Learning more about Ruamāhanga Valley aquifers

A helicopter will fly scanning equipment up and down the Ruamāhanga Valley to gain as complete a picture as possible of what’s happening below ground. 

The helicopter will fly in parallel lines approximately 200-metres apart to complete this scan. The helicopter will travel at 80-100 km/hr. So, if the helicopter passes over where you are, you’ll hear it again later when it passes by approximately 200-metres away. 

The helicopter will fly around 80-metres above the ground. The equipment suspended below the helicopter will be around 50-metres above the ground.   

The pilot will avoid towns, as well as houses in rural areas. They’ll also cross perpendicular to roads, rail lines and power lines, as metal and electricity interfere with the signal. 

The noise from the helicopter has been described as the equivalent to a truck going past on a motorway, and lasts for less than a minute.  

Watch a short video of the SkyTEM helicopter in action:

This technology is safe for people and animals. The helicopter pilot will also take extra care not to disturb livestock or horses when flying overhead. 

These videos show how horses, sheep and deer respond when the SkyTEM helicopter flies overhead: 

How horses respond

How sheep respond 

How deer respond

As your Regional Council, we’re responsible for making decisions about the Region’s water; for example, how it’s used.   

Right now, we know a lot about the water above ground in rivers, streams, lakes, and wetlands. But we don’t yet know much about the water below ground (groundwater).  

The results of this aerial survey will give us a view of our aquifers we’ve never had before. This information will: 

• Fill in the gaps in our knowledge about groundwater in the Ruamāhanga Valley 
• Give us a more complete view of the water above and below ground and help us better understand the interconnections between groundwater and surface water. 

This information will help us make better decisions about water.  

This is especially important when you consider how climate change could impact aquifers.  

Climate change projections say average temperatures in the Wairarapa will keep increasing over the coming decades, potentially resulting in water shortages. 

When complete, a 3D aquifer map, related research, and any models we develop will be made available to everyone on our website.  

These flights are not being used for compliance monitoring. We only want to know about water – not what’s happening on your property.  

Groundwater is the water found underground in the cracks and spaces in soil, sand, and rock. It is stored in and moves through geological formations of soil, sand and rocks called aquifers. 

Watch this video from GNS Science to learn more about groundwater:  

In basic terms: The electromagnetic SkyTEM system creates a gentle electrical current that travels up to 300-metres underground.  

This current behaves differently based on the materials it passes through underground. The equipment records how easily the current passes through different materials. This will help us identify what materials underground layers are made up of. For example: sand, gravel, and clay.   

It’ll take up to two years to stitch this detailed data together and create a 3D map of what’s below the surface of the Ruamāhanga Valley. 

The current generated by this equipment is safe for people and animals. It’s no different from watching an LCD or plasma TV or blow-drying your hair. 

In scientific detail: The SkyTEM system is an airborne transient electromagnetic system. The system uses a magnetic field to generate an electric current in the subsurface (an eddy current) and then measures the behaviour of that induced electric current. Such measurements can be used to infer subsurface properties relevant to understanding groundwater resources. 

As rocks are composed mostly of silicate minerals that are essentially insulators, electrical conduction is dominated by electrolytic conduction, and depends mainly upon porosity, permeability, moisture content, concentration of dissolved electrolytes, temperature and phase of pore fluid, and amount and composition of clay content. 

Groundwater acts as an electrolyte, and so increases the conductivity of water-bearing lithologies. This conductivity increase depends on the volume of water as well as the chemical composition of the water. Fresh water is resistive, but contaminants such as clays and/or salt will increase its conductivity. 

SkyTEM airborne electromagnetic survey technology was developed by the Danish Government and Universities to make efficient and effective mapping of groundwater resources possible. 

The technology has been used commercially since 2004 to map large aquifer systems in countries including Denmark, Netherlands, India, USA, Canada, Australia, and New Zealand.  

SkyTEM technology can map the subtle changes between sand, clay, silt, and gravel that define the location of groundwater resources.  

Find out more about SkyTEM 

To date, we’ve found out about the rock and water underground from drilling boreholes, which provides detailed information but in limited locations.  

