WaterCAST sediment and nutrient modelling

Scott Wilkinson

May 2009

Water for a Healthy Country

Outline

• Current modelling strengths and uncertainties• Reef Rescue monitoring and evaluation (modelling)• Issues with daily modelling and model coupling

SedNet: sediment river network budget model

Hillslopeerosion

Gully erosion

Streambank erosionHillslope

delivery

Floodplain deposition

Reservoir/ lake deposition

River linkYield from

upstream linksYield to

downstream link

Wilkinson et al., 2004

Sediment and nutrient loads to the GBR

• Sedimentation rates• Load monitoring• Load modelling

Brodie et al., 2009

SedNet N and P budgets

Downstream yield

Nutrient concentration

P equilibration, denitrificationTributary supply

River bank erosion

Gully erosion

Subsoil sediment nutrient concentration

Hillslope erosion

Topsoil sediment nutrient concentration

HSDR, Nutrient enrichment ratio

Channel resuspension, Channel, Floodplain, reservoir and lake deposition

Diffuse dissolved

loss (O&I)

Nutrient delivery

ratio

Point sources

Reservoir dissolved nutrient loss

Denitrification

Wilkinson et al., 2004

Particulate and dissolved nutrient species

• Particulate • Dissolved inorganic• Dissolved organic

0 1000 2000 3000 4000

Jacky Jacky Creek

Olive-Pascoe Rivers

Lockhart River

Stew art River

Normanby River

Jeannie River

Endeavour River

Daintree River

Mossman River

Barron River

Russell-Mulgrave River

Johnstone River

Tully River

Murray River

Herbert River

Black River

Ross River

Haughton River

Burdekin River

Don River

Proserpine River

O'Connell River

Pioneer River

Plane River

Styx River

Shoalw ater Creek

Water Park Creek

Fitzroy River

Calliope River

Boyne River

Baff le Creek

Kolan River

Burnett River

Burrum River

Mary River

Phosphorus export (t/y)

01000200030004000

Furnas (2003) phosphorus export (t/y)

PP

FRP

DOP

Furnas (2003) PP

Furnas (2003) FRP

Furnas (2003) DOP

0 5000 10000 15000 20000

Nitrogen export (t/y)

05000100001500020000

Furnas (2003) nitrogen export (t/y)

PN

DIN

DON

Furnas (2003) PN

Furnas (2003) DIN

Furnas (2003) DON

Brodie et al., 2003

Source areas and processes

(Brodie et al., 2003)

¥

Legend

Fine sediment contribution

0 - 0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 16.2

Reservoirs

Streams

Wagga Wagga

Canberra

Contribution to suspended sediment export

Yield

Supply

DepositionSupply

Uncertainties in catchment sources

• Basin source contributions• >30% uncertainty

• Sub-catchment source contributions• Gully density CV = 50–200%

• Input data improvements• Gully mapping

• Vegetation cover

• Remediation response?

Model purpose

• Identify source processes and locations• Assess their connectivity to downstream waterbodies• Simulate the effect of planned management actions to set

targets• Evaluate the effectiveness of land management changes • Modelling the effect of extreme events (eg bushfires)• Load time-series for input to receiving water models (water

quality and ecology models) • Investigating climate change effects

Reef Rescue M&E

Social & economic characteristics

DEEDI, Science providers

Land use & management Practices

Regional bodies, industry

Improvements in water quality

DERM, science providers

Subcatchment & end of catchment loads

DERM

Marine monitoring program

GBRMPA, Science providers

Plot / paddock models

DERM, Regional bodies,

science providers

Catchment models

DERM, science providers

Receiving water models

GBRMPA, science providers

Water quality / ecosystem

healthGBRMPA,

science providers

Monitoring

Modelling

$2 - $3 million available

$2 - $3 million available

($1.2 million committed this year –

Qld Govt)

$2.5 million committed – Aust Govt

Reporting &Evaluation

Reporting & EvaluationOversight: DPC

Contributors: GBRMPA, DERM, industry, Regional bodies, science providersCoordination: TBA

$0.25 – 0.5 million committed to reporting$0.9 million committed to design & set up – Aust Govt

Cross regional analysisContributors: TBACoordination: TBA

DERM: Department of Environment and Resource Management (formerly NRW & EPA)DEEDI: Department of Employment, Economic Development and Innovation (formerly DPI&F)GBRMPA: Great Barrier Reef Marine Park Authority

Options for modelling river load time-series

• Lumped statistical modelling of measured concentrations• Sediment rating curves etc

• Distributed statistical modelling of measured concentrations• EMSS, E2

• Process modelling and disaggregation to daily • SedNet

• Lumped statistical model

• WaterCAST daily process modelling• By end 2010?

WaterCAST sediment model

Hillslopeerosion

Gully erosion

Streambank erosionHillslope

delivery

Floodplain deposition

Reservoir/ lake deposition

River linkYield from

upstream linksYield to

downstream link

Deposition/ re-suspension

in channel

Model calibration

• Parameter estimation methods for automatically calibrating to observed water quality data

• Attempting to identify the response to practise change in a noisy climate-driven signal Wilkinson et al., 2009

Modelling resolution, timescale and complexity

• Adding complexity can reduce performance

• Process understanding

• Data available for parameterisation and evaluation

• Complexity increases at finer resolution and/or timescale

• e.g. water balance modelling

(Grayson and Bloschl, 2000)

(Jothityangkoon et al., 2001)

Model coupling issues

• Incorporating river load monitoring to improve modelling of the temporal dynamics

• Rating curve or statistical modelling (Kuhnert et al)

• Coastal fringe not well represented• Estuarine trapping and remobilisation

• Fitzroy

• Tidal flows• Load dependence on climate sequence

• Stochastic analysis?

• Command-line model control

References

• Grayson, R., Bloschl, G., 2000. Spatial modelling of catchment dynamics, Chapter 3 In: Grayson, R., Bloschl, G. (Eds.), Spatial patterns in catchment hydrology, Cambridge University Press (available at www.hydro.tuwien.ac.at/publications/hydrol-proc.html), 51-81.

• Jothityangkoon, C., Sivapalan, M., Farmer, D.L., 2001. Process controls on water balance variability in a large semi-arid catchment: downward approach to hydrological model development. Journal of Hydrology 254, 174-198.

• Brodie, J., McKergow, L.A., Prosser, I.P., Furnas, M., Hughes, A.O., Hunter, H., 2003. Sources of sediment and nutrient exports to the Great Barrier Reef World Heritage Area. Report Number 03/11, Australian Centre for Tropical Freshwater Research, Townsville. www.actfr.jcu.edu.au/reports/2003/index.htm.

• Wilkinson, S., Henderson, A., Chen, Y., Sherman, B., 2004. SedNet User Guide, Version 2. Client Report, CSIRO Land and Water, Canberra. www.toolkit.net.au/sednet.

• Wilkinson, S.N., Prosser, I.P., Rustomji, P., Read, A.M., 2009. Modelling and testing spatially distributed sediment budgets to relate erosion processes to suspended sediment yields. Environmental Modelling & Software 24, 489-501, doi: 10.1016/j.envsoft.2008.09.006.