The CLW Aquatic Systems Modelling Team

Barbara Robson

20 May 2009

CSIRO.

Team composition (de facto)

Most team members have a range of skills in assessing & modelling interactions between hydrodynamics, biogeochemistry and low-level ecology of aquatic systems (rivers, estuaries, reservoirs and coastal systems). Areas of particular individual focus include:

• Brad Sherman, group leader• Reservoir studies and catchment management

• Barbara Robson, team leader• Modelling biogeochemistry and primary production

• Nicky Grigg• Complex systems science

• Ian Webster• Hydrodynamics and thermodynamics

• Phillip Ford, retirement fellow• Aquatic biogeochemistry and radionucleide chemistry

CSIRO.

Key points of focus

• Use of models to diagnose and understand systems as much as (or more than) as predictive tools

• Emphasis on models based on biophysical process understanding

• Design of projects in which field work and models are complementary

• Emphasis on choosing the right model and framework for the question at hand rather than developing a single model product

CSIRO.

Some Current areas of work in the Catchment-to-Coast space

• The Coorong and Murray Mouth, S.A.• The problem: Greatly reduced flows have put the Coorong under

great stress. Salinity now 5x seawater is adversely affecting ecological values.

• Our role 1. Modelling salinity responses to management options and providing inputs to an ecological response model for long-term (100 year) scenarios.

• 2. Data-driven nutrient budgets to improve understanding of primary production.

• Models used: custom-built 1D hydrodynamic model, 1D biogeochemical model and inverse flux model

CSIRO.

FBA modelling projects: path to impact

CLLAMMecologyecological model

BigMOD (MDBC)

CSIRO Sustainable Yields Project

Climate ChangeScenarios

Cooronghydrodynamic

model

flows from the Murray River

Salinity and waterlevel in the Coorong

rainfall

Impact on fish,birds, plants andinvertebrates

CSIRO.

Calibration check

CSIRO.

Scenario comparisons – salinity time series

CSIRO.

Some current areas of work in the Catchment-to-Coast space

• The Fitzroy Estuary and Keppel Bay, Qld.• The problem: The Fitzroy is the largest river feeding into the Great

Barrier Reef Lagoon. We need to understand processes in the estuary to understand how the Fitzroy Basin affects the reef.

• Our role: Modelling hydrodynamics and sediment dynamics (with John’s team), biogeochemistry, and exports to the Great Barrier Reef Lagoon

• Using catchment model outputs (SedNet-ANNEX) as scenario inputs

• Linking models with remote sensing

• Model used: EMS

CSIRO.

Linking with remote sensing / satellite observations

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iver

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-23.2tss 07-Feb-2008

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CSIRO.

FBA modelling projects: path to impact

Impact on key environmental

assets in Keppel Bay

SedNet-ANNEXModel

WQ triggersestablished byexpert panel

On-Ground Management Action

Plans

Receiving WatersModel (EMS)

Sediment andnutrient loads from the catchment

WQ concentrationsin Keppel Bay

Changes in land useand condition

Exports to theGreat Barrier ReefLagoon

WaterCASTin future?

CSIRO.

Scenario visualisation tool

CSIRO.

Current work – Brad Sherman

• Uncertainty in great Barrier Reef Catchment soil nutrient data• Analysis of availability and accuracy of soil nutrient data across all

GBR catchments, and implications for modelling and management

• Found very sparse data (only ~25% of subcatchments had even one soil nitrogen measurement), and relative uncertainty of 75% for TN and TP estimates from SedNet and other sources

• Concludes that there is not enough data to support modelling catchment nutrient loads on higher time-scales

TP TN

CSIRO.

Current work – Barbara Robson, Ian Webster and others

• The Daly River, N.T.• The problem: Tropical rivers are relatively poorly understood in

comparison with southern counterparts. We need to understand them better if we are to manage continued development.

• Our role: • Coordinating fieldwork to characterise biogeochemical processes in the

Daly River.• Modelling hydraulics, nutrients and primary production (Spirogyra,

Nitella, Vallisineria) in the river

• Models used: HEC-RAS, custom-built sand-ripple thermodynamics model, (in preparation) custom nutrient flux and plant succession model

CSIRO.

Model domain

• xxxx

CSIRO.

Model simulation – water surface elevation

Q = 20 m3s-1

n = 0.025

CSIRO.

Current work – Nicky Grigg and Phillip Ford

• The Logan-Albert Estuary, Qld.• The problem: need to understand flow and nutrient dynamics in

order to manage algal blooms and nutrient delivery to Morton Bay.

• Flows are difficult to routinely measure, as tides affect water level at gauging stations.

• Our role: • Modelling tidal dynamics and calculating nutrient budgets• Calculating water velocity from stage height in a tidal environment

• Model used: cluster-weighted probability density function

CSIRO.

Tidal influence on stage-height

CSIRO.

Can we build stage-discharge relationships in tidally influenced reaches?

CSIRO.

Characterising nonlinear dynamics in stage-velocity relationships

Estimate a probability density function that captures relationship between velocity and time-lagged stage height using Cluster-Weighted Modelling (Gershenfeld et al, 1999)

CSIRO.

Discharge predictions: nonlinear time series model

Cluster-weighted model predictionMeasured

CSIRO.

Key points of focus

• Use of models to diagnose and understand systems as much as (or more than) as predictive tools

• Emphasis on models based on biophysical process understanding

• Design of projects in which field work and models are complementary

• Emphasis on choosing the right model and framework for the question at hand rather than developing a single model product

CSIRO.

The Future?

• Carbon flux modelling (climate change)• More focus on uncertainty in measurements and modelling• New challenges for new sites and scales e.g. Great Barrier

Reef• Complex systems science, e.g.

• Nonlinear dynamics: issues of model validation and comparison particular to nonlinear systems

• Stability and resilience of foodwebs

• More integration:• Aquatic systems with catchment models

• Biophysics with ecology

• Aquatic systems with climate models

• Biophysics with socioeconomics

• Integration of remote sensing and in situ data

CSIRO.

Thank you

CSIRO.

Model domain

1D hydrodynamic model with inverse mouth opening model

CSIRO.

Channel definition

CSIRO.

Model simulation – water surface elevation

Q = 20 m3s-1

n = 0.025

CSIRO.

Model application

CSIRO.

Ripple-induced interstitial flow

• schematic of advective flow

• flow around a porous mound (Huettel et al. 1996)

CSIRO.

Sediment-water exchange

Measured temperatures Modelled temperatures

CSIRO.

Named models

• Some of the named modelling packages that we have experience in using:

• EMS and SHOC

• SedNet-ANNEX

• CWR models: • DYRESM (1D hydrodynamic model)• ELCOM (3D hydrodynamic model)• CAEDYM (ecological model with DYRESM or CAEDYM)

• HEC-RAS (1D hydraulic model)

• Other hydrodynamic models: POM, TRIM