The trees and grasses seen in the picture were likely made possible by "farmer irrigation" or "yearly flooding."
If the context implies that the vegetation is dependent on agricultural practices, then "farmer irrigation" would be the correct choice. However, if the vegetation is more natural and dependent on environmental factors, then "yearly flooding" might be the more appropriate answer, as it can provide necessary water and nutrients.
Without additional context, both could plausibly be correct, but typically, "farmer irrigation" is a more direct human influence on vegetation.
Choose the response that best fits the context you're considering.