Appendix 3a.3

Appendix 3a.3 Wetlands Remaining Wetlands:
Basis for future methodological development
3a.3.1Introduction

This section develops the coverage of Section 5.4.3 (Other Possible Categories of Activity) of the IPCC
Guidelines by describing methodologies for estimating carbon stock changes, as well as CH4 and N2O emissions(which can be as significant as CO2 emissions) from wetlands remaining wetlands. Land conversion to wetlands
is described in Section 3.5 of this report.
The estimate of CO2 emissions in wetland has two basic elements, as shown in Equation 3a.3.1.
EQUATION 3a.3.1
CO2 EMISSIONS IN WETLAND REMAINING WETLAND
CO2 emissionsWW = CO2 emissionsWW peat+ CO2 emissionsWW flood
Where:
CO2 emissionsWW = CO2 emissions in wetland remaining wetland, Gg CO2 yr-1
CO2 emissionsWW peat = CO2 emissions from organic soils managed for peat extraction (Section 3a.3.1),
Gg CO2 yr-1
CO2 emissionsWW flood = CO2 emissions from flooded land (Section 3a.3.2), Gg CO2 yr-1
The estimate of N2O emissions has the same two basic elements, as shown in Equation 3a.3.2.
EQUATION 3a.3.2
N2O EMISSIONS FROM WETLAND REMAINING WETLAND
N2O emissions WW = N2O emissionsWW peat + N2O emissionsWW flood
Where:
N2O emissionsWW = N2O emissions from wetland remaining wetland, Gg N2O yr-1
N2O emissionsWW peat = N2O emissions from organic soils managed for peat extraction (Section 3a3.2),
Gg N2O yr-1
N2O emissionsWW flood = N2O emissions from flooded land (Section 3a.3.3), Gg N2O yr-1
At present, a default methodology for CH4 can be provided only for flooded land (Equation 3a.3.3):
EQUATION 3a.3.3
METHANE EMISSIONS FROM WETLANDS REMAINING WETLANDS
CH4 emissionsWW = CH4 emissionsWW flood
Where:
CH4 emissionsWW = CH4 emissions from wetlands remaining wetlands, Gg CH4 yr-1
CH4 emissionsWW flood = CH4 emissions from flooded land (Section 3a.3.3), Gg CH4 yr-1

3a.3.2

Organic Soils Managed for Peat Extraction

As shown in Table 3a.3.1 and Equations 3a.3.1 and 3a.3.2, methods for estimating emissions from organic soils
managed for peat extraction currently are provided only for CO2 and N2O.

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TABLE 3a.3.1
SUMMARY OF TIERS FOR ORGANIC SOILS MANAGED FOR PEAT EXTRACTION
Tier 1

Tier 2Tier 3

Change in Living
Biomass(∆CWW peat )Not estimated (or assumedzero).

Unlikely to be significant (seebelow), but may be estimatedif country-specific data are
available, following guidancein Section 3.4.1.1 (Grassland,
Changes in Carbon Stock in
Living Biomass).

Unlikely to be significant (seebelow), but may be estimatedif detailed country-specificdata or advanced methods areavailable, following guidancein Section 3.4.1.1 (Grassland,
Changes in Carbon Stock in
Living Biomass).

Change in Soil
Organic Matter)(∆ CWW peat

Emissions from peat extraction
can be estimated using default
emission factors and area data.

Estimated using moredisaggregated, countryspecific factors. If data are
available, emissions fromrestoration of peatlands andstockpiles may be estimated.

May be estimated if detailed
country-specific data oradvanced methods areavailable.

N2O

Emissions from peat extraction
can be estimated using default
emission factors and area data.

Estimated using moredisaggregated, countryspecific factors. If data are
available, emissions fromrestoration of peatlands may
be estimated.

May be estimated if detailed
country-specific data oradvanced methods areavailable.

CH4

Not estimated at present.

Estimated using countryspecific factors. If data are
available, emissions fromrestoration of peatlands may
be estimated.

May be estimated if detailed
country-specific data oradvanced methods areavailable.

LB

SOM

3a.3.2.1

CO 2 EMISSIONS FROM ORGANIC SOILS MANAGED FOR
PEAT EXTRACTION

The estimate of CO2 emissions from lands managed for peat extraction has two basic elements, as shown inEquation 3a.3.4.
EQUATION 3a.3.4
CO2 EMISSIONS IN LAND MANAGED FOR PEAT EXTRACTION
CO2 emissionsWW peat = (∆CWW peatLB + ∆CWW peatSoils ) ● 10-3 ● 44/12
Where:
CO2 emissionWWpeat = CO2 emissions from land managed for peat, Gg CO2 yr-1
∆CWW peat LB = change in carbon stock in living biomass, tonnes C yr-1
∆CWW peat Soils = change in carbon stock in soils, tonnes C yr-1
The carbon stock changes are converted to CO2 emissions (Equation 3a.3.4 is expected to result in a loss ofcarbon). Emissions are reported as positive values and removals as negative values (for more details on reporting
and the rule on the signs, see Section 3.1.7 and Annex 3A.2 Reporting Tables and Worksheets).

3a.3.2.1.1 CHANGE I N CARBON STOCKS LIVI NG BIOMASS
In general, the portion of emissions coming from the change in carbon stock in living biomass will be small
compared to the carbon emissions associated with soil organic matter. This is because vegetation is typicallyremoved on organic soils managed for peat extraction, although there may be some vegetation in drainage
ditches or along boundaries. Nevertheless substantial amounts of vegetation may be removed when the peatland
comes under management, which is addressed in Section 3.5 of this report. Due to scarcity of data and the likely
small relevance of changes in biomass on lands managed for peat extraction, no default guidance is provided
here, and it can be assumed in Tier 1 that the change in carbon stocks in living biomass on managed peatland is

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zero. However, countries in which wetlands are a key category may develop data to support the estimation ofemissions from vegetation using higher tier methods based on national expertise.

3a.3.2.1.2 CHANGE I N CARBON STOCKS IN SOILS
3a.3.2.1.2.1 Methodol ogical Issues
CO2 emissions from soil occur at several stages in the peat process, as shown in Equation 3a.3.5.
EQUATION 3a.3.5
CHANGE IN SOIL CARBON ON LANDS MANAGED FOR PEAT EXTRACTION∆CWW peatSoils = (∆CWW peatSoils, drainage + ∆CWW peatSoils, extraction + ∆CWW peatSoils, stockpiling+ ∆CWW peatSoils, restoration)
Where:∆CWW peat Soils = change in carbon stock in soils, tonnes C yr-1
∆CWW peatSoils, drainage =change in soil carbon during drainage, tonnes C yr-1

∆CWW peatSoils, extraction =change in soil carbon during peat extraction, tonnes C yr-1

∆CWW peatSoils, stockpiling = change in soil carbon during stockpiling of peat prior to removal for combustion,
tonnes C yr-1
∆CWW peatSoils, restoration =change in soils carbon due to practices undertaken to restore previously
cultivated lands, tonnes C yr-1

Currently a default method can only be provided for estimating the changes in carbon stock associated with peat
extraction (∆CWWSoils, extraction), that are essentially emissions caused by enhanced oxidation of soil organic matterat the production fields. Emissions from peat stockpiles and restoration operations are much less well understood.
Higher temperatures may cause stockpiles to release more CO2 than the excavation field, but data are not at present
sufficient to provide guidance. Countries may develop national methods for estimating the other terms in equation
3a.3.5 at higher tiers, which could also account for the effect of peatlands restoration and the dynamics which leadto higher emissions immediately after drainage compared with the period during which peat is being removed.

