Global Change Biology Global Change Biology (2015) 21, 6–8, doi: 10.1111/gcb.12705
LETTER
Revision of methane and carbon dioxide emissions from inland waters in India S I Y U E L I and R I C H A R D T . B U S H Southern Cross GeoScience, Southern Cross University, Military Road, Lismore, NSW 2480, Australia
Substantial greenhouse gas (GHG) emissions including methane (CH4) and carbon dioxide (CO2) from inland waters have captured international concern (Barros et al., 2011; Bastviken et al., 2011; Raymond et al., 2013; Panneer Selvam et al., 2014). Global freshwaters are consistently oversaturated with CO2 in contrast to atmospheric level resulting in a significant source of atmospheric CO2 (Raymond et al., 2013). Green house gas emissions from global inland waters are reported to be 0.65 Pg of C (CO2 eq) yr 1 as CH4 (Bastviken et al., 2011) and 1.2–2.1 Pg C yr 1 as CO2 (Raymond et al., 2013). However, global estimates are constrained by data paucity and poor coverage of Asia in particular. Recently Panneer Selvam et al. (2014) showed an impressive estimate of GHG emissions from inland waters in India, yielding a substantial revision of GHG emission from global freshwaters. However, the major rivers such as Ganges–Brahmaputra, Indus and Peninsular rivers are not sampled. Hence, rivers were potentially not representative for the whole of India. Moreover, current estimates suffered from data limitation on reservoirs particularly GHG emission from drawdown zone and reservoir downstream (spillways and turbines), where are recognized to be significant carbon emitters (Lima et al., 2008). This should be another major concern, for example, Lima et al. (2008) estimated annual CH4 emission of 14.2 Tg CH4 yr 1 from India’s large dams (4005 dams are modeled), and this data could be 33.4 Tg CH4 yr 1 if spillways/turbines are fully considered (Table 1). Of which, 1.1 Tg CH4 yr 1 was from the reservoir surface, three times higher than the current emission from reservoir/barrage (0.33 Tg CH4 yr 1; Panneer Selvam et al., 2014). Here, we identify a gross underestimation of GHG evasion from India with focuses on riverine CO2 emission and GHG from spillways/turbines, providing a revised and arguably more complete account for the emission of GHG from inland freshwaters of India. Aqueous partial pressure of CO2 was consistently higher than atmospheric level (ca. 390 latm), ranging Correspondence: Siyue Li, tel. +61 2 66269235, fax +61 2 6626 9499, e-mails: [email protected]; [email protected]
6
from 640 to 2700 latm (Fig. 1), hence leading to a CO2 flux ranging from 53 to 494 mmol m 2 day 1 in the major rivers of India. Our estimated area weighted CO2 flux was on average 163 mmol m 2 day 1, which was eightfold higher than the current estimate of 20 mmol m 2 day 1 (Panneer Selvam et al., 2014). Thus, the extrapolated CO2 emission could be 137.6 Tg CO2 yr 1 when the water area of 52 600 km2 for rivers/streams is considered, implying that Indian rivers/ streams contributed an extra ca. 117.8 Tg CO2 yr 1 to the global CO2 budget. Our extrapolated flux was 38.7% of CO2 emission from rivers and streams of the United States (ca. 355.7 117.3 Tg CO2 yr 1; Butman & Raymond, 2011). The estimated 5.94 Tg CH4 yr 1 and 0.71 Tg CO2 yr 1 could be released through spillways/turbines, thus increasing CO2 emission to be 3.08 Tg CO2 yr 1 and CH4 emission to be 6.27 Tg CH4 yr 1 by Indian reservoirs. The estimated CH4 emission was still much lower (ca. 44%) than prior estimate by Lima et al. (2008) (Table 1). In combination with GHG emission from other aquatic systems in India (Panneer