It is interesting that the Spanish government chose to use police yesterday to try to prevent a vote taking place, instead of just refusing to accept any possible vote in favor of Catalan independence by declaring it illegal, as they have declared it illegal anyway. It seems the police did manage to restrict turnout and make it much lower than it would have been if the vote had been free. This was at the cost of some very poor public relations for the Spanish state, as images of voters being forcibly suppressed never looks good! The Catalan regional government is claiming a turnout of just over 42%, with just under 92% of voters opting for independence. The leader of the Catalan regional government says there is now a mandate for Catalan independence, but has not declared the birth of a country yet. 
The Spanish constitution is clear that Catalonia is part of Spanish territory, and that Spain may not be divided. Legalities aside, there have been very few new countries born whose birth did not take place under questionable legality, the United States being perhaps the largest and most famous example. Proponents of national independence can always cite the principle of self-determination, which tends to be mentioned in international legal declarations, most notably within the Charter of the United Nations. Opponents can usually cite the laws and constitution of the existing power against the emergence of a new state on an old state’s territory. Few people take a truly consistent policy. Irish Republicans support Catalan independence, yet earlier rejected the majority Unionist population’s right to self-determination as part of the United Kingdom. Somewhere within every argument a value judgement is made concerning who the land “really” belongs to, usually based upon geography or religion. Argentina says the Falkland Islands “really” belong to it, despite the island never having been inhabited, as far as we know, before British discovery and settlement in the 18th century. Very few people truly accept the self-determination argument as a sole factor.
The European Union has made it clear it will take the side of the Spanish state. There are several likely reasons for that. Cynics might say it is because a real struggle now over Catalonia will smash Spain’s economic recovery, which is currently something of a weak link within the E.U.’s debt markets. There is also the likelihood that it will encourage separatists throughout the rest of Europe, including possibly part of France, Belgium, the entirety of Scotland, etc. and all these new entities would demand admission to the E.U. as new states, which would bring its own set of problems.
The Euro has sold off so far today, but not by a very large amount, and I do not see the Catalan issue as likely to be a dominant factor in the Euro’s performance just yet. This will depend upon whether independence is declared, and what means the campaign takes to try to secure it. If it leads to a lot of strikes and economic disruption, as Catalonia is the wealthiest region of Spain, it will begin to have an impact on Spanish debt markets. Serious violence seems unlikely, but if that becomes a feature, markets would be hit even harder.