Lake Eyre Basin Rivers 10 Ubiquitous waterholes along the main rivers (Fig. 1.6), some permanent, are the most reliable (and iconic) natural aquatic habitats in this system, despite varying considerably in their ephemerality (Silcock 2010). They are usually 4–6 m deep, although some can be up to 25 m deep (McMahon et al. 2008 Kingsford et al. 2014). These waterholes are critically important during dry periods, providing survival refuges for aquatic animals such as fish (see Chapters 3 and 4) and turtles (see Chapter 5). Algae around their edges drives their ecology during these dry periods, providing food for the animals (Bunn et al. 2003 Fellows et al. 2007). Even in dry times, fish may breed in these waterholes (Kerezsy et al. 2011). As dry periods continue, evaporation lowers water levels and water quality declines considerably, with drying of some waterholes causing widespread death of fish and turtles (see Chapter 4). Many of the plants stop growing or die, leaving seeds behind to germinate in a subsequent flood (Brock et al. 2006). During dry periods, concentrations of fish and shrimps inevitably mean that Australian pelicans (Pelecanus conspicillatus), cormorant species (Phalacrocorax sp.), darters (Anhinga novaehollandiae) and yellow-billed spoonbills (Platalea flavipes) often concentrate on these waterholes (Fig. 1.6). Subsequent boom periods come when the tributaries run and fill the main channels and waterholes of the major rivers. Once the waterholes are full, water spreads across the adjacent floodplain through a network of ephemeral channels. The floodplains are extensive in some places (40–80 km wide Kingsford et al. 2014). This is the Channel Country, where myriads of channels intertwine to take water out over the vast floodplains. The larger floodplains of Lake Eyre Fig. 1.6. Dry periods leave only the waterholes with water where fish, turtles and some waterbirds congregate, waiting for the next flood (photo, A. Emmott).
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