Selvam et al., 2014), we derive that a total of 140.52 Tg CO2 yr 1 and 8.07 Tg CH4 yr 1 was released from India’s inland waters. Thus, expressed as CO2 equivalents (eq), 342.3 Tg CO2 (eq) is being emitted from India’s water bodies. This is equal to around 193.4% of the estimated land sink of 177 Tg CO2 yr 1 in India. If downstream methane emission of 32.4 Tg CH4 yr 1 is used (Lima et al., 2008), the total GHG emission by India’s waters could be 1004 Tg CO2 (eq) yr 1, 5.7 times greater than the land sink of India. Regional level inaccuracy as a result of data limitation and bias in data distribution is the major source behind huge uncertainties for global scale estimates, i.e. 0.5-1.8 Pg C-CO2 yr 1 by global rivers and streams, and 0.32–0.8 Tg C-CO2 yr 1 for lakes and reservoirs (Barros et al., 2011; Raymond et al., 2013; Table 1). However, by utilizing the updated estimates (see Table 1), we are able to provide a revised estimate of GHG evasion as follows: 1.8 Pg C-CO2 yr 1 for rivers and streams (Raymond et al., 2013); 0.8 Pg C-CO2 yr 1 for lakes and reservoirs (Barros et al., 2011); 103.3 Tg CH4 yr 1 for
© 2014 John Wiley & Sons Ltd
© 2014 John Wiley & Sons Ltd, Global Change Biology, 21, 6–8
357.627 536 3000 4200 1500 340 330 2800–4540 220–360 90-150 4240–15220
Rivers & streams Lakes & reservoirs Lakes Reservoirs Hydropower reservoirs Hydropower reservoirs Lakes & reservoirs Rivers (60–100 m) Streams (60–100 m) Wetlands World large dams
28
1840 585.536 186.437 176.856 146 60 3080–6170 60.691
3.262 0.393 29.272 52.6 17.644
Rivers
Rivers Lakes River & stream
2
10 km
3
Area 2
2.94 7.31 2.01
0.72
0.03–77.1
0.32
7.8 16.6 0.87
3.2
4.7 7.2 7.2
mmol m day 1
CH4 flux 2
28.81 41.55 32.23
146.85
189-356.2 15–72 541.1
24.8
365.30 621.00 54.79
54.79
2 19.8 19.8 163 8.4
mmol m day 1
CO2 flux
104.3
72 64 4 9.7
1.5
2.13 9.1 0.46
26.6 18.1 0.9
0.33 14.2 (1.1 from upstream) 6.27
0.09 0.017 1.23
Tg yr
1
CH4 emission
6600 1173.33 1943.33 1001 176 278.7 2346.67 1100 953.33 7626.67
843.33
355.7
843.33 586.67 4106.67 22.01 141.60 19
3.08 1650
0.1 0.125 9.31 137.6 2.37
Tg yr
1
CO2 emission
3743.33 2601 276 521.2
75.26 369.1 30.5
159.83
10.62
2.35 0.55 40.06
Tg yr
1
CO2 (eq)
The CO2 equivalent was calculated as the data for CO2 plus the CH4 data multiplied by 25, on the basis of GWP for CH4 (see Appendix S1).
USA Global scale
Reservoir & Barrage
India Tropical lakes & reservoirs Tropical lakes Tropical reservoirs Tropical rivers Tropical rivers Tropical streams Tropical wetlands Total in India Total in India China Hydropower reservoirs
Lake & Pond Riverine wetland River & stream River & stream Reservoir & barrage
India India India India India India’s large dams
Category of water
Table 1 Comparison of methane and CO2 emissions in India and other large scale GHG emissions
al., 2014;
al., 2014; al., 2014; al., 2014;
Bastviken et al., 2011; Li et al., 2013; Raymond et al., 2013; Raymond et al., 2013; Barros et al., 2011; Barros et al., 2011; Barros et al., 2011; Hertwich, 2013; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Lima et al., 2008
Butman & Raymond, 2011;
This study Aufdenkampe et al., 2011; Bastviken et al., 2011; Bastviken et al., 2011; Bastviken et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Panneer Selvam et al., 2014; This study SY Li, QF Zhang, RT Bush, LA Sullivan, under review; Li et al., 2013;
Panneer Selvam et Panneer Selvam et Panneer Selvam et This study Panneer Selvam et Lima et al., 2008;
References
GREENHOUSE GAS EMISSIONS FROM INDIAN INLAND WATERS 7
600
5000
500
4000
400
3000
300
2000
200
1000
100
Mahanadi
Godavari
Krishna T.
