Table 1. The main requirements for achieving an appropriate flow regime for the Marshes. Only some of the examples are presented.

Main requirement
Examples of requirement
Why the requirement is not being met
Delivery of a sufficient overall volume of water
A minimum of 200, 000 ML of water are required to trigger a breeding event of colonial nesting waterbirds (Kingsford and Johnson 1998). Breeding events are occurring less frequently than before river regulation due to lack of sufficient volumes of water (Kingsford and Johnson 1998).
The volume of water allocated to maintaining an ecologically functioning environment is insufficient for bird breeding. Water allocated to the environment is 160,000 ML in a year when there is sufficient water in the dam for a 100% allocation (DLWC 2002).

To achieve floods that are large enough to cover vegetation that is dependent on inundation, but at less regular intervals than wetland vegetation at the wetland core, at least 400,000 ML is required over a period of 0-300 d (Kidson and Raisin 2000).
Large floods have significantly decreased in the Marshes since construction of the dam. Estimates from theoretical modeling suggest that they have decreased by at least 25% (Brereton et al. 1996), whereas mangers suggest that the decrease is much greater. Large floods are currently only possible when the dam spills.
Delivery of water at appropriate rates of flow
Flows are required at sufficient rates to prevent erosion and to generate widespread flooding. In some areas erosion is occurring in some of the wetland channels and it now takes three times the amount of water in the channels to achieve overbank flow and flooding of the surrounding wetlands (Brereton 1994).
Continuous low flows of water to service irrigation and stock contributes to the erosion (Brereton 1994), and limited size of the dam valves and restrictions on the floodplain upstream of the Marshes prevent high rates of flow.
To ensure floods persist for appropriate periods of time
Effective breeding of colonial nesting birds requires flooding of sufficient duration to ensure birds do not abandon their nests (Magrath 1991, Kingsford and Auld 2003).
Lack of sufficient overall volumes of water mean that it is difficult to achieve a tail on the flood that is long enough to ensure young birds can fledge and can build strength.
Delivery of water at appropriate times within years
The main breeding season for birds was thought to be between August and November before the construction of the dam (Masman and Johnstone 2000).
The breeding season for colonial birds in the Marshes is now two to three months later, due to the release of water from storage in spring and summer to satisfy irrigation and stock requirements (Kingsford and Auld 2003).
Delivery of water at appropriate times between years
The Marshes are adapted to natural variation in flooding between years, but this variation has been significantly altered. For example, 2001-2004 were dry years with no bird breeding events, but rain that fell in August 2003 would have been sufficient to generate a breeding event if it had not been captured by the dam (Kingsford 2004).
River regulation aims to reduce variability.