Water Quality Certification and Energy Project Improvement Act of 2023 This bill revises the water quality certification process under Section 401 of the Clean Water Act (CWA) for any activity that requires a federal license or permit and may result in a discharge of pollutants into waters of the United States. Activities that require such federal licenses or permits include hydropower, natural gas pipeline, or mining projects. Under the existing Section 401, an applicant for a federal license or permit to conduct such activities must provide the federal licensing or permitting agency with a certification. The certification must attest that the discharge will comply with enumerated sections of the CWA (i.e., Sections 301, 302, 303, 306, and 307) and with any other appropriate requirement of state law set forth in the certification. The certifying authority—usually the state in which the discharge originates, but sometimes an Indian tribe or the Environmental Protection Agency (EPA)—may grant, grant with conditions, deny, or waive certification of a proposed federal license or permit. This bill limits the scope of the certification process by eliminating the requirement that the discharge comply with appropriate state law set forth in the certification. It also requires decisions to grant or deny a request for certification to be based only on the enumerated sections of the CWA and provisions of state law that implement water quality criteria under Section 303. In addition, it also limits the certification process to activities that may directly result in a discharge into waters of the United States. In addition, the bill requires certifying authorities to identify all materials or information that are necessary to grant or deny the request within 90 days of receiving a request for certification. They must also publish requirements for their water quality certifications.