The plan so far is confined to the Western waterways between the North Sea shoreline and the cities of Amsterdam and Rotterdam, the junior minister for water management, Melanie Schultz van Hagen, said on Dutch public radio.

But other areas may benefit as well at some point, she added.

Compensating for a lack of soft water in canals and rivers with an influx of seawater poses some environmental problems, as any excess of salt hinders proper irrigation of the country's extensive agricultural and horticultural farmlands.

But any potential controversy the plan might have triggered in the environment-conscious Netherlands is defused by widespread awareness that dry soil can cause serious subsidence, threatening man-made structures with rapid and occasionally irreversible damage.

The country's vital, extensive network of dykes and embankments is at risk, as are roads, railways and buildings.

Historic buildings are the more exposed, as most are built on buried wood stalks which may rot away for lack of adequate humidity.

Water management authorities were unable to say how long the plan would remain in place. But speculation is that its scope and duration can only increase if the recent shortage of rain is to continue.

Thursday marked the end of a two-week heatwave in the Netherlands, the longest since the summer of 1976.

But the Meteorological Institute warned of a persistent drought.

TERRA.WIRE