality at the local scale. Furthermore eutrophication potential in freshwater is not reflected in the indicator due to lack of global data.
(b) scope of metric	The CEP indicator is applied at site level.
(c) biodiversity component of metric	The CEP is an ecosystem-level nature indicator. It assesses ecosystem structure by providing an indicator for the chemical state of the ecosystem.
(d) covered geographies	The CEP indicator has global coverage.
(e) integration of ecological thresholds	The CEP indicator relates to the planetary boundaries of freshwater change and biochemical flows.
(f) frequency of monitoring, baseline condition and period	The CEP indicator is based on hydrological modelling representing baseline values for the year 2000. Official updates of the indicator remain to be confirmed.
(g) data type (primary, secondary, modelled, expert judgement	The CEP indicator relies on modelled data.

Relevance for TNFD

The CEP 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 Blue Water Scarcity indicator represents one out of three water pollution indicators explicitly required to use as a pressure-sensitive State of Nature indicator in SBTN Step 1: Assess and Step 2: Interpret & Prioritize.

SBTN Data & Tool Criteria	Evaluation	Comment
Relevance	✅	CEP contributes to the pressure-sensitive state of nature metric water pollution required by SBTN methodology.
Representative	✅	CEP data represents a close fit with the SBTN characterization of the water pollution issue and is appropriate to be applied under Step 1 & 2.
Spatial and Temporal Resolution	✅	The CEP indicator is provided at the spatial resolution of level 6 of Hydrological sub-basin (HydroBASINS 6). The CEP values provided by SBTN are based on hydrological modelling representing annual baseline values for the year 2000.
Stability and Preservation	✅	CEP data sets are likely to be maintained and preserved long-term as they are provided by the World Resource Institute and directly implemented into a data layer provided by SBTN.
Accessibility	✅	The CEP data is readily accessible online.
Interpretability	✅	The CEP indicator is sufficiently interpretable and generates an appropriate input for the SBTN methodology.
Coverage	✅	CEP has global coverage.
Authoritative and Accurate	✅	CEP data is science-based, peer-reviewed and explicitly required by SBTN.