Krishna M.
0
Narmada 2
Indus 1
Brahmuputra
G-B
Narmada 1
390 μatm
0
CO2 flux (mmol m–2 d–1)
6000
Indus 2
pCO2 (μatm)
8 S. LI & R. T. BUSH
–100
River Fig. 1 pCO2 (latm) and CO2 flux (mmol m 2 d 1) in major rivers of India (whisker plots denote pCO2, red squares denote CO2 flux) (G-B is Ganges–Brahmaputra, Indus 1 is from Kari and Veizer (2002), Indus 2 is from Li et al. (2013); Narmada 1 is the data in monsoonal season, while Narmada 2 in nonmonsoonal season; Krishna M. represents mainstream, while Krishna T. represents tributaries).
rivers, lakes, and reservoirs (Bastviken et al., 2011); 100.8 Tg CH4 yr 1 from reservoirs’ spillways and turbines. This corresponds to 4.0 Pg C-CO2 (eq)/y. Combining rivers, lakes, and reservoirs with wetland provides a total GHG evasion of 8.9 Pg C-CO2 (eq) yr 1 from all inland waters (2.1 Pg C-CO2 yr 1 is from wetlands (Aufdenkampe et al., 2011); 177.4–640 Tg CH4 yr 1 is from global wetlands if we used the averaged CH4 emission rate in India’s wetlands to upscale to global scale, and a surface area of 42.4152.2 9 105 km2 for wetlands is considered). This implies that methane evasion from inland waters (613 Tg CH4 yr 1) is higher than anthropogenic CH4 source (ca. 450 Tg CH4 yr 1), and CO2 emission from inland waters is 49.5% of global human’s carbon source (9.5 Tg C yr 1). With these revisions, some uncertainty is addressed and enables a more complete, revised estimate of GHGs emissions of some 141.6 Tg CO2 yr 1 and 9.1 Tg CH4 yr 1 is released by India’s inland waters. This corresponds to 369 Tg CO2 (eq) yr 1, which is 4.9-fold higher than the current estimate and 2.1 times greater than the estimated land carbon sink of India (Panneer Selvam et al. (2014). To improve on the current quantification of GHGs on a national scale, new and more efforts to measure flux data associated with dams and data through the monsoon season are urgently needed in India and elsewhere in Asia.
References Aufdenkampe AK, Mayorga E, Raymond PA et al. (2011) Riverine coupling of biogeochemical cycles between land, oceans, and atmosphere. Frontiers in Ecology and the Environment, 9, 53–60. Barros N, Cole JJ, Tranvik LJ et al. (2011) Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude. Nature Geoscience, 4, 593–596. Bastviken D, Tranvik LJ, Downing JA, Crill PM, Enrich-Prast A (2011) Freshwater methane emissions offset the continental carbon sink. Science, 331, 50. Butman D, Raymond PA (2011) Significant efflux of carbon dioxide from streams and rivers in the United States. Nature Geoscience, 4, 839–842. Hertwich EG (2013) Addressing biogenic greenhouse gas emissions from hydropower in LCA. Environmental Science and Technology, 47, 9604–9611. Li SY, Lu XX, Bush RT (2013) CO2 partial pressure and CO2 emission in the Lower Mekong River. Journal of Hydrology, 504, 40–56. Lima IBT, Ramos FM, Bambace LAW, Rosa RR (2008) Methane emissions from large dams as renewable energy resources: a developing nation perspective. Mitig Adap Strategies Global Change Biology, 13, 193–206. Panneer Selvam B, Natchimuthu S, Arunachalam L, Bastviken D (2014) Methane and carbon dioxide emissions from inland waters in India - implications for large scale greenhouse gas balances. Glob Chang Biol, 20, 3397–3407. Raymond PA, Hartmann J, Lauerwald R, et al. (2013) Global carbon dioxide emissions from inland waters. Nature, 503, 355–359.
Supporting Information Additional Supporting Information may be found in the online version of this article: Appendix S1. Methodology and uncertainty analyses.
