Groundwater Management Unit
Groundwater Management Unit: Oakey Creek Management Area
Introduction
The groundwater resource characteristics for the Oakey Creek Management Area groundwater managment unit are presented below. This includes technical detail on aquifer properties and water level change for key monitoring bores.
What is the character of Oakey Creek Management Area's groundwater resource?
Vital Statistics:
| Area | 213 km2 |
|---|---|
| Total Water Allocated | 9,663 ML/yr |
| Total Water Used | 3,798 ML/yr |
| Average Salinity | 1,345 mg/L |
| Sustainable Yield | 7,000 ML/yr |
| Depth to top of aquifer | 16 m |
Link to Queensland's GMU Cross-section diagrams: to view or to print
Aquifer Description:
The Oakey Creek Management Area GMU consists of a number of unconfined/semi-confined alluvial aquifers. The unconsolidated sediments of sand, clay and gravel occur as a continuous deposit within the geological formation known as the Oakey Creek Alluvium of Quaternary age.
The aquifers consist of silty and claybound sands and gravels of coarse to very coarse grain size. The aquifer material is moderately well sorted and generally the grain size coarsens with depth. The average saturated thickness of the aquifers is approximately 9m with the average depth to the top of the water bearing strata being approximately 16m. Clays of up to 2 m in thickness often divide the coarser basal deposits.
The specific yield of the aquifers derived from pump testing vary between 4 % and 12 %. An average of 8 % has been adopted in previous groundwater studies. Transmissivity ranges between 140 and 3000 sq m/d with an average of 650 sq m/d.
Upstream of Oakey, the alluvial aquifer deposits are shallow and extensive. The upstream aquifers are predominantly unconfined. Recharge to these shallow aquifers is good due to the incising of the Oakey Creek into the water table providing connection between surface water and groundwater.
Downstream of Oakey, the aquifers are both semi- confined and unconfined. The downstream alluvial aquifers are up to 40 m deep and extend to a width approaching 7 km. Oakey Creek is poorly incised here and any interaction between the creek and the aquifers is limited.
Aquifer recharge occurs due to losses from Oakey Creek and its tributaries and infiltration through the overburden. Recharge due to streamflow infiltration is more significant upstream of Oakey than downstream. Treated sewage effluent, discharged from the Toowoomba City Councils sewage treatment, provides significant baseflow to Oakey Creek which contributes to aquifer recharge.
Method used for determining sustainable yield:
In 1990, the sustainable yield for the alluvial aquifers of the Oakey Creek Management Area GMU was estimated to be 7000 ML/y using a water balance method.
Assumptions used for allocating development categories:
The sustainable yield of the Oakey Creek Management Area GMU is reported to be 7000 ML/yr.
The allocation volume for the GMU is reported to be 9600 ML/yr. The allocation is greater than the sustainable yield and can be assigned to Category 4.
Abtraction bores in the GMU are metered. Of the 9600 ML/yr allocated, only 4200 ML/yr is abstracted. This equates to approximately 60 % of the sustainable yield and can consequently be assigned to Category 2 or medium level resource abstraction.
Are groundwater levels changing?
Technical information on the key groundwater bores and monitoring stations is presented below, including hydrographs where available. Link to a discussion on groundwater levels and trends at a State level as it relates to dryland salinity.
| Bore ID | Start record | End record | Depth of bore (m) | Reduced level (m) |
|---|---|---|---|---|
| QLD42230934 | 30-Jan-76 | 06-Sep-99 | 59 | 386 |
| QLD42230955 | 08-Oct-76 | 07-Sep-99 | 33 | 506 |
| QLD42231295 | 27-Dec-84 | 07-Jul-99 | 42 | 379 |
| QLD42231299 | 07-Jan-86 | 06-Sep-99 | 42 | 409 |
| QLD42231300 | 07-Jan-86 | 06-Sep-99 | 24 | 435 |
| QLD42231302 | 04-Mar-86 | 06-Sep-99 | 20 | 425 |
| QLD42231303 | 07-Jan-86 | 06-Sep-99 | 59 | 413 |
| QLD42231304 | 07-Jan-86 | 06-Sep-99 | 16 | 414 |
| QLD42231305 | 07-Jan-86 | 06-Sep-99 | 64 | 414 |
| QLD42231307 | 07-Jan-86 | 06-Sep-99 | 28 | 402 |
| QLD42231382 | 08-Feb-88 | 06-Sep-99 | 38 | 406 |
| QLD42231395 | 31-Oct-90 | 06-Sep-99 | 26 | 386 |
| QLD42231396 | 13-Jun-90 | 06-Sep-99 | 29 | 392 |
| QLD42231398 | 09-Aug-90 | 06-Sep-99 | 25 | 392 |
| QLD42231399 | 08-Aug-90 | 12-May-99 | 38 | 396 |
| QLD42231400 | 14-Jun-90 | 06-Sep-99 | 26 | 395 |
| QLD42231401 | 20-Jun-90 | 06-Sep-99 | 75 | 396 |
| QLD42231404 | 21-Jun-90 | 06-Sep-99 | 17 | 400 |
| QLD42231405 | 27-Jun-90 | 06-Sep-99 | 21 | 421 |
| QLD42231406 | 09-Aug-90 | 06-Sep-99 | 15 | 437 |
The following groundwater management units also occur in Clarence-Morton Province:
- Alstonville Basalt (NSW)
- Central Lockyer Valley (QLD)
- Condamine - Condamine Groundwater Management Area Sub-Area 4 (QLD)
- Condamine River Alluvium (Cunningham to Ellangowan) (QLD)
- Condamine River Alluvium (Killarney to Murrays Bridge) (QLD)
- Condamine River Alluvium (Murrays Bridge to Cunningham) (QLD)
- Dalrymple Creek Alluvium (QLD)
- Flagstone Creek (QLD)
- Glengallan Creek (QLD)
- Kings Creek Alluvium (QLD)
- Laidley Creek (Upper Reach) (QLD)
- Lockyer - Helidon (QLD)
- Logan / Albert Rivers (QLD)
- Lower Lockyer Creek (QLD)
- Lower Oakey Creek Alluvium (QLD)
- Ma Ma Creek (QLD)
- Myall / Moola Creek North (QLD)
- Myall Creek (QLD)
- Nobby Basalts (QLD)
- North Coast Fractured Rocks (NSW)
- Richmond Coastal Sands (NSW)
- Richmond River Alluvium (NSW)
- Sandy Creek (QLD)
- Swan Creek Alluvium (QLD)
- Tenthill Creek (QLD)
- Toowoomba City Basalt (QLD)
- Unincorporated Area - Clarence Moreton (QLD)
- Unincorporated Area - Clarence-Morton Basin (NSW)
- Upper Hodgson Creek (QLD)
- Upper Lockyer Creek (QLD)
Further information
- Queensland Water Resources Assessment 2000 Report
- Queensland Water Resources Assessment 2000 Technical Report
- For more information about water and other natural resource issues link to www.nrm.qld.gov.au.
- Link to data available for download on the Groundwater management units and provinces - ARC/INFO export
- Link to Map maker to make a map using this information.
Key
Links to an another web site
Opens a pop-up window