Switzerland will further tap its strategic fuel stocks as imports along the River Rhine to the land-locked country have almost come to a standstill. 

Earlier this week, a key gauge of the river’s depth fell to about 30cm, the lowest for the time of year since at least 1990. The Rhine is a vital transport route for Europe’s inland economies, including Switzerland. 

The government will release another 490,000 cubic meters -- about 3 million barrels -- of fuel until the end of September. That will take inventories to almost a fifth below mandated levels, following a previous release in July, according to a Swiss government statement dated Aug. 18.

Switzerland relies on the fuel it refines domestically as well as deliveries across land and by river, making the Rhine a vital conduit.

Following a heat wave across Europe, the measured water-level on the Rhine at Kaub in Germany hasn’t been this low at this time of year since at least 1990, according to official data compiled by Bloomberg. Prior to November 2013, data are tallied on a daily, rather than intraday basis. 

In addition to the dwindling water levels, there have also been cancellations and delays in cross-border rail traffic due to staff shortages and construction work, the Swiss government said. That has hobbled an alternative import route.