Choice of m ethod
The Tier 1 method relies on basic area identification and default emission factors, while the Tier 2 method is
disaggregated to smaller spatial scales and uses country-specific emission factors where available. Given thecurrent state of the science, few countries will use Tier 3 methods, and so only the main elements for a Tier 3
method are described.
Tier 1: Tier 1 estimates only emissions directly associated with the change in soil carbon during peat extraction(fugitive emissions from the production fields). The emissions from the peat extracted are covered by theemissions from peat combustion which are reported in the Energy Sector. In Tier 1, Equation 3a.3.6 is applied at
an aggregate level to a country’s area of organic soils managed for peat extraction, using default emission factors.
EQUATION 3a.3.6
CO2 EMISSIONS FROM ORGANIC SOILS MANAGED FOR PEAT EXTRACTION∆CWW peatSoils, extraction = Apeat Nrich ● EFpeat Nrich + Apeat Npoor ● EFpeat Npoor
Where:∆CWW peat Soils, extraction =CO2 emission from organic soils managed for peat extraction expressed ascarbon, tonnes C yr-1

Apeat Nrich =area of nutrient rich organic soils managed for peat extraction, including abandoned areas inwhich drainage is still present, ha

Apeat Npoor =area of nutrient poor organic soils managed for peat extraction, including abandoned areasin which drainage is still present, ha

EFpeat Nrich = emission factors for CO2 from nutrient rich organic soils managed for peat extraction,
tonnes C ha-1 yr-1

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EFpeatNpoor = emission factors for CO2 from nutrient poor organic soils managed for peat extraction,
tonnes C ha-1 yr-1
Tier 2: The Tier 2 method can be applied if area data and country-specific emission factors are available. It may
be possible to subdivide activity data and emission factors according to soil fertility, site type and drainage level,and previous land use such as forest or cropland. Emission factors for sub-categories such as peat stockpiles,
drained and restored peatlands could also be included. In addition, it may be possible to develop emission factorsthat reflect differences in emission levels between the period directly after drainage and the period of ongoingpeat extraction.
Tier 3: Tier 3 methods would require statistics on the area of organic soils managed for peat extraction according
to site type, fertility, time since drainage, time since restoration, which could be combined with appropriate
emission factors, and or/process based models. Studies utilising information on changes in soil bulk density andcarbon content could also be used to detect changes in soil carbon stocks provided the sampling was of sufficient
intensity. Such data could also be used to develop appropriate emission factors for CO2, correcting for carbon losses
as dissolved organic carbon leaching, losses of dead organic matter through runoff or as CH4 emissions.

Choice of em ission factors
Tier 1: Implementation of the Tier 1 method requires default emission factors for EFpeat. Default emission
factors for Tier 1 are presented in Table 3a.3.2. These factors are identical to those provided in Table 3.5.2(Emission factors and associated uncertainty for organic soils after drainage) to estimate CO2 emissions
associated with the drainage of land for peat extraction (a land conversion described in Section 3.5). Although it
is recognised that emissions in the period immediately following drainage will be higher than those duringongoing peat extraction, there are currently no sufficient data to develop specific default emission factors for
those activities. As noted above, under Tier 2, countries may be able to develop more disaggregated countryspecific emission factors and differentiate between emission rates during land conversion to peat land and theongoing fugitive emissions during peat extraction.
TABLE 3A.3.2
EMISSION FACTORS FOR CO2-C AND ASSOCIATED UNCERTAINTY FOR ORGANIC SOILS AFTER DRAINAGE
Region/Peat Type

Emission Factor
tonnes C ha-1 yr-1

Boreal and Temperate
Nutrient Poor
EFNpoorNutrient Rich
EFNrich0.2
1.1

Uncertainty atonnes C ha-1 yr-1
0 to 0.63
0.03 to 2.9

Reference/Comment b
Laine and Minkkinen, 1996; Alm et al., 1999;
Laine et al., 1996; Minkkinen et al., 2002
Laine et al., 1996; LUSTRA, 2002;
Minkkinen et al., 2002; Sundh et al., 2000

TropicalEFa2.0

0.06 to 6.0

Calculated from the relative difference
between temperate (nutrient poor) andtropical in Table 3.3.5.

Range of underlying datab

The boreal and temperate values have been developed as the mean from a review of paired plot measurements, assuming thatconditions on organic soils converted to peat extraction are lightly drained only. Most of the data are from Europe.

Nutrient-poor bogs predominate in boreal regions, whilst in temperate regions, nutrient-rich fens and mires are
more common. Boreal countries that do not have information on areas of nutrient-rich and nutrient-poor
peatlands should use the emission factor for nutrient-poor peatlands. Temperate countries that do not have suchdata should use the emission factor for nutrient-rich peatlands. Only one default factor is provided for tropicalregions, so disaggregating peatland area by soil fertility is not necessary for tropical countries using the Tier 1
method. The uncertainty values come from a lognormal distribution and represent a 95% confidence interval.
Tiers 2 and Tier 3: Tiers 2 and 3 require country-specific data that accounts for management practices such as
drainage of different peat types. The literature is sparse and results sometimes contrasting. Countries areencouraged to derive country-specific emission factors by measurements against appropriate reference virginsites. Data should be shared between countries with similar environmental conditions.

Choice of activity data
Tier 1: The activity data required for all tiers is the area of organic soil managed for peat extraction. Ideally,
under Tier 1 countries will obtain national data on the area of peat extraction. In boreal and temperate regions,these area data need to be disaggregated by soil fertility to correspond to the default emission factors presented
in Table 3a.3.2. Possible sources of such data are national statistics, peat mining companies and government

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ministries responsible for land use. Peat extraction area can also be estimated using statistics on peat production
for fuel and horticultural use if the national average extraction rate is known. If this rate is unavailable it can beroughly assumed that the extraction rate is 0.04 million m³/km² or 0.016 million t/km².
If neither of these approaches is possible, default data on areas in peat can be obtained from estimates in theliterature. Data on organic soils areas for other countries and an estimate of the proportion of tropical versus
temperate and boreal peatlands are available from Table 1 in Andriesse (1988). Table 3a.3.3 provides roughestimates of the drainage of wetlands at the continental scale. These data do not necessarily apply to organic soils
and do not distinguish site type. However they can be regarded as a first crude estimate of land use on peatlands
where more detailed data are unavailable. Additional data on peatland areas can be obtained from the following:
Andriesse (1988), Lappalainen (1996), OECD/IUCN (1996), Tarnocai, et al.. (2000), Umeda and Inoue (1996),
Xuehui and Yan (1996). Other sources of data are http://www.worldenergy.org/wec-geis/publications/reports/ser/peat/peat.asp and http://www.wetlands.org.
Tiers 2 and 3: Countries should assess the total area of organic soils managed for peat extraction including
abandoned areas on which drainage or the effects of former peat extraction are still present to the level ofdisaggregation required by the tier calculation or the modelling approach being used. If possible, countries areencouraged to collect data on the areas of fens versus bogs and drainage level to enable the use of moredisaggregated default emission factors or country-specific factors. If restoration is underway, countries areencouraged to report separately the areas of restored organic soils formerly managed for peat extraction andestimate emissions from peat extraction lands.

