Aargau trial finds emergency groundwater pumping works but is illegal

A trial in the Suhrental valley in the canton of Aargau showed that groundwater can be pumped 18 kilometres uphill from Aarau to Reitnau, but only with considerable effort and in breach of the applicable concession rules, Swiss broadcaster SRF reported.

Over 16 days in August, municipalities pumped a total of 3,000 cubic metres of groundwater from the Aare groundwater flow to Reitnau. The stepped pumping stations operated for 10 to 12 hours at a time.

Aarau voluntarily supplied the groundwater for the short-term trial. However, the city had pumped up too much groundwater and exceeded its canton-issued concession, making the operation technically illegal.

The Suhrental municipalities carried out the test because groundwater levels in the valley remain very low. The trial was intended to determine whether water from Aarau, at the bottom of the valley, could be transported through the municipalities to Reitnau.

The existing pipelines were not designed for this purpose. Many Swiss municipalities have connected their water supplies through ring pipelines so that neighbouring communities can share water if a reservoir becomes contaminated. They were not built to move groundwater through the valley during periods of extreme heat.

The pumping process had to be carried out in stages. Water was pumped from one reservoir to the next, released into the following village and then pumped uphill again. Operators repeatedly monitored the systems, checking reservoir levels and deciding how much water could be moved.

Walter Wyler, president of the Suhrental Groundwater Association, said the system could not be operated by pressing a single button in Aarau. A central operating system would require further investment.

The trial has nevertheless provided the municipalities with a short-term option for what they call a water crisis. Wyler stressed that pumping water up the valley would only be possible in exceptional cases and would not replace calls for residents to reduce their consumption.

Residents were already asked during the summer not to water gardens, wash cars or fill swimming pools. Despite these measures, groundwater levels continued to fall.

The situation remains tense. If there is no rain for several weeks, the municipalities may again ask residents to save water. While previous appeals were voluntary, future orders could carry fines.