Climate change impacts on our rivers and wetlands

Rivers and wetlands benefit NSW’s people, by providing:

• sources of freshwater for town water supplies
• areas for Aboriginal cultural practices and connecting to Country
• areas for recreation, connecting with nature and fishing
• water that seeps underground to replenish the groundwater reserves that many NSW communities and industries depend on.

Rivers and wetlands also help protect against the impacts of hazards such as floods, droughts and bushfires.

NSW’s rivers and wetlands provide important habitats, food and breeding grounds for wildlife. Across the state, they include:

• habitats for around 118 species of freshwater fish including Australia’s largest freshwater fish – the Murray cod – which can weigh over 100 kilograms
• 12 wetlands of international significance listed under the Ramsar convention
• groundwater dependent ecosystems which are valuable sources of water in drier parts of NSW.

Rivers and wetlands support the NSW economy by providing water for important industries such as agriculture and tourism.

Wetlands benefit agriculture in many ways. They support bird species which feed on farm pests such as grasshoppers. This beneficial relationship between wetlands and farms offers a cheaper, easier and more environmentally friendly form of pest control.

Rivers and wetlands support NSW’s large tourism industry by providing areas for water sports, camping, swimming, fishing and nature connection.

Healthy rivers and wetlands also support the NSW economy in less tangible ways, for example:

• native plants growing along riverbanks help prevent erosion – without these plants we will need to invest in structures to control erosion
• wetlands act as natural water filters, removing nutrients, pollutants and sediments from water – without wetlands, we would need to develop new structures and processes to manage water quality.

Higher temperatures affect rivers and wetlands in several ways: 

• Species distribution and survival – species that can’t tolerate warmer water conditions decline, while heat tolerant or non-native species (such as the European carp) may thrive.
• Breeding and behaviour – many native fish rely on seasonal temperature cues to breed; altered timing can disrupt life cycles.
• Water quality – warmer water holds less dissolved oxygen, increasing stress on fish and other aquatic life that need oxygen-rich waters. This is particularly important during low flow events.
• Algal blooms – higher temperatures combined with nutrient loads can cause harmful algal blooms which reduce water quality and threaten ecosystems.
• Evaporation losses – increased evaporation from rivers and wetlands reduce water availability for people, Country and the environment. 

Climate change affects key climate drivers such as east coast lows, El Niño–Southern Oscillation, Indian Ocean Dipole, Interdecadal Pacific Oscillation and Southern Annular Mode. Changes to these drivers will alter the frequency and magnitude of rainfall events over NSW. 

For rivers and wetlands, this means: 

• longer dry spells between flows, reducing connectivity for unregulated rivers and floodplain wetlands
• less predictable inflows to water storages (such as lakes and reservoirs), making it harder to maintain water security and water for environmental flows
• more intense rainfall events, which can cause flash flooding, erode riverbanks and wash sediment and pollutants into waterways
• greater stress on ecosystems that depend on regular flooding or minimum flow levels. 

Many rivers and wetlands throughout NSW rely on occasional floods, such as the Macquarie Marshes. This cycle of flooding allows wildlife such as fish and waterbirds to move into new locations to feed and breed. Climate change is affecting these cycles, with dry periods between floods becoming longer and harsher. This prevents fish and waterbirds from moving to important feeding and breeding grounds. 

In coastal rivers and wetlands, drought can disconnect the waterways from the ocean. This can reduce water quality upstream, as naturally occurring salts and nutrients in the water are unable to be flushed out to sea. 

When intense rainfall occurs after long dry periods, large amounts of leaf litter and organic material are often washed, into rivers and wetlands from the surrounding land. This can cause poor water quality and fish kill events, as oxygen is removed from the water through the breakdown of the organic material. 

As climate change causes sea levels to rise, rivers and wetlands can experience increased erosion, flooding, and poor water quality as saltwater is pushed further upstream, where aquatic plants and animals are not adapted to saltwater. This contributes to higher flood risks for properties in low-lying areas along waterways.  

Wetlands have slowly absorbed carbon dioxide over hundreds of years. When they are burnt or destroyed, they release carbon dioxide back into the atmosphere, contributing to further climate change. 

After bushfires, ash and exposed soil can wash into waterways, reducing water quality and harming aquatic plants and animals. 

We can reduce the impact of climate change on our coastal rivers and wetlands by: 

• creating better infrastructure such as climate-smart urban design to manage the impacts of more extreme storms and floods
• managing estuaries and coastal wetlands to allow floodwaters to flow into the ocean. 

Inland rivers and wetlands will be more affected by drought than coastal areas. These areas must be carefully managed to balance the different needs for water by people, industries and ecosystems. This can include: 

• water efficiency programs and infrastructure for towns, farms and industries
• delivering water to drying wetlands to mimic the natural flooding cycle with much less water.