Understanding how water flows in the catchment

To effectively manage a catchment it is important to have a collective understanding of how the catchment works. This Map Journal gathers information from experts and other data sources to provide that understanding. The information was gathered using the walking the landscape process, where experts systematically worked through a catchment in a facilitated workshop, to incorporate diverse knowledge on the landscape features and processes, both natural and human. It focussed on water flow 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.

*Lower Tenthill Creek, provided by Lockyer Valley Regional Council

How to view this Map Journal

Map Journal for the Lockyer Catchment - water movement

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

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

Lockyer Catchment Story

The Lockyer catchment is located west of Brisbane and east of Toowoomba, within the local government boundaries of Lockyer Valley Regional Council, Somerset Regional Council, Ipswich City Council, and Toowoomba Regional Council.

It covers approximately 3,000 square kilometres, with the main channel, Lockyer Creek, surrounded by several sub-catchments. (click to play animation)

Water enters the Brisbane River from a number of catchments. The Upper Brisbane and Stanley catchments join from the north, via Wivenhoe Dam.

The Lockyer joins the Brisbane River in the Mid Brisbane section. The Bremer, Lower Brisbane and Oxley catchments join the Brisbane River downstream, east of the Lockyer, before reaching Moreton Bay

Values of the catchment

With a population of more than 35,000 people, the Lockyer catchment provides significant environmental, economic and social values. It contains areas of World Heritage listed Gondwana Rainforest and a number of other conservation areas.

Values of the catchment

The Lockyer Valley has some of the most fertile land for agricultural production in the world. The combination of its relatively flat topography, rich alluvial soils, and ideal growing climate has provided the opportunity for the Lockyer Valley to become a major supplier of vegetables, horticulture, and grains, producing 35% of Queenslands vegetable supply The catchment is also used extensively for grazing, mostly on native vegetation.

This soil is the result of catchment processes over thousands of years. Erosion in the steep slopes generates sediment, which is then deposited in the floodplains, creating the fertile soils for which the catchment is known.

Values of the catchment

The catchment also provides recreational activities such as bush walking, mountain biking, bird watching, canoeing, water skiing and fishing. These activities not only provide substantial social and health benefits but they are also very important for tourism.

Photos provided by Lockyer Valley Regional Council. Top left image: Alice Creek, Helidon Hills; Top right image: Lake Dyer; Bottom left image: Ma Ma Creek, Fordsdale; Bottom right image: Laidley Lookout, Buhse's Hill.

Natural features of the catchment - geology and topography

On the slopes of the southern and eastern side of the catchment, the landscape contains basalts.

Basalts usually enable high amounts of water infiltration and recharge the groundwater system with good quality water. However, some of the basalt in the lower parts of the catchment has a lower recharge potential.

Much of the remaining catchment is underlain by sandstone formations which aid water infiltration, but can also produce naturally saline groundwater.

Impermeable rocks to the north foster water run-off, with very limited water infiltration.

Around the main channel of Lockyer Creek, deep alluvial plains, made up of permeable silts, sands and gravels, absorb and hold water, and recharge groundwater systems.

Natural Features – Rainfall

The Lockyer Catchment experiences high rainfall in the south and parts of the north. The rest of the catchment has moderate to low rainfall, with some low rainfall areas around Ma Ma Creek.

Due to the steep slopes in the upper reaches of the catchment, many streams can experience high flows despite the relatively low rainfall.

Natural features of the catchment – vegetation

Historically, the catchment contained Iron bark woodlands, Semi-evergreen vine thickets, Brigalow, and Forest Red Gums with grasslands such as Black Spear grass, Kangaroo grass and Queensland Blue grass.^

This native vegetation slowed water, retaining it longer in the landscape and recharging groundwater aquifers, and reduced the erosion potential and the loss of soil from the catchment affects how water flows through the catchment, and this process is affected by land use and management practices.

Modified features - vegetation and land use

Half the catchment has now been cleared (click to see animation) for agriculture, urban development and industries. Some areas of vegetation have regrown since initial clearing.

While all of these developments are important, they do impact on water flow within the catchment. Clearing for urban development, and levelling of the land surface, creates impermeable surfaces, alters water flow paths and introduces the requirement for wastewater management. This leads to an increase in the amount and speed of surface water runoff carrying nutrients, sediments and pathogens.

Modified features - channels and infrastructure

Levees, though often used for flood mitigation, funnel water into channels, increasing water flow rate, which creates impacts further downstream, such as increased bank erosion.

