The process requires some considerable expertise to calibrate the data and produce reliable mapping outputs so it is recommended that you obtain some quotes before you start mapping your salinity using this technology.
Ask to see samples of finished property salinity maps (both surface and Depth EM) to give you some further guidance in selection of a suitable contractor.
The EM equipment is now available in most States of Australia and you should initially make enquiries at your local Department of Agriculture to identify any local service providers.
The image on the left is the GPS plot of the route taken by the quad bike across Kevin Moir’s property in Western Australia. The track lines on this map are made by the GPS recordings taken as the quad bike went up and down the paddock at 45 meters intervals. You can see on this map where the bike has had to deviate to avoid gullies, trees and other obstacles.
The image on the right is the arial photo of the property surveyed. You can superimpose the bike tracks onto the property topography to determine the extent of the coverage of the survey. Note that most bush areas weren’t mapped as it was impossible to get the bike in amongst the trees.
The map below was produced by the EM38 unit which measures salinity within the top 0.75 metre of the soil and subsurface. Areas of high salinity are clearly shown in red. These show up on the ground as bare salt scalds, often with the white salt crystals at the surface.
At a first glance it appears that the property does not have a major salinity problem and that salinity is confined to a few gullies. However, this map does not tell the full story with salinity on this property.
The second map below was produced for the Moir property by the EM31 unit which measures and averages salinity below the surface to a depth of 6 metres. You can clearly see from this map that the subsurface salinity problem is much more widespread and could potentially cause serious problems if water tables are allowed to rise. The property owner must try to ensure that water table does not rise bringing with it increased salt level to the surface where plant roots are trying to grow.
The comparison between the EM38 Surface salinity map and the EM31 Salinity at depth map is best seen when you place them side by side.
Notice how, while the gullies on the property remain the worst areas for salinity both at the surace and at depth, the other areas show that the salinity is sitting below the surface, on top of the water table and the salt could easily rise to the surface and kill off pasture if water tables rise.
These two maps would also be very valuable information in terms of where to site new dams to ensure best chances of getting fresh water inflows.
To contact Topoclimate Services Pty Ltd visit the website www.topoclimate.com or email me garyh@topoclimate.com.
