Options for the environmental future of the River Murray

The Environment Institute Water Research Centre Water Wednesday Managing the Murray Icon Sites: can engineering save the environment

WATER WEDNESDAY Options for the environmental future of the River Murray Judy Goode SA River Murray Environmental Manager SA MDB NRM Board

Presentation Outline – Overview of the River Murray – Environmental challenges – Functions and processes – The Living Murray – Chowilla as a case study – The Future?

Distribution of Australia’s surface runoff 20.3% 23.3% 1.0% 0.4% 21.1% 1.9% 0.3% 0% 1.7% 6.1% 10.6% Source: Water and the Australian Economy – April 1999 13.3%

What sort of river is the Murray? Naturally the river is: – Extremely low gradient (1m:30km from Lake Victoria to Murray Mouth) – Slow flowing – Saline – Turbid – A river of extremes and now in addition to these attributes: – Highly regulated – Greatly reduced flow – Prolonged drought

How has the river changed? • Before diversions and regulation the mean (average) annual runoff was ~25 000 gigalitres, of which 50% reached the sea after evapo-transpiration, seepage and retention in wetlands etc • Between 1920 and 2000, the level of diversion increased from ~2000 gigalitres/year to ~12 000 gigalitres/year • Extractions tripled in the 50 years to 1994 • In 2000, 61% diversions in NSW, 30% Victoria, 5.5% Queensland and 3.5% SA – almost equivalent to the mean natural discharge pre-development • Changes to flood flows due to storages and regulation • Contemporary thinking is that a river is likely to exhibit significant stress if flow regime is reduced below 2/3 of natural (TLM SRP) • Medium floods reduced from 1:3 to 1:8 years

Menindee Lakes Lake Victoria Hume Dam Barmah Choke Dartmouth Dam

Factors Affecting the health of the system • Significantly fewer floods - changes to flood frequency, timing and duration due to regulation and over-allocation • Unseasonal delivery of water to support consumptive uses - high flows now predominantly delivered in summer/autumn cf natural delivery in winter-spring • Limited capacity to deliver water to SA • Salinity build up on floodplain with limited flooding • Flow times exacerbating management issues • Risk of algal blooms due to low flows • Deterioration of “river health” due to loss of connectivity between the river and the floodplain • Conflicting management objectives – eg static water levels for irrigation and tourism vs weir pool manipulation for environmental outcomes • Climate change and other risks

CSIRO Sustainable Yields Project • Provides govts with estimate of water availability in the MDB on an individual catchment and aquifer basis, taking into account climate change and other risks • Reduced run off and end of system flows under median and extreme dry climate change scenarios (assuming current development and allocation policies, and no recovery of e-water) – Best estimate median 2030 climate average annual runoff reduced by 10 per cent – Extreme estimates range from 41% reduction in the Murray (dry extreme) to 7% increase (wet extreme) • Significant increases in the average time between beneficial floods • These hydrologic changes would have very serious consequences for ecosystem health • Wet extreme would lead to little change in flood frequency

What challenges does this present? Achieving a balance between the social, economic and environmental outcomes of water management is a complex task facing water managers and governments – Decisions taken in the past exploited the landscape for development and wealth – Development over the last 100 years has resulted in biophysical, landscape scale change that we don‟t fully understand – river health has declined as the critical connection with floodplains has been reduced – Biodiversity has significantly declined, including loss of native species and changes in vegetation – e.g. native fish populations estimated to be 10% of original numbers – The long-term reliability and viability of all users depend on river health – We are currently borrowing from the future What are the shared and individual rights to the natural resources of the Basin and how are those rights to be managed?

What challenges does this present? The River Murray is a highly regulated river that supports communities and regional/State economies, at the expense of the environment. How do we redress the imbalance? • More water is clearly the answer, but we also: – Need to „do more with less‟ – Important to identify key environmental assets using scientifically robust and consistent criteria, prioritisation frameworks and methodologies – Take a one-River approach – Basin Plan? – System approach – scalar – Restoration projects - identify and agree key ecological processes – Adaptive management approach – requires significant investment in monitoring, data interpretation – Innovative solutions – engineering? – Make explicit trade-offs and recognise the impacts

FUNCTIONS AND PROCESSES • Owing to the inherent complexity of rivers and an incomplete understanding of river systems, restoration projects that focus on reinstating ecological process are likely to be more successful than those which focus on fixed end points, particularly when:  There is a recognition that process and hence restoration projects are ongoing.  They are conducted at an appropriate scale.  They are conducted with appropriate and sufficient scientific monitoring.  They are conducted within a multi-disciplinary and adaptive management framework. • Restoration of processes focuses on the causes of system degradation rather than the symptoms

