Managing Hydrological DroughtsThe Australian Experience

Dr Dasarath (Jaya) JayasuriyaBureau of Meteorology, Australia

Inter-Regional Workshop on Indices and Early Warning Systems for Droughts 8-11 December, 2009, Lincoln Nebraska

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

Flood warnings issued

Recent Drought Situation

Rainfall Deciles (12 months)

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

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

Australian drought policy: Objectives

• To encourage primary producers and other sections to adopt self-reliant 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)

Australian drought policy: Applications

• Government support through ‘Safety Net’ and ‘Exceptional Circumstances’

• The event must be “rare” (one in 20-25 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 2010-2011

• Greater efficiency on consumptive water use, restrictions

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 interceptedby farm dams and various land management changes?

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)

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 thatthey negatively affect the community where the drought is occurring.

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….

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, 2051-21004. The Rainfall Deciles-base Drought Index and Soil-Moisture Deciles-

based Drought Index – climate modelling B1, A1F1, CSIRO Mk3, 2030

5. 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

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

Gnangara Mound Water Levels

Impact of climate change

A step change in climate necessitated timely action, reduced available options and increase importance of climate independence

Annual Inflow to Melbourne's Four Major Harvesting Reservoirs(Thomson, Upper Yarra, O'Shannassy and Maroondah Reservoirs)

Inflow 2007 372 GL

Average Inflow 1913 to 1996 615 GL/year

Average Inflow 1997-2006 387 GL/year

0

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Year

Inflo

w to

Sto

rage

(GL)

System Yield - Variation over different periods

360,000ML/aLast 10years (as per CRSWS method)

430,000ML/a1913 to 2006

535,000ML/a1913 to 2002

>600,000ML/a1913-1980

Estimated System Yield (ML/a)Streamflow Period

Water System Storage as of 16 April 2009

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

Murray-Darling Basin

• 1 million square km

• 14% of Australia

• Major river systems

–Murray River 2,530 km

–Darling River 2,740 km

Canberra

Sydney

Brisbane

NEW SOUTH WALES

QUEENSLAND

VICTORIA

SOUTHAUSTRALIA

Melbourne

Swan Hil l

MilduraMorgan

Menindee

MenindeLakes

LakeVi ctoria

Albury

Forbes

Dubbo

Moree

Charleville

Bourke

MurrayMurrumbidgie

Lachlan

Darling Macquarie

Border

Balonne

Barwon

Warrego

Adelaide

200 km

Murray Bridge

Hume Dam

•3000 GL reservoir

•50m high

•Completed 1936 raised 1961

•Main operating storage

The River Murray SystemSchematic of primary regulating structures

26

2 3 4 5 6 7 8 9 10 11

1

Barrages

Weirs/Locks

Lake Victoria

Menindee Lakes

15

Euston Weir

Torrumbarry Weir

YarrawongaWeir

HumeReservoir

DartmouthReservoir

SA

NSW

Vic

River Murray

Murrumbidgee

Edward Wakool System

Lach

lan R

iver

Redbank WeirMaude Weir

Interface with Snowy Mountains Scheme

RiverDar

ling

Riv

er

Barmah-MillewaForest

Mulwala Canal

Goulburn

River

Murray-Darling Basin - Inflow

•Lowest in2006-07

Below average

This year slightly higher

Sample Probabilistic outlook

Distribution of Total Storage (excluding Menindee)August - October Dry Tercile Years Only

0

500

1000

1500

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2500

3000

3500

4000

4500

JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY

End of Month

Sto

rage

(GL)

0%5%25%50%75%100%

Based on Standard Allocation Policy in 2007/08

Irrigated and non-irrigated agriculture

• Equitable water entitlements (high and low security) and allocations system

• Active water market (see www.watermove.com)

• 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)

The Icon Sites

Nov-Jan Rainfall Outlook, National Climate Centre

• Streamflow will add to existing outlooks

• Dry in east due to El Niño

Breakthrough seasonal flow forecasting at BOMBayesian Joint Probability (BJP) Overview (Wang et al. @ WIRADA)

Bayesian statistical parameter inference is performed using Markov Chain Monte Carlo sampling

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

Model predictions are probabilistic, providing a measure of uncertainty

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

How good are we with seasonal flow predictions?

Predictability of seasonal streamflows

Future projectionsreduced water availability

• Catchment runoff in south of MDB over past decade ~ 1 in 300 year event.

• 2030 Projections in far south vary from little change to a reduction of 50 per cent below historical.

Source: MDBSY, CSIRO 2008

User needs of drought predictions

• Improved accuracy and reliability

• Benefits key decisions (timing, relevance)

• Locally relevant information (not only regional)

• Accessible and understandable, including uncertainties and probabilities

• Reduced misinterpretation/confusion.

Begin with the end (users) in mindStephen 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

All cartoons: acknowledgement to Queensland Dept of Primary Industries and Fisheries and the Emerging Technology Company

Can not plan for a drought when you are in a drought

Thank you…

Acknowledgement: Colleagues in WIRADA, MDBA, and DPIE&F (Queensland)

Dr Dasarath (Jaya) Jayasuriyad.jayasuriya@bom.gov.au