Who gains from saving nature
Ledger 1 : 33 — For each dollar financing nature-based solutions in 2023, about $33 financed activities harmful to nature. (UNEP)
Cases / Wind, hydro and other renewables · European Union / United States · 2002–2021

EU taxonomy hydropower exemption and California large hydro exclusion

Nature's voice · report
No measurement of the harm done to me here is on record.
Did nature suffer? Not measured. Disputed
What the record lacks: 3 none on record · 1 insufficient · 1 not measured · 2 disputed See the gaps
Accounts of the harm differ
Should hydropower above 5 W/m² be exempt from life-cycle emissions analysis?
  • Company or project International Hydropower Association: Welcomed the EU's recognition of sustainable hydropower in investment rules. International Hydropower Association
  • Government and regulators Government of Norway: Supported the exemption.
  • Researchers Deemer and colleagues (2016): Reservoir surfaces emit about 0.8 billion tonnes CO2e a year, about 80% of it methane.
Is large hydropower renewable?
  • Standard-setters and registries IRENA and EU definitions: Classify hydropower as renewable.
  • Government and regulators State of California: Has not counted hydropower above 30 MW towards its renewable quota since 2002, citing its effect on river ecology. California Senate

In 2021 the EU taxonomy exempted hydropower above 5 W/m² power density, and run-of-river plants, from life-cycle emissions analysis. California has not counted hydropower above 30 MW towards its renewable quota since 2002, citing river ecology.

5 W/m²Power-density threshold below which the EU taxonomy requires life-cycle analysis of hydropower
Plants above the threshold, and run-of-river plants, are exempt (EU, 30 April 2021). California's cut-off is 30 MW installed capacity.

Status As of the latest sources: the EU exemption (30 April 2021) and California's 30 MW rule (since 2002) remain on record; a 2025 proposal to change the California rule is noted without detail.

What?
Two rules set different bars for counting hydropower as green: the EU taxonomy exempts it above 5 W/m² from life-cycle analysis, and California excludes plants above 30 MW from its renewable quota. International Hydropower Association
Where?
European Union (taxonomy) and California, United States.
When?
California since 2002; EU taxonomy on 30 April 2021. International Hydropower Association
Who?
Gained
Lost
None on record
Harmed
  • River ecosystems — California cites the effect on river ecology as the reason for excluding large hydropower from its renewable quota. California Senate
Why?
California cites the effect on river ecology; the sources reviewed do not give the EU's stated reasons. California Senate
How?
The EU rule uses a power-density threshold of 5 W/m²; California's uses an installed-capacity threshold of 30 MW. International Hydropower Association
6 of 6 questions answered from the record

What happened

The record, in order.

Under California law, hydropower plants above 30 MW have not counted towards the state's renewable energy quota since 2002. The reason recorded is the effect on river ecology. According to the California Senate analysis of SB 971 (24 April 2012), large hydropower supplied up to 16% of state generation in some years.

On 30 April 2021 the EU taxonomy for green investment exempted hydropower plants with a power density above 5 W/m², and run-of-river plants, from life-cycle emissions analysis. The entry records a threshold of 100 g CO2e/kWh and treats all pumped storage as making a "substantial contribution". The International Hydropower Association welcomed the decision and the Norwegian government supported the exemption.

Power density is installed capacity divided by the area of the reservoir. The UN Clean Development Mechanism had set its own thresholds in 2006: plants at or below 4 W/m² were not eligible, those between 4 and 10 W/m² were assigned 90 g CO2/kWh, and above 10 W/m² reservoir emissions were counted as zero.

Research cited in the sources reviewed describes impacts that these labels do not capture. A 2016 global synthesis by Deemer and colleagues estimated that reservoir surfaces emit about 0.8 billion tonnes of CO2 equivalent a year, about 80% of it methane. The IPCC added a methane accounting for flooded land in its 2019 refinement, but Paris Agreement parties are not required to use it. Reservoirs hold 5% of lake storage but account for 16% of evaporation (2022), and evaporation from Lake Nasser in Egypt was 10.6 to 17.4 billion cubic metres a year depending on the method.

IRENA and EU definitions classify hydropower as renewable, so the same dam is counted as renewable in the IRENA statistics but would not count under California's rule.

  1. 2002California stops counting hydropower above 30 MW towards its renewable quota
  2. 2006UN Clean Development Mechanism Executive Board (meeting 23) sets power-density thresholds of 4 and 10 W/m²
  3. 201224 April: California Senate analysis of SB 971 records the 30 MW rule and its river-ecology rationale
  4. 2016Deemer and colleagues estimate global reservoir emissions at about 0.8 billion tonnes CO2e a year
  5. 2019IPCC supplementary guidance adds methane accounting for flooded land; Paris parties not required to use it
  6. 202130 April: EU taxonomy exempts hydropower above 5 W/m² and run-of-river plants from life-cycle analysis; hydropower association welcomes it
  7. 2025A proposal to change California's rule is recorded; its content is not on record in the sources reviewed

What was said

Claims, in the words of those who made them.

