Reclaimed wastewater and desalination have been implemented across the globe to bolster water availability for agricultural production, drinking water supplies, and industrial uses. While these alternative water resources offer significant promise, implementation also presents notable financial, health, and environmental challenges. We analyze key findings from existing literature and present a comprehensive summary of the potential applications and costs associated with alternative water sources. We explore the current uses of alternative water and the benefits accrued from adoption. We then dive into four major challenges associated with implementation---pollution, ecological degradation, public health risks, and financial constraints---that impede widescale adoption of alternative water projects. Our findings underscore the importance of treating alternative water sources as complementary tools to support existing water systems, as well as an opportunity to think more holistically about how we design water resource infrastructure in the future.