TABLE 3a.3.3
ESTIMATES OF PEATLAND AREAS AND USE FOR TIER 1 IN 1000 HECTARESCountry or
regionPeatland area
total
(Unmanaged +managed)Agriculture,drained(Cropland +grassland)

1000 ha1000 haEurope95695

Belarus2939

Managed forest,
drained1000 ha

Peat
extraction(Industrial
peatlands)% in tropicsb

Reference

0

1, 9

0

1, 2

1000 ha a(56-65% of wetlands drained for
agriculture and forestry)
900(small)109

Denmark

142

140(small)

1.2

0

1, 2

Estonia

1009

130

320

258

0

1, 2

Finland

8920

350

3540

53

0

1, 2, 3

France10055(small)(small)0

1, 2Germany1420

210(small)

32

0

1, 2

Great Britain

1754

500

500

5.4

0

1, 2

0.2

0

1, 2

0

1, 2

0

1, 2

Hungary

100

80

0

Iceland1000

120(small)Ireland

1176

90

45

Italy

120

30

Latvia

669

160

50

82
(small)

0

1, 2

27

0

1, 2

Lithuania

352

25

190

36

0

1, 2

Netherlands

279

250

(small)

3.6

0

1, 2

Norway

2370

190

280

2.5

0

1, 2

Poland

1255

760

370

2.5

0

1, 2

Slovenia

100

30

0

(small)0

1, 2

Sweden

10379

300

524

12

0

1, 2

Ukraine

1008

19

0

1, 2

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TABLE 3A.3.3 (CONTINUED)
ESTIMATES OF PEATLAND AREAS AND USE FOR TIER 1 IN 1000 HECTARESCountry or
regionAsia

Peatland area
total
(Unmanaged +managed)1000 ha24446

Agriculture, Managed forest,
draineddrained(Cropland +grassland)
1000 ha1000 ha
(27% of wetlands drained for
agriculture and forestry,increasing)

Peat
extraction(Industrial
peatlands)
1000 ha a% in tropicsb

Reference

4b, 9

Burma

965

China

1044-3480

135

104

Indonesia

17000-27000

400

3.6 (fuel only)

100

4

30

4b, 5

100

4

Iraq

1790

100

4

Japan

201

0

4b, 6

100

4b

685

100

4b

104-240

100

4b

0

1, 2

0

4b

30

8

Malaysia
Papua New
GuineaPhillipines

2250-2730

Russia39000-76000

South Korea

630

New Zealand

165

500

700

2500

9120

(2% of wetlands drained for
agriculture and forestry)

Africa5840

Guinea

525

100

4a

Nigeria

700

100

4a

South Africa

950

100

4a

Uganda

1420

100

4a

Zambia

1106

100

4a

North AmericacCanadaUSA
Alaska:S of 49°N:
Central andSouth America
Brazil173500111328(56-65% of wetlands drained for
agriculture and forestry)
25
100

4a, 11

4c, 9
16

49400
10240
11222

0

7

0
2.5

8

(6% of wetlands drained for
agriculture and forestry)4c, 91500-3500

100

4c

Chile

1047

10

4c

Cuba

658

100

4c

Guyana

814

100

4c

Honduras

453

100

4c

Mexico

1000

100

4c

Nicaragua

371

100

4c

Venezuela
1000
100
4c
References: 1 Lappalainen (1996), 2 European wetlands inventory review, draft national reports (http://www.wetlands.org),
3 national inventory, 4a-c Lappalainen and Zurek (1996), 5 Xuehui and Yan (1996), 6 Umeda and Inoue (1996), 7
Tarnocai, et al. (2000), 8 Andriesse (1988), 9 OECD/IUCN (1996)aPeat extraction for fuel: http://www.worldenergy.org/wec-geis/publications/reports/ser/peat/peat.aspbAndriesse (1988); The definition for tropics used by Andriesse (1988) is broader than the commonly used area between the between the
Tropic of Cancer (25o N) and the Tropic of Capricorn (25o S). Using this definition, e.g. land areas of New Zealand and Iraq would not beclassified as tropical.
c

Total area affected by hydroelectric reservoir construction estimated to exceed 9000km2.

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3 A .3.2.1.2.2 Uncertai nty Assessment
Tier 1: The key uncertainties in Tier 1 are the default emission factors and area estimates. Emission factors andparameters have been developed from only a few (less than 10) data points, and may not be representative forlarge areas or climate zones. The standard deviation of the emission factors easily exceeds 100% of the mean,
but underlying probability functions are likely to be non-normal. Countries are encouraged to use the range
rather than the standard deviation.
The area of drained peatlands may have an uncertainty of 50% in Europe and North America, but may be afactor of 2 in the rest of the world. Uncertainty in Southeast Asia is extremely high and the peatlands are underparticular pressure, mainly because of urbanisation and intensification of agriculture and forestry, and possibly
also for peat extraction.
Tier 2: Countries with significant areas of organic soils managed for peat extraction that use a Tier 2 method
are encouraged to provide an assessment of total uncertainty (see Chapter 5, Section 5.2, Identifying andQuantifying Uncertainties of this report) for all significant contributions to the emissions (drainage / rewetting,area, country-specific parameters).
Tier 3: Process-based models will in principle provide more realistic estimates but need to be calibrated andvalidated against measurements. Generic guidance on uncertainty assessment for advanced methods is given in
Chapter 5 (Section 5.2 Identifying and Quantifying Uncertainties) of this report. Since drainage of peatlands
leads to peat compaction and oxidation the stock change approach to monitor CO2 fluxes can be imprecise. If
used, it should be calibrated with appropriate flux measurements.

