Water Availability in the Goulburn-Broken, Campaspe and Loddon-Avoca Murray-Darling Basin Sustainable Yields Project 12 May 2008
Project terms of reference • Water Summit: PM and First Ministers, Nov 2006 • CSIRO to report progressively through to mid 2008 on sustainable yields of surface and groundwater systems within the MDB • Estimate current and likely future (~2030) water availability in each catchment/aquifer and for the entire MDB considering: • climate change and other risks • surface-groundwater interactions • Compare the estimated current and future water availability to that required to meet the current levels of extractive use
Project Context Environmental impacts of Water alternate allocation regimes This Project resource Assessments Socio-economic impacts of planning, of current & alternate allocation regimes management future water and availability Stakeholder and investment community consultation This project will not, in itself, determine sustainable yields or set a new cap on diversions
Overview of methods
Scenarios A: Historic climate (1895-2006) & current development B: Recent climate (1997-2006) & current development C: Future climate & current development Autumn Summer MAM SON D: Future climate & future development • Future climate • 2030 climate based on 4AR IPCC results • 3 global warming levels (low, mid, high) • 15 global climate models • Future development • Commercial forestry plantations • Farm dams • Groundwater extractions DJF Winter JJA Spring
Development • Commercial forestry plantations • projections for MDB regions • distribute projections in areas suitable for plantations • Farm dams • current levels, trend analyses, policy controls • Groundwater extractions • growth in extraction as per State advice
Rainfall-runoff modelling • SIMHYD and Sacramento models on 5 x 5 km grids • Run for scenarios A and B (single runs) • Run for Scenario C (15 GCMs x 3 global warming levels) • From C select dry, mid, wet future: modify for Scenario D • Scenario D • Modify 3 runoff series from C for forest expansion • Adjust daily flows using “Forest Cover Flow Change” model • Modify 3 runoff series from C for farm dams • Adjust daily flows using a dam water balance model • Considers rainfall, evaporation, demands, inflows and spills
River system modelling • Many different river models in use in Basin • Mostly daily time step, link-node models • These are being extended to 1895–2006 • Groundwater exchanges being quantified • Models being linked and automated • Scenario modelled runoff series transformed as inflows • Some new models being developed • DSE Goulburn Simulation Model (GSM)
Groundwater recharge • Diffuse recharge • WAVES: considers plant physiology and soil physics • Run at 20 point locations across MDB rain gradient • Consider range of land uses and soil types • Run scenarios A, B, Cdry, Cmid, Cwet • Analyse results to obtain recharge scaling factors • Apply across all groundwater management units on 5 km grid • Irrigation recharge • 1-D modelling for key irrigation areas, plus literature values
Groundwater modelling • Prioritise groundwater management units (GMUs) • Extraction level, development level, potential for stream impact • 12 high & medium priority GMUs (~80% of resource) • Existing and new numerical groundwater models • Run models with scenario recharge series and current SW–GW flux for 111 years (to equilibrium) and further 111 years • Provide equilibrium flux back to river models • Simple assessments for low priority GMUs • Connectivity mapping across all regions • Southern Riverine Plains Groundwater Model
