Australian Natural Resources Atlas

Natural Resource Topics

Water resources - Management and Development - Queensland

Location map of Dawson River (Cracow to Theodore)

Groundwater Management Unit: Dawson River (Cracow to Theodore)

Introduction

Management Context:

In 1987, water quality was noted as the major limiting factor in the development and use of groundwater resources in the Dawson River groundwater management unit. Until February 1985, Theodore obtained town water supplies from bores in the Dawson River alluvium with an average annual use of approximately 150 ml/yr between the years of 1972 and 1985. However, as a result of deteriorating water quality, Theodore's town water supply is now obtained from the Dawson River. The high salinity of most of the groundwater resources in the Dawson River GMU precludes use for domestic purposes and limits usage for irrigation.

The combination of rising groundwater levels and the existing high salinity could eventually result in saline discharges to the Dawson River and may affect the productivity of overlying soil through the development of salt scald patches, and/or waterlogging. Continued saline discharges to the Dawson River will inevitably result in a deterioration of water quality in the Dawson River which may compromise other beneficial uses downstream.

Rising water levels in the Dawson River GMU are attributed to a variety of influences. Inflow from the Castle Creek catchment is a primary contributer to rising water levels due to water balance modifications in the catchment and valley floor following land clearing. In addition, infiltration and recharge from the network of earth channels and drains that comprise part of the infrastructure of the Dawson Irrigation Scheme also contribute to rising water levels. Other influences are the insitu deep drainage through the alluvium following rainfall, irrigation infiltration, run off and seepage from the adjacent and underlying bedrock. However, should Nathan Dam proceed, the monitoring network will require expansion to monitor impacts of increased surface water usage on groundwater system. If this development does proceed, it is expected that groundwater usage will reduce in favour of surface water and rising water tables may become a problem.

Priority issues

Declining Water Levels

 NO

Salt Water Intrusion

 NO

SALINISATION

Dryland

 NO

Irrigation

 YES

Groundwater

 YES

Surface Water

 YES

Urban

 NO

Point Source Pollution

 NO

Diffuse Source Pollution

 NO

Subsidence

 NO

Artificial Recharge (ML/yr)

 no data

Ecosystems Protection

 YES

Surface Water Interaction

 YES

Management Plans

 NO

Defined Minimum Water Level

 NO

Comment: Concern over rising water levels in the Dawson River alluvium was raised in 1987, due to potential problems developing with respect to salinization and/or water logging.

Comments on Management Responses

2020 Management Response:

The estimate of 8000 Ml/yr for the forecast use for the year 2020 is based upon the GMU's assessed sustainable yield, development potential and the desired level of resource management.

2050 Management Response:

The estimate of 8000 Ml/yr for the forecast use for the year 2050 is based upon the GMU's assessed sustainable yield, development potential and the desired level of resource management.

See QLD Water Resources Assessment 2000 Technical Report for a review of management responses.

Assessment of monitoring in Dawson River (Cracow to Theodore)

Efficacy of the network:

The current monitoring network for the Dawson River groundwater management unit consists of 46 observation bores, with a proposed bi-annual to quarterly monitoring frequency.

Regular monitoring of water levels in observation bores situated on the alluvium of the Dawson River commenced in 1970/71. Water levels have been read on a quarterly basis since the commencement of monitoring, with the exception of the years between 1986 and 1988 when the frequency of monitoring was increased due to concern over the progressively rising water level. The monitoring network was expanded in 1993 to monitor in areas of increased groundwater usage south of Theodore.

In 1988, the introduction of a combined surface and groundwater monitoring network was proposed in order to establish an adequate information system to assess water quality changes, or detect water quality trends in the Dawson River groundwater management unit. Such a comprehensive water quality database would allow for well informed management decisions to be made. The proposed monitoring program that incorporates surface water monitoring stations, drain outlets and groundwater bores, would be adopted for 5 years, which is considered to be the minimum period to detect any long term trend in water quality, after which, this additional network would be reviewed and modified accordingly.