© 2014 John Wiley & Sons Ltd, Global Change Biology, 21, 6–8
LETTER
Revision of methane and carbon dioxide emissions from inland waters in India S I Y U E L I and R I C H A R D T . B U S H Southern Cross GeoScience, Southern Cross University, Military Road, Lismore, NSW 2480, Australia
Substantial greenhouse gas (GHG) emissions including methane (CH4) and carbon dioxide (CO2) from inland waters have captured international concern (Barros et al., 2011; Bastviken et al., 2011; Raymond et al., 2013; Panneer Selvam et al., 2014). Global freshwaters are consistently oversaturated with CO2 in contrast to atmospheric level resulting in a significant source of atmospheric CO2 (Raymond et al., 2013). Green house gas emissions from global inland waters are reported to be 0.65 Pg of C (CO2 eq) yr 1 as CH4 (Bastviken et al., 2011) and 1.2–2.1 Pg C yr 1 as CO2 (Raymond et al., 2013). However, global estimates are constrained by data paucity and poor coverage of Asia in particular. Recently Panneer Selvam et al. (2014) showed an impressive estimate of GHG emissions from inland waters in India, yielding a substantial revision of GHG emission from global freshwaters. However, the major rivers such as Ganges–Brahmaputra, Indus and Peninsular rivers are not sampled. Hence, rivers were potentially not representative for the whole of India. Moreover, current estimates suffered from data limitation on reservoirs particularly GHG emission from drawdown zone and reservoir downstream (spillways and turbines), where are recognized to be significant carbon emitters (Lima et al., 2008). This should be another major concern, for example, Lima et al. (2008) estimated annual CH4 emission of 14.2 Tg CH4 yr 1 from India’s large dams (4005 dams are modeled), and this data could be 33.4 Tg CH4 yr 1 if spillways/turbines are fully considered (Table 1). Of which, 1.1 Tg CH4 yr 1 was from the reservoir surface, three times higher than the current emission from reservoir/barrage (0.33 Tg CH4 yr 1; Panneer Selvam et al., 2014). Here, we identify a gross underestimation of GHG evasion from India with focuses on riverine CO2 emission and GHG from spillways/turbines, providing a revised and arguably more complete account for the emission of GHG from inland freshwaters of India. Aqueous partial pressure of CO2 was consistently higher than atmospheric level (ca. 390 latm), ranging Correspondence: Siyue Li, tel. +61 2 66269235, fax +61 2 6626 9499, e-mails: [email protected]; [email protected]
6
from 640 to 2700 latm (Fig. 1), hence leading to a CO2 flux ranging from 53 to 494 mmol m 2 day 1 in the major rivers of India. Our estimated area weighted CO2 flux was on average 163 mmol m 2 day 1, which was eightfold higher than the current estimate of 20 mmol m 2 day 1 (Panneer Selvam et al., 2014). Thus, the extrapolated CO2 emission could be 137.6 Tg CO2 yr 1 when the water area of 52 600 km2 for rivers/streams is considered, implying that Indian rivers/ streams contributed an extra ca. 117.8 Tg CO2 yr 1 to the global CO2 budget. Our extrapolated flux was 38.7% of CO2 emission from rivers and streams of the United States (ca. 355.7 117.3 Tg CO2 yr 1; Butman & Raymond, 2011). The estimated 5.94 Tg CH4 yr 1 and 0.71 Tg CO2 yr 1 could be released through spillways/turbines, thus increasing CO2 emission to be 3.08 Tg CO2 yr 1 and CH4 emission to be 6.27 Tg CH4 yr 1 by Indian reservoirs. The estimated CH4 emission was still much lower (ca. 44%) than prior estimate by Lima et al. (2008) (Table 1). In combination with GHG emission from other aquatic systems in India (Panneer Selvam et al., 2014), we