SkyTEM groundwater survey of the Katfish Section

SkyTEM Katfish Australia

SkyTEM Australia is conducting the first-ever three-dimensional groundwater survey of the Katfish Reach section of the floodplain and part of the Gurra Gurra Lakes complex.

Data from the airborne geophysical survey will shape future management of the floodplain to restore flora and fauna including native river red gums.

Read article in ABC Riverland here.

Video of SkyTEM Survey over Reunion Island 2014

SkyTEM EM survey over Reunion Island

BRGM (Bureau de Recherches Géologiques et Minières – the French Geological Survey) has published a video from the SkyTEM survey over the French island Reunion conducted in 2014.

Reunion is a volcanic island with a unique morphology, located in the Indian Ocean. The purpose of the survey was to scan the top 200 metres for a 3D visualization of the subsurface of the entire island in order to map aquifers, salt water encroachment, exploitable minerals, possible landslides and other geological features. This magnetic and electromagnetic survey comprising 10,000 line kilometers using the SkyTEM technology made it possible to produce high resolution maps of the subsurface even in areas with complex, or even inaccessible, terrain. The data collected represents an immense source of useful information for geologists and will be made available to the public.

The video is in French but shows the challenging terrain of the beautiful island, and the animations give a good comprehension of the unique SkyTEM technique and equipment as well as of the 3D images created from the data collection.

See the video on BRGM’s website here.

XRI Conducts SkyTEM Survey in Eastern Nebraska

SkyTEM system

Exploration Resources International Inc. (XRI) is conducting an Airborne Electromagnetic (AEM) Survey under contract to the Eastern Nebraska Water Resources Assessment (ENWRA). ENWRA is a coalition of six Natural Resources Districts (NRD’s) in the glaciated area of eastern Nebraska Including Lewis in Clark, Lower Elkhorn, Papio-Missouri, Lower Platte North, Lower Platte South, and Nemaha. XRI will collect the AEM data using the SkyTEM (Aarhus, Denmark) SkyTEM508 system flown by SkyTEM Canada Inc. (Ontario, Canada ) with subcontractors Southern Helicopters Inc. (Baton Rouge, LA) and Devbrio Geophysique Inc. (Quebec, Canada).

This survey is to continue a reconnaissance study of eastern Nebraska, that was begun in the northern portions of eastern Nebraska in October of 2014, by collecting approximately  700 line miles of data south of the Platte River to the Kansas State boarder in Butler, Saunders, Seward, Sharpy, Douglas, Lancaster, Cass, Otoe, Johnson, Nemaha, Richardson, Pawnee, and Gage counties.  XRI will use the AEM data collected to develop a hydrogeological framework of the area.  Results of this study will be delivered to ENWRA in July of 2015.

SkyTEM is currently mapping groundwater in Western Australia

Mapping groundwater in WA

The Government of Western Australia – Department of Water has commissioned SkyTEM Australia to conduct an airborne electromagnetic survey over the Murchison and Greenough River catchment basins as part of a Royalties for Regions funded regional water provision and management initiative.

The survey forms part of a four-year project to map groundwater resources and assess aquifer sustainability. The purpose is to assess the quantity, quality, availability and recharge of the groundwater resources in a key region which has a great demand for large supplies of low salinity water for urban water supplies, mining and agriculture without compromising the environment.

This survey, which comprises some 15,000 line kilometres of helicopter flying and covers an area of 57,000 square kilometres, is one of the largest of its kind in WA. The survey commenced in late January and will continue for several months.

“We are very proud that SkyTEM was selected for this project”, says Steven Johnson, General Manager of SkyTEM Australia. “It substantiates that the SkyTEM technology is regarded as the premier system worldwide for airborne electromagnetic groundwater mapping. The SkyTEM308 system provides accurate and reliable high-resolution data in a quick and cost-effective way”.

Read more about it here: http://www.abc.net.au/news/2015-02-25/ancient-water-channels-to-be-mapped-in-the-murchison/6262688

Yarwun Tailings Storage Facility

Yarwun-Tailngs-Storage-FacilitySkyTEM Surveys’ Australian partner, GroundProbe, conducted an airborne suvery for Rio Tinto Alcan to assess current and potential impacts of planned expansions to its Yarwun Tailngs Storage Facility (TSF).

Using the unique high-resolution and calibrated SkyTEM airborne system, GroundProbe was able to clearly define several major geological structures that are possible conduits for groundwater flow from the USF and therefore need to be investigated carefully.

