The CLW Aquatic Systems Modelling Team

1. The CLW Aquatic Systems Modelling Team Barbara Robson 20 May 2009

2. 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.

3. 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.

4. 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.

5. FBA modelling projects: path to impact CSIRO Sustainable Yields Project Climate Change Scenarios rainfall flows from the Murray River BigMOD (MDBC) Salinity and water level in the Coorong Coorong hydrodynamic model CLLAMMecology ecological model Impact on fish, birds, plants and invertebrates CSIRO.

6. Calibration check CSIRO.

7. Scenario comparisons – salinity time series CSIRO.

8. 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.

9. Linking with remote sensing / satellite observations CSIRO.

10. FBA modelling projects: path to impact Changes in land use and condition On-Ground Management Action Plans Sediment and nutrient loads from the catchment SedNet-ANNEX Model WQ concentrations in Keppel Bay WaterCAST in future? Receiving Waters Model (EMS) WQ triggers established by expert panel Impact on key environmental assets in Keppel Bay Exports to the Great Barrier Reef Lagoon CSIRO.

11. Scenario visualisation tool CSIRO.

12. TP TN 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 CSIRO.

13. 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.

14. Model domain • xxxx CSIRO.

15. Model simulation – water surface elevation Q = 20 m3s-1 n = 0.025 CSIRO.

16. 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.

17. Tidal influence on stage-height CSIRO.

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

19. 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.

20. Discharge predictions: nonlinear time series model Cluster-weighted model prediction Measured CSIRO.

21. 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.

22. 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.

23. Thank you CSIRO.

24. Model domain 1D hydrodynamic model with inverse mouth opening model CSIRO.

25. Channel definition CSIRO.

26. Model simulation – water surface elevation Q = 20 m3s-1 n = 0.025 CSIRO.

27. Model application CSIRO.

28. Ripple-induced interstitial flow • schematic of advective flow • flow around a porous mound (Huettel et al. 1996) CSIRO.

29. Sediment-water exchange Measured temperatures Modelled temperatures CSIRO.

30. 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 CSIRO.