3a.3.2.2

N 2 O EMISSIONS FROM DRAI NED PEATLAND

3a.3.2.2.1 Methodological Issues
The method for estimating N2O emissions from drained peatlands is shown in the equation below.
EQUATION 3a.3.7
N2O EMISSIONS FROM DRAINED WETLANDS
Direct N2O emissions WW peat = (A peatNrich ● EF peat Nrich + A peat Npoor ● EF peat Npoor)● 44/28 ● 10-6
Where:
N2O emissions WW peat = emissions of N2O, Gg N2O yr-1
ApeatNrich = area of drained nutrient rich organic soils, ha
ApeatNpoor = area of drained nutrient poor organic soils, ha
EFpeat Nrich = emission factor for drained nutrient rich wetlands organic soils, kg N2O-N ha-1 yr-1
EFpeat Npoor = emission factor for drained nutrient poor organic soils, kg N2O-N ha-1 yr-1

Choice of m ethod
Tier 1: The Tier 1 method for estimating N2O emissions from drained wetlands is similar to that described fordrained agricultural soils in the IPCC Guidelines, and for drained forest soils (Appendix 3a.2 Non-CO2
emissions from drainage and rewetting of forest soils: Basis for future methodological development) and isshown in Equation 3a.3.7. The area of drainage (disaggregated as appropriate) is multiplied by a corresponding
emission factor. As with drained forest lands, under the Tier 1 method, the default factors for temperate andboreal lands are provided for nutrient poor and nutrient rich soils. As only a single emission factor is provided
for tropical regions, it is not necessary to disaggregate by soil fertility in this case.
Tier 2: Under Tier 2, land area is disaggregated by additional factors such as fertility, site type and drainage
level and disaggregated country-specific emission factors are used.
Tier 3: Process-based models will in principle provide a more realistic estimate but need to be calibrated andvalidated against measurements. Sufficient representative measurements are needed for validation purposes.
Generic guidance on uncertainty assessment for advanced methods is given in Section 5.2, Identifying andQuantifying Uncertainties.

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Choice of em ission/rem oval factors
Tier 1: Default emission factors for the Tier 1 method are provided in Table 3a.3.4.
TABLE 3a.3.4
DEFAULT EMISSION FACTORS FOR N2O EMISSIONS FROM WETLANDS
Climate Zone
and Soil Type

Emission Factor
EF2 peatkg N2O-N ha-1 yr-1

Uncertainty range*
kg N2O-N ha-1 yr-1

0.1

0 to 0.3

1.8

0.2 to 2.5

Boreal andTemperate Climate
Nutrient Poor
Organic Soil
Nutrient Rich
Organic Soil

Tropical Climate

18

2 to 25

Reference/ Comments

Alm et al., 1999; Laine et al., 1996;
Martikainen et al., 1995; Minkkinen et al.,
2002; Regina et al., 1996
The value for tropical areas is calculated fromthe relative difference between temperate andtropical in Chapter 4 of the IPCC Guidelines
and GPG2000. The same approach was used inTable 3.2.2 and the orders of magnitude aresimilar.

* The uncertainty values come from a lognormal distribution and represent a 95% confidence interval.

Tier 2: Tier 2 integrates country-specific data, if available, especially data that accounts for management
practices such as drainage of different peat types. Since literature is sparse and results sometimes contrasting,countries are encouraged to derive country-specific emission factors by measurements against appropriate
reference virgin sites. Specific guidance on how to derive country-specific emission factors for N2O is given inBox 4.1.of GPG2000 (page 4.62).
Tier 3: Tier 3 incorporates models that should be validated against measurements. The suitability to countryspecific conditions should be proven.

Choice of activity data
The same activity data should be used for estimating CO2 and N2O emissions from organic soils managed forpeat extraction, and information on obtaining these data is provided in Section 3a.3.3.3.1 above. For countries inboreal and temperate regions using the Tier 1 method, area data should be stratified by soil fertility, since thedefault values are provided for nutrient rich and nutrient poor soils. National data should be available from soil
services and from wetland surveys, e.g., for international conventions. If it is not possible to stratify by peat
fertility, countries may rely on expert judgement. Boreal climates tend to promote nutrient-poor raised bogs,
while temperate and oceanic climates tend to promote the formation of nutrient-richer peatlands.
Further stratification may be possible under Tier 2. For example, area could also be distinguished bymanagement practices such as drainage of different peat types, fertility (e.g., bog versus fen, nitrogen status), andtree type. Chapter 2 provides guidance on the approaches available to classify land area.
Tier 3 may require additional, possibly geo-referenced, information about soil properties, management andclimate conditions depending on the input to models or other sophisticated methodologies.

3a.3.2.2.2 Uncertaint y assessment
Tier 1: The default emission factors of Tier 1 are based on fewer than 20 paired data sets from a limited numberof studies with geographical focus on Europe. For these reasons, they should be considered highly uncertain. The
standard deviation of the emission factors easily exceeds 100% of the mean, but underlying probability functions
are likely to be non-normal. Therefore, both the standard deviation of the mean and the range of the underlying
data are given below. Given the preliminary nature of the underlying data, countries are encouraged to use therange rather than the standard deviation. Uncertainties for the default emission factors for EF2WW in Tier 1 aregiven in Table 3a.3.4.
The uncertainty in the area of peatlands and its division between nutrient-poor (ombrotrophic, bogs) andnutrient-rich (minerotrophic, fens) peat types is best calculated by a country-specific assessment of uncertainties.
Present estimates of areas of drained and rewetted forest peatlands within a country vary in a wide range
between different data sources and may have an uncertainty of 50% or more.
Tier 2: Where country-specific emission factors are used, the uncertainty should be calculated as part of theprocess of developing the factors. Guidance in derivation of country-specific emission factors is described inBox 4.1, Good Practice in Derivation of Country-Specific Emission Factors, GPG2000.

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The area of peatlands and its division between nutrient-poor and nutrient-rich peat types needs a country-specificassessment of uncertainties, which can be conducted by comparing various sources of data and applying different
area statistics, e.g., in sensitivity or Monte Carlo analyses (Section 5.2, Identifying and Quantifying Uncertainties).
Tier 3: Process-based models will probably provide a more accurate estimate of emissions but they need to becalibrated and validated against measurements. Sufficiently representative measurements are needed forvalidation purposes. Generic guidance on uncertainty assessment is given in Section 5.2, Identifying andQuantifying Uncertainties.

3a.3.2.3

C OMPLETENESS

A complete inventory should estimate emissions from all industrial peatlands including abandoned peat mining
areas in which drainage is still active, and areas drained for future peat extraction.

3a.3.2.4

D EVELOPING A CO NSISTENT TIME SERIES

General guidance on consistency in time series can be found in Section 5.6 (Time Series Consistency and
Recalculations). The emission estimation method should be applied consistently to every year in the time series,
at the same level of disaggregation. Moreover, when country-specific data are used, national inventories agency
should use same measurements protocol (sampling strategy, method, etc.). If it is not possible to use the same
method or measurement protocol throughout the time series, the guidance on recalculation in Chapter 5 should
be followed. The area of organic soils managed for peat extraction may need to be interpolated for longer timeseries or trends. Consistency checks should be made (i.e., by contacting peat-mining companies), to gather
temporal information about areas affected by former or future peat extraction, and differences in emissions
between inventory years should be explained, e.g., by demonstrating changes in areas of industrial peatlands orby updated emission factors. Differences in emissions between inventory years should be explained, e.g., bydemonstrating changes in areas of peatlands or by updated emission factors.