Infrastructure such as roads, railways and creek crossings also create impermeable surfaces and barriers that redirect water through single points or culverts, leading to channelling of water and increasing water flow rates.

Modified features – dams

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

Seqwater owns and operates a number of water storages and weirs in the Lockyer Catchment which supply water to the Central Lockyer irrigation scheme, supporting local producers.

Lake Atkinson is located west of Clarendon township, near Buaraba Creek. The lake provides a range of recreational opportunities for visitors to enjoy including boating, water skiing, fishing and swimming.

Lake Clarendon is an offstream storage located east of Gatton. The lake provides recreational opportunities for paddle craft, fishing and bird watching activities.

Lake Dyer (Bill Gunn Dam), which is located west of Laidley, is an offstream storage filled by diverted flows from Laidley Creek. Boating, water skiing, fishing and swimming are recreational activities permitted at the lake.

Modified features - dams and weirs

Weirs have been constructed in the Lockyer Catchment to allow groundwater systems to recharge and provide water supply for irrigation activities. However, weirs can also significantly reduce the amount of water that can leave the catchment and can retain sediments and saline water until a high rainfall event occurs.

Rural water storages collect surface water for irrigation and stock watering, but this reduces the amount of water that would otherwise enter creek and wetland systems and recharge groundwater systems.

Modified features – sediment

Increases in the amount and speed of runoff can cause an increase in erosion in the landscape and the stream channels, resulting in sediment being carried downstream.

In the 2011 and 2013 flood events, more than 1 million tonnes of top soil entered Moreton Bay. Much of this soil came from the Lockyer catchment. In addition, parts of the Lockyer catchment are considered to have high salinity levels*.

Water flow

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 runoff 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 flood plain. These creeks pass through alluvial areas which have formed over thousands of years and are made up of silt, sand and gravels and other materials deposited by rivers. They store and release water like a sponge.

Groundwater generally flows from alluvia into nearby streams prolonging the time they are in 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 catchments, which form tributaries to the main watercourse within the catchment.*

The Lockyer catchment consists of many sub-catchments hosting a range of water environments, including groundwater reserves, creeks and rivers, lakes, reservoirs and wetlands.

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

*Definition sourced from the Gold Coast City Council website

Laidley Creek

Laidley Creek often receives high rainfall in the upper reaches . There are large areas of basalt and good vegetation cover. This helps to slow surface water runoff and gives the groundwater system time to recharge.

In the mid-section the geology changes to sandstone and the vegetation cover has been reduced through clearing. This reduces the potential of water to recharge underground systems, increases the amount and speed of surface water runoff, and increases the erosion potential and loss of soil.

Once the water reaches the lower section, the floodplain, the speed of water coming down the system, combined with significant reduction in riparian vegetation coverage and increase in infrastructure leads to many creek channels over topping and depositing sediment.

Sandy Creek/Forest Hill

Half of the Sandy Creek/Forest Hill area contains sandstones that produce naturally saline groundwater. The saline groundwater makes its way into the creek and alluvial groundwater systems, reducing the potential to use the water for irrigation activities. Therefore to collect good quality water for agriculture, surface water runoff is often captured in rural water storages, particularly in the lower parts of the sub-catchment. This reduces the ability to flush out saline groundwater from the sub-catchment.

Tenthill Creek

The upper section of Tenthill Creek generally receives very high rainfall and combined with the very steep slopes leads to rapid creek flows. In the mid-section, sediment is transported down the creeks due to the rapid flow of water, which is exacerbated by the reduced vegetation, infrastructure placement and human induced straightening of the creek. This has resulted in a number of areas where the creek breaks out of the channel. In high rainfall events, large cobbles and pebbles can be deposited leading to changes in creek paths.

The water loses energy and slows down when it reaches the floodplain and this is where fine sediment such as soil is often deposited.

Ma Ma Creek

Channel erosion and some soil loss occurs in the Ma Ma Creek sub-catchment due to its steep slopes and vegetation clearing, which promotes increased run-off. Due to the presence of saline sandstones there can also be some salinity issues.

Flagstone Creek

Flagstone Creek sub catchment contains very steep slopes and the rock types in the area have a lower groundwater recharge potential. Due to the generally lower quantity of water flows and good vegetation coverage in the upper sections, sediment or soil loss is minimised.

Gatton Creek

The upper section of Gatton Creek is very steep promoting water runoff and rapid creek flow. With vegetation clearing in the mid to lower parts of the catchment, sediment and soil loss can be significant.

