Local Giralang resident Denise Kay find dead fish in Giralang Pond.

Giralang resident Denise Kay finds dead fish in Giralang Pond. Photo: Elesa Kurtz

Recent images of carp dying in Giralang Pond have reinvigorated the debate about the health of Canberra's lakes. The likely reason for the carp dying was the recent spell of high temperatures that, with low rainfall, had resulted in reduced oxygen in the water.

This localised example of an urban wetland under stress provides the opportunity for a broader conversation about the management of Canberra's water catchments as a whole - a conversation we must have as we face the real impacts of climate change and learn to live with a drier, hotter city.

Canberra is an inland river city. Unlike the other Australian capitals, we send our waste water inland, rather than to the sea, and so we are responsible for the quality of the water we return to the river system. This was highlighted in the debate about our role in the Murray-Darling Basin Plan. We must be mindful not just of the amount of water we take, but also the quality of the water we return to our precious river system through our catchments, and to all the communities downstream.

Our waterways in Canberra, once natural creeklines, are now used as stormwater channels. So when our stormwater carries high nutrient loads, from urban gardens and leaves from street trees, it all ends up in our lakes and ponds. This high nutrient level is a major contributor to the algal blooms.

Canberrans have sadly grown to expect the worst of our lakes - they are often closed due to algal blooms in summer, we don't swim in them as we once did, and we have become accustomed to seeing rubbish building up. This loss of amenity has been allowed to take place in spite of the fact that our lakes and waterways have so much to offer us, both environmentally and recreationally.

It was this that struck me early in 2011 after heavy flooding in December of the previous year and the outbreaks of blue-green algae that led to the cancellation of several sporting events on Lake Burley Griffin. Constituents had contacted me about their concerns with water quality in other catchments. And as a triathlete, and therefore regular lake user, I had become tired of the increasing number of lake closures. It became clear that it wasn't just Lake Burley Griffin, the jewel in Canberra's crown, that needed attention - Lake Tuggeranong, Lake Ginninderra, as well as Gungahlin and Yerrabi Ponds, all have their own problems with algae and pollution. This is a sad state of affairs for a modern city, and one that the Greens believe needs to be remedied.

In 2011, as ACT Greens environment spokesman, I moved a motion in the Assembly that resulted in an investigation into the health of the lakes and waterways by the ACT Commissioner for Sustainability and the Environment. The resulting report was instructive, both about many specific remedies needed to improve the quality of our waterways, as well as the governance structures needed to implement those improvements.

One of the key challenges to improving the quality of water in our catchments that is repeatedly raised is that there are so many parties involved - federal, ACT and NSW governments. Sometimes it is unclear who is actually responsible. The Environment Commissioner recommended that a dedicated governance group be established, with representation from all jurisdictions.

It is somewhat astounding that Canberra, Australia's biggest inland river city, doesn't already have a catchment management authority in place. Perhaps it is due to the complicated history of our governance - a territory geographically surrounded by another state, once governed entirely by the Commonwealth that now manages its own affairs. We all know that old adage that the environment doesn't recognise our man-made borders - it is precisely because of this scenario that we need a co-ordinated governance structure to deliver environmental benefits in the most strategic way.

A catchment management authority is best placed to consider the whole river system in its entirety, including the wetlands, lakes and stormwater system. It can bring all the responsible parties to the table, work to clearly identify the responsibilities of each agency and help co-ordinate their efforts. It can set objectives for water quality and environmental flows, and steer the management of our lakes and waterways to meet the future impacts of urban development and climate change.

In the 2012 Greens-Labor parliamentary agreement, there is a commitment to restore the health of Canberra's lakes and catchments by establishing a catchment management authority, and directing $85 million of Commonwealth funds promised to the ACT to this important task. The resources and co-ordination flowing from this can tackle the key problems identified in the Environment Commissioner's report - stopping nutrient inflows, reducing carp populations, pinpointing and monitoring major pollution point sources, and providing community grants to support the dedicated volunteers working on the ground.

It will take a bit of time to turn things around, but by putting the right structures in place, and getting started now, we can turn our lakes and wetlands into the urban oases for humans and fauna that they should be.

Shane Rattenbury is the Minister for Territory and Municipal Services.