Source Catchments Paddock to Reef integrated Monitoring and

Modelling Program

Dr Gillian McCloskey

DERM Senior Catchment Modeller

Reef WQ Targets By 2013, at the end of catchment there will be a minimum: 50% Reduction in Nitrogen & Phosphorus 50% Reduction in pesticides, and 50% late dry season groundcover on dry tropical grazing land By 2020, at the end of catchment there will be a minimum 20% reduction in sediment loads

Banti Fentie Rob Ellis Cameron Dougall Louise Hateley Gill McCloskey Helle Vittinghus

Model Key Objectives

Modelled load estimates for: •  Pre-European •  Baseline 2008 -2009 •  Annual report cards for 3 yrs

To assess and report on progress towards meeting Reef Water Quality targets

Simulate and quantify impact of current and improved management practises on stream constituents, loads and water quality in the GBR catchments

Region Size Km2

Climate Zone

Rainfall (mm/yr)

Dominant Land use

Cape York 42,793 Tropical 800 - 2400

Grazing 52% Nature

Conservation 46%

Wet Tropics 22,000 Tropical 716 – 3015

Grazing 46 % Nature

conservation 33 % Sugar 9 %

Burdekin 138,245 Dry tropics

649 - 1800

Grazing 94 % Forest and Nature Conservation 2.5 %

Sugar cane 1 %

Mackay /

Whitsundays

9021 Dry tropics

600 - 3000

Grazing 47 % Forest and Nature Conservation 26 %

Sugar 19 %

Fitzroy 142,000 Dry tropics/

Sub tropics

526 - 2065

Grazing 82 % Forest and Nature Conservation 9.4 %

Cropping 6.7 %

Burnett/ Mary

51,722 Sub tropics

600-2000 Grazing 78% Forest 15.5 %

Cropping 4.3 %

Total modelled Area = 361488 km2

Whole GBR catchment needs to be comparable and as close to real life as possible

–  Loads quantifiable – one number –  Same scale and time step: sub catchments and daily –  Functional units: 9 standard, up to 3 regional FU’s –  Storages, Extractions and Inflow as per DERM Water Planning –  Same rules for gauge inclusion; Quality codes and time series

Model Setup in Source Catchments

• 1 Outlet: All sub catchment with GBR outlet runs through one outlet node

• Landuse in to 11 Functional units

• Storages added as Link models, Storage-demand added as node models on the node immediately downstream

• Water extractions added as node models

• Gauges used for calibration from 1970 – 2010, sorted by min 10 years data, not downstream of a storage

Model Setup Whole GBR Catchment and each region

Source Catchment Components Region Number of Sub

catchment Size of Sub

catchment in km2 Number of nodes/

links Storages Extractions after

IQQM

Cape York 545 50 546/545 - -

Wet Tropics 450 30 451/450 2 2

Burdekin 1564 50 1565/1564 5 10

Mackay /

Whitsundays

191 30 192/191 9 5/2

Fitzroy 1600 50 1601/1600 ? ?/?

Burnett/ Mary

597 50 598/597 14 22

Hydrology Calibration - PEST PEST – Parameter Estimation Tool

GBR Models – size, number of FU’s

Each FU has a RR model, & each RR model has many parameters (SimHyd – 9)

CYP example – 545 subcatchments, 10 FU’s, 7 adjustable SimHyd params, 2 routing parameters = 49050

Too many parameters! Will affect computing power.

Hydrology Calibration - PEST Condense number of FU’s (no. of FU’s x no. of regions x 7 adjustable SimHyd params) + (no. of regions x 2 flow routing params) = 414 parameters (in Cape York)

Objectives: Daily Nash-Sutcliffe of 0.5, Monthly NS of 0.8 and modelled vs measured flows within 10-20%

Initial approach – regionalisation regions based on areas with similar rainfall, soil type & geology etc

Next approach – one region per gauge

•  14 gauges (all three objective functions met)

•  3 gauges (two objective functions met)

•  1 gauge (one objective function met)

Parameterisation 1 Parameterisation 2 Parameterisation 3 Parameterisation 4 Parameterisation 5

Hydrology Calibration - PEST

End of system Barron River 110001A

Picnic Crossing head waters of the Barron 110003A

Flaggy Creek Rainforest 110011B

Where we are at

Dynamic SedNet testing: in progress

Incorporation of paddock scale modelling outputs

Report due: 30 May. This year. (Dave: how many days is that?)

Whats next future