The Catchment Science: Interactions of Hydrology, Biology & Geochemistry Gordon Research Conference will be held in conjunction with the Catchment Science: Interactions of Hydrology, Biology & Geochemistry Gordon Research Seminar. Those interested in attending both meetings must submit an application for the GRS in addition to an application for the GRC. Please refer to the Catchment Science: Interactions of Hydrology, Biology & Geochemistry GRS web page for more information. Observing, predicting, and understanding the consequences and feedbacks of environmental thresholds are crucial for predicting future changes in catchment systems across interacting hydrological, biological and geochemical processes. This GRC will focus on new research, including thresholds, early warning indicators, and resilience using long-term data, experimental studies, theory, and modeling approaches to study the behavior of catchments systems under changing conditions such as climate variability or land use/cover changes.