A River in Crisis: The Lower River Murray, Australia - River Conservation and Management - page 338

Table 29.1 A sample of research findings relevant to understanding the Lower Murray ecosystem, 1990-2010.

Authors Findings

1990 Pressey, 1990 Decline of wetland species linked to reduced frequency,

duration and magnitude of flooding

1990 Margules et al . , 1990 Declines in eucalypt woodlands

1992-1993 Walker et al . , 1992; Walker

and Thoms, 1993

Disturbance in floodplain-river ecosystem due to stable
water levels associated with weirs

1992, 1994 Walker et al . , 1992, 1994 Over-bank spring flows trigger breeding and regeneration

in key floodplain species

1995, 1998 Puckridge et al . , 1998;

Walker et al . , 1995

Floodplain communities characterized as 'flood driven';
vegetation adapted to changeable flows

1995 Maheshwari et al . , 1995 About 80% of system's mean annual discharge is diverted,

mainly for irrigation

Large floods ( > 100 000 ML d −1 ) needed to ameliorate water
and salt stress for black box trees

1999 Slavich et al . , 1999

2000 Jensen et al . , 2000; Thoms

et al . , 2000

Need to reinstate key elements of natural hydrograph as
environmental flows

2001 Roberts and Marston , 2000;

Robertson et al . , 2001

Flooding is a primary trigger for regeneration in riverine
wetland communities

2000-2002 Thoms et al ., 2000; Young

2001; Jones et al ., 2002

Loss of small to medium spring flows critical in decline of
biodiversity and wetland health; flows specified for a
'healthy working river'

2002-2003 Jensen, 2002a; Walker, 2002;

Nicol et al ., 2003

Environmental flows based on presumption that flooding
will promote recruitment; critical elements include
connectivity, rate of drawdown and depth

2001-2003 Jolly et al . , 2001; Roberts,

2003

Decline in vegetation health attributed to changed
floodplain inundation. Dry phases more frequent,
growing conditions drier. Expected shift in species
composition, resilience reduced

2003, 2005 MDBC, 2003, 2005; George

et al ., 2005

More than 75% of mature trees along 700 km of Murray
Valley dead, dying or stressed

2006 Walker, 2006 Serious ecological impacts of changed hydrological regime

2007-2008 Jensen et al. , 2007, 2008a,

2008b

River red gums have aerial seed banks; timing of seed
release coincides with highest chance of soil moisture,
reduced seed from stressed trees

2010 Wen et al., 2010 Red gums exhibit stress after 5-8 yr dry

flows, river flows did not reach the floodplain until
December, later than the ecological optimum. If
the inundation fails to replenish freshwater lenses,
many stressed trees are likely to die.

et al . , 1991; Jensen et al . , 2003). In 2005, a
spring flush in the Barmah-Millewa Forest, a
Ramsar-listed river red gum woodland in the
middle reaches of the Murray, was augmented
to extend over-bank flows for 2 months, in
support of waterbird and fish recruitment (King
et al . , 2010). Other watering trials in Lower
Murray wetlands since 2000 have promoted
aquatic macrophytes, macroinvertebrates and river
red gum seedlings (Jensen, 2002a, b) and other
floodplain plants (Siebentritt et al ., 2004). Although
serial watering brings added benefits, including

Environmental flows
The challenges in deployment of 'environmental
flow' allocations are to understand the
relationships between flow regimes and ecosystem
processes,

to identify changed elements of

the hydrograph and to translate them into a

programme of water allocations (Arthington