derive that a total of 140.52 Tg CO2 yr 1 and 8.07 Tg CH4 yr 1 was released from India’s inland waters. Thus, expressed as CO2 equivalents (eq), 342.3 Tg CO2 (eq) is being emitted from India’s water bodies. This is equal to around 193.4% of the estimated land sink of 177 Tg CO2 yr 1 in India. If downstream methane emission of 32.4 Tg CH4 yr 1 is used (Lima et al., 2008), the total GHG emission by India’s waters could be 1004 Tg CO2 (eq) yr 1, 5.7 times greater than the land sink of India. Regional level inaccuracy as a result of data limitation and bias in data distribution is the major source behind huge uncertainties for global scale estimates, i.e. 0.5-1.8 Pg C-CO2 yr 1 by global rivers and streams, and 0.32–0.8 Tg C-CO2 yr 1 for lakes and reservoirs (Barros et al., 2011; Raymond et al., 2013; Table 1). However, by utilizing the updated estimates (see Table 1), we are able to provide a revised estimate of GHG evasion as follows: 1.8 Pg C-CO2 yr 1 for rivers and streams (Raymond et al., 2013); 0.8 Pg C-CO2 yr 1 for lakes and reservoirs (Barros et al., 2011); 103.3 Tg CH4 yr 1 for
© 2014 John Wiley & Sons Ltd
© 2014 John Wiley & Sons Ltd, Global Change Biology, 21, 6–8
357.627 536 3000 4200 1500 340 330 2800–4540 220–360 90-150 4240–15220
Rivers & streams Lakes & reservoirs Lakes Reservoirs Hydropower reservoirs Hydropower reservoirs Lakes & reservoirs Rivers (60–100 m) Streams (60–100 m) Wetlands World large dams
28
1840 585.536 186.437 176.856 146 60 3080–6170 60.691
3.262 0.393 29.272 52.6 17.644
Rivers
Rivers Lakes River & stream
2
10 km
3
Area 2
2.94 7.31 2.01
0.72
0.03–77.1
0.32
7.8 16.6 0.87
3.2
4.7 7.2 7.2
mmol m day 1
CH4 flux 2
28.81 41.55 32.23
146.85
189-356.2 15–72 541.1
24.8
365.30 621.00 54.79
54.79
2 19.8 19.8 163 8.4
mmol m day 1
CO2 flux
104.3
72 64 4 9.7
1.5
2.13 9.1 0.46
26.6 18.1 0.9
0.33 14.2 (1.1 from upstream) 6.27
0.09 0.017 1.23
Tg yr
1
CH4 emission
6600 1173.33 1943.33 1001 176 278.7 2346.67 1100 953.33 7626.67
843.33
355.7
843.33 586.67 4106.67 22.01 141.60 19
3.08 1650
0.1 0.125 9.31 137.6 2.37
Tg yr
1
CO2 emission
3743.33 2601 276 521.2
75.26 369.1 30.5
159.83
10.62
2.35 0.55 40.06
Tg yr
1
CO2 (eq)
The CO2 equivalent was calculated as the data for CO2 plus the CH4 data multiplied by 25, on the basis of GWP for CH4 (see Appendix S1).
USA Global scale
Reservoir & Barrage
India Tropical lakes & reservoirs Tropical lakes Tropical reservoirs Tropical rivers Tropical rivers Tropical streams Tropical wetlands Total in India Total in India China Hydropower reservoirs
Lake & Pond Riverine wetland River & stream River & stream Reservoir & barrage
India India India India India India’s large dams
Category of water
Table 1 Comparison of methane and CO2 emissions in India and other large scale GHG emissions
al., 2014;
al., 2014; al., 2014; al., 2014;
Bastviken et al., 2011; Li et al., 2013; Raymond et al., 2013; Raymond et al., 2013; Barros et al., 2011; Barros et al., 2011; Barros et al., 2011; Hertwich, 2013; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Lima et al., 2008
Butman & Raymond, 2011;
This study Aufdenkampe et al., 2011; Bastviken et al., 2011; Bastviken et al., 2011; Bastviken et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Aufdenkampe et al., 2011; Panneer Selvam et al., 2014; This study SY Li, QF Zhang, RT Bush, LA Sullivan, under review; Li et al., 2013;
Panneer Selvam et Panneer Selvam et Panneer Selvam et This study Panneer Selvam et Lima et al., 2008;
References
GREENHOUSE GAS EMISSIONS FROM INDIAN INLAND WATERS 7
600
5000
500
4000
400
3000
300
2000
200
1000
100
Mahanadi
Godavari
Krishna T.
