Hydro Process


Hydroelectric power projects are complex and can be lengthy and expensive to construct. Hydropower projects usually have high initial costs, low operating costs and project lives of 50 years or more. Even with excellent hydro resources, engineering must be thorough to insure a positive return on investment. This consists of an involved process with many things to consider. Project development phases include reconnaissance , feasibility , licensing & design , and finally construction .    


A reconnaissance study is a preliminary feasibility study that serves to determine if the project warrants a full feasibility study. This is usually the very first step when considering a hydroelectric project for project development.                        

Tazimina Falls

Tazimina Falls in Western Alaska

 A reconnaissance study is performed as follows:    

  • Hydrology - This study includes a site evaluation of resources, stream gage data collection and stream-flow modeling.
  • Reconnaissance - This involves a variety of tasks of various disciplines. These tasks include:
    • Assessment of physical works
    • Development of power requirement forecast
    • Project description and location including licensing and land ownership claims
    • Discussion of construction methods and materials
    • Development of Power Benefit Stream and Cost of Energy
    • Cost Estimates for Licensing, Design, and Construction
    • Economic Feasibility
    • Identification of Critical Issues
    • Assessment of Constraints involving Legal/Institutional, Licensing and Environmental, and Engineering Site issues.
    • Preliminary Discussion of Environmental Impact
  • Final Report - Summary of findings with a recommendation for next course of action regarding the project.
  • Other Considerations - Any other issue not previously considered in the reconnaissance including:
    • Fish Stream Issues
    • Seasonality Issues
    • Seasonal Load Pattern
    • Geology
    • Prior Studies
    • Data Availability
    • Data Quality


A feasibility study is a detailed study to determine the technical, economic, and environmental feasibility of potential hydroelectric development. Considerable time is spent in the examination and asessment of the proposed project. Decisions are made at this stage to determine if the project should be continued.

Possible Intake location at the proposed site for the Tenakee Springs Hydroelectric Project    

A feasibility study is performed as follows:            

  • Pre-construction Investigations and Evaluations including:
    • Surveying and Topographic Mapping
    • Geotechnical/Geophysical Investigations
    • Hydrologic Studies and Stream Gauging
    • Permitting - Environmental and Fish Studies
  • Project Description - a description of what the project wishes to accomplish, who will benefit from the project, and the construction techniques involved with the project.
  • Project Alternatives - exploration of changes in various aspects of the project including routes, energy sources, materials, location, and others.
  • Conceptual Engineering - comments and thoughts for all parts of the hydroelectric system including:
    • Diversion
    • Intake/Outlet
    • Major Equipment Selection
    • Power Conduit
    • Powerhouse
    • Spillway
    • Switchyard
    • Transmission Lines
    • Tunnel
  • Identification of Physical Works - determination of penstock route, powerhouse location, project access, and intertie connections
  • Computation of Project Power Output
  • Confirmation of Power Demand
  • Development of Project Cost Estimate and Schedule
  • Economic Evaluation - examines the long-term financial benefits of the project
  • Preliminary Site Control Plan - Plan to consider safety, logistics, and other matters involved with construction.
  • Identification of Critical Issues
  • Assessment of Legal, Institutional, and Financial Issues
  • Documentation of Findings from the Feasibility Study
  • Other Considerations - any other issue not considered in the feasibility study including:
    • Monthly Stream Flow Distributions
    • Flood Hydrographs
    • Reservoir Area-Capacity Curves
    • Annual Firm Energy
    • Average Annual Energy
    • Installed Capacity
    • Active Storage Capacity

Licensing & Design

The design process is the time when the characteristics and features of the project are explored, determined, and integrated together. This involves complex modeling, in-depth analysis of the site and materials, and integration of the parts into one large system.

Control Room for the Blue Lake Dam in Sitka

Tasks done in the design phase include:            

  • Completion of License Application and Permits
  • Performance of Engineering Calculations for Mathematical Support of the Project
  • Preparation of a detailed Engineering Design Report
  • Preparation of Final Design Drawings and Specifications
  • Preparation for Payments for Materials Acquisition
  • Establishment of QA/QC requirements for project construction, testing, and equipment installation.


Construction is the final stage of the process in hydroelectric development. This is the act of building the system and installing it into the hydro site. This is the most visible stage of the project.

Chunisaxx Creek Power Plant during construction            

Further Information regarding the process of hydroelectric development can be found on the Federal Energy Regulatory Commission (FERC) and Alaska Dam Safety websites.

Program Information


Renewable Energy Fund Projects 
Hydro Links  

For more information please contact

Daniel Hertrich, P.E., Project Manager
Hydroelectric Programs
Tel. (907) 771-3045
Fax (907) 771-3044
E-mail: dhertrich@aidea.org