Managing Hydrological Droughts The Australian Experience

Transcription

1 Managing Hydrological Droughts The Australian Experience Dr Dasarath (Jaya) Jayasuriya Bureau of Meteorology, Australia Inter-Regional Workshop on Indices and Early Warning Systems for Droughts 8-11 December, 2009, Lincoln Nebraska

2 Presentation outline Drought in historical context Policy response and the Water Initiative Drought indices few with flows Managing drought affected Urban, irrigated agriculture and environmental users A break-through development in forecasting seasonal flows Stakeholder and user needs

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6 Flood warnings issued

7 Recent Drought Situation Rainfall Deciles (12 months)

8 Historical context - Australia Up until 1989, official (& public) view was that drought was a natural disaster Relief was via State Governments, and increasingly, the national Government. Often on an ad hoc basis. In 1989-early 1990s, official view changed Drought should be viewed as a natural part of environment, Water resource managers and farmers should adopt a risk management approach In July 1992, a National Drought Policy was developed

9 Bureau s Role in Monitoring Drought Bureau of Meteorology monitors rainfall deficiencies across Australia. The declaration of drought and the provision of drought assistance is the responsibility of the relevant State and Federal Government departments, which consider many factors apart from rainfall. Drought is ultimately the end result of exceptionally low rainfall and the Bureau of Meteorology highlights areas suffering serious or severe rainfall deficiency

10 Australian drought policy: Objectives To encourage primary producers and other sections to adopt selfreliant approaches to managing risk To limit damage to agricultural, water and environmental resource base and the sectoral users during drought To ensure early recovery consistent with long-term sustainability Proactive sharing of climate risk.. Strategies to manager, or address, the effects of climate change, (after Water Act 2007) The environmentally sustainable of take.. the amount which, if exceeded, would compromise key environmental values or the productive base of the water resource, (after Water Act 2007)

11 Australian drought policy: Applications Government support through Safety Net and Exceptional Circumstances The event must be rare (one in years), and severe (lasting more than 12 months, and significant in spatial scale) Sustainable diversion limits: provides inter-annual variability in water availability Flourishing water market Greater focus on dry years and critical humane needs Enduring ecosystem functionality Increase administrative certainty Perfect water share New Murray Darling Basin Plan Greater efficiency on consumptive water use, restrictions

12 The questions we need to answer How much water is available in different parts of the country today (and how does it compare with history)? How much water is likely to be available in the coming days, weeks, months and years? (ie forecast) How much water is the environment getting? How is water quality changing? How much water is being intercepted by farm dams and various land management changes?

13 The hydrometeorology information dilemma* Inadequate coverage, especially streamflow Variant quality (spatial and temporal) Analysis ~ non repeatable, inconsistent assumptions and variant from case to case Institutional rivalry and hesitancy to share 2007 Water Act, 2008 Water Regulations Act in Australia and the $450Million over 10 years Water Information initiative * Drought Monitoring and Early Warning- Concepts, progress and future challenges WMO No 1006 (pp11)

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15 Major types of drought The most commonly used drought types are meteorological, agricultural, hydrological and socioeconomic. A meteorological drought is defined as a deviation from normal precipitation conditions over a period of time for a specific region. An agricultural drought occurs after a meteorological drought and is the lack of adequate soil moisture needed for a certain crop to grow and thrive during a particular time. A hydrological drought occurs when precipitation has been reduced for an extended period of time, and water supplies found in streams, lakes, rivers, and reservoirs are deficient with demand exceeding supply. A socioeconomic drought is a condition when the physical water supplies are so low that they negatively affect the community where the drought is occurring.

16 Hydrological drought indices Precipitation Anomalies, Rainfall Deciles Standardised Precipitation Index (SPI) Rainfall Depreciation Method Palmer Drought Severity Index (PDSI) Bhalme-Mooley Drought Index (BMDI) Keetch-Byram Drought Index (KBDI) Agro-Hydro Potential (AHP) Reclamation drought index (RDI) Crop Moisture Index (CMI) Surface Water Supply Index (SWSI). and more.

17 Indices used in Australia 1. In Australia: ADI, SPI and SWSI in Yarra River in Victoria- Management of water resources 2. SPI, SWVI, NDVI: in Murray-Darling Basin, Remote sensing 3. PDSI climate modelling, continental scale, The Rainfall Deciles-base Drought Index and Soil-Moisture Decilesbased Drought Index climate modelling B1, A1F1, CSIRO Mk3, PDSI, Bhalme-Mooley Drought Index (BMDI), Surface Water Supply Index and Rainfall Deciles Melbourne water supply planning 6. KBDI and Soil Dryness Index (SDI) for predicting forest fire danger

18 Managing hydrological droughts is a multidimensional problem Lags a meteorological drought Regulated Vs unregulated systems Carryover storage Vs annual fill, spill and empty Urban users (large population, public health and industry) Irrigated agriculture political clout Environmental icons and values, increasing in importance Recreational use and fishing

