A landscape of contrasts
In the semi-arid landscape of southwest Queensland, Currawinya National Park holds a remarkable hydrological anomaly. The park has two large lakes, Lake Numalla and Lake Wyara, that sit only three kilometers apart but possess entirely different chemistries. Lake Numalla is a freshwater lake, while Lake Wyara is saline, often becoming a vast, white saltpan during dry periods.
This striking difference is due to their distinct catchments. Lake Numalla is periodically flushed by floodwaters from the Paroo River, one of the last free-flowing rivers in the entire Murray-Darling Basin. These floods replenish its freshwater supply. Lake Wyara, however, occupies a closed catchment, receiving only local rainfall and occasional extreme overflows. Evaporation concentrates its salts, creating a hypersaline environment. This wetland system, designated a Ramsar site of international importance on March 11, 1996, also includes over 70 artesian springs that tap into the Great Artesian Basin, one of the world's largest underground water reservoirs.
An explosion of life
For years, the lakes are often dry claypans. When the infrequent floods do arrive, the landscape transforms. The system explodes with life in a "boom" cycle. Waterbird numbers can exceed 100,000, and on some occasions, more than 250,000 birds have been recorded at one time. Over 200 bird species are found in the park, which is recognized as a globally Important Bird Area.
The wetlands provide a critical refuge and breeding ground. One of the most spectacular inhabitants is the Banded Stilt (Cladorhynchus leucocephalus). These nomadic birds spend most of their lives on the coast but travel hundreds or even thousands of kilometers inland to breed in ephemeral salt lakes like Wyara. They arrive just as the lakes fill, somehow anticipating the floods from afar. Their breeding is timed to coincide with the hatching of brine shrimp, whose eggs lie dormant in the dry lakebed for years. Lake Wyara also supports major breeding events for Australian pelicans (Pelecanus conspicillatus), black swans (Cygnus atratus), and the rare freckled duck (Stictonetta naevosa). The park is also an important conservation site for the greater bilby (Macrotis lagotis), with a 25-square-kilometer predator-proof enclosure supporting a captive breeding and reintroduction program.