This electromagnetic scan will provide a more complete picture of the Ruamāhanga Valley’s complex geology and water, up to 300-metres underground.  

The image below is from Denmark. It shows the limited information gained from drilling 518 boreholes (Figure 1) compared to the rich information gathered through conducting electromagnetic scans from the ground in 1,400 locations (Figure 2): 

Purple and blue areas in these maps indicate aquifers. The transient electromagnetic (TEM) scans:  

• Provide a more accurate picture of the aquifers below ground 
• Revealed completely unknown aquifers in the area. 

The TEM scan results were verified by drilling new boreholes. 

In the example above, TEM electromagnetic scanning equipment was used. TEM uses the same technology as the SkyTEM equipment we’ll use, but the difference is that scans are carried out from the ground.  

SkyTEM technology makes it possible to scan large areas quickly from the air. This airborne approach is more cost-effective. Plus, scanning from the air means you can capture data from more locations, which provides a more accurate picture of what’s underground than a ground-based TEM survey. 

Reference: Rethink Water & Danish Water Forum. 2013. Groundwater mapping and sustainable groundwater management. White Paper. http://skytem.com/wp-content/uploads/2014/12/Greater-water-security-with-groundwater.pdf 

The table below shows where we’re planning on flying next. But since we need settled weather to survey a location, any wind or rain could mean we need to adjust this plan ‘on the fly’.  

This means the information below is just an indication of when we’ll be in a specific spot. If weather conditions change our flight plan will too.   

When	Where	Map
3 March 2023	And that’s a wrap! Thanks to a few good days of weather, we were able to finish our final flights and wave goodbye to the helicopter and loop. We collected a huge amount of data about Wairarapa aquifers during these flights! So, it’ll take two years to analyse this data and develop a 3D map of the Ruamāhanga Valley’s aquifers.	Click for full picture
23 Feb - 2 Mar 2023	We’ve passed the halfway point in this survey!   Over the last few days, we’ve been surveying the area west of Greytown, Carterton, and Masterton.  From 23 February we’ll fly around the outside of these towns and to the east of Masterton.  Important note: We don’t fly over towns, just rural areas. That’s because metal interferes with the equipment signal and there is a lot of metal in buildings in urban areas.   Do you know how high we fly?  Our helicopter files around 80-metres above the ground. That means the survey equipment suspended below it will be around 50-metres above the ground. People have told us the level of noise is like a big truck driving past on the highway.	Click for full picture
21 – 22 Feb 2023	Next, we’ll focus on the northern part of the Wairarapa Valley, which includes working around the edges of Greytown, Carterton and Masterton.  But, we don’t fly over towns, just rural areas. So you won’t see us in the air over these towns.	Click for full picture
18 – 20 Feb 2023	If the weather is fine enough – we’ll carry on surveying the area we were covering before Cyclone Gabrielle. This area was the central and northern part of Lake Wairarapa - extending across to Martinborough and the hills to the east. Work in this location had been taking a bit longer than we originally planned due to poor weather conditions.  A reminder that we don’t fly over towns, just rural areas. So you won’t see us in the air over Martinborough or Featherston.	Click for full picture
14 Feb 2023	We’ve had to pause flights due to severe weather and strong winds caused by Cyclone Gabrielle. We’ll update you again when flights resume.
11 – 13 Feb 2023	Flights continue over the central and northern part of Lake Wairarapa and extend across to Martinborough and the hills to the east.  If the weather is fine and settled, we’ll start approaching the southern edge of Featherston.  But we don’t fly over towns, just rural areas. So you won’t see us in the air over Martinborough or Featherston.	Click for full picture
8 - 10 Feb 2023	We’re planning to fly north of Lake Onoke - potentially as far north as central Lake Wairarapa.	Click for full image
3 - 7 Feb 2023	We’ll continue flying in long lines across the valley to calibrate our equipment.   Then we’ll start surveying from the coast in the south to the southern end of Lake Wairarapa. But at the time of posting rain is predicted, so this plan could change.  Note: Strong winds impacted this flight plan.	Click for full image
29 Jan – 2 Feb 2023	We’re conducting initial flights across the Ruamāhanga Valley to help us prepare to survey specific areas.	Click for full image