How Environmental Water “Equivalents”were Measured in MDBA Planning

and are they Equivalent?

Ian Overton

Overview

1. Hydrology ≡ Environment?

2. MDB Plan Environmental Equivalence Method

3. What are we trying to achieve with equivalence?

Hydrology ≡ Environment?

Volume• 2/3 Natural• 2,750 GL/yr (long term average)• 62,000 ML/d

≡ Environment• Healthy working river• Restoring the balance• High likelihood of good

environmental condition

Source: MDBA

• volume or flow magnitude• flood extent• rivers, wetlands and/or floodplains

• duration of flood or high flow• flooding frequency• inter-flood period (dry period)• clustering of flood/drought events• seasonality

Hydrology is a bit more complex than that…

• velocity of water movement• rate of rise and fall• stabilisation of river flows• permanent inundation• depth of river, wetland or floodplain

• temperature• turbidity• oxygen concentration• salinity• acidity• nutrients• algae, etc

• Water volume• Flow rates• Depth markers• Water samples• Flood extent• 2D models• 3D hydrodynamic models

• Beyond that it gets very local and time dependent• National Water Commission project

• 577 long term ecological datasets• Majority not useful for analysis as water was not

recorded at the same time as the ecology

How do we ‘count’ the water?

• Volume = ecological response

• Connectivity (up/down, lateral)

• Hydrological diversity

• Habitat suitability modelling

• Hydrograph ‘building blocks’

• Bayesian models

• Expert panels

Ecosystem Response

Source: Bunn and Arthington 2002

Can artificial events replicate natural ones?• Designed to mimic parts of the hydrology - but does not replicate all components• May produce unintended consequences such as reducing connectivity or prolonging inundation

in some areas

For example - a regulator used to produce a ‘flood’ Can replicate area of inundation (although not the same area) Can replicate duration, timing, frequency

(although at what rate? and requires foresight)x Not flow velocities – fish triggersx Not water qualityx Not biological triggers – bird breeding, seed dispersal, etc

Hydrology ≡ Environment?

• To increase consumptive water the SDL can be adjusted through works and measures

• These are environmental works or changes to river operations or practices that enable the same environmental outcomes to be achieved with less water

MDB Plan SDL Adjustment MechanismEcological Elements Method

3 types of water delivery:

1. Overbank flow

2. Water retention

3. Water pumping

Environmental Equivalence

• The test must compare regional environmental outcome scores for the 2,750 GL/yr long-term average reduction in diversions under the Basin Plan (benchmark scenario) and a package of proposed supply measures (SDL-adjusted scenario)

• SDL adjustment can only go ahead if the package of supply measures produces at least the same region environmental outcome score as the benchmark (and other safeguards are also met)

• Has to be sensitive enough to detect changes in ecological outcomes for the flow changes proposed

• Can use preference curves and rules for reach and regional scales• Can use weightings for EE and areas as environmental

significance is a work in progress for MDBA and jurisdictions

Ecological Elements

• The Ecological Elements are defined as broad ecological groups that are known to be: • representative, of the ecology of floodplains of the southern Murray-Darling Basin• complete, in covering a broad range of species and processes that respond to flow• efficient, where relationships can be underpinned by data and scientific advice

• The Ecological Elements are a subset of those represented as objectives in the ESLT

• Vegetation, waterbirds and fish were chosen as Ecological Classes, with individual species or groups within these classes being identified as Ecological Elements

Ecological Elements

Ecological Elements

Source: MDBA

• Modelling framework represents rivers in the Murray-Darling Basin

• It includes dams, weirs, water supply towns, irrigators and agriculture, etc

• Modelling period: 114 years historical record (1895-2009)

• Hydrological indicator sites

Flow Modelling

Ecological Targets and SFIs

CONDITION (ECOLOGICAL STATE) VALUE DEFINITION OF CONDITION (ECOLOGICAL STATE – SITE SPECIFIC)

Good 0.9 A large number of species and individuals in good body condition

Medium 0.6 A moderate number of species and individuals in moderate body condition

Poor 0.1 A low to moderate number of species and individuals, in poor to moderate body condition

Critical 0 A very low number of individuals, in poor body condition - most birds have left the area

General abundance and health – all waterbirds

• These determine how they transition through a set of states or conditions given an annual sequence of event-based SFIs being achieved or not

• Percentage flooding frequency and maximum dry spell where tested and shown to be insensitive and lacked scientific rigour

• Response relationships are characterised as being either preference curves or rules

