Transcript

Understanding how water flows in the catchment

It is difficult to manage catchments unless there is collective understanding by all stakeholders of how the catchment works. This Map Journal gathers together information from expert input and data sources to provide that understanding.

The information was gathered using the ‘walking the landscape’ process, where experts systematically worked through a catchment landscape in a facilitated workshop, to incorporate diverse knowledge on the landscape components and processes, both natural and human. It is focused on water flows and the key factors that affect water movement.

The Map Journal was prepared by the Queensland Wetlands Program in the Queensland Department of Environment and Science in collaboration with local partners.

Main photo: W. Jones - Pristine and alive Bremer River (Ipswich) - provided by Ipswich City Council.

How to view this map journal

Please note that the use of the terms 'Catchment' and 'Basin' are sometimes used interchangeably. In this map journal the term 'Catchment' has been used.

Map journal for the Bremer Catchment—water movement

This Map Journal describes the location, extent and values of the Bremer catchment. It demonstrates the key features which influence water flow, including geology, topography, rainfall and run-off, natural features and human modifications and land uses.

Knowing how water moves in the landscape is fundamental to sustainably manage the catchment and the values it provides.

Bremer Catchment Story

The Bremer River catchment is located west of Brisbane within the local government boundaries of Ipswich City Council and Scenic Rim Regional Council.

The Bremer catchment covers approximately 203 000ha, with the main channel, the Bremer River, surrounded by several sub-catchments. (click to play animation).

Although the Warrill Creek is the longest waterway in the area, the Bremer River was discovered earlier by John Oxley in 1824* and therefore named it the main channel of the catchment.

It flows into the Brisbane River which also receives water from the Lockyer, Upper Brisbane, Stanley and Mid Brisbane catchments prior to the Bremer catchment. The Brisbane River continues east where it is joined by the Lower Brisbane catchment, before reaching Moreton Bay.

*The Bremer River (Page 9), Robyn Buchanan, Ipswich, Ipswich City Council, 2009.

Values of the catchment

The Bremer Catchment contains many environmental, economic and social values.

There are a number of parks, reserves and protected areas in the Bremer catchment from Mount Goolman, Flinders Peak and Ivory's Rock, to Mount French (North), Mount Moon, and Mount Greville (part of Moogarah Peaks National Park). The Bremer Catchment also includes Main Range National Park, a World Heritage area - with features such as Spicers Gap, Cunninghams Gap, Mount Mitchell, Mount Cordeaux and Mount Castle.

The many recreational areas including areas for camping, bushwalking and water based activities. The natural beauty of the Bremer catchment provides a recreational retreat for many and adds significant value to the catchment.

Values of the catchment - flora and fauna

The catchment contains threatened vegetation communities, like the endangered Swamp Tea-tree Forest, found only in few areas in South East Queensland. The catchment also contains areas of Brigalow scrub and other rare flora such as Boonah Tuckeroo, Grevillea linsmithii, Eucalyptus dunnii (Dunns white gum), Arundinella grevillensis, Callitris baileyi, Marsdenia coronate (slender milk vine), Melaleuca groveana (Grove's paperbark), and Notelaea lloydii (Lloyd's olive).

This catchment is also home to threatened animal species including the endangered lungfish, Spotted tailed Quoll, koala, black-breasted Button-quail, Glossy black cockatoo and Black necked Stork.

Values of the catchment - land use

The catchment supports a diverse range of land uses which include agriculture, grazing, natural areas, mining, industry and urban development.

Since European settlement this catchment has had intense industry and agriculture. The remnants can still be seen, such as the old coal mine pillars and cleared salt affected lands. Some  of which some are being converted to wetlands teaming with birdlife.

Saline geologies in the area can also contribute to salinity in waterbodies and soils.

Image Main: from 3bp blogspot - example of a pillar from an old mine not from Ipswich.

Natural features – geology and topology

The geology in the Bremer River catchment underlies the steep slopes in the ranges. In these areas there are sections of highly permeable basalt, which can recharge groundwater, supporting groundwater dependant ecosystems.

Not all of the surface water recharges the groundwater system. Surface water will run off the steep slopes (animation), often draining quickly into the creek network, especially in high rainfall events.

In the lower parts of the catchment there are large areas of alluvium. Alluvium is formed from particles such as gravel, sand, silt or clay, deposited by river processes in river channels or on floodplains. These deposits readily store and transmit groundwater.

In the Ipswich CBD, there is a small area of magnesian limestone which acts in a similar way to the weathered basalts of the upper regions in the catchment, and can also store and transmit groundwater. This area of limestone is unique in South East Queensland.

Floodplain conceptual models

Natural features – rainfall

The Bremer catchment experiences good rainfall (over 1000mm/year) along its steeper sections to the south and east. The remainder of the catchment experiences average rainfall (under 1000mm/year).

