Howard Springs Nature Park: Synthesis of What We Know
How the Waterhole Functions
The waterhole is part of a functioning ecosystem. The waterhole and creek immediately upstream is surrounded by rainforest containing for example, a colony of bats. Within the waterhole water plants occur naturally. These plants are an essential part of a healthy functioning aquatic ecosystem; they provide habitat for organisms that help to improve water quality, stabilise sediments, help to reduce the amount of suspended solids in water columns, and remove nutrients from sediment.
Abundant aquatic life including turtles and a number of large barramundi can also be found.
The waterhole receives water from the spring upstream and the surrounding catchment (during the wet), which is sufficient to ensure that for part of the year the waterhole is flushed. As water flows decline and then cease late in the dry, the waterhole becomes a “closed system” in which nutrients and contaminants are contained and largely removed only by natural processes operating within the waterhole itself.
The significant sources of nutrients and contaminant bacteria in the waterhole relate to these natural functions of the ecosystem. Leaf litter from surrounding vegetation and faeces from the fruit bat colony provide a continuous source of nutrients from above. Within the water itself the large barramundi for example, excrete the equivalent of an adult human per day. Fed by these sources of nutrients, uncontrolled blooms of water plants regularly fill much of the pool. At these levels water plants can have a damaging effect on water quality, recreational values and aquatic ecosystem health. They can create a safety hazard for visitors by increasing the risk of entanglement and the floating mats are visually unappealing. Fed by increased nutrients, harmful bacteria thrive both in the water and bottom layers of sediment. Swimming and removal of water plants stir up these sediments, further releasing bacteria into the water.
Figure 2 summarises the natural processes in the waterhole