Where accounts differ

Each party's account, side by side, with its source. The record does not settle these points; it shows them.

Should hydropower above 5 W/m² be exempt from life-cycle emissions analysis?
Company or project
International Hydropower Association

Welcomed the EU's recognition of sustainable hydropower in investment rules.

International Hydropower Association
Government and regulators
Government of Norway

Supported the exemption.

Researchers
Deemer and colleagues (2016)

Reservoir surfaces emit about 0.8 billion tonnes CO2e a year, about 80% of it methane.

Is large hydropower renewable?
Standard-setters and registries
IRENA and EU definitions

Classify hydropower as renewable.

Government and regulators
State of California

Has not counted hydropower above 30 MW towards its renewable quota since 2002, citing its effect on river ecology.

California Senate

How it looked

What was shown, beside what was recorded.

Shown

Recorded

  • Since 2002 California does not count hydropower above 30 MW towards its renewable quota; the reason is the effect on river ecology; large hydropower supplied up to 16% of state generation in some years
    California Senate
  • EU taxonomy, 30 April 2021: hydropower above 5 W/m² and run-of-river plants exempt from life-cycle analysis; threshold 100 g CO2e/kWh; all pumped storage treated as substantial contribution
    International Hydropower Association
  • Reservoir surfaces emit about 0.8 billion tonnes CO2e a year, about 80% methane (Deemer and colleagues, 2016)
  • Reservoirs hold 5% of lake storage but account for 16% of evaporation (2022)

Who gained

Money that reached nature, beside money that stayed elsewhere.

Reached nature or the ground

Not published
No figure published.

Gained elsewhere

Not totalled
Currency: USD · Window: 2002-2021. All figures cover the same period. * Estimate built from cited figures.

Responses on record

  • iha (30 April 2021): Welcomed the EU recognition of sustainable hydropower in investment rules. · International Hydropower Association
  • norway-government (2021): Supported the exemption in the EU taxonomy.

In court and with insurers

Every proceeding and every insurer decision on record.

Lawsuits and rulings

No court case on record. No court has ruled on this case.

Insurers

No insurer decision on record.

What nature saw

Outcomes measured on the ground, and nature's note.

Nature's report opens this page. Below: further outcomes measured on the ground.

Reservoir emissions
About 0.8 Gt CO2e/yr
Global synthesis, Deemer and colleagues, 2016; about 80% methane
Share of lake evaporation
16%
From reservoirs holding 5% of lake storage (2022)
Life-cycle analysis in the EU taxonomy
Exempt above 5 W/m²
Also exempt for run-of-river plants (30 April 2021)

What we don't know

Undisclosed, unproven, untried: recorded as data.
Under standard-setter review

Nature

  • Not measured Harm to nature: The record holds no measurement of harm to nature.
  • Disputed Should hydropower above 5 W/m² be exempt from life-cycle emissions analysis?
  • Disputed Is large hydropower renewable?

Record

  • None on record Paris Agreement parties are not required to use the IPCC's 2019 methane accounting for flooded land.
  • None on record Content of the 2025 proposal to change California's rule: not on record in the sources reviewed.
  • Insufficient Reported but not independently verified: that hydropower stood at 1,296 GW, 25.1% of renewable capacity, at the end of 2025.
  • None on record Emission values after 2006 under the Clean Development Mechanism thresholds: the sources reviewed do not say whether they changed.

Did the harm stop?

Not applicable as a single event. California's rule has been in force since 2002; the EU exemption took effect on 30 April 2021.

Who paid?

Not stated in the sources reviewed.

Sources

Voices on record: ✓ Company or project✓ Government and regulators— Courts— Press and investigations— Communities and civil society— Researchers

Company or project

  1. IHA welcomes EU recognition of sustainable hydropower in investment rules
    International Hydropower Association · 2021-04-30

Government and regulators

  1. SB 971 bill analysis
    California Senate · 2012-04-24

Connected cases

Related matters, and cases linked to this one through the same organisations, with the role each played in both.
Terms used on this page

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Biomass, root-to-shoot ratio, carbon fraction
Biomass is the dry weight of living plants per hectare. The root-to-shoot ratio adds the weight of roots. The carbon fraction is the share of that weight that is carbon, about 47% in tropical forests.
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