View
780
Download
0
Category
Tags:
Preview:
Citation preview
1
IWCEnvironmental Flows and Management
Scenarios
December 2009
Prof. Angela Arthington
Australian Rivers Institute, Griffith University
Room 1.09C, Building N13
3735 7403
Rivers and floodplains are the world’s most threatened ecosystems
Global declines in river healthLoss of freshwater biodiversityDeclining food fisheriesLoss of human cultural values
Impacts on river flow regimes
levee banks on floodplainstsurface and groundwater
abstraction
weirs
high valuefree-flowing rivers
Minimal flow regime change
impacts ofwater gridsand IBTs
dam release rules
2
Environmental FlowsEnvironmental flows describe the quantity, timing and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-b i th t d d thbeing that depend upon these systems
Brisbane Declaration 2007International Environmental Flows
Conference, Brisbane, September 2007750 delegates from over 50 countries
Management Scenario 1
Determining e-flows for a new reservoir on a river like the Li Jiang
• Rapid assessment, with limited resources and data
DRIFT MethodologyDownstream Response to Imposed Flow Transformation
• Comprehensive assessment, with time to collect field data
ELOHA Framework
Ecological Limits of Hydrologic Alteration
Management Scenario 2
Prioritising e-flows for multiple assets when there is limited water available because of other demands
Which wetlands should be given water and how much, when,?g
Water allocations to sustain commercial fisheries
• Rapid assessment, with limited resources and data
Flow Restoration Methodology
• Comprehensive assessment, with time to collect field data
ELOHA Framework
3
Ecological Significance of Natural Flow Regime
1. Poff et al. 1997. Natural Flow Regime Paradigm
2. Bunn & Arthington 2002Basic principles and ecological consequences of altered flow
regimes for aquatic biodiversity
3. Nilsson & Svedmark 2002Basic principles and ecological consequences of changing water
regimes: riparian plant communities
4. Pinay et al. 2002Basic principles and ecological consequences of changing water
regimes on nitrogen cycling in fluvial systems
5. Naiman, Bunn et al. 2002Legitimising fluvial ecosystems as users of water: An overview
Ecological Significance of FlowNatural Flow Regime Paradigm
Poff et al. (1997)
• The ecological structure and function of flowing water systems depends largely on their natural dynamic flow regime
• Stream flow is a “master variable” that influences physical and chemical characteristics, e.g.characteristics, e.g.
- water quality- sediment regime and substrate characteristics- channel morphology, habitat structure and diversity- energy sources that fuel the aquatic food web
• Stream flow characteristics influence the distribution, abundance and biotic interactions of river and floodplain species
• Alteration of the natural flow regime of a river can have physical, chemical and ecological impacts
Rivers differ in their natural flow regimes
0
10
20
30Mekong
0
0.2
0.4
0.6
0.8 Darling
0
2
4
6
8 Mississippi
0
10
20
Columbia
0
2
4
6 Murray
0
2
4
6
8Cooper Creek
4
Components of natural flow regimes
Natural Flow Regime Paradigm - Poff et al. (1997)
• Magnitude of flow – discharge Q
• Frequency of occurrence – relates to a particular magnitude, e g zero flow or 100 year flood etce.g. zero flow, or 100 year flood, etc
• Duratione.g. number of days of low flow, or number of days thefloodplain is inundated, or composite values from flow
duration curve
• Timing, seasonality and predictability
• Rate of change, or flashiness
Bunn, S.E. and Arthington, A.H. (2002) Basic principles and ecological consequences of altered
flow regimes for aquatic biodiversity. Environmental Management 30: 492-507
1. Flow is a major determinant of physical habitat in streams, which in turn is a major determinant of biotic composition
2. Aquatic Species have evolved life history strategies primarily in direct response to the natural flow regime
3. Maintenance of natural patterns of longitudinal and lateral connectivity is essential to the viability of populations of many riverine species
4. The invasion and success of exotic and introduced species in rivers is facilitated by the alteration of flow regimes
Aquatic biodiversity and natural flow regimes
channel formhabitat complexitypatch disturbance
biotic diversity
Principle 1lateral connectivitylongitudinal connectivity
Principle 3
spatesaccess to
Flow-ecology principles Bunn & Arthington (2002) Env. Management
Life history patterns • spawning• recruitment
Principle 2
natural regime discourages invasions
Principle 4
Time
Dis
cha
rge
spates
seasonalitypredictability
reproductive triggers
variability
floodplains
dispersaltriggers
stable baseflowsdrought
5
Macro-scale(channel form)
Meso-scale (hydraulic units)
Flow creates and maintains:
•hydraulic habitat units- riffles, pools, floodplain wetlands
•channel form - headwater tributaries, main channels, lowland floodplains
•patches of habitat- undercut banks, boulders - gravel & sand beds, - aquatic plants- woody debris – snags- leaf litter packs
Micro-scale(patches within hydraulic units)
Images: Mark Kennard, Griffith University
