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Groundwater monitoring - How and Why ?

GW0021
Salinty Extension Group, Bendigo
Published: June 2002

Why monitor groundwater?

  • Measure depth to watertable.
  • Measure trends of watertable and salinity.
  • Understand the causes of salinity.
  • Monitor the effectiveness of salinity management options.

When to monitor groundwater?

Figure 1: Bore Monitoring
Figure 1. Bore monitoring
  • Measure water levels monthly or as specified.
  • Measure at the same time each period.
  • Bail or flush the bore annually, but always prior to  salinity measurement.

Definitions

Figure 2. A bailer Figure 3. A Fox whistle
Figure 2. A bailer Figure 3. A Fox whistle

Salinity management options 

The adoption of perennial pastures, tree lots etc.

Bailer

Plastic tube with a hole and ball bearing valve used to sample the groundwater

Fox Whistle

Hollow metal or plastic tube with narrow air hole suspended at the end of a measuring tape. Make sure the fox whistle is calibrated correctly - the base should be equivalent to 0 cm on the tape.

Casing

PVC pipe that forms the wall of the bore, often  protected by a steel cover at the surface.

How to measure groundwater depth?

Lower the fox whistle into the bore

  • Stop lowering when the first whistle is heard, pull tape up slightly, and jiggle up and down to accurately establish the depth of whistle, hence groundwater level.
  • Read the depth off the tape at the top of the casing, check zero is the bottom of the whistle.
  • Record depth in the groundwater data booklet.

How to measure salinity?

Figure 4. A hand held EC meter
Figure 4. A hand held EC meter
  • Lower the bailer to the bottom of the bore, allow it to fill and withdraw it.  
  • Clear any muddy water at the bottom of the bailer by pushing the ball valve up slightly to release it.  
  • Rinse the measuring vessel with the bore water and fill with bore water.  
  • Put the EC meter in the water so the electrodes are covered, take the reading and record. Remember to record the units (usuallyµS/cm).   

Looking after your bore

To maintain meaningful records and ensure bore life, make sure:- 
  • The vented bore lid is always in place, to prevent debris and rainfall entering.  
  • The casing is in good condition. The bore may be prone to damage from vandalism and / or livestock. 
  • The bore is stable in the ground. If not, it may need to be cemented. 
  • The bore is marked and labelled, according to the CLPR system.

What to do with the data collected?

Record sheets should be forwarded to your NRE Salinity Extension Officer or CLPR every 6 months.

Your information is entered into the statewide dryland salinity groundwater database at CLPR in Bendigo, where it is used by hydrogeologists to interpret groundwater trends and processes.

Monitoring equipment can be obtained from NRE or through CLPR.

Further information

For further information contact your NRE Salinity Extension Officer or CLPR, NRE Bendigo  ph. 5430 4444.


Acknowledgments

This Information Note was developed by Salinty Extension Group, Bendigo