National Wetlands Update February 2013
Issue No. 22, February 2013
Tracking flooding from space for Macquarie Marshes environmental water management
Rachael Thomas and Debbie Love, NSW Office of Environment and Heritage
Flooding in the Macquarie Marshes, December
Recent flooding has seen the iconic Macquarie Marshes, a Ramsar wetland, burst into life with an abundance of waterbirds, fish and frogs supported by a lush mosaic of interconnected wetland habitats in the semi-arid region of the Murray-Darling Basin. Wetland plants and animals depend on floods which vary greatly in size over short and long time periods. Therefore, imagery captured from the Landsat space satellite is being used to track flooding at the Macquarie Marshes.
Environmental water is a volume of water used for the specific purpose of maintaining ecological integrity in the Macquarie Marshes and other significant sites. It is essential during times of drought and complementary to large flood events. Using water purchased through the Australian and New South Wales governments' water buyback and irrigation efficiency programs, the NSW Office of Environment and Heritage (OEH) manages environmental water delivery to sustain wetland health, improve ecosystem resilience and recover degraded wetlands.
Fundamental to the management of environmental water is knowing where and when different parts of the Macquarie Marshes are flooded as a result of environmental water delivery or natural flood events. At OEH scientists use imagery captured from the Landsat space satellite to identify water and accurately map flooding over large areas. A unique satellite, Landsat has been capturing images from the same locations on Earth's surface for 40 years providing insight into flooding patterns over months, years and decades.
Like many other wetlands in the Murray-Darling Basin, the Macquarie Marshes, a wetland of international importance, experienced an extended drought during the 2000-2010 decade. Small environmental water volumes were used in this period and flooded a fraction (less than 15 000 hectares) of the 50 000 hectare core wetland but importantly nourished refuge habitat of semi-permanent wetland and river red gums. In contrast, a period of drought-breaking catchment rainfall began in mid-2010, increasing river flows to flood 74 000 hectares of the Macquarie Marshes. This was followed by extensive flooding (200 000 hectares) in December 2010. Environmental water delivered almost 37 000 hectares of flooding during the spring months of 2011 and after March 2012 dam spills, expanded flooding to 80 000 hectares. The variable nature of flooding in inland wetlands highlights the importance of satellite imagery and robust techniques to track flood distribution as a key tool for environmental water managers. With a better understanding of flooding patterns OEH managers and scientists can together assess the ecological outcomes of flooding from river flows for improved wetland conservation.