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Groundwater monitoring bores

There are two types of groundwater monitoring bores: testwells and piezometers.

Testwells measure the level of the local watertable and can highlight the potential for salinity before it becomes a problem. Testwells placed at several locations can provide an overall picture of groundwater levels in an area to assist in making salinity management decisions.

A testwell is made by placing a slotted PVC pipe in an augured hole, usually no more than 3 meters deep. The hole is then backfilled with gravel and clay and sealed with a bentonite plug. A floating marker flag can be placed in the testwell to indicate the approximate depth to the watertable.

Piezometers are special monitoring bores that are used to monitor regional groundwater levels. Piezometers measure the water pressure in an aquifer or the soil and can also be used to measure the depth to the watertable and the quality of water.

Piezometers consist of sealed PVC pipe of 20 - 40 mm diameter, with narrow slots cut in the bottom 25 cm to allow water entry. Because piezometers are drilled into an aquifer, they are usually installed at a depth greater than three metres. When three or more are installed at the same depth, horizontal groundwater movement can be determined; when installed at different depths at the same site, vertical water movement is monitored, indicating whether the site is acting as a recharge or discharge area, or an area of lateral water flow.

Measuring groundwater and salinity levels should be done regularly - about once a fortnight during irrigation and monthly during winter. To gain a good understanding of a groundwater system, groundwater levels should be monitored over several years.