Response Relationships

00.10.20.30.40.50.60.70.80.9

1

0 2 4 6 8

Valu

e

Years since wetGood Medium Poor Critical

00.10.20.30.40.50.60.70.80.9

1

0 1 2 3 4V

alue

Years since dry year

Good Medium Poor Critical

General abundance and health – all waterbirds(a) dry spell and (b) (b) wet spell periods

Preference Curves

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10 12 14 16

Valu

e

Years since SFI metGood Medium PoorCritical Intermediate

Short-lived Fish

Source: MDBA

ID SFI ENVIRONMENTAL STATE (EVENT) VALUE

No SFIs reached (dry year) 0

0 40,000 ML/d for a total duration of 30 days (with min duration of 7 consecutive days) between Jun & Dec SFI 0 reached but not the others 0.1

1 40,000 ML/d for a total duration of 90 days (with min duration of 7 consecutive days) between Jun & Dec SFI 1 reached but not the others 0.3

2 60,000 ML/d for a total duration of 60 days (with min duration of 7 consecutive days) between Jun & Dec SFI 2 reached but not the others 0.3

3 80,000 ML/d for a total duration of 30 days (with min duration of 7 consecutive days) between Jun & May SFI 3 reached but not the others 0.3

SFI 0 and 1 reached 0.3

SFI 0 and 2 reached 0.6

SFI 0 and 3 reached 0.6

SFI 1 and 2 reached 0.6

SFI 1 and 3 reached 0.6

SFI 2 and 3 reached 0.6

All SFIs reached 0.9

Rule-Based Combinations

Method• Scores are calculated for each EE within an SFI, for a given flow scenario• Scores are weighted by the area of the EE, normalised to the total area of the EE within the reach (sum of 1 for all works and non-works areas)• Weighted scores are averaged to give three EC scores per reach• EC reach scores are then averaged to give a Reach score• Reach scores are averaged to give a Region score• For the supply contribution scenario, scores are determined separately for inside and outside the area of environmental work supply measures, and then aggregated to generate the Reach score. The method allows for disaggregation of the final score.

Response to Works

Bitterns, Crakes and Rails under the Benchmark and SDL Adjusted Inside Works scenarios

Increasing water volumes required for SFIs

Increasing Flows

River Red Gum Forest at River Murray Lower reach under the Proxy Benchmark scenario for (a) 40 GL/day 30d(b) 40 Gl/day 90d(c) 60 GL/day 60d(d) 80 GL/day 30d

The EE method allows trade-offs within and/or between river reaches (e.g. improved outcomes in one reach and decreased outcomes in another reach),

or a trade-off between different ecological classes and elements (e.g. improved outcomes for plants and decreased outcomes for fish).

The limits of change in the default method in the Basin Plan limit extreme hydrological changes.

Trade-offs

• Pragmatic approach to a particular management assessment• The method has been designed to use the most appropriate flooding frequency metrics that

can be linked to ecological response using annual flood and dry spells• A range of Ecological Elements across three Ecological Classes are used in the method and

represent a range of floodplain inundation flora and fauna• The condition of the EE prior to the flood/dry spell is considered• The type of water supply is considered• Method takes non-equivalent hydrology into consideration• Recommendation was that Supply measures should be considered and operated using best-

practice principles to avoid environmental harm that the Ecological Elements Method cannot address, including flooding of durations less than desirable, prolonged flooding greater than desired durations, and inundation that restricts connectivity

• A model is a model

Conclusions

What are we Trying to Achieve?

Assumptions:

• Hydrology can be simplified and ‘counted’

• Hydrology ≡ Environment

• Trade-offs can be found by societal choice

• But do we have the decision processes to find

the ‘Goal’?

• And then can we manage these modified

environments?

Is Balance the Goal?

Source: Forslund et al, 2009

• Sector-wide priorities for QldEcosystem Equivalence

ResilienceHigh HighLow

Level of ManagementLow LowHigh

Natural Managed Artificial

0

2

4

6

8

Triple Bottom Line Accounting

Environment Economy Society

Reducing Contention through Depolarising and Accounting for Universal Stakeholder Metrics

Benefits

Condition

Resilience

BCR Accounting

The right balance between winners and losers?

Legitimate, fair and wise decisions

BENEFITSBasin EcologicalOutcomesEcosystem servicesSocial outcomesEconomic outcomesDisbenefits/Risks

RESILIENCESustainabilityTrendsAdaptive capacityEnv/soc/econHazards/Risks CONDITION

Energy fluxDiversity/Food websConnectivitySpatial prioritiesEnv/soc/econRisks

Thank you