3a.3.2.5

R EPORTI NG AND DOCUMENTATION

It is appropriate to document and archive all information required to produce the national emissions/removals
inventory estimates as outlined in Chapter 5 of this report subject to the following specific considerations.
Emissions from land managed for peat extraction are not explicitly mentioned in the IPCC Guidelines butcorrespond in aggregate to the IPCC category 5E “Other”.
Emission factors: Since the literature data are so sparse, the scientific basis of new country-specific emission
factors, parameters and models should be fully described and documented. This includes defining the input
parameters and describing the process by which the emission factors, parameters and models were derived, as
well as describing sources of uncertainties.
Activity data: Sources of all activity data used in the calculations (data sources, databases and soil map
references) should be recorded, plus (subject to any confidentiality considerations) communication withcompanies dealing with peat extraction. This documentation should cover the frequency of data collection andestimation, and estimates of accuracy and precision, and reasons for significant changes in emission levels.
Emission results: Significant fluctuations in emissions between years should be explained. A distinction should
be made between changes in activity levels and changes in emission factors, parameters and methods from year
to year, and the reasons for these changes documented. If different emission factors, parameters and methods areused for different years, the reasons for this should be explained and documented.

3a.3.2.6

I NVENTORY QA/QC

Quality assurance/quality control (QA/QC) checks should be implemented as outlined in Chapter 5 (Section 5.5)of this report. Additional quality control checks as outlined in Tier 2 procedures in Chapter 8, QA/QC, of
GPG2000, and quality assurance procedures may also be applicable, particularly if higher tier methods are used
to quantify emissions from this source category. Where country-specific emission factors are being used theyshould be based on high quality experimental data, developed using a rigorous measurement programme, and beadequately documented.

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It is, at present, not possible to cross-check emissions estimates from organic soils managed for peat extraction
with other measurement methods. However, the inventory agency should ensure that emission estimates undergo
quality control by:•

Cross-referencing reported country-specific emissions factors with default values and data from othercountries;•

Checking the plausibility of estimates by cross-referencing areas of organic soils managed for peat
extraction with data of peat industries and peat production.

3a.3.3

Flooded Land Remaining Flooded Land

Flooded lands are defined as water bodies regulated by human activities for energy production, irrigation,navigation, recreation, etc., and where substantial changes in water area due to water level regulation occur.
Regulated lakes and rivers, where the main pre-flooded ecosystem was a natural lake or river, are not considered
as flooded lands. Rice paddies are addressed in the Agriculture chapter of the IPCC Guidelines and GPG 2000.
There is little statistical evidence to suggest that greenhouse gas emissions from flooded lands vary with time
(Duchemin et al., 1999; Duchemin, 2000; Duchemin et al., 2000 and 2002a; Keller and Stallard, 1994), although
recent studies suggest that CO2 emissions for the first ten years after flooding are as a result of decay of organic
matter on the land prior to flooding, whereas subsequent CO2 emissions are from material transferred into theflooded area (S. Houel, 2002; Hélie, 2003). If this is true, then the CO2 emissions attributed to flooding alone
would be limited to approximately 10 years.
This section provides preliminary information on how to estimate emissions of CO2, CH4 and N2O from flooded
lands. This information is drawn from available literature and may be useful to countries that want to begin
estimating emissions from this source. Due to the close linkage between CO2, CH4 and N2O emissions andmethodologies, all three gas species are addressed in this section and no distinction for emissions from flooded
land is made based on the age of the reservoir. The emissions from changes in living aboveground biomass due
the conversion to flooded land are addressed in Section 3.5.2.2.

3a.3.3.1

M ETHODOLO GICAL I SSUESGreenhouse gas emissions from flooded lands can occur via the following pathways after flooding has occurred:•

Molecular diffusion across the air-water interface for CO2, CH4 and N2O (diffusive emissions);•

Bubbles of CH4 from the sediment through the water column (bubble emissions);•

Emissions resulting from the water passing through a turbine and/or through the spillway and turbulence
downstream (degassing emissions); and•Emissions from decay of above-water biomass1.

The first two pathways – diffusive emissions and bubble emissions – are estimated in the Tier 1 method. For
hydroelectric reservoirs, degassing emissions, which are caused by an increase in dissolved CO2 and CH4 in thewater due to flooding and are released to the atmosphere when water is passing through the turbine or over the
spillway (Galy-Lacaux and al., 1997), can be included in Tier 2 if data are available.. In tropical regions,emissions from the decay of above-water biomass can be an important pathway (Fearnside, 2002) and related
emissions can be estimated at Tier 3. CO2 and CH4 emissions from reservoirs are affected by season. In boreal
and temperate regions CO2 and CH4 will be accumulated under ice and release at break-up (Duchemin, 2000).

CHOICE OF METHOD
The following discussion describes how to estimate emissions from reservoirs under various tiers, withincreasing level of accuracy associated with higher tier methods. Within the discussion of particular tiers,
specific issues related to estimating emissions of CO2, CH4 and N2O are covered.

1

Above-water biomass is the biomass in trees not submerged by the flooding, especially located in shallow flooded zones(Fearnside, 2002)

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Tier 1The Tier 1 approach provides a simplified approach to estimating greenhouse gas emissions from reservoirs
using default emission data and highly aggregated area data. Unless otherwise indicated the area used in Tier 1
calculations is the flooded total surface area, which includes any areas covered with water before the flooding,because area data minus these previously flooded areas are generally not available.
CO2 emissions
The method in Section 3.5.2.2 to estimate the carbon stock change in aboveground living biomass due to land
conversion to flooded land assumes that all aboveground biomass is converted into CO2 in the first year
following the conversion. In actuality, the part of the above-ground biomass that is left on site before flooding
will decompose more slowly. Decay of soil carbon will also contribute to the emissions and a Tier 1 method forthese CO2 emissions is shown in Equation 3a.3.8:
EQUATION 3a.3.8
CO2 EMISSIONS FROM FLOODED LANDS (TIER 1)
CO2 emissionsWW flood = P ● E(CO2)diff ● Aflood, total surface
Where:
CO2 emissionsWW flood= total CO2 emissions from flooded lands, Gg CO2 yr-1

