With reservoirs at significantly low levels and no substantial rainfall predicted, regional authorities are hoping to subsist until a desalination plant is completed in May next year.
The regional government of Catalonia, of which Barcelona is the capital, said six ships a month will bring in a total of 1.66 million cubic metres of water.
That is roughly enough to satisfy six per cent of the monthly needs of the region's 5.5 million inhabitants.
The shipments are scheduled to last at least three months.
Leonard Carcole, director-general of Aguas de Barcelona, the city's water utility, said: "It has been one of the driest years ever, and Barcelona has found itself in need of water."
Catalonia's reservoirs are only at about a fifth of their capacity, compared with reservoirs that are on average half full nationally.
Authorities fear reservoirs could drop to 15 per cent of their capacity, a level at which it is no longer recommended that water be used for human consumption.
Authorities hope a new desalination plant, one of the biggest in Europe, will be operational in May of next year and resolve much of Catalonia's water woes.
Ana Rosa Martinez, a mother of two who lives in Barcelona, said: "I try and show my kids how to be responsible with water.
"We collect water while the hot tap runs before the hot water comes out, which we then use on the plants. My kids don't leave the water running while they brush their teeth."
With the summer tourist season ahead, the region has frantically been moving to avoid serious cuts in supply.
Already city fountains and beach showers have been turned off and restrictions placed on filling large swimming pools.
Last month, Catalonia reached an agreement with Spain's central government for a temporary water transfer from the Ebro River.
That has upset two southern regions, Valencia and Murcia, that were denied permission for a permanent, major diversion of water from the Ebro. The two areas are dependent on tourism and agriculture.
Meanwhile, farmers based in Tarragona, where the water for Barcelona was originally headed, say they need it more than the city.
Ecologists say Spain's agriculture sector, with out-of-date irrigation systems and crops that need disproportionate amounts of water, uses up to 70 per cent of the country's water.
They add that a tourism model based on huge resorts and golf courses is also unsustainable.