Data management requirements:

Queensland groundwater monitoring data, both water level and water quality, is stored within the Groundwater Database (GWDB) system. The new system is based on web technology and is available through the Department's intranet. Allocation and use data is obtained through the Water Entitlements Registration Database (WERD) which is an electronic database for water licence details. Both databases are managed locally at district level, with respect to the collection and entering of water monitoring, allocation and use data; and are accessed statewide.

Protective management:

Management of the groundwater resource of the Dawson River groundwater management unit aims at maintaining a longterm, sustainable resource and therefore, requires the accurate monitoring of groundwater extraction, water level and water quality fluctuations. Monitoring and assessment are required to ensure that the groundwter table in the northern section of the GMU does not rise to the extent that it becomes a problem in the Theodore Irrigation Area to ensure that brackish water does not discharge into the Dawson River.

Options for monitoring:

Options for Commonwealth and State agencies to address data and information gaps include:

the installation of data loggers to better monitor the hydrologic processes that are occurring.

See QLD Water Resources Assessment 2000 Technical Report for a review of monitoring.

What is the estimated demand for groundwater?

Sustainable Yield

Comment about sustainable yield figure: 

An assessment of 8000 Ml/yr for specific yield was determined in 1999 based upon previous exploratory investigation drilling and testing of production bores which provided both the yield and hydraulic characteristics of the aquifer.

Sustainable yield:

ML/yr

Threshold year for sustainable year:

2,010 

Abstraction Volume 1996/1997:

4,000 ML 

Current Resource development categorisation:

Estimated Use in 2020

Comment:

Estimated use in 2020:

8,000 ML 

% change from 1996/1997:

100 

Resource development categorisation:

Estimated in 2050

Comment:

Estimated use in 2050:

8,000 ML 

% change from 1996/1997:

100 

Resource development categorisation:

 

What assumptions were used in this assessment

Development Potential:

Allowing for constraints such as water quality and supply rates, moderate potential for development and use of the groundwater resource exists in the Dawson River groundwater management unit. The alluvium downsteam of Nathan Gorge appears to have significant groundwater storage that is currently within sustainable levels as a source of water supply for irrigation purposes. However, water quality is the major limiting factor in the development and use of groundwater resources within the Dawson River groundwater management unit.

The combination of rising groundwater tables and existing poor water quality could eventually cause saline discharges into the Dawson River and affect the productivity of the overlying soil by developing scald patches and/or waterlogging. Changes in the water quality of the Dawson River will inevitably occur with any new surface water irrigation development upstream and within the groundwater management unit. Deterioration of the water quality in the Dawson River would possibly compromise other beneficial uses downstream.

Estimate of Use:

The estimate of 8000 Ml/yr for the forecast use for the years 2020 and 2050 is based upon the GMU's assessed sustainable yield, development potential and the desired level of resource management.

Data Availability,Gaps and Recommendations

Data Availablility:

Approximately 100 observation bores, both private and State owned, are located within the Dawson River GMU. The availability of water level data is high, with continuous water level monitoring from 1971 to the present in 46 observation bores. Comprehensive water quality data exists for 56 observation bores within the GMU, with recent analyses from 1991 to the present.

Current Gaps and Recommendations:

Data Gaps: Formal use and allocation data is not available for the Dawson River GMU, as it is not located within a declared sub-artesian or irrigation area.

Recommendations: Groundwater abstraction south of Theordore requires monitoring to identify whether overdevelopment of the groundwater resource is occurring. Should Nathan Dam proceed, the monitoring network will require expansion to monitor impacts of increased surface water usage on groundwater system. If this development does proceed, it is expected that groundwater usage will reduce in favour of surface water and rising water tables may become a problem.

Future Gaps:

Groundwater abstraction south of Theordore requires monitoring to identify whether overdevelopment of the groundwater resource is occurring. Should Nathan Dam proceed, the monitoring network will require expansion to monitor impacts of increased surface water usage on groundwater system. If this development does proceed, it is expected that groundwater usage will reduce in favour of surface water and rising water tables may become a problem.

Further information

Key

   Links to an another web site
   Opens a pop-up window