Cascade reservoir regulations on nitrogen source and transformation in the Tibetan Plateau river: Constraints from high frequency data of Lancang river
•Significant nitrogen retention by cascade reservoirs (25.0 % for TN, 11.2 % for NO3–).•Reservoir development alters riverine nitrogen sources, with sewage and manure dominant in natural channels.•Ammonium fertilizers and soil nitrogen are key contributors in reservoir areas.•Cascade reservoirs impa...
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| Published in: | Journal of hydrology (Amsterdam) Vol. 650; p. 132563 |
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| Main Authors: | , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Elsevier B.V
01.04.2025
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| Subjects: | |
| ISSN: | 0022-1694 |
| Online Access: | Get full text |
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| Summary: | •Significant nitrogen retention by cascade reservoirs (25.0 % for TN, 11.2 % for NO3–).•Reservoir development alters riverine nitrogen sources, with sewage and manure dominant in natural channels.•Ammonium fertilizers and soil nitrogen are key contributors in reservoir areas.•Cascade reservoirs impact nitrogen cycles: nitrification in streams, and nitrification and denitrification in reservoirs.
The development of cascade reservoirs has significantly modified the biogeochemical cycling of nutrients in global rivers. However, the mechanisms about how the cascade reservoir construction regulates the migration and transformation of nitrogen in alpine rivers which are sensitive to climate change and human disturbing has not been well constrained. This study analyzed the nitrogen sources and transformation in the Lancang River, a large river on the Qinghai-Tibet Plateau with intense cascade reservoir development, using the stable isotope techniques, source apportionment model, and statistical analysis. We found contrasting major nitrate sources in the natural river channel and reservoir section of the Lancang River, with sewage and manure as the primary sources of nitrate in the former (accounting for 42.5 %, 27.8 % and 37.3 % during the dry, wet, and normal water periods), while with ammonium fertilizers and soil nitrogen as the main nitrate contributors in the latter (accounting for 58.6 %, 64.1 % and 61.5 % during the dry, wet, and normal water periods). It is revealed that cascade reservoir has a significant retention effect on nitrogen (the average retention rate is 25.0 % and 11.2 % for total nitrogen and nitrate, respectively). Last but not least, there is evidence that the cascade reservoir is highlighted with denitrification, especially for normal water period, while the natural river channel and downstream dam areas are characterized with nitrification during nitrogen migration and transformation. These findings provide a deeper understanding of the effects of cascade reservoir development on the nitrogen cycle in riverine ecosystems and offer a scientific basis for future water resource management and water environmental protection strategies. |
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| ISSN: | 0022-1694 |
| DOI: | 10.1016/j.jhydrol.2024.132563 |