Bring water and broth to a boil in saucepan. Reduce heat and keep simmering.
Heat oil in nonstick saucepan and add onion. Reduce heat and saute 1 minute.
Add rice. Cook, stirring to coat, about 2 minutes. Add 1 cup of broth mixture; cook, stirring, until liquid is absorbed.
Add 1/2 cup of broth and asparagus. Cook, stirring, until the liquid is absorbed. Continue to add the broth, 1/2 cup at a time, stirring until it is absorbed before adding more, until the rice is just tender. Total cooking time for the rice should be about 25-30 minutes.
Stir in scallops, lemon juice, lemon zest, salt and pepper. Cook until the scallops are opaque, the rice tender, and the liquid is absorbed, about 2 minutes.