Impacts by dams: From water quality modelling to management optimization

Dams are prone to causing negative effects on downstream ecosystems by their potential to alter riverine water quality. In the case of Itezhi-Tezhi Reservoir (Zambia), a nutrient-poor wetland located downstream is affected by low oxygen concentrations owing to the withdrawal of deep reservoir water and by low nitrogen (N) and phosphorus (P) loads due to reservoir-internal nutrient depletion. We quantified the decrease in oxygen and nutrients by estimating mass balances as well as outflow concentrations by applying a biogeochemical reservoir model. From the mass balances, retention rates of similar to 50% of N and similar to 60% of P inputs were estimated. Hypoxic conditions during similar to 190 d in the outflow may be avoided if 50% of hypolimnetic turbine withdrawal are replaced by epilimnetic water. This optimized scenario yielded five-times higher dissolved N and P output loads. This study presents a generally applicable optimization procedure to minimize effects on downstream water quality.

Schleiss, Aj
Decesare, G
Franca, Mj
Pfister, M
Published in:
River Flow 2014, 2357-2362
Presented at:
7th International Conference on Fluvial Hydraulics (River Flow), EPFL, Lausanne, Sept, 2014
Boca Raton, Crc Press-Taylor & Francis Group
978-1-4987-0442-7; 978-1-138-02674-2

 Record created 2015-02-20, last modified 2018-03-17

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