The Arc project is designed to study how land forms in the Sacramento-San Joaquin Delta interact with freshwater inputs and tides to create habitat favored by native fishes. The investigation focuses on regions in the North Delta where fish surveys have shown relatively high populations of native fishes - regions including Suisun Marsh, the flooded Sherman Island and the Cache and Lindsey sloughs. The areas together form an arc, inspiring the project name "North Delta Arc of Native Fishes."

The California Environmental Flows Framework (CEFF) provides an approach for determining ecological flow criteria and guidance for developing environmental flow recommendations that can accommodate a variety of stream types and biological communities, while supporting regulatory and management agency programs aimed at protecting beneficial uses for aquatic life. CEFF applies a Functional Flows approach and provides ecological flow criteria based on the natural variability of ecologically-relevant functional flow metrics. It provides a process for considering physical and biological constraints within a stream system and provides guidance on developing environmental flow recommendations that balance ecological and water management objectives.