Assessment of Natural Stream Sites for Hydroelectric Dams in the Pacific Northwest Region
Douglas G. Hall, INL Kristine L. Verdin, USGS Randy D. Lee, INL
March 2012
SUMMARY
Resource assessments of United States natural streams to determine the magnitude of the resource and identify opportunities for conventional hydropower development have been conducted most recently over the past 20 years and were conducted even prior to this period. During the 1990s the Idaho National Laboratory (INL) conducted a nationwide assessment of hydropower development opportunities based primarily on sites for which a preliminary permit had been issued by the Federal Energy Regulatory Commission, but were undeveloped at the time of the assessment. During the first decade of the 21st century, INL conducted a comprehensive assessment of the gross power potential of all U.S. streams, and a subsequent assessment of feasible development sites and the developable power than could be produced at those sites assuming a damless small hydropower development model.
The more recent assessments have benefitted from several technological advancements:
Digital elevation models with 30 m resolution provided by the National Elevation Dataset (NED)
Derivatives of the NED, Elevation Derivatives for National Applications (EDNA) that produced three dimensional hydrography with associated stream reach catchments
Hydrologic modeling that provides the means to estimate the annual average flow rate on any stream in the 50 states
Geographic information systems (GIS) tools that provide the means to combine geospatial data to produce new attributes while retaining the attributes of the original data.
Development of geographic coordinates for dams listed in the Army Corps of Engineers National Inventory of Dams (NID) that placed each dam on its stream of residence in the high resolution hydrography provided by the U.S. Geological Surveys National Hydrography Dataset (NHD)
Addition of flow rate estimates and other attributes to the medium resolution NHD hydrography issued as the National Hydrography Dataset Plus (NHD Plus).
While recent assessments have provided estimates of the gross power potential of all U.S. natural streams on a reach by reach basis, and even estimates of the developable power potential of feasibly developable reaches (development sites), they did not provide basic physical project characteristics that would be required and result if a greenfield site was developed using a conventional stream obstructing dam. The Bureau of Reclamation, Bureau of Land Management, and individual developers have taken site evaluation to this level for specific sites. The objective of the present study was to develop and demonstrate a methodology capable of comprehensively modeling sites in a large region using a stream obstructing dam development model that provides basic project characteristics including power potential, dimensions of the principal dam, the need for any auxiliary dams, the total length of the impoundment constructed boundary, and the size of the inundation area (reservoir).
vi
The individual stream reaches in Hydrologic Region 17 as defined by the medium resolution NHD as provided by NHD Plus were used as the site population to be modeled. Hydrologic Region 17 encompasses most of Idaho, Oregon, and Washington. The power potential of each site was estimated by combining the elevation difference between the upstream and downstream end of the reach with the unit runoff model predicted flow rate provided by NHD Plus. To obtain project physical characteristics, the modeling approach identified all points in a raster digital elevation model (DEM) having the same elevation as the upstream end of a stream reach thus defining the inundation area (reservoir) that would result from placing a stream obstructing dam at the downstream end of the reach. The height of the dam was that necessary to impound water up to the upstream end of the reach and therefore was equal to the difference in elevation between the upstream and downstream ends of the reach plus an assumed freeboard percentage. The length of the dam was determined by where its ends encountered places on the catchment boundary where the topography is of sufficient elevation to complete the impoundment boundary. Gaps in the impoundment boundary where the elevation of the topography was insufficient to contain the water in the reservoir were considered places requiring an auxiliary dam. In this pilot study, the potential project site population was limited to single stream reaches. Sites where multiple reaches could be ganged together to form larger projects is the subject of a subsequent study.
