The Improvement Act's firm water supplies have coincided with dramatic increases of Pacific Flyway migrating waterfowl. Several factors are at play here, including plentiful precipitation in the birds' nesting grounds and other state and federal conservation programs, but firm water supplies in the wetlands and refuges have certainly played an important role. Resident and migratory bird use of Central Valley refuges has increased markedly with the Improvement Act. Additional public benefits from firm water supplies to Central Valley wetlands include improved educational and recreational opportunities, such as wildlife viewing and duck hunting, which generate revenue for local economies. One dam alone, the Friant Dam on the San Joaquin River, eliminated a run of chinook salmon that once numbered over 100,000 returning spawners annually.
Similar statistics apply to other streams and rivers controlled by the project.
Commercial, sport and tribal fisheries suffered as a result of decimated Central Valley fish populations. A central purpose of the Improvement Act is to restore the Central Valley's once vibrant anadromous fish populations. Critical to this effort are provisions dedicating water to instream use for fish and wildlife. Because of the Improvement Act's dedicated yield provision, Department of the Interior biologists have been able to secure flow improvements for salmon and other fish in major Central Valley rivers since 1993. It is difficult to quantify the benefits to the fish, given the length of the salmon's life cycle and the numerous variables in salmon survival, such as hydrology and ocean conditions.