Natural features – vegetation

In its natural condition, the majority of the Bremer catchment consisted of open Eucalypt forest, including areas of swamp tea tree, with some small pockets of rainforest and acacia woodland and scrub in parts of the upland areas. Other special ecosystems to note that were in the Bremer catchment include blue gum forest, freshwater swamps and fringing forest.

The vegetation throughout the catchment was sparse although more dense in the upper areas.

This thicker vegetation played a very important ecological role - it slowed the surface water run-off. This helped stabilise stream banks, reduced the erosion potential and the loss of soil from the catchment and allowed some of the water to enter the groundwater system, supporting groundwater dependent ecosystems.

Modified features – vegetation and land use

There have been significant changes throughout the catchment since the first European arrived in the catchment.

The majority of the catchment has now been cleared* for agricultural production, mining, industrial activities and urban development.

*Explore the Swipe Map using either of the options below. Depending on your internet browser, you may experience issues with one or the other. Please note this application takes time to load. (click the blue link to see the Swipe Maps):

• Explore and go to the interactive Swipe App where you can use the swipe bar. Use the white slide bar at the bottom of the map for a comparison. (HTML version)
• Explore and go to the interactive Swipe App where you can zoom into areas and use the swipe bar. Please note this application takes time to load. (ESRI version)

Modified features – channels and infrastructure

Some areas in the Upper Bremer River and Mid Warrill Creek have been leveed to expand agricultural production. This has reduced the area for surface water to spread out and slow down, channelling water into a concentrated channel during high flows.

There are also irrigation channels around the catchment in areas such as Kalbar, Radford and Harrisville, in the flatter areas of the catchment.

Urban development has resulted in the creation of hard, impervious surfaces and reduced the area of flood plains. This decreases that ability of water to slow down and enter the groundwater system, resulting in more surface water rapidly entering the creek systems.

Urban development is not just housing - roads, railways and creek crossings also modify the flow of water as they often act as barriers, redirecting water through single points or culverts.

Modified features – dams and weirs

Dams and weirs can also modify the natural water flow patterns, by holding water and controlling the timing and quantity of releases.

Some of the waterway barriers are being converted to fish ways.

Moogerah Dam is located in Reynolds Creek near Boonah. It is an ungated dam, supplying water to Warrill Creek and Warrill Valley farmers through a series of diversions and drinking water for recreational users of the lake. Water is also released to Reynolds Creek from Moogerah Dam for use at the Boonah Kalbar Water Treatment Plant which supplies the local area with drinking water.

Water is held in Moogerah Dam to meet the needs of a variety of land uses, however, this reduces the volume of natural water flow downstream.

Water quality

Water quality is influenced by run-off, septic tank seepage and stormwater discharge and point source inputs such as sewage treatment plants and industry. There are sewage treatment plants at Aratula, Kalbar, Rosewood and Bundamba.

In 2016, Healthy Waterways graded the overall Environmental Condition Grade of the Bremer Catchment as D+.

The overall environmental condition of Bremer was described as poor, however the catchment improved slightly from 2015 due to improved estuarine water quality and freshwater stream health. The catchment retains a very low proportion of freshwater habitat, compared to pre-cleared. Freshwater stream health remained fair, however slightly improved due to improved fish community health. Pollutant loads remained very low. Riparian condition remains very poor. Estuarine water quality improved from very poor to poor due to improved oxygen, algae and nitrogen concentrations in parts of the estuary.

Water flow

Water flows across the landscape into streams and eventually into the Bremer River. (click to play animation)

The remaining water either sinks into the ground where it supports a variety of terrestrial and groundwater dependent ecosystems or is used for other purposes.

The upper reaches of the catchment have relatively steep slopes which create the potential for increased run-off which may lead to flooding in areas where the floodplain has restricted channels and gullies.

The restricted channels and gullies eventually flatten out to form waterways that meander across the floodplain. They pass through alluvial areas which store and release water, prolonging the time streams flow.

The sub-catchments

A catchment is an area with a natural boundary (for example ridges, hills or mountains) where all surface water drains to a common channel to form rivers or creeks.

Larger catchments are made up of smaller areas, sometimes called sub-catchments. The Bremer Catchment consists of large and small sub-catchments.

The characteristics of each sub-catchment are different, and therefore water will flow differently in each one.

Reynolds Creek

Reynolds Creek sits in the upper sections of the Bremer catchment.

The headwaters of the creek are within Main Range National Park, with the majority of the catchment being grazed.

The headwaters are underlain by basalts, which readily absorb water and have near permanent flows. The majority of the catchment below this area is impervious, and little to no water infiltrates. These are high run-off areas. Further downstream, there is some alluvial development.

There are some smaller areas of modified pastures, and Moogerah Dam is located in the mid sections of the sub-catchment. This dam is an important feature of the Reynolds Creek sub-catchment, supplying both water for irrigation and pastures as well as for drinking water.

