If you're from an "average" American parish, you most likely use the OCP missalettes. There's a decent setting called "I Saw Water Flowing" by Randall DeBruyn in there. It's one of the only good pieces of ritual music in those hymnals.
We sang the "I Saw Water" that is in the new Canadian missal. It is much too short for our parish. I'm not sure that I liked the silence on Easter Sunday. I think the Vidi Aquam would also be too short here. Here is something for me to think about/research for next year.
We used the I Saw Water on p. 99 of the Vatican II Hymnal, which is more than adequately extendable. However, I second redsox1 on Dr. Nestor's arrangement.
For years it was "floating around." I worked for Leo so that's how I got my copy. It is now available in Worship IV. I'm wondering if GIA might be planning on selling it separately as an octavo. It wouldn't hurt to call them and inquire as they now hold the copyright.
There are good, and pretty straightforwad, four-voice settings of the Vidi Aquam by Spanish polyphonists Victoria and Morales, both written in four short sections (antiphon, verse, Gloria Patri, partial repeat of antiphon), so you can repeat or stop as needed.
This year at my parish we did a really amazing setting from the Lambeth Choirbook for SATTB. Just the first "Vidi" is 90 measures, though - you gotta have a pretty big sanctuary for that much music/sprinkling.
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