The Netherlands declared an official water shortage following an unusually dry summer with no rain forecast for the coming two weeks.
The Dutch government said it was eyeing further measures to conserve water amid a drought, and authorities have already imposed limits on farming and shipping.
The country is protected from the sea by a famed system of dams, dykes and canals but remains particularly vulnerable to climate change.
"The Netherlands is a land of water, but here too our water is precious," Infrastructure and Water Management Minister Mark Harbers said in a statement.
Southern provinces of Zeeland and Limburg in the Netherlands have already banned farmers from spraying their crops with surface water, in a blow for the world's second largest agricultural exporter after the US.
Some canal locks for shipping have also been suspended, with salt water from the sea creeping back into some rivers as their water levels are so low, Mr Harbers added.
With two-thirds of the Dutch population living below sea level, droughts can quickly become an acute problem in the Netherlands, leading to rivers silting up and hampering water traffic.
A further problem arises from dykes drying out, and many require the weight of water itself to remain strong.
"Priority would now be given to ensuring that vital dikes remain safe, and then to drinking water and energy supplies," he said.
The drought was "becoming increasingly visible in nature" and it was "conceivable that the drought will affect more social interests.
"That is why I ask all Dutch people to think carefully about whether they should wash their car or fill their inflatable swimming pool completely," he said.
In July, the Netherlands recorded its third-highest temperature since records began.
Heatwaves gripped large parts of Europe and the United States last month, bringing about calls for more efforts to tackle global warming, which scientists say makes spells of extremely hot weather more frequent and deadly.
"We have been seeing it get drier in the Netherlands for several weeks now because of evaporation in our own country and very low river flows from abroad," said Michele Blom of the country's Public Works and Water Management agency.
At the moment, barges on the lower Rhine (an important route for transporting coal from Rotterdam inland to German steelmakers and power producers) are operating at less than half capacity.
The Dutch ministry of infrastructure and transportation said that as of yesterday, water was flowing through the Rhine at 850cubic metres per second at Lobith.
Levels were better in the Maas, also known as the Meuse, which flows from France into the Netherlands.
The IJselmeer, a large artificial freshwater lake in the north of the country that was carved out from the North Sea in the last century, is reasonably filled and can supply water to the province of Groningen.
However, groundwater levels are sinking and "are very low in places in the south," the ministry said, leading to algae blooms and fish death. Drinking water is not affected.