Shaoda Liu
Taylor Maavara
Xiankun Yang
Lee E. Brown- 1State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, China
- 2Yale School of the Environment, Yale University, New Haven, CT, United States
- 3Yale Institute for Biospheric Studies, Yale University, New Haven, CT, United States
- 4School of Geography and Remote Sensing, Guangzhou University, Guangzhou, China
- 5School of Geography & Water@leeds, University of Leeds, Leeds, United Kingdom
Editorial on the Research Topic
Riverine Biogeochemistry Under Increasing Damming: Processes and Impacts
Rivers around the world are increasingly impounded by dams to secure water supplies to local communities, irrigated agriculture and industries, and to provide public services including hydropower production, flood control, inland navigation and recreation (Zarfl et al., 2015). Dammed reservoirs supply around 30%–40% of the world’s irrigation water (Yoshikawa et al., 2014) and 16% of the world’s electricity (REN21, 2016). It is estimated that more than 6,700 dams with backwater surface areas larger than 0.01 km2 have been constructed on the world’s rivers and the total number of all dams exceeds 16 million, with a total water storage volume of 8,069 km3 (Lehner et al., 2011; Messager et al., 2016). As a consequence, only 37% of the world’s large rivers longer than 1,000 km remain free flowing (Grill et al., 2019).
River damming redistributes seasonal and annual water flows, and causes major changes to the ecology and biogeochemistry of rivers and downstream ecosystems (Poff et al., 2007). Most importantly, reservoirs substantially extend water residence time, causing enhanced instream metabolism, nutrient retention and greenhouse gas emissions from reservoirs and downstream rivers (Chen et al., 2020; Maavara et al., 2020). These processes substantially change the role of river systems as “reactors,” yet these effects are not well understood due to their large spatial and seasonal variability within both natural rivers and reservoirs. To quantity and manage perturbations by river impoundments necessitates improved mechanistic understanding of the causes, strength, and duration of reservoir-specific processes. Considering large seasonal variability in both natural and managed reservoirs, year-round field or modeling studies are particularly important.
The aim of this research topic is to gather studies that extend our understandings of how reservoirs perturb the hydrology, biogeochemistry and ecology of rivers through novel field and/or theoretical investigations on relevant mechanisms and processes. The research topic includes five primary research articles that cover three different topics: greenhouse gas emissions from reservoirs (Sawakuchi et al.; Wu et al.; Yan et al.), the impact of dam operation on riparian vegetation (Swanson and Bohlman), and the modeling of dissolved gas saturation during spillway water releases from high dams (Peng et al.). Investigated regions included subtropical reservoirs in southwest China (Peng et al.; Wu et al.), tropical lowland reservoirs in Amazonia (Sawakuchi et al.; Swanson and Bohlman) and a global scale study (Yan et al.). These studies provide new perspectives that enhance the scientific community’s understanding of dam related riverine perturbations in different geographic contexts.
Sawakuchi et al. examined CH4 dynamics in the main channel and downstream of the Santo Antônio hydroelectric reservoir, a large run-of-river reservoir in tropical Amazonia. Their results suggest substantial CH4 production in the reservoir’s littoral sediment, but simultaneous high CH4 oxidation in the main channel which kept the concentration and fluxes of CH4 low. It was suggested that, in comparison to impoundment reservoirs, the run-of-river design of the reservoir was able to maintain high mixing and oxygenation in the reservoir’s water column with the potential to mitigate CH4 emissions.
Wu et al. investigated the spatial and seasonal dynamics of N2O emission from cascade reservoirs on the Wubu River in southwest China. In contrast to effective oxidation of CH4 in the tropical run-of-river reservoir (Sawakuchi et al.), their results suggest higher N2O concentration and emission rates in the reservoirs and released waters than in upstream river sections, making the cascade reservoirs hotspots for N2O emission. They concluded that long water residence times, high nutrient loads and high biological activities could enhance nitrogen release, transformation and N2O emission from cascade reservoirs.
