Finding Groundwater for a Durian Orchard using TEM
In this geophysics case story, Transient Electromagnetic (TEM) investigations were successfully deployed to identify a deep groundwater-bearing zone in Bentong, Malaysia. This discovery provided a vital, cost-effective irrigation resource for a local Durian orchard, demonstrating the efficacy of finding groundwater in complex geological settings.
Groundwater well at the same location as the WalkTEM 2 sounding.
The Project
Method: TEM
Solution: ABEM WalkTEM 2
Measurement: TL-1k6, 40 x 40m Transmitter Loop, RC-5 Receiver Coils, 12V
Software for processing and interpretation: Aarhus SPIA TEM
The Challenge: High Irrigation Demands
To fully maximize fruit growth at a Durian orchard in Bentong, Malaysia, the growers faced a critical water shortage. Durian trees are water-intensive, with each tree requiring approximately 6-8 liters of water per day.
To make the operation cost-effective, the orchard needed a sustainable local water source rather than transporting water in. The primary challenge was that the groundwater level was expected to be located within bedrock at a significant depth – likely 50 meters or more. Traditional drilling without prior data would be high-risk and costly.
Durian fruit
The Solution: Transient Electromagnetic (TEM) Survey
To accurately map the subsurface and succeed in finding groundwater at depths exceeding 50 meters, geophysics offered the most reliable solution. Specifically, the Transient Electromagnetic (TEM) method was selected for its efficiency in detecting conductive zones (like water) at great depths over large areas.
The survey was conducted using the ABEM WalkTEM 2. This instrument allowed the team to perform rapid soundings at various locations around the orchard to identify the most promising drilling sites.
Field investigations with ABEM WalkTEM 2
Why TEM for this project?
- Depth of Investigation: Capable of penetrating deep bedrock (up to 220m in this configuration).
- Efficiency: Rapid setup and data collection ideal for covering large orchards.
- Accuracy: Excellent differentiation between conductive groundwater zones and resistive bedrock.
ABEM WalkTEM 2 results. Left: Raw data. Right: 1D inversion to create a layered model. The resistivity decreases significantly at approximately 100 meters depth.
Results & Conclusion
The geophysical data provided clear insights. One of the TEM soundings revealed a significant drop in resistivity values at depth. In the context of the local geology, this low-resistivity anomaly strongly indicated a fracture zone or groundwater-bearing zone.
Based on these geophysics results, a location was selected for drilling. The interpretation proved accurate:
- Target Identified: The TEM data pinpointed the location of the aquifer.
- Verification: A well was drilled at the recommended site.
- Outcome: Fresh groundwater was struck at a depth of approximately 100 meters, securing a long-term water supply for the orchard.
