Hydrology

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The Burdekin River Basin forms part of Australia's North East Coast Drainage Division (NLWRA 2002). Within the division it is bound by the Fitzroy River Basin to its southeast, by the Herbert River Basin to the north and small coastal catchments to the east. Its western margin adjoins two other drainage divisions, the Gulf of Carpentaria Drainage Division to the northwest and the internal Lake Eyre Drainage Division to the southwest. The Burdekin River is one of Australia's largest. It carries a massive sediment load and is on average the biggest single source of sediment and fresh water to the Great Barrier Reef lagoon (NR&M 2000).

The region is comprised of several distinct sub-catchments. These include two larger basins, the Upper Burdekin which drains the north west of the region including the western side of the coastal ranges, and the Belyando- Suttor which drains more arid inland areas in the south and the central west via the smaller Cape River. These two major basins flow to Lake Dalrymple formed by the Burdekin Falls Dam at the top of the Burdekin Gorge.

Another significant Burdekin sub-catchment the Bowen- Broken joins downstream from the Burdekin Gorge. From Clare downstream the drainage of localised rainfall and overbank flows is generally away from the main river via a number of prior river channels, which form floodplain and delta distributaries. These include the Barratta, Sheep Station, Plantation and Saltwater Creek systems.

An additional fourteen coastal catchment management units are recognised to the northern boundary of the region including the Haughton and Ross Rivers ( TTLA 2001) and seven to the southern margin of the region including the Don River ( BBIFMAC 2000).

River flows within the region reflect rainfall patterns (see table), but are also affected by river regulation. Natural flows peaks from December to April and are low to negligible from May to November. At this time many smaller tributaries cease flowing. In general, flows are dominated by large cyclone or monsoon driven events. There are pronounced annual fluctuations and variability from year to year. High flows may be followed by extended dry periods. The catchments that drain the wetter coastal ranges i.e. the Upper Burdekin and the Bowen-Broken contribute more flow relative to their area than semi arid inland basins such as the Belyando-Suttor.

On the Burdekin River flows below Lake Dalrymple are regulated by releases from the Burdekin Falls Dam. The Burdekin Falls Dam dominates flow regulation with an ability to store 1 860 000 ML of water which represents about 88% of the total constructed basin storage capacity (Roth et al. 2002).

Flows on the Bowen-Broken system are regulated by the Eungella Dam with some inter basin transfers out of the system to service nearby coal mining areas (NR&M 2000).

Other smaller dams, weirs and river extractions also affect river flows in the region these include Paluma Dam, two weirs in the Upper Burdekin, the Collinsville Weir in the Bowen River, six weirs in the Belyando-Suttor and three weirs in the lower Burdekin and two on the Haughton (Roth et al. 2002).

The hydrology of the Lower Burdekin catchment is highly modified. Historically flows within the river and floodplain distributary systems were very seasonal but are now regulated. Some of the regulated flow is extracted from the river by several large pumping stations. These stations supply water to the Burdekin Haughton Water Supply Scheme (BHWSS) on the Burdekin and Haughton Floodplains. This is undertaken via distributary streams and constructed channels and the North Burdekin Water boards aquifer replenishment schemes on the Burdekin Delta. Smaller sand dam and drop board structures that form part of these schemes and irrigation tail water flows, also affect the hydrology of receiving water bodies, including streams and wetlands.

Surface water flows and wetland hydrology within the region's coastal catchments including the Haughton and Ross Rivers are also modified by a range of dams, weirs, tidal barrages, constructed drainage networks, bund walls for ponded pasture and water extraction.

A major storage on the Upper Ross River, the Ross River Reservoir provides the primary water supply for the city of Townsville. This reservoir has a pipeline connecting it to the Haughton Balancing Storage for emergency augmentation effectively drought proofing Townsville. The pipeline is an important element in the future growth in this area.

Townsville's other main piped water supply is sourced from Paluma Dam which is part of the Burdekin River catchment.

In most areas of the region rainfall is far less than the amount of water used by plants for transpiration, therefore in general terms there is not much water that passes through the soil to recharge groundwater aquifers (Roth et al. 2002). However heavy monsoonal rainfall during the wet season will usually give some recharge. There is limited water balance and groundwater resources information available and tends to be for areas where shallow groundwater aquifers are important for irrigation, industrial or residential water resources. These include the Don and Burdekin River deltas and the lower Ross and Black River catchments.

Wetland Ranges.jpg

Sub-catchment Area(km2) %Area Burdekin Basin at Clare Sub-catchment annual contribution (ML/a) %of Total flow

Upper Burdekin

36,181

28%

4,067,000

52%

Belyando/Suttor

73,828

57%

2,554,500

33%

Bowen/Broken

9,413

7%

1,021,760

13%

Lower Burdekin

10,028

8%

132,700

2%

Total at Clare

129,450

100%

7,775,960

100%

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