Monday, February 2, 2015
Water Down Under: A Report from Australia by Barb Cosens: Post 3: Resilience and the Lake Eyre Basin, Australia
One of the primary goals of my time in Australia is to apply the lessons from theAdaptive Water Governance Project that looks at six North American Water Basins to a water basin in Australia. That basin will be the Lake Eyre Basin (LEB) and will include its connections to the Great Artesian Basin, and I am assisted in that by substantial research by Australian scientists including a new colleague who has provided a wealth of information, Angela Arthington at Griffith University. The LEB covers roughly 16% of Australia including much of what we think of as the outback. It contains two Ramsar wetlands, has been considered for World Heritage listing, and is currently a free flowing river system with 97% of the basin aquatic species thought to be indigenous. The LEB is one of those places in the world uniquely defined by both water and its absence. Like the basins of the Great Salt, Pyramid, Walker and Mono Lakes in the western United States, the LEB is an internally drained basin. While these North American internally drained basins are fed by spring runoff from snowmelt, the LEB receives water during major flood events in the wet season of Northern Queensland where rainfall of 400-500 mm (15-20 inches) not only exceeds the less than 100 mm (4 inches) at Lake Eyre, but tends to come in short duration high intensity storms. In short, the rainforest feeds the desert of Australia. Major floods, as occurred this year shortly after my arrival, are necessary to get water all the way to Lake Eyre, yet do not occur every year. (see current status of Lake Eyre). When they do, they can bring up to 35% of the basin together in one mighty river, reconnecting isolated waterholes and providing habitat and breeding grounds for many species of birds. High variability and extreme flood events drive the biological system of the LEB. Floods bring an influx of nutrients from channel banks and floodplains resulting in boom in the basin fishery. Sequential floods over a short time period may have the greatest impact because they fill wetlands first allowing later even moderate floods to reach farther into the basin. Because groundwater plays a role in contributing to waterholes only within a few locations in the basin, evaporative loss (estimated at greater than 3 m/year (10 feet)) and increasing salinity dominates waterhole hydrology and water quality between flood events. As floods subside, the larger persistent waterholes serve as refugia for fish and those lucky enough to end up in a waterhole that persists until the next flood serve to re-colonize other areas when the water returns. An interesting trait of species that are resilient and, in fact, thrive in this variable habitat is to be somewhat indifferent about what they eat. Like the common Australian phrase no worries -- no access to the floodplain, no worries, I can eat the algal bathtub ring around the waterhole. Blea -- clearly takes a unique form of life to like this habitat. Human alteration of the LEB hydrology is currently minimal, but loss of wetlands in neighboring basins such as the Murray-Darling, increase dependence on the LEB by water birds. Pastoral use of arid lands for livestock, small homesteads and towns use limited amounts of water. Dams have not yet been built to store flood runoff. The major tributaries from Queensland were declared wild, however, the Liberal Party in power since 2012 considered eliminating this status to develop the rivers for irrigation. The basin’s critical natural hydrograph may have received a temporary reprieve in the recent landslide win of the Labor Party in Queensland. In addition to Queensland, the LEB crosses into the Northern Territories, New South Wales, and has its terminus in South Australia. An intergovernmental agreement among the four governments agrees to prevent cross-border harm, but leaves internal management and allocation to the states and territories. The greatest challenge facing the basin is whether to develop or to decide collectively to prioritize protection of this unique habitat and thus make permanent the maintenance of the natural hydrograph. In addition, basin managers have just begun to consider the connections (or lack thereof) between the Great Artesian Basin and the LEB. This and the potential threats to groundwater from mining will be the subject of a future blog. And, as everywhere, climate change may be the ultimate game changer.