Second Draft Definition of Low Impact Pumped Storage Hydropower

In collaboration with an external Advisory Group representing a broad cross section of the hydropower community, and in response to comments on the initial draft definition, the Low Impact Hydropower Institute (LIHI) has developed this Revised Second Draft Definition of Low Impact Pumped Storage Hydropower (LI-PSH). The definition and supporting documentation could help provide an outline for best practices in developing and operating LI-PSH projects.

Comments on the initial draft definition were incorporated into this revised second draft definition with a new public comment period open from December 1, 2025 until January 30, 2026. 

We welcome your additional comments on the second draft definition.  We are particularly interested in your input on:

  • Ways in which LIHI could implement the definition,
  • Whether a certification program would be valuable, and
  • What factors LIHI should consider in developing such a program 

Please click on the image below to review or download the Low Impact Pumped Storage Hydropower Revised Second Draft Definition.

Pumped Storage Hydro

Proposed February 2025

Low Impact Pumped Storage Hydropower Revised Draft Definition

Results of Initial Draft Definition Comments

The first public comment period opened on February 19, 2025 and closed on May 20, 2025. LIHI staff, the LIHI board's LI-PSH Task Force, and the Advisory Group reviewed the comments and developed this revised definition. A summary of the public comments received and LIHI staff responses can be found HERE.  

Any questions on the revised second draft definition can be directed to either Shannon Ames or Maryalice Fischer.

Background 

LIHI’s certification program has explicitly excluded PSH primarily because fossil fuels supplied by regional electric grids were (and still are) the most common source of power for the PSH pumping cycle. Yet, recognizing the increasing penetration of wind and solar power since LIHI’s founding in 1999, the idea of potentially expanding the certification program to include PSH projects has percolated for several years. Over the last year, a cross-disciplined Advisory Group developed the draft definition based on the following objectives:

  • Determine what aspects of natural, social, cultural resources could be impacted by the construction and operation of new and existing pumped storage projects in the US.
  • Clearly articulate stringent but achievable goals that would lead to the optimal outcome to minimize impacts for each resource type.
  • Define science- and knowledge-based standards for demonstrating that goals have been met.
  • Publish results with sufficient detail such that PSH projects can evaluate their impacts and inform design of future projects.

The resulting second draft definition encompasses eleven impact areas, along with goals and alternative standards for each impact area that can characterize PSH projects as being low impact. For more background information on the draft definition, please click HERE.

Once the definition finalized, the LIHI Governing Board may consider creating a Low Impact certification program for LI-PSH projects.