pool
riffle
run
flow
• few species• streamlined body form • many species
• intermediate # species• streamlined body
Fish habitat preferences in riffles,
runs and pools
streamlined body form • many species• diverse body shapes
Images: Mark Kennard & Brad Pusey, Griffith University
Water surface
0.6
0.4
0.2
Purple spotted gudgeon(benthic species)
Rainbowfish(open water schooling species)
Relative water
Position in Water Column
0 20 40 60Stream bed
1
0.8
0 10 20 30
depth
Frequency (% of individuals)
Images: Mark Kennard & Brad Pusey, Griffith University
6
Substrate composition
0
10
20
30Availability
Frequency of use
0
10
20
30
Substrate composition
0
10
20
30
Images: Mark Kennard & Brad Pusey, Griffith University
Microhabitat structure
Availability
Frequency of use
5
10
15
10
15
20 Juveniles
Adults
0
Microhabitat structure
0
5
Microhabitat structure
Images: Mark Kennard & Brad Pusey, Griffith University
Impacts of flow regime alterations that change habitat downstream of dams and g
weirs
7
Impacts of water loss and habitat change downstream of dams and weirs
Sudden loss of flow and water depth, fish stranding
The Lower Murray – a River of Lakes
Weir pools favour lentic Gastropods. River gastropods decline.Caused by loss of river habitat & food resources (biofilms)
Blue-green algal blooms in theDarling River 1990-1991
Caused by:
• Stable low flows• Loss of flushing flows• Elevated nutrients• Ample light • Suitable water temps• Less grazing pressure
8
Brisbane River d/s Wivenhoe Dam:Unregulated vs Regulated Flow
80000100000120000140000160000180000
150
200
250
300
low
ML
mon
thly
flo
w
020000400006000080000
JAN
FE
B
MA
R
AP
R
MA
Y
JUN
JUL
AU
G
SE
P
OC
T
NO
V
DE
C
0
50
100
Mean Monthly Unregulated Mean Monthly RegulatedCoefficient of Variation Unregulated Coefficient of Variation Regulated
F
CV
of
m
• Reduced mean monthly flows• Reduced flood peaks & “stepped” flow releases • Elevated & more stable low flows• Loss of flow variability at most flow magnitudes
Elevated, more stable low flows create habitat for dense, extensive aquatic plant beds
Impacts:• altered water quality, e.g. DO• habitat much less diverse• lower diversity of invertebrates and fish• reduced flood conveyance
Red water milfoil
Effects of Natural Flow RegimeEffects of Natural Flow Regimeon Riparian Vegetationon Riparian Vegetation
Before Flow RegulationLateral & longitudinalseed dispersal by hydrochory
Zonation of vegetationby flood frequency &duration e.g. herbs, shrubs, trees
Spatially and temporally heterogeneousplant community composition and structure
Biologically activezone e.g. decomposition
Usually diverseflora in comparisonto surrounding terrestrial system
9
HydroHydro--ecological relationships: riparian ecological relationships: riparian vegetationvegetation
Tall She-oak (Casuarina cunninghamiana) riparian Along the channel verge there is a
bl b d f h h
Mature grassy open eucalypt (E. tereticornis) & bloodwood (Corymbia
tessellaris) woodland
Typical Typical zonation of riparian vegetation for SEQof riparian vegetation for SEQ
forest with mesic subcanopyspecies on channel terraces
stable band of reophytes such as Watergum (Tristaniopsis exilliflora),
Callistemon viminalis.& the Mat rush (Lomandra sp.)
Effects of changing the Flow RegimeEffects of changing the Flow Regimeon Riparian Vegetationon Riparian Vegetation
After Flow Regulation After Flow Regulation by Damby Dam
Barriers to seed dispersalby hydrochory, particularlyaffecting short-floating seedsStreamward migration
of vegetation zones,i.e. replacement ofhydrophytic species byy p y p ymore mesic/ xeric species.e.g. encroachment of forest Decomposition rates
decline with floodelimination
Homogenisation ofplant community composition & structure
Severe effects of reduced flood frequency on floodplain wetlands and waterbirds
Wetland loss in Australia:
•• 90 % loss in M90 % loss in M--D BasinD Basin•• 75 % loss on Swan Coastal Plain, WA75 % loss on Swan Coastal Plain, WA•• 50 % loss NSW coastal rivers50 % loss NSW coastal rivers
10
Aquatic biodiversity and natural flow regimes
channel formhabitat complexitypatch disturbance
biotic diversity
Principle 1lateral connectivitylongitudinal connectivity
Principle 3
spatesaccess to
Principle 2Life History Patterns
Life history patterns • spawning• recruitment
Principle 2
natural regime discourages invasions
Principle 4
Time
Dis
cha
rge
spates
seasonalitypredictability
reproductive triggers
variability
floodplains
dispersaltriggers
stable baseflowsdrought
Life History and Recruitment Strategies
Low flow recruitment Spawn during stable low flows in spring & summer, window of opportunity to access habitat/food for larval fishesN. Armstrong
No flow recruitment Spawning in standing water bodies N. Armstrong
Flow / flood pulse recruitmentSpawn during rising water levels or floods in spring & summer,
recruitment enhanced by backwater & floodplain inundation
Merrick & Schmida
Spawning in standing water bodieswith no flow, e.g. river pools, waterholes on floodplains
Eel-tailed catfish
R. Kuiter
Catfish spawns into a ‘nest’ in well-oxygenated water, water level fluctuations can inhibit spawning
