Test pumpings and managed aquifer recharge tests

Long-term test pumping

To reliably determine the yiled of the groundwater formation and the quality of the groundwater, long-term test pumping is needed. A normal duration of the test pumping in a waterworks project is from 4 to 12 months, but we also implement longer test pumpings. The advantage of the long-term test pumpings is that the impacts of the water withdrawal can be assessed very reliably. Thus, they also make water permit processes smoother and faster. For short-term investigations, where the hydraulic conductivity of a certain point needs to be assessed, we have developed a unique measurement system to be used instead of test pumping.

The most typical way to implement a test pumping is to build a screen tube well and install a submersible pump in it below the groundwater level. This enables choosing the location of the test pumping regardless of the groundwater level. Typically, these test wells are constructed to reach the core layers of the aquifer to reach high yields and good quality groundwater. The test wells that we implement can also be used after the test pumping as the actual well of the waterworks.

The test pumping can also be implemented by installing suction tubes with screens below the groundwater level. After the test pumping the tubes are typically removed. If the groundwater level is more than 7 meters below the ground elevation, the test pumping cannot be implemented with suction tubes.

The groundwater pumped during the test pumping can be directed for example to a lake.

Managed aquifer recharge investigations and tests

Managed aquifer recharge tests are typically implemented for a MAR plant project. The MAR tests are a requirement to ensure the functionality of the MAR plant, to assess the impacts and to get a permit for the MAR plant. Thus, the tests typically last over a year. In the test, water from the same groundwater formation or from a surface water body is recharged to the formation. The methods for MAR are sprinkling, basin and well recharge.

We have implemented wide and technically challenging MAR tests in nearly all Finnish MAR plant projects.

Sprinkling recharge is one of the options for MAR tests.

When implemented correctly, the recharge is possible also in winter conditions!

Monitoring the impacts of test pumpings and managed aquifer recharge tests

In test pumpings and MAR tests, the groundwater levels, the pumped and recharged water flows and the water quality need to be monitored closely and frequently. We use our wide range of measurement systems for the monitoring, for example oxygen content and temperature profile measurements and flow velocity measurements. In this way, we get vital information about the properties of the area and the impacts of the activity for reporting and water permit process.

We recommend the use of automatic monitoring system for monitoring groundwater levels and the water flows in the test pumping and MAR tests, as it gives plenty of reliable and precise measurement data for computations and it requires less manual work than manual measurements. We developed and used our own automatic measurement systems in the tests in 1987–2016, and currently we are using measurement systems provided by our collaborator.