1.1.5 Surface water hydrology and surface water quality


The hydrology and water quality section includes analysis of (i) surface water systems, including discussion about rainfall, evaporation, river systems, flooding history and water storage infrastructure in each of the relevant river basins, (ii) surface water quality, including existing monitoring, load estimates and key water quality issues including acid sulfate soils; and (iii) surface water flow, which describes existing stream flow monitoring locations and data available.

The Clarence-Moreton bioregion covers an area from south-east Queensland to north-east New South Wales and includes seven Australian Water Resources Council catchments: three in Queensland and four in New South Wales (Figure 21). The ones in Queensland include the Brisbane river basin, Logan-Albert river basin and South Coast basin and in New South Wales the Tweed river basin, Brunswick river basin, Richmond river basin and Clarence river basin. The Clarence-Moreton bioregion boundary does not follow the full extents of these river basins but does include parts of each of them.

River basin sizes in the Clarence-Moreton bioregion range from 508 km2 for the Brunswick river basin to over 22,000 km2 for the Clarence river basin. Rainfall ranges from an annual mean of 922 mm for the Brisbane river basin to 1879 mm for the Brunswick river basin. Mean annual evaporation ranges from 800 to 1131 mm and runoff coefficients (runoff divided by rainfall) vary by a factor of more than two (0.14–0.40) across the Clarence-Moreton bioregion. The Clarence river basin has the largest annual runoff of all of the river basins in the Clarence-Moreton bioregion. Water storages exist in all river basins but the largest is the South East Queensland (SEQ) Water Grid (Queensland Water Commission, 2010) which connects many of the river basins and population centres in south-east Queensland through more than 535 km of pipeline.

The largest total export of sediment in the Clarence-Moreton bioregion comes from the Clarence river basin which has loads nearly 200 times higher than those from pre-European conditions. The largest sediment export rate (per unit area) comes from the Tweed River. Total phosphorus export is the highest for the Brisbane river basin which has loads more than five times those from pre-European conditions. Although the largest annual total nitrogen export comes from the Clarence river basin, the Logan-Albert River exports the highest amount of nitrogen per unit area. Serious water quality problems are associated with the drainage of acid sulfate soils located in the coastal areas of New South Wales with 14,700 ha of the Clarence wetlands being affected by drainage activities. Drainage of acid sulfate soils results in the flow of acidic (low pH) water into the surface water system, with reported pH as low as 2.5.

All river basins that are represented in the Clarence-Moreton bioregion have active or discontinued river gauging stations. However, in some river basins there are no gauges located within the defined boundaries of the Clarence-Moreton bioregion. Flooding is a regular occurrence in all river basins of the Clarence-Moreton bioregion and is most commonly associated with the remnants of cyclonic activity, which bring heavy rains to the region.

Figure 21

Figure 21 Clarence-Moreton bioregion and associated river basins

Last updated:
8 January 2018
Thumbnail images of the Clarence-Moreton bioregion

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