How Flux Measurements Helped Dunea Get Insights into Their Groundwater Dynamics

Managing groundwater has always been challenging because you can't see what's happening under the surface. Dutch water company Dunea pumps 8 billion liters annually for drinking water production at their Solleveld-site near The Hague. A collaboration with iFLUX using flux sensors and real-time monitoring provided the insights they needed to better understand groundwater dynamics.

The Challenge: What's Really Happening Underground?

Traditional groundwater monitoring only provides snapshots through periodic measurements. Operational managers have to make important decisions based on limited information about how water moves through the aquifer. At Dunea's coastal site in Solleveld, this became more complicated after the 2011 ‘Zandmotor project’, a nature based coastal fortification by creating a peninsula with dredged sand from the North sea, that changed existing underground flow patterns.

Dunea needed answers to critical questions:

• How did the Zandmotor affect the freshwater-saltwater boundary?
• Were protective screen wells still working effectively?
• What was the actual risk of contamination?

The Solution: Measuring Groundwater Flow in Real Time

Through the European EIC Accelerator program, iFLUX installed a network of flux sensors that measured actual groundwater movement. These sensors captured:

• Horizontal flux measurements showing groundwater flow direction and velocity
• Potential risks for saltwater intrusion 
• Real-time changes in watershed location
• Aquifer responses based on automated changes in pumping regimes

What the Data Revealed

This year-long monitoring campaign showed just how dynamic the groundwater system really was. Flux measurements revealed water movement ranging from 1 cm per day or less to over 4 meters per day. The underground system responded much faster and further inland than expected when screen wells were temporarily shut down.

Most importantly, the data confirmed that Dunea's protective screen wells remained essential for preventing saltwater intrusion and contamination, but need to be optimized in the future for resilient and sustainable drinking water production. Under their current management approach, the contamination risk remained under control. There was further room for optimization: the flux measurements revealed opportunities to reduce both freshwater losses and energy consumption. The data thus provided baseline information readily at hand for future planned system optimizations.

Anne De Graaf, Hydrologist at Dunea, explained: "iFLUX helped us gain insights into the dynamic behavior of groundwater in our drinking water extraction at Solleveld. Our measurement setup was located close to the coast where water behavior is very dynamic. We could clearly observe the effect of our extractions on groundwater flows and direction. Especially in dynamic groundwater systems, iFLUX can offer many insights."

Kevin Joosten, Program Manager at Dunea, added: "It was a very pleasant collaboration with open communication and good, substantive discussions at the center. Worth repeating."

Practical Benefits of Underground Monitoring

The flux measurements enabled Dunea to:

• See actual flow patterns 
• Detect changes in underground conditions
• Verify that their protective systems worked sufficiently
• Base decisions on real data 

While the intensive monitoring phase ended after answering Dunea's key questions, the project demonstrated the practical value of understanding underground water movement. The network is ready for re-deployment when planned pumping locations and configurations change in the coming years.