When Petrarch isn't writing love poems to or about his beloved Laura, he's focused on Italy. Sometimes, he mixes it up and writes about the two of them at one time. One thing is for certain: if you spend any time with Petrarch's poetry, you'll notice a constant reference to geographic locations—most of them in Italy and many of them to rivers.
He does this for a couple of reasons. First, it helps to reinforce his voice and identity in the poem: he's Petrarch, son of a prominent Tuscan family and a man who has suffered exile (which makes him deeply attached to his homeland). Also, he's known for his references to nature, especially to the flora and fauna immediately around him. This makes him a local, free-range poet, right? Just check out the rest of his Canzoniere for other examples.