Wetlands or swamps provide a natural source of stored water that can continue to supply water into the river system long after the rain has stopped. Shannon Brennan, Rivercare Officer for the Southern Rivers Catchment Management Authority explains what they are, why they are worth looking after and what to do if they are at risk.
Swamps are gully lines and reaches of streams that have no channels. They have porous sediments so water can move through them sideways. They are also referred to as ‘chain-of-ponds’, swampy meadows, valley fills or upland wetlands.
Soils in swamps have a significant capacity to store and slowly release water into our river systems (like a giant sponge). For example, a swamp of 1 hectare and 3 metres depth would contain 6 megalitres of water (6 million litres). Thus, every swamp makes a difference and every swamp lost means less water available to be shared. They act like large sponges that quickly soak up water during rain and release it back into streams over long periods of time.
Bega Valley floodplain swamp
Swamps also provide a valuable ecological and farming value to the valley. With careful management these swamps can provide farmers with significant areas that sustain agriculture well into and through a drought – an important resource in a changing climate.
Before European settlement swamps were widespread across a number of landscapes but many of these have been lost due to catchment clearing, artificial draining, pest animal and weed infestations and other land management practices.
Erosion of swamps significantly reduces their water holding effectiveness. Once a swamp is incised, the water table is lowered to the depth of the erosion and the surrounding swamp is drained very quickly. This leads to a drying out of the surrounding landscape. The coarse sediment released by erosion of swamps is also a major cause of large volumes of sediment in our rivers, for example the Bega River. This sediment can take decades to move through the river system.
Rehabilitation of swamps takes time and depends on the degree and type of damage. In some cases, simple approaches such as fencing and revegetation may be sufficient in slowing down the velocity of water through an incised swamp. Over time, sediment may gradually build up in the area, raising the level of the bed and retaining
Log sill installed at Packers Swamp
water in the landscape, thereby improving the overall water storage capacity of the catchment. Sometimes works including rock ramps and log sills may be required to control erosion points and allow vegetation to recover.
Fencing swamps can give landholders more control over when stock have access to these areas. This can help prevent damage to swamps during wet times and also improve livestock health by reducing exposure to liver fluke and other animal health issues.
Southern Rivers CMA can help landholders identify swamps on their properties and provide technical advice on possible solutions for their restoration.
from CMN Newsletter Autumn 2011
