While it is a beautiful and powerful poem, it's written in free verse, which means it doesn't adhere to a strict rhyme scheme or meter, unlike sonnets.
Sonnets are typically 14 lines long and follow specific rhyme schemes, such as ABAB CDCD EFEF GG or ABBAABBA CDECDE.
"A River" is a more open and fluid poem, reflecting the nature of the river itself.