Moogerah Dam is also an important regional recreational asset providing many nature based and aquatic opportunities for visitors.

Franklin Vale Creek, Bremer River and Warrill Creek

The ranges around Franklin Vale Creek, Bremer River and Warrill Creek are steep, but the slope of the main channel through these areas is less and the floodplains larger than compared to the upper parts of Western Creek and Reynolds Creek.

The reduced steepness in the landscape and broader floodplains provide the means for the surface water to slow.

Bremer River and Warrill Creek

The majority of the Bremer River and Warrill Creek exist on a gently undulating landscape.

These lower lying areas tend to have even broader alluvial plains*, and contain numerous wetlands scattered throughout.

The mid-Warrill area contains a broad floodplain* that can transmit water on the land between the main channel of Warrill Creek and Kents Lagoon. This area also contains a lot of alluvium.

Surface water from rainfall events will spread out over the floodplain, reducing the speed that it enters the creek system.

*Note that the alluvium layer has been used to describe a general area of the floodplain. It does not describe the actual floodplain or define where floods will happen.

Bremer River and Warrill Creek (continued)

The alluvial plain surrounding the mid reaches of the Bremer River is also engaged from fast flows off the ranges (animation). These flows can rise rapidly in the broad floodplains at their base.

Purga and Warrill

The Purga and Lower Warrill sub-catchments converge just with the lower reaches of the Bremer River just before Ipswich City. This area is a major water backup area, especially in times when all three catchments receive high flows. The main channel will usually flow back up the tributary. The flows then become rechannelled through a constriction in the floodplain, before entering the lower Bremer River.

Lower Bremer

The lower Bremer River is the most complex part of the catchment in relation to water flow with a varied landscape of undulating terrain, and tidal influences.

The river channel itself has only a slight slope, and water movement is usually quite slow, with numerous small breakout areas where flood waters slowly rise and spread. This is the lowest reach of the catchment which drains into the Brisbane River.

The lower Bremer River has the highest volume of flow in the catchment, attributed with the flows entering from the smaller creeks running into it.

Further exacerbating the situation is that all of these flows can be impacted by tidal influence of the Brisbane River to which it drains into. Tidal flow can back water up into the Bremer from the Brisbane River.

Main photo: Joseph Brady Park, Barellan Point - provided by Ipswich City Council

Bremer River Catchment

The Bremer River catchment is a diverse landscape with many different flow patterns.

Flow patterns in this catchment are influenced by several factors ranging from natural slopes, groundwater interactions, landscape modifications and the Brisbane River.

Understanding the nature of water movement in the catchment is vital to inform management actions in times of high and low water flow. Every drop of rain that falls in the Bremer catchment has its own story, its own journey from landfall to the Brisbane River and finally the ocean.

Knowing how the catchment functions is also important for future planning, including climate resilience. With this knowledge, we can make better decisions about how we manage this vital area.

Acknowledgements

Developed by the Queensland Wetlands Program in the Department of Environment and Science in partnership with:

Ipswich City Council

Scenic Rim Regional Council

Council of Mayors South East Queensland

Healthy Waterways (Healthy Waterways and Catchments)

Seqwater

This resource should be cited as: Walking the Landscape – Bremer Catchment Map Journal v1.0 (2016), presentation, Department of Environment and Science, Queensland.

Photos provided by: SEQ Catchments, Healthy Waterways, Ipswich City Council, Scenic Rim Regional Council

The Queensland Wetlands Program supports projects and activities that result in long-term benefits to the sustainable management, wise use and protection of wetlands in Queensland. The tools developed by the Program help wetlands landholders, managers and decision makers in government and industry.

Contact wetlands♲des.qld.gov.au or visit wetlandinfo.des.qld.gov.au

Additional reports provided by regional and local groups are provided on WetlandSummary.

Disclaimer:

This map journal has been prepared with all due diligence and care, based on the best available information at the time of publication. The department holds no responsibility for any errors or omissions within the document. Any decisions made by other parties based on this document are solely the responsibility of those parties. Information contained in this education module is from a number of sources and, as such, does not necessarily represent government or departmental policy.

Data sources, links and information

Software Used

ArcGIS for Desktop | ArcGIS Online | Story map journal

Some of the information used to put together this map journal can be viewed on the QLD Globe.

The Queensland Globe is an interactive online tool that can be opened inside the Google Earth™ application.

Queensland Globe allows you to view and explore Queensland spatial data and imagery. You can also download a cadastral Smartmap or purchase and download a current titles search.

More information about the layers used can be found here:

Source Data Table

Other References

Bremer Catchment fly-through via Moogerah Dam (Google Earth kmz file)

Flood information: Scenic Rim Regional Council, Ipswich City Council

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Last updated: 25 August 2021