Process based river restoration: Time scales • Long-term strategies for managing flow regimes, land use and native biota are critical for restoring ecological integrity to rivers • Temporal considerations are fundamental to river restoration.  The natural timing, frequency, duration, magnitude and rates of change of flow are each vital in restoring ecological processes • Rare events (e.g. large floods which change river morphology) are also important and can have long lasting effects • Temporal considerations need to recognize that natural variability is an inherent feature of river systems • Hence restoration of an acceptable range of processes is more likely to succeed than restoration aimed at a fixed end point

Process based river restoration: Spatial scales • Connectivity is an important ecological process • Restoration projects should consider key processes and linkages beyond the channel reach, e.g. upstream/downstream connectivity, floodplain and hypoheic/groundwater connectivity • Because physical, chemical, and biological processes are interconnected in complex ways across river systems, projects undertaken at this scale are more likely to be successful • Because both technical and social constraints often preclude „full‟ restoration , rehabilitation should focus on the causes of system degradation through attainable reestablishment of processes and elements

Theories and mechanisms of landscape ecology and hydrology Purposeful move away from traditional focus on localised restoration to a landscape perspective (eg. habitat restoration and protection). • Is there a response to local habitat reintroduction? • How does the distribution of (restored) habitat influence the response of plants and animals? • Where in the landscape should we invest for best outcomes? • How do we prioritise environmental assets for water and works?

Example – managing individual habitats/issues Erosion control Riparian revegetation Removing willows Re-snagging Wetlands • Often isolated and uncoordinated interventions at isolated sites Environmental flows Source: Nick Bond

Example – restoring populations & communities Spawning habitat Spawning habitat Residential habitat Refuge Residential habitat habitat Residential •Coordinated restoration so habitat that interactions occur among ‘sites’. Source: Nick Bond

Scalable Site Management Critical Important Optional Desirable Water Availability Drought Average Flood Less More

Flow manipulation Some local benefits but many higher floodplain areas still under-watered

Picture courtesy Fosters

Lake Littra pre-watering 13/9/2004

Lake Littra post-watering 23/3/2006

Twin Creeks pre-watering 2004

Twin Creeks post-watering 2004

Monoman Island Horseshoe pre -watering August 2004 General Description

Monoman Island Horseshoe post watering December 2004

Impacts of short-term actions • Not sustainable long-term • Does not address issues of connectivity • Localised and small scale • Expensive • Only benefits some communities • Not system approach • Dose not necessarily target the highest priorities

Case Study - Chowilla Regulator

Current condition

Do Nothing 30 yr

Chowilla Ck Regulator

Natural inundation at 10,000 ML/day

Area inundated with regulator at 10,000 ML/day

Natural inundation at 70,000 ML/day

Regulator Operation • Can be used at all flows to about 50,000 ML/day • Levels can be raised up to 19.87 – 3.5 m increase • Lock 6 to be raised 62 cm to top of piers • Flow maintained through Chowilla Ck at all times • Maintenance of velocity is important • Likely to be operated 1 year in 3 on average • Preference for >10,000 ML/day QSA for full operation

Flow 20000 40000 60000 80000 100000 120000 0 3/1/77 3/1/78 3/1/79 3/1/80 3/1/81 3/1/82 3/1/83 3/1/84 3/1/85 3/1/86 3/1/87 3/1/88 3/1/89 3/1/90 3/1/91 Year 3/1/92 3/1/93 3/1/94 3/1/95 3/1/96 3/1/97 3/1/98 3/1/99 3/1/00 Recorded flow to SA (1977-2005) 3/1/01 recorded flow to SA 3/1/02 3/1/03 3/1/04 3/1/05

Flow 20000 40000 60000 80000 100000 120000 0 3/1/77 3/1/78 3/1/79 3/1/80 3/1/81 3/1/82 3/1/83 3/1/84 3/1/85 3/1/86 3/1/87 3/1/88 3/1/89 3/1/90 3/1/91 Year 3/1/92 9 operations in 29 years 3/1/93 3/1/94 3/1/95 3/1/96 3/1/97 3/1/98 3/1/99 3/1/00 recorded flow to SA Hypothetical Operational Regime 3/1/01 3/1/02 simulated flow w ith regulator 3/1/03 3/1/04 3/1/05

Benefits • Restoration of a floodplain regime that more closely resembles natural • Enable 78% of RRG and 31% Black Box woodlands to be restored • Inundation of large areas of other floodplain communities, including 91% of wetlands and other watercourses, 75% of river coobah and 58% of floodplain grasslands

Risks • Real time salinity impacts • Inhibits large bodied fish movement • Blackwater events • Weed infestation • Algal blooms • Operational objectives?

QUESTIONS?

Options for the environmental future of the River Murray

by University of Adelaide on Oct 22, 2009

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