There are several synonyms for the phrase "are dependent upon." Some of the commonly used alternatives are "rely on," "hinge on," "rest on," "rest upon," "count on," and "be conditional on." All these synonyms convey the essence that something is based on something else and cannot exist or happen independently without it. In academic writing, using varying phrases and synonyms adds more depth and variety to the text, making it more engaging for the reader. As such, it is essential to use these synonyms contextually and appropriately to ensure a coherent and well-structured tone in writing.