Balancing Competing Water Needs in an Unregulated Seasonal Watershed Subject to Distributed Diversion Pressures

Abstract:

River managers must balance the needs of the ecosystems that rely on the river by leaving water instream, often while facing demands from human diversions. It is especially difficult to balance these water needs in systems that are highly seasonal and have no instream storage (e.g., reservoirs) since the amount of water instream is completely determined by the climate. An example of a watershed that has both of these characteristics is the South Fork Eel River in coastal northern California. In order to evaluate tradeoffs between human and ecological demands in this system, a water allocation model with water management scenarios, and environmental flow requirement scenarios were developed in collaboration with stakeholders and decision-makers. The water allocation model is capable of considering permitted water diversions, as well as unpermitted diversions for cannabis, which are a significant water user in forested California watersheds. In total, 11 different human water demand scenarios and 14 different environmental flow requirement ecological demand scenarios were evaluated to identify tradeoffs and facilitate management efforts. To aid in decision making processes, an interactive GUI is also being collaboratively developed to provide visualizations and performance metrics of model results.