Impacts of hydrological changes onImpacts of hydrological changes on
phytoplankton succession in the Swanphytoplankton succession in the Swan
River, Western AustraliaRiver, Western Australia
Terence U. Chan, Barbara J. Robson, David P. Hamilton, Chris DallimoreTerence U. Chan, Barbara J. Robson, David P. Hamilton, Chris Dallimore
Centre for Water Research, University of Western AustraliaCentre for Water Research, University of Western Australia
and Ben R. Hodges and Ben R. Hodges
Dept. of Civil Engineering, University of Texas at AustinDept. of Civil Engineering, University of Texas at Austin
Upper Swan River estuary phytoplankton succession
summer autumn winter spring summer
Objective: determine to what
extent this succession is the
result of anthropogenic changes
121,000 km2
Perth
The Swan-Avon Catchment
•• Extensive clearing for agriculture (~35% remains natural) Extensive clearing for agriculture (~35% remains natural)
•• Urbanization around estuary Urbanization around estuary
•• Construction of reservoirs Construction of reservoirs
•• River River ““trainingtraining”” to handle increased flows to handle increased flows
•• Removal of estuary sill Removal of estuary sill
HydrologicalHydrological
changeschanges
Agricultural clearingAgricultural clearing
with minimal retentionwith minimal retention
of riparian zoneof riparian zone
Perth
Urban drains and groundwater intrusion
dominate the summer inflows in the estuary
350
25
1.2
90% of
the
annual
inflow
Present
hydrology
Avon Avon ““RiverRiver””
during theduring the
summersummer
Catchment effects ofCatchment effects of
anthropogenic changesanthropogenic changes
Based onBased on
LASCAMLASCAM
model of model of VineyViney
and and SivapalanSivapalan
~ 5 fold~ 5 fold
~ 16 fold~ 16 fold
~ 40 fold~ 40 fold
Increased runoff due to clearing Increased runoff due to clearing
Increased nutrient loads from agriculture Increased nutrient loads from agriculture
Increased sediment yield Increased sediment yield
Salinity field data,
Sept 26, 1995
to
July 1, 1996
Salt-wedge
estuary during
summer in the
upper reaches
Sill at 2m
deepened
to 14 m
“Snapshot” comparison of field data
and 3D hydrodynamic model ELCOM
Computational Aquatic
Ecosystem Dynamics Model
CAEDYM
lines = CAEDYM/ELCOM model
points = field data
field vs base case simulationfield data
baseline
model results
Model scenariosModel scenarios
Reduced catchment flowsReduced catchment flows
Reduced nutrient loadsReduced nutrient loads
Removal of reservoirsRemoval of reservoirs
Restoration of Fremantle sillRestoration of Fremantle sill
ELCOM
model
salinity
results
baseline
reduced
catchment
flows
CAEDYM-
ELCOM
model
chlorophyte
results
baseline
reduced
catchment
flows and
nutrients
baseline
model results
reservoirs removed
model results
baseline
model results
reduced nutrient load
model results
baseline
model results
reduced nutrient load
and reduced flow
model results
reduced nutrient load
and reduced flow
model results
reduced nutrient load
model results
Work in progress – effect of the sill on salinity
ELCOM
model
results
baseline
sill
restored
Further WorkFurther Work
Apply longer run-up time to reduceApply longer run-up time to reduce
initialization artifactsinitialization artifacts
Model management targets for reducedModel management targets for reduced
nutrient loadsnutrient loads
Conclusions
Calibrated 3D model for water quality can capture
phytoplankton succession in the Swan River estuary
Anthropogenic nutrient loads have increased
phytoplankton biomass
Phytoplankton succession appears altered by changes in
flow and loads
Acknowledgements
• Western Australian Estuarine ResearchFoundation (WAERF)
• Water and Rivers Commission of WesternAustralia (W&RC);
• WA Department of Transport;
• WA Department of Environmental Protection;
• Dr. David Horn
For further info contact: [email protected]