CASE STUDY streamflow forecasts toaidwatermanagement. Waterworking withMelbourne toimprove seasonal resource management.Soin2010,theBureau started development—posed challengestoMelbourne’s water and variableclimate,populationgrowth andurban combined withprojected impactsduetoachanging Severity ofthe1997–2009MillenniumDrought— resource management Forecasting toimprove ’swater communication onforecast performance. making withinthewaterindustry, andenabledbetter Bureau onhowtheforecasts cansupportdecision- forecasts Water, forMelbourne offered insightforthe to thecontinueddevelopmentofseasonalstreamflow Collaboration betweenthetwoorganisationshasled the nextthree months. indicate thelikelyvolumeofcatchmentinflowsintocity’s majorwatersupply reservoirs for improved informationtoaidwaterresource Theseforecasts managementforMelbourne. The Bureau ofMeteorology’s seasonalstreamflow forecasts provide with forecasts for Melbourne Better water resources Top image:Maroondah reservoir catchmentsÿandÿreservoirs Melbourne’sÿwaterÿsupply Geelong GreenvaleÿReservoir YanÿYeanÿReservoir 0 Sÿtÿrÿaÿiÿt kilometres Bÿaÿsÿs # 20 Werribee Portsea MELBOURNE Pÿhÿiÿlÿlÿiÿp 40 Pÿoÿrÿt Bÿaÿy Craigieburn MapÿRef:ÿÿ20160278ÿÿÿÿÿ11/05/2016 Wallan Flinders Whittlesea

YarraÿRiver Frankston Hastings Hurstbridge Dandenong Reservoir Sugarloaf Kinglake Belgrave Lilydale Cranbourne Western Healesville Yea Port Pakenham River Gembrook n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n Reservoir Maroondah LangÿLang Warburton Maroondah, O’Shannassy, UpperYarra and Thomson— locations forMelbourne’s fourmajor reservoirs— the accuracyofmonthlyforecasts atfivemajorinflow Together, theBureauWater andMelbourne evaluated Testing theforecast accuracy using historicalstreamflow records. substantially higherusingtheBureau’s model,than was observed(alsocalledthe‘tercile hitrate’)was the numberoftimesforecast matchedwhat the informationpreviously available.Foreachoutlook, The Bureau’s modelproduced betterforecasts than for forecasting inflowsforeachlocationandseason. the useofhistoricalstreamflow records (orclimatology) comparing theBureau’s forecasting modeloutputto n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n Reservoir O'Shannassy n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n CardiniaÿReservoir TaragoÿReservoir SilvanÿReservoir Reservoir UpperÿYarra n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n Reservoir Thomson planning WaterMelbourne Forecasts support

1.0 Bureau’s models show About Melbourne Water 0. improved forecast As the wholesale supplier of Melbourne’s drinking

ercile hit rate ercile 0. water, Melbourne Water is responsible for managing 0. the catchments, treating water and transferring 0.33 it to their customers—primarily , 0.2 South East Water and , as well as

0.0 JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ DJF , Gippsland Water, South Gippsland orecast period Water, Western Water and Westernport Water. The anuary, ebruary, arch customers then supply water to individual homes ureau model and businesses, serving a metropolitan and regional Climatology population of over 4 million. Melbourne Water also Commonwealth of 2015 Australian ureau of eteorology stores and releases water on behalf of the Victorian Environmental Water Holder for environmental Tercile hit rate represents the number of times the forecast matched what was observed for the total inflow to the Thomson uses and Southern Rural Water for irrigation Reservoir (1950–2010). The dotted red line represents the purposes. In addition, Melbourne Water treats and chance (0.33 or one in three) of a correct forecast (of either low, supplies recycled water, removes and treats most near-median, or high flows) when using only historical data. The blue bars show the forecast was correct more often when using of Melbourne’s sewage, and manages waterways the Bureau’s forecasts. and major drainage systems in the Port Phillip and Westernport region. Improved forecasts Melbourne Water uses the Bureau’s seasonal streamflow forecasts: The Bureau and Melbourne Water now work together to deliver forecasts at the five major inflow locations in the • to aid water supply planning and operations and Melbourne . manage environmental water resources; and • as an input in developing the annual Water Outlook At the beginning of each month, Melbourne Water for Melbourne, which guides water security provides net inflow data from the previous month at management and drought response planning each location. The Bureau feeds the inflow data into its (see www.melbournewater.com.au). forecast model and issues a seasonal forecast for each location via a public website. Seasonal streamflow forecasting service The Bureau also provides additional information to demonstrate how often a forecast matches the observed What are seasonal streamflow forecasts? streamflows, giving Melbourne Water and other industry Forecasts issued monthly by the Bureau showing how users valuable guidance on forecast performance much water is expected to flow into selected streams at different times of the year. This has enhanced and catchments over the next three months. They are understanding of the forecasts and increased adoption presented as probabilities—that is the likelihood or across the industry. chance of a given volume of water flowing into a stream, based on recent climate and catchment conditions.

Melbourne Water Why are they important? orecasts support Inflow Australian streamflows are among the most variable elbourne Water planning data in the world. Streamflow forecasts are vital in helping water managers and users make informed decisions. For example, they help water managers decide which water source to use or whether environmental flows should be allocated. Inflow forecast Bureau of Meteorology What areas do the forecasts cover? bservations for They presently cover 140 locations across Australia, ureau forecasts increasing from just 21 locations when the service was launched in 2010.

To learn more about the Bureau’s seasonal streamflow forecasts, visit www.bom.gov.au/water/ssf or email [email protected]. FIND OUT MORE Melbourne Water: www.melbournewater.com.au, email enquiry@ melbournewater.com.au or call 131 722.

With the exception of logos and photography, this information sheet is licenced under the Creative Commons Australia Attribution Licence. © Commonwealth of Australia 2015. Published by the Bureau of Meteorology 2015. 150909-9