This short poem consists entirely of a single sentence, which is drawn out over the course of eight lines using enjambment. Each line spills over into the next, creating a casual, free-flowing sensation that contributes to the poem's calm, meditative tone. Note how quickly the image would rush by were the lines not enjambed:
so much depends upon a red wheelbarrow glazed with rainwater beside the white chickens
Doesn't feel quite as poetic, does it? The enjambment slows down the poem, ensuring the reader is surveying the scene with the same focus and intent as the speaker. The image described in "The Red Wheelbarrow" is not just a feature of the poem, but is the poem—if the reader were to skim through it, they would miss out on the poem entirely. And just as "so much depends upon a red wheel barrow," each line in the poem depends upon the line that follows for its meaning to become apparent, for the poem's image to clearly emerge.
The enjambment also works to break down the image into its various parts. The compound word "wheelbarrow," for instance, is broken into its two parts, as is the word "rainwater." The same is basically true for "white chickens": although this phrase is comprised of two words, the word "white" is an adjective describing the color of the chickens, and thus "white" can also be understood as being part of the chickens. The lines continue to break down the image into smaller pieces, suggesting the value of closely observing and appreciating simple things.
In a similar vein, the enjambment can also be thought of as complicating the image, demonstrating how even mundane objects can become complex upon further examination. The entirety of the poem describes a pretty simple, maybe even boring, scene: a wheelbarrow sitting outside. However, as the speaker continues to describe the scene, it gathers details that paint a more interesting portrait: the wheelbarrow is not simply wet but is "glazed with rain / water." The wheelbarrow is not just outside, but "beside" chickens that are "white." The scene becomes more detailed, and thus, more intimate as it goes along. The enjambment highlights these details, allotting them plenty of space on the page in order to demonstrate their importance.