Common Assumptions

Common Assumptions is an effort to develop consistency and improve efficiency among the surface storage investigations. Common Assumptions is a joint effort by DWR, Reclamation, and the California Bay-Delta Authority. It was initiated in 2002. The objectives of the Common Assumptions effort are:

• Provide a framework for a defensible basis for collaborative decision-making regarding the surface storage investigations
• Improve the consistency in application of overarching policy decisions
• Identify common water facilities, operations, management, and regulations
• Develop and refine a common analytical framework including tools and methods for integrated hydrologic and economic analyses
• Support application of common policy and analytical framework and ensure quality control

Common Assumptions Evolution

Originally developed for the surface storage investigations feasibility studies for the following purposes:

• Comply with CEQA, NEPA, federal Principles and Guidelines, Clean Water Act Section 404, ESA, etc.
• Complete necessary studies and reports

Common Assumptions has been influenced by other Delta and Central Valley projects and investigations, and its use by other DWR and Reclamation projects and investigations is evolving.

Facilitated Policy Decisions

• Established important dates and timelines for existing and future no-action conditions
• Identified likely future projects/programs in 2030

Developed Analytical Framework

• Common Model Package
• Application protocols
• Economic analysis methods and protocols

Characterized and Quantified Water Management Actions

• Urban water use conservation
• Agricultural water use efficiency
• Recycling and desalination
• Groundwater storage for conjunctive management
• Water transfers

• Common Assumptions Teams

• Development of Common Model Package

• Email at common_assumptions@water.ca.gov