P = period, days (usually 365 for annual inventory estimates)
E(CO2)diff = averaged daily diffusive emissions, Gg CO2 ha-1 day-1
Aflood, total surface = total flooded surface area, including flooded land, flooded lake and flooded river surface
area, haThe CO2 estimation method is simple – the only emission pathway that is estimated under Tier 1 is diffusion
emission during ice-free and ice-cover periods. CO2 bubble emissions are not significant. The default assumption
is that the CO2 emissions would be limited to approximately 10 years after the flooding took place.
The CO2 emissions estimated with the equation 3a.3.8 are highly uncertain and will depend on the site-specificconditions (soil type in particular). The use of the Equation 3a.3.8 may also lead to overestimation of theemissions when used together with the Equation 3.5.6 in Section 3.5.2.2. If countries use a Tier 2 method they
can more accurately represent the proper time profile of the CO2 emissions following flooding. Guidance on Tier
2 methods is given below.
CH4 emissions
The Tier 1 method for estimating CH4 emissions from flooded lands includes the diffusion and bubble pathways(Equation 3a.3.9):
EQUATION 3a.3.9
CH4 EMISSIONS FROM FLOODED LANDS (TIER 1)
CH4 emissionsWW flood = P ● E(CH4)diff ● Aflood, total surface + P ● E(CH4)bubble ● Aflood, total surface
Where:
CH4 emissionsWW flood= total CH4 emissions from flooded land, Gg CH4 yr-1

P = period, days (usually 365 for annual inventory estimates)
E(CH4)diff = averaged daily diffusive emissions, Gg CH4 ha-1 day-1
E(CH4)bubble = averaged bubbles emissions, Gg CH4 ha-1 day-1
Aflood, total surface = total flooded surface area, including flooded land, flooded lake and flooded river surface
area, haN2O emissions
The Tier 1 method for estimating N2O emissions from flooded lands includes the diffusion pathway only. N2Oemissions via the bubble pathway are not significant (Equation 3a.3.10):

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EQUATION 3a.3.10
N2O EMISSIONS FROM FLOODED LANDS (TIER 1)
N2O emissionsww flood = P ● E(N2O)diff ● Aflood, total surface
Where:= total N2O emissions from flooded land, Gg N2O yr-1

N2O emissionsWW flood

P = period, days (usually 365 for annual inventory estimates)
Ef(N2O)diff = averaged daily diffusive emissions, Gg N2O ha-1 day-1
Aflood, surface =total flooded surface area, including flooded land, flooded lake and flooded river surface
area, haTier 2CO2 emissions
In Tier 2, CO2 emissions can be estimated from reservoirs following the approach shown in Equation 3a.3.11.
The CO2 emissions from flooded lands should be estimated only for ten years after flooding when using Tier 2 or
3 methods unless country-specific research indicates otherwise.
Depending on the amount of data available, both diffusive and degassing emissions can be estimated when usinga Tier 2 approach. For the estimation of diffusive emissions, default emission factors can be used or countryspecific factors can be developed. For estimation of degassing emissions, country-specific factors are necessary.
The estimation of diffusion emissions can also be extended to distinguish between periods in which thereservoirs are ice-free and those in which they are ice-covered. This may be a significant improvement inaccuracy for countries in colder climates. Flooded land surface area rather than total flooded area data can beused, depending on data availability. The flooded land area may be further disaggregated by climatic zone.
EQUATION 3a.3.11
CO2 EMISSIONS FROM FLOODED LANDS (TIER 2)
CO2 emissionsWW flood = (Pf ● Ef(CO2)diff ● Aflood,land) + (Pi ● Ei(CO2)diff ● Aflood, land) + (([CO2]diss –[CO2]equ) ● Outflow ● 10-6) + (([CO2]spillway – [CO2]equ) ● Spillway ● 10-6)
Where:
CO2 emissionsWW flood = total CO2 emissions from flooded land, Gg CO2 yr-1
Pf = ice-free period, days
Pi = period with ice cover, days
Ef(CO2)diff = averaged daily diffusive emissions from air water-interface during the ice-free period,
Gg CO2 ha-1 day-1
Ei(CO2)i = diffusive emissions related to the ice-cover period, Gg CO2 ha-1 day-1
Aflood, land = flooded land area, ha[CO2]diss = averaged concentrations of CO2 before the turbines (water intake depth), kg l-1[CO2]equ = averaged concentrations of CO2 dissolved gases downstream of the dam or at equilibriumwith the atmosphere, kg l-1[CO2]spillway = averaged concentrations of CO2 before the spillway (water intake depth), kg l-1
Outflow = the averaged annual outflow rate in litres at the turbines, per hydroelectric reservoir, l yr-1
Spillway = the averaged annual outflow rate in litres at the spillway, per hydroelectric reservoir, l yr-1

CH4 emissions
Tier 2 can extend the Tier 1 method by replacing default values with country-specific emission factors, byaccounting for differences in diffusion and bubble emissions during periods when reservoirs are ice-free or ice-

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covered (for countries in the “boreal, wet” climate zone), by including (if data are available) degassing emissions
from outflows and spillways (mostly hydroelectric reservoirs), and by correcting area estimates to flooded landarea. Flooded land area may also be disaggregated by climatic zone. Tier 2 is described in Equation 3a.3.12:

EQUATION 3a.3.12
CH4 EMISSIONS FROM FLOODED LANDS (TIER 2)
CH4 emissionsWW flood = (Pf ● E(CH4)diff ● Aflood, land) + (Pf ● E(CH4)b ● Aflood, land) + Pi ● (Ei(CH4)diff+ Ei(CH4)bubble) ● Aflood, land + (([CH4]diss – [CH4]equ.) ● Outflow● 10-6) + (([CH4]spillway – [CH4]equ)● Spillway ● 10-6)
Where:
CH4 emissionsWW flood = total CH4 emissions from flooded lands per year, Gg CH4 yr-1
Pf = ice-free period, days
Pi = period with ice cover, days
E(CH4)diff = averaged daily diffusive emissions from air water-interface, Gg CH4 ha-1 day-1
E(CH4)bubble = averaged bubbles emissions from air water-interface, Gg CH4 ha-1 day-1
Aflood, land = flooded land area, ha[CH4]diss = averaged concentrations of CH4 before the turbines (water intake depth), kg l-1[CH4 ]equ. = averaged concentrations of CH4 dissolved gases downstream of the dam or at equilibriumwith the atmosphere, kg l-1[CH4]spillway = averaged concentrations of CH4 before the spillway (water intake depth), kg l-1
Outflow = the averaged annual outflow rate in litre at the turbines, per hydroelectric reservoir, l yr-1
Spillway = the averaged annual outflow rate in litre at the spillway, per hydroelectric reservoir, l yr-1
N2O emissions
The Tier 2 method for estimating N2O emissions from flooded lands is the same as shown in Equation 3a.3.10,
except that country-specific emission factors can be used, and (where data are available) flooded land surface
area should be used rather than total flooded surface area.

Tier 3
The Tier 3 methods for estimating emissions of all gases are more comprehensive and can include additionalcountry-specific data, such as emissions from above-water biomass. Tier 3 requires partitioning between emissions
from the degradation of flooded organic matter and from the decay of organic matter that comes from the watershed.