Basic project characteristics were produced for the nearly 232,000 stream reaches in Hydrologic Region 17. As an illustration of how these data can be used to define a population of candidate sites having technically reasonable characteristics, the full population was decomposed into subsets having progressively greater value for further assessment. The datasets from the successive decompositions, the number of reaches (sites) and their total capacity potential in each are shown in the following table:
http://hydropower.inel.gov/resourceassessment/pdfs/hydro-assessment2012.pdf
Douglas G. Hall, INL Kristine L. Verdin, USGS Randy D. Lee, INL
March 2012
SUMMARY
Resource assessments of United States natural streams to determine the magnitude of the resource and identify opportunities for conventional hydropower development have been conducted most recently over the past 20 years and were conducted even prior to this period. During the 1990s the Idaho National Laboratory (INL) conducted a nationwide assessment of hydropower development opportunities based primarily on sites for which a preliminary permit had been issued by the Federal Energy Regulatory Commission, but were undeveloped at the time of the assessment. During the first decade of the 21st century, INL conducted a comprehensive assessment of the gross power potential of all U.S. streams, and a subsequent assessment of feasible development sites and the developable power than could be produced at those sites assuming a damless small hydropower development model.
The more recent assessments have benefitted from several technological advancements:
Digital elevation models with 30 m resolution provided by the National Elevation Dataset (NED)
Derivatives of the NED, Elevation Derivatives for National Applications (EDNA) that produced three dimensional hydrography with associated stream reach catchments
Hydrologic modeling that provides the means to estimate the annual average flow rate on any stream in the 50 states
Geographic information systems (GIS) tools that provide the means to combine geospatial data to produce new attributes while retaining the attributes of the original data.
Development of geographic coordinates for dams listed in the Army Corps of Engineers National Inventory of Dams (NID) that placed each dam on its stream of residence in the high resolution hydrography provided by the U.S. Geological Surveys National Hydrography Dataset (NHD)
Addition of flow rate estimates and other attributes to the medium resolution NHD hydrography issued as the National Hydrography Dataset Plus (NHD Plus).
While recent assessments have provided estimates of the gross power potential of all U.S. natural streams on a reach by reach basis, and even estimates of the developable power potential of feasibly developable reaches (development sites), they did not provide basic physical project characteristics that would be required and result if a greenfield site was developed using a conventional stream obstructing dam. The Bureau of Reclamation, Bureau of Land Management, and individual developers have taken site evaluation to this level for specific sites. The objective of the present study was to develop and demonstrate a methodology capable of comprehensively modeling sites in a large region using a stream obstructing dam development model that provides basic project characteristics including power potential, dimensions of the principal dam, the need for any auxiliary dams, the total length of the impoundment constructed boundary, and the size of the inundation area (reservoir).
vi
The individual stream reaches in Hydrologic Region 17 as defined by the medium resolution NHD as provided by NHD Plus were used as the site population to be modeled. Hydrologic Region 17 encompasses most of Idaho, Oregon, and Washington. The power potential of each site was estimated by combining the elevation difference between the upstream and downstream end of the reach with the unit runoff model predicted flow rate provided by NHD Plus. To obtain project physical characteristics, the modeling approach identified all points in a raster digital elevation model (DEM) having the same elevation as the upstream end of a stream reach thus defining the inundation area (reservoir) that would result from placing a stream obstructing dam at the downstream end of the reach. The height of the dam was that necessary to impound water up to the upstream end of the reach and therefore was equal to the difference in elevation between the upstream and downstream ends of the reach plus an assumed freeboard percentage. The length of the dam was determined by where its ends encountered places on the catchment boundary where the topography is of sufficient elevation to complete the impoundment boundary. Gaps in the impoundment boundary where the elevation of the topography was insufficient to contain the water in the reservoir were considered places requiring an auxiliary dam. In this pilot study, the potential project site population was limited to single stream reaches. Sites where multiple reaches could be ganged together to form larger projects is the subject of a subsequent study.
Basic project characteristics were produced for the nearly 232,000 stream reaches in Hydrologic Region 17. As an illustration of how these data can be used to define a population of candidate sites having technically reasonable characteristics, the full population was decomposed into subsets having progressively greater value for further assessment. The datasets from the successive decompositions, the number of reaches (sites) and their total capacity potential in each are shown in the following table:
http://hydropower.inel.gov/resourceassessment/pdfs/hydro-assessment2012.pdf
