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Savanna Explorer > Kimberley > Waterways and Wetlands

Rainforests and riverbanks

by Tony Start, CALM WA

Rainforests

There are numerous rainforest patches in the region but they are more common and more extensive in high rainfall, near-coastal areas of the north and west Kimberley. They are usually islands in a sea of savanna woodland and seldom larger than a few hectares. Although they do not conform to the popular image of vast, lush, tropical forests, they have closed canopies (at least when all the trees have leaves for many are deciduous) and the plants in them are rainforest species which cannot survive the fire regimes of the surrounding savanna woodlands. Rainbow pittas and orange-footed scrubfowl feed on the forest floor, while figbirds and pied imperial pigeons which feed on the soft fruits are important transporters of seed between patches. Unlike the highly visible birds and plants, some of the most interesting inhabitants are hard to find, particularly in the dry because they retreat underground. These are earthworms and land snails. Many are unable to move between patches because many of them have their own endemic species.

Wetlands

In the wet, numerous depressions fill with water, rivers flow and floodplains flood. Each has its own characteristic suite of aquatic biota. Flying animals (e.g. waterbirds, dragonflies) and plants with wind-borne seed (e.g. cumbungi) are widespread, but some less mobile species with particular habitat requirements have very restricted distributions. As the dry advances, rivers retreat to series of pools and wetlands dry out, although a few billabongs will hold water all year. Waterbirds concentrate on the remaining wetlands and perennial, riparian plants tough it out but many species depend on drought-hardy stages such as seeds, bulbs, rhizomes or drought-resistant eggs. Examples of all these features can be found at Parry Lagoons.

Ord River

A watercourse in the more arid southern Kimberley

A watercourse in the more arid southern Kimberley

The Ord River has been dammed at two places to create Lake Argyle and a diversion dam at Kununurra. Lake Argyle is the largest freshwater body in the Kimberley but fluctuating water levels limit the development of extensive riparian areas. Nevertheless, fish, and their predators (e.g. fresh-water crocodiles and cormorants) are common. Large numbers of waterbirds use inundated vegetation in shallow water at the southern end but most shores are too steep for them.

In contrast, the stable level in the diversion dam has encouraged development of rich riparian vegetation. Many water birds, including comb-crested jacanas, white-browed crakes and darters use the dam while emerald doves, shining flycatchers and azure kingfishers occur in riparian areas. Because water is now released continuously from the diversion dam the once-seasonal lower Ord flows year round and riparian vegetation is considerably more extensive in the channel than it used to be but stock, weeds and less flooding have degraded riparian vegetation of the levees. The significance of the dams as wetlands is recognised by their declaration as wetlands of international importance under the Ramsar convention.