Resilience of a dammed tropical river. Zambezi river...Kariba Dam. DAFNE project

1. Resilience scales of a dammed tropical river
References
Elisa Calamita 1, Martin Schmid 2, Bernhard Wehrli 1,2
ETH Zürich, Environmental Systems Sciences - Aquatic Chemistry; elisa.calamita@usys.ethz.ch
1
2
...the reversible/irreversible
classification is not straightforward
because of the complexity of the
river systems.
• artificial river impoundments disrupt the seasonality and dynamics of thermal, chemical, morphological
and ecological regimes in river systems
‘river continuum’ discontinuity element downstream ecosystem
motivation
resilience scales
multisystem modelling
Physical
runoff (Q)
temperature (T)
sediment supply (sed)
light
Chemical
oxygen (O2)
CO2 and CH4
pH
nitrogen (N)
organic matter (OM)
phosphorus (P)
total suspended solids (TSS)
Biological
plankton (PP)
benthos (ben)
fish
reversible or irreversible?
Impoundment alterations on downstream river systems:
Zambezi River…Kariba Dam • biogeochemical model for Lake Kariba by using GLM
• water quality survey
• assessment of released water quality
• quantification of seasonal water quality alterations
• spatio-temporal river water quality modelling
time [month]
opened in 1959 for hydropower production
total capacity: 180 km3
second largest artificial lake in Africa
preliminary results
The water temperature resilience is shown
already 40 km downstream the reservoir,
the seasonality starts to be recovered…
…at the same location the
discharge doesn’t show
any seasonal variability.
The resilience scale is a
measure of the disruption of
the continuum river system…
..it is a measure of the
longitudinal extent of the
physicochemical alterations.
[Wikipedia]
[Wikipedia]
• river systems resilience downstream the dam has never been quantified
[Wikipedia]
maximum water depth: 97 m
Ward and Stanfard, 1983. The Serial Discontinuity Concept of lotic ecosystems. In: Fontaine, TD, Bartell, SM (Eds), Dynamics of lotic ecosystems Ann Arbor Science, Ann Arbor, Michigan: 29-42.
Straskraba, Tundisi and Duncan, 1993. State-of-the-art of reservoir limnology and water quality management. Comparative reservoir limnology and water quality management: 213-288.
Oliver, Dahlgren and Deas, 2014. The upside-down river: reservoirs, algal blooms, and tributaries affect temporal and spatial patterns in nitrogen and phosphorus in the Klamath River, USA. Journal of hydrology 519: 164-176.
Piccolroaz, Calamita, Majone, Gallice, Siviglia and Toffolon, 2016. Prediction of river water temperature: a comparison between a new family of hybrid models and statistical approaches. Hydrological processes 30: 3901—3917
Teodoru, Nyoni, Borges, Darchambeau, Nyambe and Bouillon, 2015. Dynamics of greenhouse gases (CO2, CH4, N2O) along the Zambezi River and major tributaries, and their importance in the riverine carbon budget. Biogeosciences 12: 2431-2453.
DAFNE project
• the Zambezi River is one of the most dammed river of Africa, with further
dams already planned to be installed
• little is known about the longitudinal distance that rivers need to partially restore
their physical, chemical and biological integrity
The reversibility of some characteristics is intimately
linked to the equilibrium between the river and
surrounding environment (atmosphere, streambed,..)
EU project supported by
Horizon 2020 Research
and Innovation Action:
Decision-Analytic Framework to
explore the water-energy-food Nexus
in complex and transboundary water
resources systems of fast growing
developing countries.
DAFNE How are dams changing water quality in
tropical African rivers?
time [day]
depth
35
16
T[°C]
water temperature
coordination WEF drivers analysis and modelling socio-economy trade-off results impact communication
WP1 WP2
WP3
WP4 WP5 WP6 WP7
www.dafne.ethz.ch
Temperature[°C]Discharge[m3/s]