Water accounts 423001 Warrego River @ Fords Bridge c 423004 Warrego River @ Barringun #2 Upstream gauge Reach length (km) 141 This is a strongly losing reach. Flows are dominated by inflows from Area (km 2 ) 5500 upstream. • For nearly 600 river reaches across Outflow/inflow ratio 0.33 Most of the inflow is gauged. Estimated local runoff explains most of Net losing reach the ungauged gains but large adjustment of runoff model estimates was required. There are few diversions. Ungauged losses are large Land use ha % and attributed to wetland and floodplain losses. Dryland 192,715 35 the MDB independently assess: Irrigable area - - Baseline model performance is modest. Accounting explains Open water* - - observed flows moderately. The projected scenario changes are of River and wetlands 357,315 65 similar order to the uncertainty for CH and CM scenarios, and greater Open water* - - than uncertainty for P and CL scenarios. * averages for 1990-2006 Gauging data Inflows Outflows Overall • Inflows 400 and gains and losses unattributed Fraction of total gains 300 0.67 0.22 0.44 Gauged Reach gains and losses (GL/y) ungauged Attributed 0.92 0.89 0.91 200 gains Fraction of variance gauged Gauged 0.55 0.34 0.44 100 gains Attributed 0.95 0.99 0.97 • Outflows 0 unattributed losses -100 Correlation with ungauged Gains Losses Linear adjustment ungauged normal ranked normal ranked losses -0.92 -0.86 -200 Main gauge inflows -0.26 -0.05 Tributary inflows - - - - gauged -300 -0.87 losses Main gauge outflows -0.46 -0.19 -0.43 • Diversions Distributary outflows - - - - -400 Recorded Diversions - - - - 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 -0.57 Estimated local runoff -0.30 -0.02 -0.26 1000 gauged Monthly streamflow (GL/mo) 100 • Floodplain losses accounted 10 model 1 0.1 0.01 • Direct evaporation 0.001 Jun-90 Jun-91 Jun-92 Jun-93 Jun-94 Jun-95 Jun-96 Jun-97 Jun-98 Jun-99 Jun-00 Jun-01 Jun-02 Jun-03 Jun-04 Jun-05 Water balance Model (A) Accounts Difference Model efficiency Model (A) Accounts 1000 Jul 1990 – Jun 2006 Monthly Gains GL/y GL/y GL/y Normal <0 0.48 • Exchanges with groundwater 100 Main stem inflows 79 85 -6 Log-normalised - - Tributary inflows 0 0 0 Ranked 0.68 0.28 Monthly streamflow (GL/mo) . Local inflows 75 33 42 Low flows only - - 10 <0 <0 Unattributed gains and noise - 10 - High flows only Losses GL/y GL/y GL/y Annual Main stem outflows 73 28 45 Normal <0 0.72 1 Distributary outflows 0 0 0 Log-normalised - - • Storages (rivers, lakes, Net diversions 7 0 7 Ranked 0.72 0.97 0.1 River flux to groundwater 0 - - River and floodplain losses 0 86 -86 Definitions: Unspecified losses 75 - - - low flows (flows<10% percentile ) : 0.0 GL/mo 0.01 14 Unattributed losses and noise - - - high flows (flows>90% percentile) : 5.0 GL/mo reservoirs) 0.001 Change-uncertainty ratios 0 20 40 60 80 100 P CH CM CL DH DM DL Pecentage of months flow is exceeded Annual streamflow 2.7 0.5 1.0 5.6 - - - Monthly streamflow 2.8 0.6 1.0 5.4 - - - gauged 100 450 • Assess river model performance P C D A 400 Monthly Change-Uncertainty Ratio + high P - low 350 10 Annual streamflow (GL/y) O medium 300 CH 250 CM 1 200 0.01 0.1 1 10 100 CL 150 DH 0.1 100 DM 50 DL 0.01 0 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 Annual Change-Uncertainty Ratio
Goulburn-Broken region • Area: ~2% of MDB • Pop: 144,000, 7% of MDB • Land use: dryland cereal cropping and grazing, irrigated dairy and horticulture • Irrigation: 177,600 ha in 2000 • Water use: ~14% of the surface water diverted for irrigation in the MDB & ~5.4% of MDB GW use
Campaspe region • Area: ~0.4% of MDB • Pop: 42,000, 2% of MDB • Land use: • dryland grazing • irrigated dairy • Irrigation: 32,500 ha in 2000 • Water use: • ~0.2% of the surface water diverted for irrigation in the MDB • ~1.7% of MDB GW use
Loddon-Avoca region • Area: 2.3% of MDB • Pop: 142,000 (7% of MDB) • Land use • cereal cropping and grazing • irrigated dairy • Irrigation: 127,000 ha in 2000 • Water use: • ~0.8% of the surface water diverted for irrigation in the MDB • ~1.7% of MDB GW use • Kerang Lakes – Ramsar site
River System Model
Groundwater model GMUs • Shepparton • Goorambat • Nagambie • Kialla
Groundwater model GMUs • Ellesmere • Campaspe Deep Lead GMUs • Mid-Loddon
Scenarios A: Historic climate (1895-2006) & current development B: Recent climate (1997-2006) & current development C: Future climate & current development D: Future (~2030) climate & future development • Future climate • Mid, Dry, Wet • Future development • Farm dams • Commercial forestry plantations • Groundwater extractions
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