The Spanish Mediterranean coast is very similar in a lot of ways to Southern California. The climate is more or less the same; Barcelona gets a bit colder in the winter than LA does and also gets a bit more rain. Like Southern California, this very pleasant climate area wasn't densely populated in the pre-technology days; the huge booms in population in both places occurred only after the locals got hold of enough capital to attract extensive outside investment, which happened about the turn of the last century in both California and Catalonia. One of the things they had to do in both places was assure a supply of water, and aqueducts (much larger in LA than in Barcelona) formed the basis for the further expansion of those areas. I would figure that nearly half the people in Spain live along the Mediterranean--figure six million in Catalonia, four million in Valencia, a million in Murcia, seven million in Andalusia, and a million in the Balearics for a total of nineteen million out of Spain's forty million.
Anyway, the Mediterranean regions of Spain desperately need more water. There are millions of people living along a narrow coastal strip with a dry climate. The small rivers in southeastern Spain, the Júcar and the Segura, just don't provide enough water, especially with the drought that's affected that area over the last few years. So what they want to do is spend a bunch of government money on what's called the National Hydrological Plan, which would ship water from the Ebro River, the only large river in Spain that flows into the Med, south to Valencia and Alicante, and would purchase water from the Rhone in France, which carries an inexhaustible supply of fresh water out of the Alps, to be carried to the Barcelona area by aqueduct. (They say in Barcelona that the Rhone is the river that empties the most water into the Med. That would imply that it carries more water than the Danube, the Nile, and the Dnieper. I don't know whether this is true, but the Rhone is certainly an impressively big river when you see it at, say, Avignon. The Ebro's really not too much of a river by American standards; it's wide but shallow. The Rhone is deep.)
A good many people are against this plan, mostly Aragonese from the Ebro Valley, who want the Ebro's water to be used for irrigation in Aragon itself rather than farther south. The Catalans from the Ebro Delta are against it, too, because they fear that the rich Ebro Delta rice-growing area might dry up--the Plan says that won't happen, that only excess water unnecessary to sustain the lower river valley and delta will be sent south. The Ebro Delta Catalans don't particularly trust the government, though.
This plan has created beaucoup de political problems. The conservative governing PP has lost support in Aragon, maybe even enough to put Aragon in Socialist hands at the next elections. The PP never had much support anyway in Catalonia, but the Plan serves as something for enemies of the government to rally around. But in Valencia, a PP stronghold, the Plan is quite popular, and the Valencian Socialists are in trouble, since they can't oppose it like the Aragonese and Catalan Socialists can. The Valencian Socialists' support base is in favor of the plan, so they're left with a dilemma: support the Plan, which would imply supporting their enemies, the governing PP, or oppose the plan and anger their base. The Greens are agitating against the Plan, which makes sense, and the Communists are too, which doesn't. Both groups might pick up some single-issue support in the next elections but I doubt that either will make anything more than minor, very short-term gains.