By combining the airborne data with borehole logging and sampling information, an integrated hydrogeological investigation and analysis of the area was performed. This resulted in a more accurate hydrogeological model than would be otherwise possible, as shown below.

The result fo this process is that the cuyrrent TSF at Yarwun can now be managed in a more effective manner and the planned expansions designed ensuring there will be minimum impacts on the area’s groundwater regime.

combining airborne data with borehole logging

Map of results with air photo, clearly showing important features

Exploration of buried valleys / paleochannels

Exploration-buried-valleysSetting

Denmark is a world leader in mapping groundwater resources. In the 1990s in order to locate and protect the country’s natural resources the Danish Government embanked on the ambitious plan to map the subsurface of the entire country. The Danish Environmental Protection Agency (EPA) set out to determine the extent of the groundwater resources in the country as well as to gain an understanding of where they could be vulnerable and in need of protection.

Solution

The SkyTEM TDEM method is designed to be sensitive to subtle resistivity variations in soil and rock and is the ideal tool for mapping the interface between the quarternary sediments and the more conductive sticky tertiary clay. For this reason the EPA and the hydrogeological team in Denmark quickly identified the SkyTEM method as the method for outlining the lower boundary of the aquifers. They were able to rapidly collect and assess valuable information describing the lower boundary of the quarternary sediments. These were characterized by a large number of distinct paleochannels/buried valleys ranging in depth from 10 to 20 m and down to more than 300 m.

Findings

Depth to a strong conductor (surface of the tertiary clay) was extracted by modeling the results of the TEM data.

The paleohannels can be traced over long distances. Typically the channels can be divided into primary and secondary channels (secondary channels are those drained by the primary channels). It can be seen that few of the boreholdes drilled into the aquifer are deeper than a few tens of metres. It is obvious that a leap of faith and some creativity would be required to arrive at an interpretation similar to that provided by the SkyTEM system.

An area that was going to be developed as a new industrial area was located directly above one of the primary groundwater aquifers. To protect the water, the country re-evaluated these plans and it was decided to leave the land as farmland and forest to avoid the risk of contaminating the aquifers. The farmers subsequently made agreements with the local water works to reduce the usage of fertilizer and pesticides/herbicides.

Conclusion

This new knowledge made it possible to determine the size of groundwater resources as well as to understand where to protect them. These results have had a significant influence on urban planning. This case is evidence that the SkyTEM method is a valuable investment, a major step towards securing clean drinking water for future generations and an essential input for sustainable groundwater management planning.

Mapping salinity

Setting:

The Danish Hydrology Research Center, HOBE wanted to balance the water budget calculations of a catchment area. They suspected the aquifer was discharging into a lagoon via a buried channel and investigated the area to determine the channel’s significance in submarine groundwater discharge (SGD).

Technology:

The SkyTEM 304 was flown at an average speed of 50 kph. The transmitter was set for low (LM)and high (HM) transmitter moments of 5000 and 179000 Am2 respectively. This permitted measurement of 20 unbiased gates (11.7 ?s – 450 ?s) in LM and 21 gates (94 ?s- 8 ms) in HM and maximized the response from the upper layer concurrently while mapping to a depth of over 300 m.

Findings:

The hydrogeological setting was found to be complex as the geology was dominated by stratified deposits with a homogeneous structure of alternating layers. In addition to mapping the stratified geology SkyTEM mapped the buried valleys beneath the lagoon. The system was able to penetrate through the layers to a depth greater than 300m and showed that the valleys were saturated with sea water (see slice at 100-110 m depth). Mapping salinity distribution helped to outline an intricate flow system beneath both the coastal area and the lagoon and answered questions on how and where freshwater was moving. This changed previous assumptions on the heterogeneity of the area.

 

Conclusion:

Because of the extremely high SNR, sensitivity and accuracy are enhanced and subtle differences in resistivity can be resolved. An interesting discovery is that accurate bathymetric and salinity level maps can be produced from the SkyTEM method. It suggests as well that the method can be used for mapping layered features within a water column, such as haloclines.

Mapping fresh water and saltwater encroachment

Setting:

The Galapagos Island of Santa Cruz. Santa Cruz supports 13,000 inhabitants and 120,000 annual visitors and there is very little evidence of groundwater on the island. Drilling restrictions and challenging terrain prevent traditional hydrogeological investigation.