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20 Gnangara Mound Water Levels

21 Impact of climate change 1,400 1,200 Annual Inflow to Melbourne's Four Major Harvesting Reservoirs (Thomson, Upper Yarra, O'Shannassy and Maroondah Reservoirs) Average Inflow 1913 to GL/year Inflow to Storage (GL) 1, Average Inflow GL/year Inflow GL Year Streamflow Period to to 2006 Last 10years (as per CRSWS method) Estimated System Yield (ML/a) >600,000ML/a 535,000ML/a 430,000ML/a 360,000ML/a System Yield - Variation over different periods A step change in climate necessitated timely action, reduced available options and increase importance of climate independence

22 Water System Storage as of 16 April 2009

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24 Policy and operational response to drought Reservoir Storage Level Triggers staged actions which include various actions covering: Community education +ve Water conservation (Government incentives) +ve Water restrictions (levels progressively increasing) -ve Alternative source use (eg. recycled sewage) +ve Pricing reform -ve Infrastructure augmentation

25 Murray-Darling Basin 1 million square km 14% of Australia Major river systems Murray River 2,530 km SOUTH AUSTRALIA Menin de Lakes Lake Vi ctoria Menindee Warrego Darling NEW SOUTH WALES QUEENSLAND Bourke Lachlan Charleville Morgan Mildura Darling River Mu rray Adelaide Murr umbidgie Murray Bridge 2,740 km Swan Hill Canberra Albury Barwon Macquarie Fo rbes Moree Dubbo Balonne Border Sydn ey Brisbane VICTORIA Me lbo urne 200 km

26 Hume Dam 3000 GL reservoir 50m high Completed 1936 raised 1961 Main operating storage

27 The River Murray System Schematic of primary regulating structures Menindee Lakes SA 2 3 Lake Victoria Darling River Weirs/Locks 15 Euston Weir Maude Weir Redbank Weir Lachlan River Murrumbidgee River Edward Wakool System NSW Mulwala Canal Interface with Snowy Mountains Scheme 1 Vic River Murray Yarrawonga Weir Hume Reservoir 26 Torrumbarry Weir Goulburn River Barmah-Millewa Forest Dartmouth Reservoir Barrages

28 Murray-Darling Basin - Inflow Lowest in Below average This year slightly higher

29 Sample Probabilistic outlook Storage (GL) % 5% 25% 50% 75% 100% Distribution of Total Storage (excluding Menindee) August - October Dry Tercile Years Only Based on Standard Allocation Policy in 2007/ JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY End of Month

30 Irrigated and non-irrigated agriculture Equitable water entitlements (high and low security) and allocations system Active water market (see Streamflow Management Plans (unregulated rivers), Basin Plans to share watertied to socialised and published Drought Response Plans Sustainable diversion limits for surface water and groundwater Rationalisation of irrigation schemes (closure)

31 The Icon Sites

32 Nov-Jan Rainfall Outlook, National Climate Centre Streamflow will add to existing outlooks Dry in east due to El Niño

33 Breakthrough seasonal flow forecasting at BOM Bayesian Joint Probability (BJP) Overview (Wang et WIRADA) The BJP modelling approach produces simultaneous predictions for multiple sites within a catchment Antecedent streamflow, rainfall, climate indicators and (subjective) prior knowledge are model inputs Bayesian statistical parameter inference is performed using Markov Chain Monte Carlo sampling Model predictions are probabilistic, providing a measure of uncertainty

34 BJP modelling Stepwise selection of predictors (Wang and Robertson)

35 How good are we with seasonal flow predictions?

36 Predictability of seasonal streamflows

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39 Future projections reduced water availability Catchment runoff in south of MDB over past decade ~ 1 in 300 year event Projections in far south vary from little change to a reduction of 50 per cent below historical. Source: MDBSY, CSIRO 2008

40 Improved accuracy and reliability User needs of drought predictions Benefits key decisions (timing, relevance) Locally relevant information (not only regional) Accessible and understandable, including uncertainties and probabilities Reduced misinterpretation/confusion.

41 Begin with the end (users) in mind Stephen Covy s 7 Habits for Highly Effective Managers Indices have to have an impact to drive operational or policy decisions (Triggers for Action) These decisions have to be relevant to all affected user communities ~ urban, agriculture, environmental, industrial, recreational.. etc. Cooperative pre-planning between agencies (including political decision makers) essential Resulting outcomes (DRPs, SFMPs etc) must be socialised with the community and affected stakeholders

42 Can not plan for a drought when you are in a drought All cartoons: acknowledgement to Queensland Dept of Primary Industries and Fisheries and the Emerging Technology Company

43 Thank you Acknowledgement: Colleagues in WIRADA, MDBA, and DPIE&F (Queensland) Dr Dasarath (Jaya) Jayasuriya