AGL’s Water Portal allows members of the community to access data from our extensive network of water and weather monitoring stations across our natural gas project areas in NSW.
The Water Portal contains information from our groundwater and surface water monitoring programs. In each project there are several water monitoring sites that have “live” data (or telemetry) that is updated daily on the map. Each “live” site records water level, and possibly also water quality (salinity), at six-hourly intervals and then the data is sent from each monitoring point once daily.
All the water monitoring sites (including the “live” sites) also show recent manual downloads of the water level data and a summary of results from recent water quality analysis.
The weather stations are updated each hour.
At each live site we have installed a solar powered base station that collects signals from each groundwater monitoring bore or stream gauge via radio signal or direct cables. The base station is equipped with a 3G modem (similar to a mobile phone) that sends the data each day to a server located in Sydney. AGL’s Water Portal website then automatically reads the signal and updates the data on the website. The process of getting data from a remote site in this way is known as telemetry.
The satellite image is being read directly from Google Maps. In most areas the image is several years old and might not represent the current situation.
Groundwater is the name for all water in rocks and soil below the ground. Rainwater can seep into the soil and rock by slowly moving through tiny spaces (pores or fractures), like a sponge. The depth at which the soil or rock spaces (pores or fractures) becomes completely saturated is called the water table. Some rocks (like sandstone) allow water to move through them at faster rates than others (like shale or claystone). This is because they have more connected spaces for the water to move through so they can hold and transmit more water. These rocks are called aquifers. Rocks that don’t have a lot of connected spaces (like shale or claystone) do not let water move through them very well and they can act as a barrier to the slowly moving groundwater. These barrier-like rocks are called aquitards.
Similar to a drinking straw, a monitoring bore lets us find out what is happening with groundwater. We drill a hole into the ground and install a sealed pipe that has tiny holes at the bottom to let groundwater enter the pipe. The groundwater rises up the pipe to a water level that reflects the water pressure in that aquifer where the bore is installed.
We often put several monitoring bores next to each other, installed to various depths, to monitor groundwater in different aquifers or groundwater systems. We can then measure the water level and water quality in each of the bores to see how they relate to each other and how they change over time.
We typically measure water levels in groundwater monitoring bores in two ways. We lower a piece of equipment called a datalogger into the bore so that it sits in the water column. Every 6 hours it collects a reading of how much pressure it detects, which can then be translated to work out what the water level in the bore is. We leave the datalogger down the bore for 3 months and then manually download the data. Some of our bores transmit live water level (and sometimes salinity) data which is then updated the site daily on the Water Portal.
Another way our hydrogeologists measure groundwater levels is by manually lowering a piece of equipment down the bore, called a dipper. The dipper has a water sensor on it and will send a signal back to surface that tells us how far down the water is in the bore.
A monitoring bore has a screen of holes cut into the bore casing. This allows groundwater from the depth of the entire screen to enter the bore. So, the groundwater that we are monitoring for each bore is the groundwater that exists at the depth of the entire screen.
The water level of a groundwater system reflects the pressure in the monitored aquifer. When a monitoring bore is installed, there are holes cut into the casing towards the base of the bore (called a “screen”) which allows water at that depth to enter the bore. The water will rise up the bore to a level that reflects the pressure in that groundwater system. For a water table aquifer that is unconfined, the water inside a monitoring bore will rise to the height or level of the water table. For a deeper aquifer, there might be more water pressure and the water level might rise a long way up the bore reflecting this pressure. In some cases (in the Queensland Great Artesian Basin) deeper aquifers can have very high pressures and the water can rise above the ground in some bores. By monitoring the different water levels, or pressures, in aquifers we can understand a lot about how the groundwater systems interact with each other and also whether there are any changes over time.
Water level charts show how the water level of each bore changes over time. For our projects that have weather stations (Gloucester and Hunter) this data can be compared against daily rainfall. For some shallow groundwater monitoring bores and also surface water monitoring gauges, you can see that the water levels change a lot and quickly as a result of rainfall. Deeper groundwater levels might respond to rainfall in a more delayed or reduced way, or maybe not at all. Seeing how water levels change and also how they compare with higher or lower groundwater systems can tell us a lot about the underground environment.
Comparing rainfall against groundwater level is useful as it shows how connected the groundwater system is to the surface. Typically alluvial (shallow) groundwater responds quickly to rainfall; you will see a rise in the water level after heavy rain. Whereas, deeper groundwater systems respond later and less significantly. Groundwater systems that are not connected with the surface (at that location) will show no change in water level after rainfall.
Gaps in data may represent periods when the monitoring equipment is offline due to maintenance or faulty equipment being replaced.
We have installed telemetry equipment (allowing for live data) at many of our monitoring points, but particularly the ones that are nearby to our current production or exploration activities. We still collect data from the monitoring points that do not have telemetry equipment and the most recent data is also uploaded onto the Water Portal.
Dips or troughs in the groundwater level and/or salinity data are usually a result of a sampling event. The groundwater monitoring bore is purged (to allow new water to flow in) prior to sampling to ensure that the sample is representative of the groundwater system. In groundwater systems that have low flow (or low permeability) this can cause a dramatic drop in water levels and sometimes it can take weeks or months for the water level to return to the typical level.
This is to do with the permeability and porosity of the aquifer, or the ability for the rock to let water move through it. Groundwater systems with low permeability and/or porosity can take weeks or months for the water level to return to normal after the bore has been sampled. Whereas, shallower permeable aquifers (like river sands) will recover to normal levels almost immediately after taking a sample.
Water samples are taken by suitably qualified personnel trained in water sampling, including AGL employees and specialist consultants. Samples are taken according to the Environment Protection Authority (EPA) Approved Methods are analysed by Australian National Association of Testing Authority (NATA) accredited laboratories.
To take sample from a groundwater monitoring bore, firstly, we remove the water that has been sitting in the bore by pumping it out, to make sure the sample that we get is representative of water from the rock and hasn’t has time to settle in the bore. Once we have removed enough water, we then continue pumping so that we have enough water to fill up our sample containers. Sometimes we install special equipment inside the bores, called MicroPurge, which allows us to access deep groundwater straight from the rock. Depending on how deep the bore is and whether we have installed MicroPurge, we might pump out between about 20 litres to 200 litres from each bore before we take our sample.
Once we have the samples in containers we store them in an iced cooler box before taking them to a third party, NATA accredited laboratory for analysis. It usually takes at least 2 weeks before we get the results.
The comprehensive analysis we do on each sample depends on the purpose of each water monitoring location, whether it is to understand the groundwater systems during the early stages of our activities and to establish baseline measurements, or to monitor the groundwater and surface water systems in an area where we are testing for or producing natural gas. The water quality information on the Water Portal is a summary of analysis, and includes dissolved metals and common salts, which are very useful for understanding groundwater.
Typical salinity ranges for different water types are shown in the graph below.
There currently is no AGL weather station within the Camden Project. For our analysis and interpretation work we rely on weather data collected from the nearby Bureau of Meteorology weather stations.
The target coal seams are at different depths depending on the local geology at each project site.
The Camden Gas Project has been producing natural gas from two coal seams for NSW since 2001 – these coal seams are between about 550 and 700 meters below the ground. Each coal seam is about 3 meters thick. The coal seams are separated from the shallow groundwater resources by around 400 meters of rock, including aquitards.
The coal seams that we are exploring in the Gloucester Gas Project are between around 250 and 1000 meters below the ground.
Within the Hunter Valley, AGL has explored coal seams that are between 250 and 1000 meters below the ground.
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