Real-time monitoring helps irrigators to be water wise

The Gnangara Mound, north of Perth, is currently supplying up to 60% of Perth's drinking water. It also supports a peri-urban horticultural industry and water for private and public parks and gardens. As rainfall continues to decline, and demand for water increases, putting pressure on its reserves, better understanding of the Mound’s water balance is required.

Managing our limited groundwater resources to minimise environmental impacts, making informed water allocation decisions and implementing water-wise farming all require an accessible, reliable and continuous data stream on abstracted volumes, water level and quality changes.

Knowing when to 'turn off the pump' to avoid over-watering, managing consumption within water allocation limits or to avoid saltwater intrusion will assist the community to better manage and conserve available water resources.

The Water for a Healthy Country Flagship, in partnership with the WA Department of Environment and Schlumberger Water Services is trialling continuous acquisition, transmittal, and processing of water abstraction, groundwater level and groundwater quality data. The data resides at a central location for display of real time groundwater conditions over the Internet via a website portal. A pilot demonstration project was recently completed at Carabooda on the Gnangara Mound north of Perth using a real time monitoring system to deliver consistent, reliable data.

Flow meters were installed on abstraction bores adjacent to five monitoring wells, on five horticulture properties. The flow meters measured the volume of water extracted every hour, whilst data collected from the monitoring wells generated temperature and pressure (depth) readings of water in the aquifer.

The data was then transmitted to a data management system where it was downloaded in real-time to a central web site for immediate display and analysis. This allowed participants to access the information as needed and helped them make decisions such as when to pump and for how long.

Results show the benefits of ready access to current, consistent, and accurate data. The hourly recording of groundwater movements has provided an accurate picture of the rise and fall within the aquifer and the potential link to the volume of water extracted. The information helps each farmer see the variation in groundwater levels between seasons and over the course of the season.

The Gnangara Mound Real Time Pilot Program will provide regulators, users and the general public with a snapshot quantification of groundwater usage, localised impacts of abstraction, and water use patterns. It may also assist in the implementation of seasonally-adjusted allocation policies, as proposed under the shared-consumptive-pool approach proposed by National Water Initiative.

Additional data was also collected manually from the Department of Water monitoring wells, which surround the pilot properties to incorporate regional aspects. Data collected will supplement existing historical data provided by the WA Department of Water and will be used to calibrate groundwater models already being used to inform extraction decisions. The information will also be used to estimate aquifer properties and water use response, and ultimately to develop environmental policies and water allocation plans to manage private and public abstraction across the area. There is potential to extend this research to include other groundwater management areas on the Swan Coastal Plain.

Water meters are now being implemented on farms on the Gnangara Mound, limiting the amount of water able to be extracted. If a farmer needs extra water this will need to be purchased from a neighbour, much as occurs in the River Murray System.

The project is supported by CSIRO, in collaboration with Schlumberger Water Services, the WA Department of Environment Metering Program and the Swan Catchment Council Water-Wise on the Farm project.

For more information contact:
Dr Claus Otto, CSIRO Petroleum Resources
08 6436 8745  claus.otto@csiro.au

Figure 1 shows the effect of pumping on the groundwater level on a farm.

Figure 1: (measuring level, flow and rainfall on a farm):

• The graph shows the effect of pumping on the groundwater level on a farm. The groundwater level dropped by about 40 cm in one month (dark blue).

• The cumulative pumped volume (orange) is calculated by adding up the hourly flowrates.

• There were two periods in which the groundwater level recovered, but it is not known at this stage the relative contribution of rainfall (light blue), breaks in pumping (green) and groundwater movement and on the recovered level.

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