Engineered
Wetlands
THS v1.0 - Annex G
Engineered Wetlands constructs or restores wetland systems using deliberate hydrological engineering - water control structures, pumps, and berms - to establish and sustain the saturated, anoxic soil conditions that make wetlands among the most carbon-dense ecosystems on Earth. Unlike passively restored wetlands, this pathway actively manages water levels to maximise both carbon accumulation and co-benefits like water treatment or flood attenuation, requiring integrated monitoring of both the wetland ecosystem and the engineered hydrology system sustaining it.
How this pathway works
Wetlands accumulate carbon far faster than most terrestrial ecosystems because waterlogged, low-oxygen soil dramatically slows the microbial decomposition of dead plant matter, allowing organic sediment to build up over time rather than fully breaking down and releasing its carbon back to the atmosphere. Engineered Wetlands deliberately constructs this condition - through berms, water control structures, pumps, and managed inflow/outflow - rather than relying solely on natural hydrology, allowing project developers to establish wetland carbon accumulation on land that would not otherwise sustain a wetland, or to significantly enhance accumulation rates at degraded wetland sites.
Under the Teravent Hybrid Carbon Standard (THS v1.0) Annex G, this pathway is classified as hybrid because the wetland ecosystem's carbon performance is directly and continuously dependent on the engineered water control system - unlike passive wetland restoration credited under TNS v1.0, ongoing hydrological management is both required and monitored as an integral project component. Teravent Hybrid Credits (THC) are issued for verified net tonnes of CO₂-equivalent sequestered in wetland vegetation and sediment carbon, net of full lifecycle project emissions including any methane released from the anaerobic wetland soil itself.
THS v1.0 - Annex G
This pathway is governed exclusively by the Teravent Hybrid Carbon Standard (THS v1.0). No external registry, standard, or methodology is referenced or incorporated.
Three approved methodology variants
THS v1.0 Annex G approves three methodology types, differentiated by wetland origin and hydrological engineering approach.
Constructed treatment wetlands are engineered from the outset to filter agricultural runoff, municipal wastewater, or industrial effluent through vegetated wetland cells, with water levels and flow rates actively controlled to optimise treatment performance. This methodology credits the carbon accumulation co-benefit of these systems, which - when designed with carbon sequestration explicitly in mind alongside their primary treatment function - can accumulate substantial sediment organic carbon over their operational life.
- Water level and flow rate logs from the engineered control system
- Periodic sediment core sampling confirming organic carbon accumulation depth and rate
- Methane flux monitoring via flux chambers or eddy covariance at representative locations
- Water quality treatment performance tracked as a co-benefit indicator
Historically drained agricultural land - often former peatland converted to cropland via drainage ditches and pumps - is re-flooded by reversing or removing drainage infrastructure and installing new water control structures to establish and sustain target water levels. This methodology is particularly valuable where the underlying soil retains a legacy peat or organic-rich layer that resumes carbon accumulation once saturated conditions are restored, halting the ongoing oxidative carbon loss that drained peatland soils otherwise experience.
- Water table depth monitoring confirming target saturation levels are sustained
- Periodic sediment core sampling and subsidence/accretion measurement
- Methane flux monitoring at representative locations
- Documented baseline drainage-era carbon loss rate for additionality and net benefit calculation
Subsided or eroded coastal land - often the result of historic drainage, oil and gas extraction, or sediment starvation - can be rebuilt into functioning marsh through engineered dredge material placement (raising elevation to the appropriate tidal range) combined with water control structures managing salinity and inundation, then planted or allowed to naturally colonise with marsh vegetation. This methodology is technically demanding but addresses some of the most severely degraded coastal wetland sites, often also providing storm surge protection.
- Elevation and subsidence survey confirming marsh platform stability within target tidal range
- Vegetation establishment and cover monitoring via periodic ground survey and remote sensing
- Sediment core sampling confirming organic carbon accumulation rate
- Salinity and water control structure operation logs
Which emission sources must be counted
Measurement, reporting
& verification
Water level and flow rate are directly logged from the engineered control system, giving very high confidence in the technology component. Sediment carbon accumulation is confirmed through periodic core sampling at representative locations, while methane emissions - a critical offsetting factor for wetland carbon accounting - are measured via flux chambers or eddy covariance towers at a subset of sites, extrapolated across the project area using a validated emissions model.
Demonstrating additionality
Leakage types & deductions
Buffer pool & NPRR assessment
| Methodology | Durability Class | Buffer Pool Rate | Primary Reversal Risks |
|---|---|---|---|
| EWT-M01 Constructed Treatment | Class I (default) | 20–35% | Water control failure; treatment system discontinuation |
| EWT-M02 Re-flooded Agricultural | Class II (legacy peat) | 7–25% | Drainage reversion; water control structure failure |
| EWT-M03 Coastal Marsh | Class I (default) | 20–40% | Storm erosion; sea-level rise; subsidence |
Key registration criteria
Sustainable Development
Goal alignment
Deployment scope: Global - degraded coastal zones, drained agricultural peatlands, and municipal/agricultural treatment infrastructure worldwide.
Ready to register your
engineered wetlands project?
Submit a Project Concept Note under THS v1.0 Annex G to begin your registration. Select the EWT-M code matching your wetland design, install water control monitoring, and appoint an accredited VVB to validate your PDD.