Hydropower Dams: Converting Non-Powered Dams to Generate Hydroelectricity


The benefits of converting non-powered dams to hydropower dams are:

● Lower installation costs
● Lower levelized cost-of-energy (LCOE)
● Fewer barriers to development
● Less risk within a shorter time frame.

According to the U.S. Department of Energy, of the 80,000 dams registered in the U.S., only 3% produce power. An impressive 54,391 non-powered dams have the potential to be converted and generate electricity as hydropower dams. Energy experts have estimated that converting existing dams could add 12 GW (12,000 megawatts or MW) of renewable and reliable energy. Moreover, it will also help local communities across America move towards sustainability.

Upgrading a non-powered dam in most cases is a more cost-effective solution compared to building a new hydroelectric facility. It is also less time-intensive. By maximizing the existing infrastructure, there are often savings on permits, equipment, and construction expenses. When it comes to environmental concerns, there are fewer barriers to development when using existing dam infrastructure. Additionally, refurbishing existing non-powered dams supports local communities by adding jobs that could not be outsourced otherwise. For example, the comprehensive study done by Navigant Consulting Inc. revealed that expanding hydropower potential could create 1.4 million quality jobs in the industry.

Small Distributed Hydropower

Fortunately, new technologies such as small distributed hydropower make the hydropower more accessible for sites with a generating capacity up to 10 MW. The existing small hydropower locations make up about 75% of the current US hydropower fleet in terms of the number of plants. This number is expected to grow as the economic feasibility of developing new small hydropower projects continuously improves. In order to support the small hydropower industry, the federal government has recently simplified the permitting requirements for small hydropower facilities and approved additional funding.

When it comes to installation requirements, most small hydropower schemes fit into two main categories: run-of-river systems and integrated into existing water infrastructure, including dams.

Considerations When Converting Non-Powered Dams into a Hydropower Source

  1. Water Availability
    When analyzing the future energy potential of the non-powered dam, you should begin your research by looking at water availability and physical relief. To determine the regional water availability, you should look at the precipitation (P) and runoff (Q) ratio, also known as Q/P ratio. As a result, the locations with higher latitude and colder climates generally have higher hydropower potential. Unfortunately, high evaporation in warmer climates reduces available runoff making the water resources for hydropower less accessible. The high precipitation in humid climates also challenges possible flood operations, making these areas less attractive for development.

  2. Streamflow
    Streamflow refers to the amount of water flowing in a river. Seasonal changes alter streamflow since precipitation contributes to higher streamflows. While stream gauge monitoring is the most effective way to measure available streamflow, many non-powered dams will not have records pre-dating the 2000’s. To estimate the monthly average streamflow, you can use the formula below:

    Streamflow = Drainage Area * Runoff

    To estimate the drainage area, you can consult the National Inventory of Dams (NID) database, or the National Hydrography Dataset (NHDPlus). NHDPlus, which geospatially models the flow of water across the United States, provides the cumulative drainage area at the endpoint of most streams. In most cases, the cumulative drainage area of a stream resembles the drainage area of the stream on which a non-powered dam is located.

  3. Hydraulic Head
    This is the change in vertical height between hydro intake and discharge points. Measure the height difference between headwater and tailwater elevations to get the most accurate hydraulic head measurement if available.

  4. Power Generation and Capacity
    To calculate the potential generation capacity, you take the hydraulic head and monthly average streamflow.

Bar graph showing the hydropower regional-generation-weighted capacity factor 2001-2008

Methods for Converting Non-Powered Dams Into Hydropower Dams

There are hundreds of NPDs with potential capacities greater than 1 MW, which are mapped out below by the US Department of Energy. See the list below:

  1. Downstream penstock (Mahoning Creek Hydroelectric Project)

    Mahoning Creek Lake and Dam in Armstrong County, Pennsylvania, USA by Margaret Luzier, U.S. Army Corps of Engineers – U.S. Army Corps of Engineers Digital Visual Library


  2. Adjacent to dam (Meldahl Hydroelectric Facility, KY)

    Photo courtesy: Stantec


  3. Downstream of dam (Montgomery Locks and Dam Hydroelectric Project)Montgomery Locks and Dam Hydroelectric Project

  4. Through dam (Robert Moses Niagara Hydroelectric Power Station in Lewiston, NY)

    Robert Moses Niagara Power Plant Aerial Shot
    By Busfahrer – taken by me, from Robert Moses Parkway in Niagara County, New York State, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3941077


  5. In gate (Lower St. Anthony Falls Hydroelectric Project)Lower-St.-Anthony-Falls-Dam

  6. In lock (proposed Heidelberg Hydroelectric Project, KY)Heidelberg Hydroelectric Project Aerial View

Non-Powered Dam (NPD) Locations in the US

There are hundreds of NPDs with potential capacities greater than 1 MW, which are mapped out below by the US Department of Energy.

United States map of non-powered dams with hydropower potential capacity greater than 1 MW

Notably, the three hydrologic regions with the most hydropower potential are Ohio, Upper Mississippi, and Arkansas-White-Red. Given the amount of precipitation and low evaporation ratios, Eastern Ohio, Tennessee, and Pacific Northwest are the most favorable regions for hydropower generation. On the contrary, the Colorado River System and the Rio Grande regions have low Q/P ratio and heavily rely on storage in large reservoirs (like Hoover Dam). Due to limited water availability in these regions, there are fewer hydropower projects to be developed.

Existing regional hydropower nameplate capacity


Given that the energy potential at non-powered dams could increase the US hydropower capacity by up to 15% or to 90 GW total, converting non-powered dams is the important step to expanding renewable energy capabilities in the US. Sorensen Systems is here to support the efforts of municipalities switching to renewable energy production.

Hadjerioua, Boualem. An Assessment of Energy Potential at Non-Powered Dams in the United States. U.S. Department of Energy. https://www.energy.gov/sites/prod/files/2013/12/f5/npd_report_0.pdf