CHOICE OF EMISSI ON FACTORSThe key default values needed to implement Tier 1 method are emission factors for CO2, CH4 and N2O via thediffusion pathways, and an emission factor for CH4 via the bubbles pathways. Table 3a.3.5 provides default
emission factors for various climate zones that can be used under Tier 1. These default emission factors integrate
some spatial and temporal variations in the emissions from reservoirs, as well as fluxes at the water-air interfaceof reservoirs. All default data have been obtained from measurements in hydroelectric or flood control reservoirs.
The emissions factors for the ice-free period should be used in Tier 1 for the entire year.
For Tier 2, in addition to the above factors, data on CH4 concentrations at various points upstream anddownstream of the dam are needed to estimates degassing emissions. Country-specific emissions should be usedinstead of default factors to the extent possible. It is anticipated that a mix of default values and country-specificemission factors will be used when the latter do not cover the full range of environmental and management
conditions. The development of country-specific emission factors is discussed in Box 3a.3.1. The derivation ofcountry-specific factors should be clearly documented, and ideally published in peer reviewed literature.
Guidance in Box 3a.3.1 is applicable also for derivation of emission factors for Tier 3.

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ClimateTABLE 3A.3.5
DEFAULT EMISSIONS FACTORS FOR RESERVOIRS
Diffusive emissions (ice-free period)
Ef (GHG)diff (kg ha-1 d-1)
CH4
CO2
N2O

References

Boreal, wet

0.11
± 88%

15.5
±56%

0.008
±300%

Cold temperate, wet

0.2
±55%

9.3
±55%

nm

Duchemin, 2000; Duchemin 2002a, St-Louiset al., 2000; Smith and Lewis, 1992

0.063
± 0.032
0.096±0.074

-3.1
±3.6

nm

Duchemin 2002b

13.2
±6.9

nm

Duchemin 2002b

Tropical, wet

0.64
±330%

60.4
±145%

0.05
±100%

Tropical,moist-long dry season

0.31
±190%

11.65
±260%

nm

Tropical,moist-short dry season

0.44
±465%

35.1
±290%

nm

Pinguelli Rosa et al., 2002; Dos Santos,
2000

Tropical, dry

0.3
±115%

58.7
±270%

nm

Pinguelli Rosa et al., 2002; Dos Santos,
2000

Warm temperate, dry
Warm Temperate, wet

Duchemin, 2000; Huttunen et al., 2002;
Schlellhase, 1994, Duchemin et al., 1999

Keller et Stallard, 1994; Galy-Lacaux et al.,
1997; Duchemin et al., 2000; Pinguelli Rosa
et al., 2002
Pinguelli Rosa et al., 2002; Dos Santos,
2000

Bubbles emissions (ice-free period)
Ef (GHG)bubble (kg ha-1 d-1)
Boreal, wet

0.29
±160%

ns

ns

Duchemin, 2000, Huttunen et al., 2002;
Schlellhase, 1994

Cold temperate, wet

0.14
±70%

ns

ns

Duchemin, 2002a; St-Louis et al., 2000;
Smith and Lewis, 1992

Tropical, wet

2.83
±45%

ns

ns

Galy-Lacaux et al., 1997; Duchemin et al.,
2000; Pinguelli Rosa et al., 2002

Tropical,moist-long dry season

1.9
±155%

ns

ns

Pinguelli Rosa et al., 2002

Tropical,moist-short dry season

0.13
±135%

ns

ns

Pinguelli Rosa et al., 2002

Tropical, dry

Boreal, wet

0.3
ns
ns
±324%
Emissions associated with the ice coverperiodEi (GHG)diff + Ei (GHG)bubble(kg ha-1 d-1)
0.05
0.45
nm
±60%
±55%

Pinguelli Rosa et al., 2002

Duchemin, 2000; Duchemin et al., 2002ans : not significant, nm: not measured

CHOICE OF ACTIVI TY DATA
Several different types of activity data may be needed to estimate flooded land emissions, depending on the tierbeing implemented and the climatic zone. For Tier 1, total flooded area is required in all cases. For Tier 2,
additional activity data includes the period during which reservoirs are ice-covered or ice-free in boreal wet
regions as well as flow rates through hydroelectric outflow and spillways and flooded land area.
Flooded land area
Ideally, data on flooded area should be collected from national agencies. If such data are unavailable, however,Table 3a.3.6 contains information on total flooded surface area that can be used to estimate the emissions under
Tier 1. This table only includes surface area of flooded land that existed before 1990.
For Tier 2, flooded land area is required to estimate diffusive and bubble emissions. These data can frequently beobtained from hydro utility companies. Alternatively, countries can obtain the flooded land area by a drainage
basin cover analysis or by national dams database.

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TABLE 3a.3.6
DEFAULT RESERVOIR SURFACE AREA DATA
ICOLD
Surface area
(Mha)

Specific-country data
Surface area
(Mha)

Russia

7.32

7.96

USA

---

6.98

Canada

0

6.5

China

---

5.8

India

4.57

---

Brazil

0.69

3.98

Finland0.73---

Thailand

0.71

---

Egypt

0.70

---

Australia

0.66

---

Mexico0.60---

Zimbabwe

0.59

---

Country

Venezuela

0.58

---

Turkey0.56---

Argentina

0.50

---

Ivory coast

0.29

---

New-Zealand

0.21

---

Malik et al., 2000; US Army Corps Dams Database 1996; WCD, 2001; ICOLD 1998. Environment
Canada Reservoir Database (Duchemin, 2002a); Dos Santos, 2000.

Period of ice-free cover/Period of ice-cover
Under Tiers 2, and 3, the periods during which the reservoirs are ice-free or ice-covered are required to estimate
diffusive and bubbles emissions of CH4. These data can be obtained from national meteorological services orhydro utilitity companies.
Outflow/Spillway Volume
Under Tier 2, flooded land outflow and spillway volume are required to estimate degassing emissions of CH4.
These data can be obtained from hydro utility companies. Degassing fluxes are, mainly, a particularity ofhydroelectric reservoirs.
Tier 3 has much more extensive data requirements which can support more complex modelling of emissions
over time. Generally, this data can be compiled in a national reservoir inventory. The national reservoir
inventory should cover all types of reservoirs and include data and/or information on reservoir names, types,
surface area, depth, outflow rates, gas concentration before and after the turbines, climate conditions, water pH,
geological basement, eco-region type, and geographical coordinates (Duchemin, 2000; Duchemin et al., 1995;
Tavares de lima, 2002; Duchemin et al., 1999; Duchemin, 2002a).
CO2 and CH4 concentrations upstream and downstream of dams
Under Tiers 2 and 3, CH4 concentrations upstream and downstream of dams would be needed for estimation of
the degassing emissions. These data can be obtained as described by Fearnside (2002), Galy-Lacaux et al. (1997)
and Duchemin (2002b).

