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Arafura swamp water resources study



Arafura swamp water resources study


Williams, D.; Chudleigh, I.; Jolly, P.


E-Publications; E-Books; PublicationNT; Report ; 45/2003




Made available via the Publications (Legal Deposit) Act 2004 (NT).





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Dept. of Infrastructure, Planning and Environment

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Report ; 45/2003

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18 swamp reaches peak levels after it receives a certain volume of water. For instance in 1972/73 at the Goyder River gauging station the river rose 6.4metres, while swamp levels rose only 1.5metres (refer to Figure 12). To predict when levels will peak in the swamp requires a good knowledge of flows travelling down the Goyder as well as Gulbuwangay River. More rainfall gauges are needed in the catchment to better predict rainfall flow relationships in the catchment. The amount of spring inflow delivered by the Goyder River and other streams during the dry season controls the amount of water maintained in the swamp. The Goyder River baseflow model indicates that the Goyder River can deliver between 0.6 to 8.7 cubic metres per second of spring flow to the swamp. Data from G8250003 was used to determine the daily loss of water due to evapotranspiration (ET). ET for the swamp is approximately 5mm / day. Using these figures, Table 1 identifies the flow rate required to maintain water levels for a certain percentage of the swamp. Whilst spring inflows are responsible for maintaining a certain area of the swamp, some pools are maintained throughout the dry season from wet season runoff because the depth of water in the pool is greater than the amount evapotranspired during the dry season. Identifying these pools is important as they will be more easily affected by water quality changes and surrounding land use needs to be managed appropriately. Table 1: Flow rate required to maintain water levels for various percentages of the swamp Flow rate at G8250002 m3/s Area of Swamp where water levels maintained km2 % of Swamp where water levels maintained 1 17 3 2 35 6 3 52 9 4 70 12 5 86 15 6 104 18 One significant threat to the swamp is Mimosa. Seeds will spread slowly during a flood event and may be mostly trapped by vegetation and eventually settle. A flow model was developed to predict where seeds may be transported to during a flood event. The model assumed that at least one seed will find its way through the vegetation and the model tracks its path. The settling rate of the seeds was determined by soaking dry seeds in a bucket and counting until the majority of seeds had sunk. The seeds were then dried in the sun and the experiment redone. Seeds tend to settle slightly quicker the second time. This model could be used to assist in management of mimosa.