Krishna M.
0
Narmada 2
Indus 1
Brahmuputra
G-B
Narmada 1
390 μatm
0
CO2 flux (mmol m–2 d–1)
6000
Indus 2
pCO2 (μatm)
8 S. LI & R. T. BUSH
–100
River Fig. 1 pCO2 (latm) and CO2 flux (mmol m 2 d 1) in major rivers of India (whisker plots denote pCO2, red squares denote CO2 flux) (G-B is Ganges–Brahmaputra, Indus 1 is from Kari and Veizer (2002), Indus 2 is from Li et al. (2013); Narmada 1 is the data in monsoonal season, while Narmada 2 in nonmonsoonal season; Krishna M. represents mainstream, while Krishna T. represents tributaries).
rivers, lakes, and reservoirs (Bastviken et al., 2011); 100.8 Tg CH4 yr 1 from reservoirs’ spillways and turbines. This corresponds to 4.0 Pg C-CO2 (eq)/y. Combining rivers, lakes, and reservoirs with wetland provides a total GHG evasion of 8.9 Pg C-CO2 (eq) yr 1 from all inland waters (2.1 Pg C-CO2 yr 1 is from wetlands (Aufdenkampe et al., 2011); 177.4–640 Tg CH4 yr 1 is from global wetlands if we used the averaged CH4 emission rate in India’s wetlands to upscale to global scale, and a surface area of 42.4152.2 9 105 km2 for wetlands is considered). This implies that methane evasion from inland waters (613 Tg CH4 yr 1) is higher than anthropogenic CH4 source (ca. 450 Tg CH4 yr 1), and CO2 emission from inland waters is 49.5% of global human’s carbon source (9.5 Tg C yr 1). With these revisions, some uncertainty is addressed and enables a more complete, revised estimate of GHGs emissions of some 141.6 Tg CO2 yr 1 and 9.1 Tg CH4 yr 1 is released by India’s inland waters. This corresponds to 369 Tg CO2 (eq) yr 1, which is 4.9-fold higher than the current estimate and 2.1 times greater than the estimated land carbon sink of India (Panneer Selvam et al. (2014). To improve on the current quantification of GHGs on a national scale, new and more efforts to measure flux data associated with dams and data through the monsoon season are urgently needed in India and elsewhere in Asia.
References Aufdenkampe AK, Mayorga E, Raymond PA et al. (2011) Riverine coupling of biogeochemical cycles between land, oceans, and atmosphere. Frontiers in Ecology and the Environment, 9, 53–60. Barros N, Cole JJ, Tranvik LJ et al. (2011) Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude. Nature Geoscience, 4, 593–596. Bastviken D, Tranvik LJ, Downing JA, Crill PM, Enrich-Prast A (2011) Freshwater methane emissions offset the continental carbon sink. Science, 331, 50. Butman D, Raymond PA (2011) Significant efflux of carbon dioxide from streams and rivers in the United States. Nature Geoscience, 4, 839–842. Hertwich EG (2013) Addressing biogenic greenhouse gas emissions from hydropower in LCA. Environmental Science and Technology, 47, 9604–9611. Li SY, Lu XX, Bush RT (2013) CO2 partial pressure and CO2 emission in the Lower Mekong River. Journal of Hydrology, 504, 40–56. Lima IBT, Ramos FM, Bambace LAW, Rosa RR (2008) Methane emissions from large dams as renewable energy resources: a developing nation perspective. Mitig Adap Strategies Global Change Biology, 13, 193–206. Panneer Selvam B, Natchimuthu S, Arunachalam L, Bastviken D (2014) Methane and carbon dioxide emissions from inland waters in India - implications for large scale greenhouse gas balances. Glob Chang Biol, 20, 3397–3407. Raymond PA, Hartmann J, Lauerwald R, et al. (2013) Global carbon dioxide emissions from inland waters. Nature, 503, 355–359.
Supporting Information Additional Supporting Information may be found in the online version of this article: Appendix S1. Methodology and uncertainty analyses.
© 2014 John Wiley & Sons Ltd, Global Change Biology, 21, 6–8
