Hydropower reservoirs on the upper Mekong river modify nutrient bioavailability downstream

Chen, Qiuwen; Shi, Wenqing; Huisman, Jef; Maberly, Stephen C. ORCID:; Zhang, Jianyun; Yu, Juhua; Chen, Yuchen; Tonina, Daniele; Yi, Qitao. 2020 Hydropower reservoirs on the upper Mekong river modify nutrient bioavailability downstream. National Science Review, 7 (9). 1449-1457.

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Hydropower development is the key strategy in many developing countries for energy supply, climate-change mitigation and economic development. However, it is commonly assumed that river dams retain nutrients and therefore reduce downstream primary productivity and fishery catches, compromising food security and causing trans-boundary disputes. Contrary to expectation, here we found that a cascade of reservoirs along the upper Mekong River increased downstream bioavailability of nitrogen and phosphorus. The dams caused phytoplankton density to increase with hydraulic residence time and stratification of the stagnant reservoirs caused hypoxia at depth. This allowed the release of bioavailable phosphorus from the sediment and an increase in dissolved inorganic nitrogen as well as a shift in nitrogen species from nitrate to ammonium, which were transported downstream by the discharge of water from the base of the dam. Our findings provide a new perspective on the environmental impacts of river dams on nutrient cycling and ecosystem functioning, with potential implications for sustainable development of hydropower worldwide.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Water Resources (Science Area 2017-)
ISSN: 2095-5138
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - full text available via Official URL link.
Additional Keywords: Mekong river, cascade reservoirs, downstream nutrient bioavailability, nitrogen, phosphorus
NORA Subject Terms: Earth Sciences
Ecology and Environment
Date made live: 11 May 2020 11:41 +0 (UTC)

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