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BOX 3a.3.1
DERIVATION OF COUNTRY-SPECIFIC EMISSION FACTORSIn general, derivation of country-specific emission factors requires the measurement of emissions
by individual sub-source category (i.e., flooded land surface area, flooded land age, management
types, such as hydroelectric, agriculture, and water regulation). Emission levels vary widely
between reservoirs depending upon factors such as: area, type of ecosystems flooded, reservoir
depth and shape, local climate, geological basement the way in which the dam is operated, andecological and physical characteristics of the dammed river basin. Emissions can also vary widely
between different parts of the same reservoir (largely due to changes in depth, exposure to windand sun, and growth of water plants), and from year to year, season to season, and even between
night and day (Duchemin, 2000; Duchemin et al., 1995; Tavares de lima, 2002; Duchemin et al.,
1999; Duchemin, 2002a).
For emission factors to be representative of environmental and management conditions within the
country, measurements should be made in different flooded lands regions within a country, in allseasons, and if relevant, in different geographic regions and under different management regimes(Duchemin et al., 1999, Duchemin et al., 2002a). Appropriate selection of regions or regimes may
enable a reduction in the number of sites that must be sampled to derive a reliable flux estimate.
Maps, remote sensing data, or a dams database can provide a useful basis for delineation by
utilising the variability of a system or landscape. Aggregation errors may occur if available
measurements do not cover the actual range of environmental and flooded lands management
conditions, and inter-annual climatic variability. Validated, calibrated, and well-documented
simulation models may be a useful tool to develop area-average emission factors on the basis ofmeasurement data (Duchemin, 2000).
Regarding measurement period and frequency, emission measurements should be taken over anentire year, and preferably over a series of years, in order to reflect differences in weather
conditions, inter-annual climatic variability and flooded land evolution (Scott et al., 1999;
Duchemin, 2000; Tavares de Lima, 2002). A good description of the measurement techniques thatare available can be found in Duchemin et al. (1995), Galy-Lacaux et al. (1997), Duchemin(2000), Fearnside (2002) and Duchemin et al (2002b).
To ensure accurate emission factors of diffusive and bubble emissions, representative sites for factorsthat may influence annual and inter-annual variability of the emissions, would need to be monitored.
Such factors include depth and water level variation, water temperature, wind speed. Degassing
emission factors may vary with water temperature, which should be measured upstream of turbinesand downstream of dams so that the correlation can be established for higher tier methods.
The frequency of measurement should be consistent with the frequency of the factors that influenceannual and inter-annual variability. Emissions are likely to be variable among geographic regions,especially among different eco-regions, climatic zones and geological basements.
In general, emission factors are determined by taking the mean of the emissions of representative
sites. This averaging needs to consider the importance of each geographic zone and seasonal
period for the country.

3a.3.3.2

U NCERTAINTY ASSESSMENT

The two largest sources of uncertainty in the estimation of greenhouse gas emissions from reservoirs areassociated with the emission factors from the various pathways (diffusive, bubble and degassing) and to thereservoir surface area estimates.
Emission factors: Daily average diffusive emissions, derived from field measurements, vary by an order ofmagnitude for CH4 and by a factor of 5 for CO2 and N2O (Table 3a.3.4). Furthermore, daily average bubble
emissions of CH4 vary by more than an order of magnitude. Use of default measurements for different reservoir
types and in other regions will also result in uncertainty. Furthermore, most of the greenhouse gas flux
measurements have been undertaken on hydroelectric reservoirs, so that other types of reservoirs are notincluded in the default emissions estimates.
Flooded land surface area: Information on the flooded area retained behind larger dams should be available
and will probably be uncertain by no more than a few percent. However, information on the flooded land surface
area may be more difficult to obtain and will probably be uncertain to more than a few percent, especially in

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countries without large dams or with only a few hydroelectric reservoirs. Detailed information on the location,
type and function of smaller dams may be also difficult to obtain, though statistical inference may be possible
based on the size distribution of reservoirs for which data are available. In addition, reservoirs are created forvariety of reasons that influence the availability of data.

3a.3.3.3

C OMPLETENESS

A complete inventory should include all flooded lands. Maintaining a full area accounting, stratified by major
climate and ecosystem zones and by purposes is encouraged.

3a.3.3.4

D EVELOPING A CO NSISTENT TIME SERIES

General guidance on consistency in time series can be found in Section 5.6 (Time Series Consistency and
Recalculation). The emission estimation method should be applied consistently to every year in the time series,
at the same level of disaggregation. Moreover, when country-specific data are used, national inventories agency
should use same measurements protocol (sampling strategy, method, etc.). If it is not possible to use the same
method or measurement protocol throughout the time series, the guidance on recalculation presented in Chapter
5 should be followed. Differences in greenhouse gas emissions between inventory years should be explained,e.g., by demonstrating changes in areas of flooded lands or by updated emission factors. Consistency checks
should be made (i.e., by contacting hydro utility companies) to gather temporal information about areas affectedby former or future flooding.

3a.3.3.5

R EPORTI NG AND DOCUMENTATION

It is appropriate to document and archive all information required to produce the national inventory estimates. It issuggested that the following additional information is particularly important to document for this source category:Emission factors: The sources of the emission factors and parameters that were used (i.e., specific IPCC default
values or otherwise) should be given. If country- or region-specific emission factors and parameters were used,
and if new methods (other than IPCC default methods) were used, the scientific basis of these emission factors,
parameters and models should be well- documented. This includes defining the input parameters and describing
the process by which the emission factors, parameters and models were derived, as well as describing sources
and magnitudes of uncertainties.
Activity data: Sources of all activity data used in the calculations should be documented (i.e. complete citations
for the statistical databases from which the data were collected, communication with companies dealing withreservoirs). In cases where activity data were not available directly from databases or multiple data sets werecombined, the information, assumptions and procedures that were used to derive the activity data should be
described. This documentation should include the frequency of data collection and estimation, and estimates ofaccuracy and precision.
Emission results: Significant fluctuations in emissions between years should be explained. A distinction should
be made between changes in activity levels and changes in emission factors, parameters and methods from year
to year, and the reasons for these changes documented. If different emission factors, parameters and methods areused for different years, the reasons for this should be explained and documented.

3a.3.3.6

I NVENTORY QA/QC

It is appropriate to implement quality assurance/quality control (QA/QC) checks as outlined in Chapter 5(Section 5.5) of this report, and to conduct expert review of the emission estimates. Given the shortage of data
these reviews should be conducted regularly to take account of new research findings. Additional quality control
checks as outlined in Tier 2 procedures in Chapter 8, QA/QC, of GPG2000, and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to quantify emissions from this source
category. Where country-specific emission factors are being used they should be based on high quality
experimental data, developed using a rigorous measurement programme, and be adequately documented.
It is, at present, not possible to cross-check emissions estimates from flooded lands through externalmeasurements. However, the inventory agency should ensure that emission estimates undergo quality control by:•

Cross-referencing reported country-specific emissions factors with default values and data from othercountries;

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Cross-referencing areas of flooded land with data of hydro utility companies, with the database of theInternational Commission on Large Dams, and with data submitted to national dams safety inventories.

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