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South-East Freshwater Biogeographic Province

South-East Freshwater Biogeographic Province – Hydrology

Wet season (Jan-Apr) Average temperature (19°) Temperature varies along a NE-SW gradient Evaporation exceeds rainfall Width of riparian zone (27m) Small, medium trees Grasses Relief ratio variable Relief ratio variable Percentage of water which is base flow (12%) Annual spate duration (1 month) Annual no-flow duration (3 months) Sand Metamorphic rock High macroinvertebrate richness Low turbidity Large woody debris cover (13%) Submerged and emergent macrophyte growth forms dominant Concave bank shape category Convex bank shape category Dominant bank slope (10°-80°) Fauna Specific example – Life cycle of Tandanus

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Gauges

 

Modelled pre-development data from 52 gauges within the South-East FBP were used for these analyses. Key features of typical hydrographs over multiple temporal scales were used to characterise the following aspects.

State of the Rivers sites used in the calculation of the South-East FBP riparian vegetation features

Base flow and flood flow

On average approximately 11% of flow (by volume) is base flow and conversely 89% of flow is related directly to flood flow from rainfall events.

  Mean SE Maximum Minimum
Base Flow Index 0.12 0.004 0.22 0.036
Flood Flow Index 0.89 0.004 0.96 0.78

Information about base and flood flow

Information about methods

Magnitude of spates

Magnitude of spates averaged 0.7 to 1.1 Ml km2 day-1, but much larger and smaller average values occur within the FBP at particular sites. There is an average of 4.5 to 4.7 spates per year, with 2.5 to 2.7 of these in the wet season and 1.9 to 2.1 in the dry season. The average duration of spates is approximately 8.2 to 8.6 days.

The timing of spates is not limited to the wet season so biota that utilise spates for some part of their life history are able to be opportunistic in that they are not confined to do so during only part of the year.

The mean number of spates per year in the South-East is high with respect to other FBPs and they are typically shorter in duration. This suggests that the rate of rise and fall of spates is fairly rapid in the South-East. This also implies that spates are a fairly high disturbance to biota in these systems.

Information about magnitude of spates

Information about methods

Magnitude of Spates Mean SE Maximum Minimum
Spate run-off (Ml km2 day-1) 0.94 0.19 11.71 0.028
Frequency and Duration of Spates Mean SE Maximum Minimum
Mean number of spates per year 4.6 0.1 12.0 2.8
Mean duration of spates (days) 8.4 0.2 13.2 3.1
Mean number of wet season spates per year 2.6 0.1 5.6 1.8
Mean number of dry season spates per year 2.0 0.1 6.4 1.1

No flow spells

83 of the 91 modelled flow sites available experienced periods without flow. Sites in the FBP on average have approximately 5 to 6 no-flow spells per year, each spell lasting on average 10.2 to 12.8 days however at one site in the Brisbane catchment a spell has been recorded lasting up to 77 days. The average longest dry spell in the reporting period is approximately 6 months; however a dry spell of over 3 years has been recorded at one site in the Brisbane catchment. On average there is no flow approximately 22% of the time, but this varies with a maximum of around 80% recorded at one site in the Brisbane catchment.

The mean continuous period of flow between no flow spells is 517 days (approximately 17 months), but this can be as long as 21 years, recorded from one site in the Mary catchment, and as short as 7 days, recorded from one site in the Brisbane catchment. The average longest period of flow between no flow spells is approximately 7 years, ranging from 53 years at one site in the Logan-Albert catchment to only 151 days at one site in the Burnett catchment.

Given the general prevalence of periods without flow, aquatic biota must have traits enabling them to either survive in situ or recolonise when flows return, or else utilise drought refugia. Persistent waterholes are the most evident form of refugium in the South-East FBP. Given that waterholes connect more frequently in the South-East fauna don’t necessarily need to tolerate conditions as extreme as in other FBPs.

Information about no flow spells

Information about methods


No-Flow Spells		 Mean SE Maximum Minimum
Frequency of No Flow Spells (spells per year) 5.7 0.5 21.6 0.0
Proportion of time with no flow (%) 22.4 2.4 79.5 0.0
Longest No Flow Spell (days) 182.6 20.8 1206.0 0.0
Mean Duration of No Flow Spells (days) 11.5 1.3 77.4 0.0
Mean period between No Flow Spells (days) 516.5 168.9 7639.0 6.6
Longest period between No Flow Spells (days) 2605.0 319.2 19266.0 151.0

Rise and fall of the hydrograph

The mean rate of rise for the South-East FBP is approximately three times greater than the mean rate of fall. Similarly, the mean greatest rate of rise for the FBP is almost double the mean greatest rate of fall.

Information about the rise and fall of the hydrograph

Information about methods

Rise and Fall of the Hydrograph
(per day relative to Mean Daily Flow)		 Mean SE Maximum Minimum
Mean rate of rise 1.50 0.21 10.20 0.31
Greatest rate of rise 169.01 15.39 1062.29 21.77
Mean rate of fall 0.54 0.05 2.45 0.13
Greatest rate of fall 93.32 7.87 350.35 12.88

Wet and dry seasons

The proportion of annual flow is not evenly distributed between months. The months January through to April have a greater proportion of annual flow than May to December. Based on this, the wet season for the South-East FBP is January through to April, and the dry season May to December. Compare this pattern with the other FBPs.

Dotted line shows the mean/median flow

Information about wet and dry seasons

Information about methods

Last updated: 22 March 2013

This page should be cited as:

Department of Environment, Science and Innovation, Queensland (2013) South-East Freshwater Biogeographic Province – Hydrology, WetlandInfo website, accessed 30 August 2024. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/ecology/aquatic-ecosystems-natural/riverine/freshwater-biogeo/south-east/hydrology.html

Queensland Government
WetlandInfo   —   Department of Environment, Science and Innovation