Yan et al. investigated the spatial and temporal variations of greenhouse gas (CO2, CH4 and N2O) concentrations and emission rates in global reservoirs based on a compiled dataset. They estimated that global reservoirs emitted annually 12.9 Tg CH4-C, 50.8 Tg CO2-C, and 0.04 Tg N2O-N to the atmosphere. Importantly, the highest increase rate in reservoir greenhouse gas emissions occurred during the 1950s–1980s, corresponding a surge in reservoir construction in North America and Western Europe.
Swanson and Bohlman evaluated the impact of large reservoir construction on riparian vegetation changes in the Tocantins River of Amazonia. Their findings support the idea that reservoir filling threatens the integrity of ecosystem services provided by riparian vegetation via creating new riparian zones surrounding the reservoirs and causing deforestation downstream of dams. They concluded that the disturbances to native riparian vegetations may take decades or longer to recover.
Finally, Peng et al. developed a water renewal model which incorporates water residence time to predict total gas supersaturation during water release over the spillways of high dams. The results show that the model performed better than classical empirical models and mechanical models and was able to aid in mitigating the ecological risk of supersaturated gases generated during dam operation.
Author Contributions
All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.
Funding
SL acknowledges support from National Key Research and Development Program of China (2021YFC3200401) and Fundamental Research Funds for the Central Universities (2020NTST13). XY was funded from NSFC (41871017) and NSF of Guangdong Province (2021A1515011533). LB was funded from the EU’s Horizon 2020 research and innovation programme under the Marie-Curie project (765553).
Conflict of Interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s Note
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Acknowledgments
We would like to thank all the contributors and the Frontiers staff who have made this research topic possible.
References
Chen, Q., Shi, W., Huisman, J., Maberly, S. C., Zhang, J., Yu, J., et al. (2020). Hydropower Reservoirs on the Upper Mekong River Modify Nutrient Bioavailability Downstream. Natl. Sci. Rev. 7, 1449–1457. doi:10.1093/nsr/nwaa026
Grill, G., Lehner, B., Thieme, M., Geenen, B., Tickner, D., Antonelli, F., et al. (2019). Mapping the World's Free-Flowing Rivers. Nature 569, 215–221. doi:10.1038/s41586-019-1111-9
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Messager, M. L., Lehner, B., Grill, G., Nedeva, I., and Schmitt, O. (2016). Estimating the Volume and Age of Water Stored in Global Lakes Using a Geo-Statistical Approach. Nat. Commun. 7, 13603. doi:10.1038/ncomms13603
Poff, N. L., Olden, J. D., Merritt, D. M., and Pepin, D. M. (2007). Homogenization of Regional River Dynamics by Dams and Global Biodiversity Implications. Proc. Natl. Acad. Sci. 104, 5732–5737. doi:10.1073/pnas.0609812104
Ren21 (2016). Renewables 2016 Global Status Report. Available at: https://www.ren21.net/gsr-2016/ (Accessed March 2, 2022).
Yoshikawa, S., Cho, J., Yamada, H. G., Hanasaki, N., and Kanae, S. (2014). An Assessment of Global Net Irrigation Water Requirements from Various Water Supply Sources to Sustain Irrigation: Rivers and Reservoirs (1960-2050). Hydrol. Earth Syst. Sci. 18, 4289–4310. doi:10.5194/hess-18-4289-2014
Keywords: river, dams, reservoir, biogeochemistry, greenhouse gases, carbon, methane, nitrous oxide
Citation: Liu S, Maavara T, Yang X and Brown LE (2022) Editorial: Riverine Biogeochemistry Under Increasing Damming: Processes and Impacts. Front. Environ. Sci. 10:863255. doi: 10.3389/fenvs.2022.863255
Received: 27 January 2022; Accepted: 24 February 2022;
Published: 10 March 2022.
Edited and reviewed by:
Angela Helen Arthington, Griffith University, AustraliaCopyright © 2022 Liu, Maavara, Yang and Brown. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Shaoda Liu, liushaoda@bnu.edu.cn