Crystal Clear Lakes
Fraser Island has an amazing number of freshwater lakes and creeks. Considering the fact that Fraser Island is made up nearly completely out of sand, one would be forgiven to think the water would sing away rapidly. However there are over 40 permanent fresh water lakes on Fraser Island and even larger number of swamps and semi wet area's. It would be hard to imagine lakes clearer than those on Fraser Island. The water is so pure that the 40 or so lakes support relatively little life.
The reason the water doesn't drain away in the sand of Fraser Island, which extends in most places between 20 and 30 meter under sea level and in places up to 500 meters, is it's unique history. Some of these lakes are sitting entirely above the water table and are only being fed by rainwater, which by the way falls in abundance on Fraser Island (some of the high dunes on Fraser Island catch up to 1800mm a year). As the base of these lakes consists of coffee rock, the water can't seep away very quickly and the rainfall makes up for the little that does or evaporates.
Other lakes are so called perched lakes. Their bottom consists of sand rendered impermeable by very slowly rotting reed humus. As these lakes are very poor in nutrients, hardly any life is supported hence the slow rate of decomposing of the organic material that falls into the lake. Only several dozens of perched lakes are known all over the world and Fraser Island sports about half of them. One of these, Lake Boomanjin covers nearly 200 hectares and is the largest perched lake in the world. Other lakes again are barrage lakes and are formed by creeks, blocked by overtaking sandblows. These lakes do lose water to seepage into the sandy bottom but this loss is made up for by the continued inflow of the blocked creek. Lake Waddy is a famous example of this kind of lakes on Fraser Island. A fourth type of lakes on Fraser Island are the window lakes. These are depressions in the dunes of Fraser Island that extend below the water table, thus forming a "window" into the large aquifer that lies beneath the surface of Fraser Island.
The lakes vary enormously in colour. Some lakes on Fraser Island are crystal clear whereas others are tainted red or are nearly green. The red tainted lakes like Lake Boomanjin are being fed by not only by rain water but also by three very small creeks that carry water heavily stained by tannin from tea trees in their catchment areas.
There are three types of lakes on Fraser, window, barrage and perched lakes. Window lakes occur when the ground drops below the water table. The fine white sandy base acts as filters, giving the water its clarity. There are several window lakes including Yankee Jack, Ocean lake and Lake Wabby.
Lake Wabby is also termed a barrage lake, which is formed by the damming action of a sandblow blocking the waters on a natural spring. Wabby is relatively close to the ocean side of the island and unlike the other lakes it supports several varieties of fish. It is also a good example of the sandblow phenomena, gradually encroaching on the deep green waters of Wabby as the sandblow makes its gradual progress westward across the island.
Swimmers in the lake should not run and dive off the sandblow - the water is very shallow close to the edge of the lake. Perched lakes occur above the water table. Saucer-shaped depressions with a hard, impervious base of organic matter and sand, form a catchment for the rain eventually creating the lake. The peat-like base generally stains the water the colour of tea. In the northern half of the island, Lake Bowarrady is the highest of the perched lakes being some 120 metres above sea level. In the southern part of the island there is Lake Birrabeen and the popular Lake McKenzie. Lake Boomajin approximately 190 hectares in area is the world's largest perched dune lake.
Each of the lakes has its own particular character. Mysterious, moody and beautiful, they are excellent subjects for photography, great places to see birds, other fauna and flora and a welcome oasis for the hot Summer days. Scenic 4WD circuits and walking tracks in the southern half of the island take in some of the largest of the lakes including Lake McKenzie, Birrabeen, Benaroon and Boomajin, There is a walking track to Lake Wabby from the beach.