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Updated: Oct 15, 2025
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Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds
Published on: September 26, 2017
11.4K
Hydropower reservoirs on the upper Mekong River modify nutrient bioavailability downstream.
Qiuwen Chen1, Wenqing Shi1, Jef Huisman2
1State Key Laboratory of Hydrology-Water Resources & Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing 210029, China.
National Science Review
|October 25, 2021
Summary
Hydropower dams on the Mekong River unexpectedly boosted downstream nitrogen and phosphorus, increasing phytoplankton. This challenges the assumption that dams harm aquatic ecosystems and food security.
Area of Science:
- Environmental Science
- Ecology
- Hydrology
Background:
- Hydropower is crucial for developing nations' energy, climate mitigation, and economic growth.
- Dams are often assumed to trap nutrients, reducing downstream productivity and fisheries.
Purpose of the Study:
- To investigate the impact of a reservoir cascade on downstream nutrient bioavailability and ecosystem functioning.
- To challenge the conventional view of dams' effects on nutrient cycling.
Main Methods:
- Analyzing nutrient levels (nitrogen, phosphorus) downstream of Mekong River dams.
- Assessing phytoplankton density in relation to reservoir characteristics (residence time, stratification).
- Measuring water chemistry, including dissolved oxygen and nitrogen species.
Main Results:
- Reservoirs increased downstream nitrogen and phosphorus bioavailability.
- Phytoplankton density correlated positively with hydraulic residence time.
- Reservoir stratification led to hypoxia and nutrient release from sediments.
Conclusions:
- Mekong River dams enhance downstream nutrient availability, contrary to common assumptions.
- Dam operations can alter nutrient cycling, affecting aquatic ecosystems.
- Findings offer new insights for sustainable hydropower development globally.
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