Solution:

The Darwing Foundation and several universities employed the SkyTEM304 to collect data over the island. Helicopter flying speed was 45 km/h sensor altitude was 35-45 m and South-North flight lines had a spacing of 200 m. A few lines were flown cross island to obtain a full picture of the salt-fresh water interface. SkyTEM filters avoid smoothing of early time data and the near-surface resistivity variations were enhanced. Later times data were more severe filtered to obtain as much depth penetration as possible. The data were gathered into soundings with a spatial distance of about 25 m. The SkyTEM method was sensitive to low-resistivity layers of hydrogeological interest [50-200 ohm-m] to a depth of approximately 300 m.

Findings:

The resistivity data below shows the electrical properties of the Santa Cruz rock. High resistivity values (reds) indicate competent rock, or basalts, while low resistivities (reds) represent gravels and soils. Unit IV, shown in blue-green to yellow is a perched aquifer that lies beneath the weathered, vegetated and permeable layer (yellow). Downward movement of water is constrained by impermeable Unit I (orange) basalts that make up the bulk of the volcano’s composition. Unit II is electrically conductive and is a seawater intrusion wedge underlying the island. Unit III, outcrop, has the same geophysical signature of Unit IV but is interpreted differently based on existing geological data. Large-scale faults that facilitate internal drainage were identified and helped explain the absence of surface seepage.

 

Conclusions:

An aquifer can be difficult to identify due to similarities in resistivity of the aquifer and the layers masking it. SkyTEM however was able to delineate the subtle contrasts required for accurate interpretation. The unique spatial resolution and 3-D view of the subsurfface resistivity structures allowed identification of the previously unknown perched aquifer and the salt-water wedge in the basal aquifer, located with an accuracy of a few meters. Beyond the vital implications for water resource and ecosystem management the high resolution SkyTEM data has forced scientists to reconsider their established conceptual flow models of volcanic islands.

Postscript:

The identification of weathered layers in a volcanic edifice may help to explain the cuase of potentially catastrophic landslides. In 2011 the US Geological Survey contracted SkyTEM to map the slopes and bases of Mt St Helens and Mt Iliamna, two volcanoes in the USA, to study slope stability and the presence of water.

Large-Scale Groundwater Exploration in Selangor, Malaysia

A SkyTEM airborne TDEM survey performed by SkyTEM ApS and DanWater Malaysia Sdn Bhd is being carried out as part of a groundwater exploration programme by Sime Darby Water Resources Sdn Bhd. The TDEM data are modelled by SkyTEM ApS.

Client:
Sime Darby Water Resources Sdn Bhd Malaysia

Survey operator and data modelling:
DanWater Malaysia Sdn Bhd Malaysia
SkyTEM ApS Denmark

Download complete case study –
Large-Scale Groundwater Exploration in Selangor, Malaysia (PDF)

Introduction

The Kuala Lumpur area has an estimated population of 7.6 million people, and almost all fresh water supply for the city is provided by large surface reservoirs dependent on rainfall.

In 1998 the vulnerability of these reservoirs was demonstrated by a long period of drought causing a massive water shortage. Since then, the Malaysian government is focusing on extending the water supply of Kuala Lumpur to include alternative sources such as groundwater.

A SkyTEM airborne TDEM survey performed by SkyTEM ApS and DanWater Malaysia Sdn Bhd is being carried out as part of a groundwater exploration program by Sime Darby Water Resources Sdn Bhd. The TDEM data are modelled by SkyTEM ApS.

SkyTEM airborne system setup:

  • Dual TDEM moment
  • 314 m2 transmitter loop
  • Peak moment of 150000 Am2 (high moment) and 15000 Am2 (low moment)
  • Two receivers recording the Z-and the X-component of secondary magnetic field

Benefits

  • The high peak moment enables great penetration depth and the low peak moment ensures detailed resolution of near surfaces anomalies within the same flight
  • The two-component receiver system secures more information of shape and orientation of a recognized conductor

Survey objectives

The short term objective is to localize possible groundwater resources in selected areas in the state of Selangor using the SkyTEM TDEM airborne system. The results from the geophysical survey will be applied to choose optimal drilling locations in the selected areas.

The long term objective is to establish a sustainable groundwater abstraction and supply the treated water to the cities of Kuala Lumpur and Putrajaya as well as the state of Selangor.