R. McDowall
G. Schmida
11
Flows trigger spawning in Clanwilliam Yellowfish
Spawning stimulated by flow cues below dams
Larval growth requires warm water
Skelton 1993
requires warm water and diverse food items
Seasonal reproductive cycles of fish species in the Fitzroy River system, QLD
A. agA. perAr. g.G. apr.pH. lep.Hyp. c.M. mog.N. aterOx. lin.P. gr.Scl. l.Sc. h.T. tan.
J A S O N D J F M A M J
wet seasonSummer temps
low & stable flowsSpring temps
Inversion of normal seasonal flow pattern below large dams
Flow and temperaturepatterns no longer match
L f fl d fl
Median monthly flowsMurray River at Albury, NSW
Loss of flood flows
Fish spawning failure
Loss of wetland biodiversityand functions
12
Flow effects on different processes during a plant life cycle
Ecological responses to various temporal and spatial scale of flow disturbance
Adult
Growth and maturity
Flowering, seed set and release
JuvenileSeed
Seedling
Dispersal
Germination Establishment
y
Predation, competition
Aquatic biodiversity and natural flow regimes
channel formhabitat complexitypatch disturbance
biotic diversity
Principle 1lateral connectivitylongitudinal connectivity
Principle 3
spatesaccess to
Principle 3Movement and migration
Life history patterns • spawning• recruitment
Principle 2
natural regime discourages invasions
Principle 4
Time
Dis
cha
rge
spates
seasonalitypredictability
reproductive triggers
variability
floodplains
dispersaltriggers
stable baseflowsdrought
Movement and Migration
Freshwater Fishes of North-Eastern AustraliaPusey, Kennard & Arthington 2004
Merrick & Schmida 1984
13
Giant Mekong Catfish(2.35 m and 260 kg)
“Construction of mainstream dams
that obstruct spawning migrations
may seal its fate”
Dudgeon, 2001Overfishing has caused failure of the Overfishing has caused failure of the
fisheryfishery
Importance ofconnectivity
Bust• Drying waterhole• Fish mortality 93%
Flood March200013,471 km2
• Fish return towaterholes
• Floodplain inundation• Fish breeding• Movement of all life stages
to floodplain• Growth and juvenile
recruitment
Channel flows• Connectivity• Movement• Fish breeding
Connectivity
Connectivity
Boom
11/12 native species move from river to inundated floodplains to feed and grow
14
Water flowing to sea is not “wasted”
Year
Ann
ual f
low
(G
L)
Tota
l cat
ch (
tonn
es)
1945 1950 1955 1960 1965 1970 19750
200
400
600
800
1000
1200
1400
1600
Total fish catch
Total flow
Fish catch in Moreton Bay vs Logan River flow
Loneragan & Bunn 1999Aust. J. Ecol. 24: 431-440
1 000 000100 00010 000
0
10
100
kings
total
Cat
ch
(to
nn
es)
Summer flow (ML)
Prawn catch in Logan estuary vs total summer flow
Mechanisms:• catchability• habitat & food resources • life history
Aquatic biodiversity and natural flow regimes
channel formhabitat complexitypatch disturbance
biotic diversity
Principle 1lateral connectivitylongitudinal connectivity
Principle 3
spatesaccess to
Principle 4Alien and translocated species
Life history patterns • spawning• recruitment
Principle 2
natural regime discourages invasions
Principle 4
Time
Dis
cha
rge
spates
seasonalitypredictability
reproductive triggers
variability
floodplains
dispersaltriggers
stable baseflowsdrought
15
Impoundments provide habitat for exotic fish and plants (e.g. water hyacinth)
Ye
Mozambique tilapiahas established self-
maintaining populations n Wivenhoe and
North Pine Dams
Fish species diversity has declined with increasing degree of flow regulation in the
Murray-Darling Basin
-- more stable flows, - less frequent flooding- modified habitat, food,
spawning conditions
- native fish have declined
Annual proportional flow deviation
- exotic species dominate, especially carp
Water fern – Salvinia - covering a riverine impoundment
16
Effects of weirs on riparian & aquatic
vegetation
Between Marian and DumbletonWeir Pools - Pioneer R (Site 5)
Reach with natural flows
more stable water levels few native aquatic plants exotic species proliferate
Weir Pools - Pioneer R (Site 5)
Weir pool
Weir pool
Environmental FlowsEnvironmental flows describe the quantity, timing and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-b i th t d d thbeing that depend upon these systems
Brisbane Declaration 2007International Environmental Flows
Conference, Brisbane, September 2007750 delegates from over 50 countries
Recommended