Murphy's Creek

The head waters of Murphys Creek are very steep, where water run-off is high and confined channels, which appear gorge like in places.* This often results in extremely rapid water flows, with the water being funnelled down the sub catchment. The power of the water is so high that large boulders can be moved down the creeks^.

In the mid-section, creek channels are less confined by the hill-slopes. Below the township of Murphys Creek, the creek channel steepens as it enters a bedrock gorge for several kilometres and includes tributary junctions of 15 Mile Creek and

Paradise Creek where it becomes Lockyer Creek. In high rainfall events this section has very high water flow rates.

In the lower section the water slows due to flatter terrain and the presence of vegetation.

Sandy Creek – Grantham

In heavy rainfall events, the Sandy Creek/Grantham area has fast flowing water in its creeks, due to the steep slopes and rocks with low permeability which promotes surface water runoff. However, the system generally does not receive high rainfall and the groundwater recharge potential is quite low, so the creeks do not flow all year round. The lower section is flat and creek channels have been modified by historical in-stream sand and gravel extraction.

Buaraba Creek

Buaraba Creek has a high water runoff in the upper section due to the presence of an array of rocks with low permeability.

In the mid-section, significant widening of the creek channel has occurred as a result of modification to channels, reduced vegetation and sand and gravel extraction.

Once the flatter areas are reached the water slows down considerably, but will break across the channels in high rainfall events.

Woolshed and Plain Creeks

In Woolshed and Plain creeks the water rushes off the upper part of the catchment then hits a flat landscape relatively quickly, spreading out over the area and sitting in a string of small gullies and pools.

Due to the presence of vast areas of naturally saline sandstones in this area and shallow water tables, surface water readily evaporates, leaving saline deposits such as salt pans*. Non-sewered urban subdivisions bring even more contaminants into the creek system.

There is a natural geological constriction at the mouth of the sub catchment which limits the flow of water and contaminants out of the sub catchment.

Combined, all of these factors lead to poor water quality, which can weaken infrastructure such as roads and bridges. Unfortunately, water quality in the sub catchment is not improved until there is a high rainfall event where these contaminants can be washed out. If a high rainfall event has come down the Lockyer creek, water can flow up the lower sections of Woolshed and Plain creeks, flooding areas when this sub catchment may not have received significant rain.

Lockyer Creek

All of the water from the creek systems in these sub catchments flows into Lockyer Creek. The sub-catchments the water flows have originated from, and the intensity of the rainfall, determine the quality and quantity of the water in Lockyer Creek.

Lockyer Creek is described as being a macro-channel. This is a large channel that contains all levels of flood, except in the most extreme events. The volume and force of this water can pose a flood risk, especially if townships and infrastructure are within the channel or located downstream on the floodplain.

The quantity and quality of water is also affected by the large number of weirs and levees within the Lockyer Creek. Vegetation removal across all sub catchments has decreased the potential of groundwater recharge.

The construction of artificial levees confines water flows within the Lockyer creek, however, these levees increase water flow rates, erosion and removal of sediments. In times of high flows, this can create impacts downstream in the Mid Brisbane and Lower Brisbane catchments. During high flood events in the Lockyer Catchment, increased sediment is released into the Mid-Brisbane River which can impact on the Mt Crosby Treatment Plant, affecting the quality of drinking water for Brisbane residents, and contributes to the sedimentation in Moreton Bay Marine Park.

Conclusion

To reduce the amount of soil being lost from the Lockyer catchment and reducing salinity levels requires an understanding on how water flows within the catchment and how these flows are affected by the natural and modified features of the landscape.

Knowing how the catchment functions is paramount for implementing strategic actions that improve climate resilience, as it is forecasted that high rainfall events will be more intense and frequent.

With this knowledge, better decisions about how we sustainably manage this catchment can be made

Credits

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

The Lockyer Valley Regional Council

Somerset Regional Council

Ipswich City Council

Toowoomba Regional Council

Council of Mayors South East Queensland

Healthy Waterways (Healthy Waterways and Catchments)

SEQ Catchments

Seqwater

Queensland Wetlands Program (2016) Walking the Landscape - Lockyer Catchment Summary. Department of Environment and Science, Brisbane.

Photos provided by: the Department of Environment and Science, Department of National Parks, Sport and Racing, SEQ Catchments, Lockyer Valley 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

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

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Last updated: 25 August 2021