Guest Blogger Dr Anne Jensen gives a summary of her visit to the River Murray Floods.
Guest Post by Dr Anne Jensen, Dr Anne Jensen is an environmental consultant with extensive experience in natural resources management particularly relating to water issues and the environment. She is a Consulting Scientist to the Water Research Centre of the Environment Institute. Anne competed her PhD study in 2008 with the School of Earth & Environmental Sciences at the University of Adelaide on the topic, ‘The role of seed banks and soil moisture in recruitment of semi-arid floodplain plants: the River Murray, Australia,’ with the goal of investigating optimum conditions for application of environmental flows. Previously Anne was CEO of WetlandCare Australia, a not-for-profit conservation company which has coordinated multiple wetland projects in South Australia, New South Wales and Queensland. She has strong international networks in wetland and natural resource management through involvement with Ramsar, UNESCO, Ducks Unlimited, and government agencies in the UK, USA, Canada and Denmark.
The Lower River Murray has been given a reprieve. The sustained flows coming into South Australia since October 2010 have been at a level which will do minimal damage to infrastructure and property while providing major benefits to the stressed ecosystem.
The wetlands of the River Murray below the Darling Junction at Wentworth have been severely affected by drought conditions since 2002. Prior to the drought effect, water for wetlands was much reduced due to the effects of dams retaining small to medium floods in order to provide water for irrigation and town supplies. Wetlands of the Lower Murray floodplain had not seen effective over-bank flows since 1996, and the drying impacts were apparent with more than 75% of river red gums along the length of the valley dead, dying or stressed.
The current floods bring a precious opportunity to recover from 14 years without over-bank flows. There is enough water available to allow it to spill out onto the floodplain in sheet flows, to infiltrate into the soils and replenish the shallow freshwater lenses which overlie the highly saline regional groundwater. These lenses were exhausted by the lack of floods and the extended drought, so that the river red gums had their roots in salt water. Now they will get a new lease of life from the floods, and the moisture reserves will be topped up for future years.
At the flood peak, I revisited my PhD study sites on the Chowilla floodplain near Renmark and Clarks Floodplain near Berri, and reported significant recovery in response to prolonged and extensive inundation. The mainstream is flowing swiftly, demonstrating the healthy pulse of production in the ecosystem with large surface mats of bright green native duckweed and floating fern (Lemna spp. and Azolla sp.). Approximately 80% of the floodplains are inundated, with reports of high numbers of frogs, fish and waterbirds breeding.
Photo’s included in this post show the recovery at previously stressed sites. However, there are many instances of long term damage, with dead river red gum (Eucalyptus camaldulensis) and black box (E. largiflorens) beyond recovery due to their reduced resilience as a result of water deprivation prior to extended drought stress. The floods have provided a reprieve and significant recovery, but the issue of securing water in the future to maintain a healthy river ecosystem remains.
Guest Post by Dr Anne Jensen, if you would like to contribute your research to a guest blog on The Environment Institute Blog email firstname.lastname@example.org.