Droughts in Australia and their Management

Droughts in Australia and their Management Dr Dasarath (Jaya) Jayasuriya A/Deputy Director Climate and Water Australian Bureau of Meteorology Expert G...
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Droughts in Australia and their Management Dr Dasarath (Jaya) Jayasuriya A/Deputy Director Climate and Water Australian Bureau of Meteorology Expert Group meeting on Hydrological Drought Indices September 2011, Geneva, Switzerland

Presentation outline • Drought in historical context • Recent Australian drought (1997-2009) • Wet conditions – 2010 – Rainfall, water storages, NDVI, soil moisture

• Approach to managing drought • Hydrological drought indices • Summary

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

1996-2010 rainfall deficiencies Impact on population centres

Recent Drought Situation

• Very high rainfall in NE, E, SE Australia • South-west of WA lowest rainfall

Current drought service: rainfall maps

• maps of 1, 3, 6, 9, 12, 18, 24, 36 months and wet season for ‘drought’, deciles, percentages etc

Gibbs and Maher 1967 Rainfall Deciles as drought indicators

Seasonal Rainfall Outlook: August to October 2011

Impact of La Niña event

Dam storages - Melbourne • Melbourne storages (SE Australia) - Exceptionally wet 2010-11 lifts storage fro 36% to 60%

Dam storages - Perth

• • • • •

Now only 30% full Compared to 27% 2010 Steady increase - July 2011 Lowest inflow in 2010 Only 16GL

1000

Yearly Streamflow for Major Surface Water Sources - IWSS

Annual Total

900

1911 to 1974 av (338 G L) 1975 to 1996 av (177 G L)

800

1997 to 2010 av (101 G L) 2001 to 2010 av (83 GL)

700

600

500

400

300

200

100

0

Note:

A year is taken as May to April

Normalised Difference Vegetation Index: July 2011

Soil moisture Week ending 14 Aug 2011

Upper layer CSIRO, http://www.eoc.csiro.au/awap/

Lower layer

Urban sector approach • Use of water restrictions (different levels with increasing severity L1 to L4) • Based on water storage levels • Pre cooked operating rules to meet increasing demands (function of population) • Use of HDI sparse, except experimental and for internal consumption by management

Rural irrigated agricultural sector • Clear water entitlements (say 300GL) • Annual allocations determined based on storage levels and forecasted inflows (may get 80% of 300GL) • Tradable water entitlement regime • Competitive water market – (water move - https://www.watermove.com.au/Default.aspx)

• Use of HDI patchy, inconsistent and adhoc

Rural run of river irrigators and ecological services • Restricted supply based on low flow characteristics • Basic ecological services provided (survival flows) and the remainder rationed equitably • The environment is often the looser (non voter and no voice) • Some ecological assets need droughts (with less flow allocated) to regenerate certain assets (the Growling Grass Frog)

Bureau’s role in assisting drought management (1) • Monitoring Australian climate, including rainfall deficiencies, weekly updates, NDVI, etc • Drought statements, weekly rainfall updates • Seasonal Climate Outlooks • New water information products – Water storages, soil moisture, streamflow forecasts, etc

• Advice to Governments, industry and the public • www.bom.gov.au/climate/drought/

Bureau’s role in assisting drought management (2) • Improving understanding and predictability of Australian droughts through R&D, e.g. – Develop improved global climate models and statistical prediction systems • Seasonal forecasts (weeks to seasons) • Longer-term predictions – Better understand the role of climate variability and climate change in recent rainfall trends – Better understanding of decadal climate variability

Indices used in Australia

• In Australia: ADI, SPI and SWSI in Yarra River in Victoria- Management of water resources •

SPI, SWVI, NDVI: in Murray-Darling Basin, Remote sensing



PDSI – climate modelling, continental scale, 2051-2100

• The Rainfall Deciles-base Drought Index and Soil-Moisture Deciles-based Drought Index – climate modelling B1, A1F1, CSIRO Mk3, 2030 • PDSI, Bhalme-Mooley Drought Index (BMDI), Surface Water Supply Index and Rainfall Deciles – Melbourne water supply planning • KBDI and Soil Dryness Index (SDI) for predicting forest fire danger

Summary • There is confusion about the type, value and use of drought indices • All types of indices are used and sometimes, misused • The knowledge is patchy and there is no agency responsible for (or taking the leadership) for forecasting drought conditions. BOM is developing a business case • Stakeholders remain disconnected from some of the climate products available • Individual agencies use fit for purpose HDI, mostly internal consumption or research

Thank you Visit www.bom.gov.au/water Dr Dasarath (Jaya) Jayasuriya [email protected] +61 3 86388251

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