Combine water, 2 cups chopped leek, 1 cup parsley, 1/2 cup basil, 1/2 teaspoon salt, and next 5 ingredients (salt through celery) in a large Dutch oven. Bring to a boil over medium heat. Reduce heat; simmer, uncovered, 35 minutes. Strain broth through a sieve into a large bowl; discard solids. Reserve 5 1/2 cups broth; reserve remaining broth for another use.
Bring 5 1/2 cups broth and saffron to a simmer in a small saucepan (do not boil). Keep warm over low heat. Melt butter in a large saucepan over medium-high heat. Add 4 cups chopped leek; sauté 5 minutes. Add rice; cook 2 minutes. Add wine; cook 1 minute or until the liquid is nearly absorbed. Stir in 2 cups broth; cook 5 minutes or until the liquid is nearly absorbed, stirring constantly. Add remaining broth, 1/2 cup at a time, stirring constantly until each portion of broth is absorbed before adding the next (about 15 minutes total). Add 1 cup parsley, 1/2 cup basil, mascarpone, lemon rind, salt, and pepper; cook 1 minute or until mascarpone melts. Sprinkle with Parmesan.