The conservation and management of freshwater ecosystems are of the utmost importance to the well-being and long-term interests of life on earth. An important step toward protecting our rivers and streams is to expand monitoring efforts. Tracking the abundance and diversity of benthic macroinvertebrate (BMI) species offers an effective way to assess how well a stream’s ecosystem is functioning and its ability to provide essential ecosystem goods and services. In September 2025, the freshwater ecology class of California State University Monterey Bay conducted a bioassessment of a 150 meter reach of Agua Mala Creek, near the confluence of Rana Creek, to determine the ecological health of the stream. Agua Mala Creek is a first-order stream with a length of 1.91 km. It is situated within Rana Creek Preserve in the upper Carmel Valley in central California. This bioassessment followed the California SWAMP Standard Operating Procedures (SOP) for wadeable streams. The California Stream Condition Index (CSCI) was used to quantify stream conditions in California based on biological and physical data. The CSCI 0.47 score indicates that the stream is very likely altered. The MMI 0.63 score suggests that the stream’s ecological structure and function are dominated by species that tolerate degraded conditions, while the O/E 0.31 metric indicates that the number of species present is lower than what would be expected in a healthy stream system. In general, the poor CSCI score suggests that Agua Mala Creek might be more biologically productive were not for decades of disturbed landscape spanning a range of physical habitat degradation, primarily associated with livestock grazing, the possibility of over-pumping groundwater from the numerous wells on-site, and some altered channel geomorphology: including erosion and sediment pollution. Removing cattle from the stream corridor is recommended to reduce bank erosion, sediment input, and nutrient loading, allowing riparian vegetation and stream habitat to recover. In addition, continued collaboration with the Esselen Tribe—on whose traditional homeland Rana Creek Ranch is located—should be prioritized.