Dams can increase the risk of flooding and impose irreversible changes that damage forests, wetlands, fisheries and farmland, nor should the devastating Queensland floods cause any delay to Murray-Darling reforms, Greens Leader Bob Brown said today.

"Dams may prevent smaller floods but can increase damage during exceptionally large floods when severe weather events cause a sudden release of water," Senator Brown said.

"Tony Abbott's plan is ill-conceived."

"Australia's flood history shows that major floods can top dams built in their way."

"The bigger the flood the less is their potential flood mitigation effect. Furthermore, the potential mitigation effect of a dam decreases in a downstream direction," according to the Attorney-General's Department's Emergency Management Planning for Floods Affected by Dams.

"Murray-Darling Basin reforms, to ensure the health of the river and its communities, should be in parliament by the end of the year," Senator Brown said.

"Downstream impacts of dams can include the loss of fisheries, poorer water quality and damage to the fertility of farmlands and forests. As well as degrading water quality, rotting vegetation trapped upstream of dams also releases greenhouse gases, contributing to global warming."

"Dams and diversions are the main reason why one-third of the world's freshwater fish species are extinct, endangered or vulnerable," Senator Brown said.

"Research by International Rivers also shows many shellfish, frogs, plant and bird species that depend on freshwater habitats are also extinct or at risk as dams reduce biodiversity."

Media contact: Marion Rae 0438 376 082