Bulletin 17C

Bulletin 17C

The Guidelines for determining flood flow frequency—Bulletin 17C were published online by the U.S. Geological Survey on March 29, 2018 and are available from the USGS. A minor revision (version 1.1) was released May 31, 2019 (corrections to Appendix 8 - MOVE example). 

The Hydrologic Frequency Analysis Work Group (HFAWG) has revised the US National Flood Frequency Guidelines. As presented (England et al., H51Q) at the AGU Fall 2013 meeting, this revision is called Bulletin 17C. At the ASCE EWRI 2016 Congress, we presented an overview of Bulletin 17C as part of a panel session on the 17C revisions.

The purpose of this page is to provide information to the flood hazard community for several areas related to these revisions. Main topics are listed in the table of contents at the top pf this page.

If you would like to help or be involved in future revisions, please contact me.

Some background information on these revisions can also be found in meeting minutes, documents, and other materials available on the HFAWG web page. Most of the people that were involved in this effort are listed on the HFAWG member page; we also have help and support from several of Jery Stedinger's current and former graduate students, especially Jonathan Lamontagne and Veronica Webster.

Web Page REVISIONS in progress 31-Aug-2021; migration to new google sites - many links need repairs and fixing.

St Vrain Creek, Lyons, Colorado, September 2013 flood

Diverse Data useful with EMA/17C

While retaining the basic structure of Bulletin 17B that uses the method of moments in log-space with the log-Pearson Type III (LP3) distribution and weighted skew coefficient, the HFAWG recommended the adoption of several corrections and extensions to those procedures. Most of these revisions that are in Bulletin 17C follow from the list of needed research included in Bulletin 17A and 17B. All of the changes found in Bulletin 17C are in the spirit of the procedures that were in Bulletin 17B.

Revisions

Why Change?

The use of EMA has three advantages.

The Recommended Revisions to Bulletin 17B memorandum, submitted to the Subcommittee on Hydrology, describes the changes that are made, and includes additional details. Table 1 (page 4) of the memo lists report sections in Bulletin 17B and recommended changes; Table 2 (page 5) lists the Appendix sections and recommended changes.  See also Stedinger and Griffis (2008).

Flood Data with Multiple Thresholds

New Confidence Intervals include Skew Uncertainty

Use of MGBT Reduces Influence of Low Floods

Bulletin 17C Report

The Bulletin 17C report is available from the USGS Publications Warehouse.

An Archive of Public Review Materials is available on the Bulletin 17C web page.

Refer to the Subcommittee on Hydrology - Hydrologic Frequency Analysis Bulletin 17C web page to obtain the report, software links, appendix materials, and additional details.

Bulletin 17C Appendix Materials

Appendix 4 - Initial Data Analysis includes example text files and an R script.

Appendix 8 - Record Extension with Nearby Sites - example to be added.

Appendix 10 - Flood Frequency Examples includes seven examples; input and output text files used with USGS PeakFQ and peakfqSA are provided. USACE HEC-SSP provides example files distributed with that software.

Regional Skew Information is available through the Bulletin 17C Flood Frequency Resources web page.

Software that Implements LP-III/EMA methods in Bulletin 17C

USGS PeakFQ version 7.2 USGS Peak-Flow Frequency Analysis software (MS Windows GUI)

PeakfqSA-usace  - stand-alone (console) software for Linux and Windows with quantiles for dam safety

HEC-SSP - USACE Statistical Software Package that includes Bulletin 17C methods (MS Windows GUI)

We list a brief chronology of some flood frequency studies that are relevant to the Bulletin 17C improvements. The focus is on EMA development history, as it retains the basic method of moments and LP3 distribution from Bulletin 17B. We note that most of this work listed here has been done by current and former members of HFAWG and collaborators. See further details in Griffis and Stedinger (2007a) and Stedinger and Griffis (2008), and the citations with links to publications (as available) listed in the References and Documents section.

1986

1987

1991

1995

1996

1997

1998

1999

2000

2001

2003

2004

2005

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

We list a brief chronology of some flood frequency applications with EMA/LP3 that are relevant to the Bulletin 17C improvements. These practical studies demonstrate that the revisions to Bulletin 17B are effective, and are needed to adequately address the complex flood frequency problems in the United States.

1999

2000

2002

2003

2004

2006

2009

2010

2011

2012

2013

2014-present

Data and Methods

The revisions in Bulletin 17C have been subjected to various kinds of testing. This testing includes evaluating EMA and Bulletin 17B using peak-flow data from 82 sites within the U.S. and Monte-Carlo experiments. In addition, numerous technical papers and applications studies describe the performance and use of EMA/LP3, demonstrating that EMA/LP3 is effective for flood frequency analysis.

The overall testing plan is described in HFAWG (2007). Along with testing, HFAWG members have conducted outreach presentations and papers to communicate the Bulletin 17B revisions, testing plan, and results.

The peak-flow data used for testing is summarized in a spreadsheet.

As part of testing, two software packages were used - PeakfqSA and a beta version of USGS PeakFQ. Input and output files for the 82 data sets used in testing are available here for PeakfqSA and here for PeakFQ. These files are provided so that the results shown in the testing report can be reproduced.

Evaluation Report

The HFAWG  has completed a testing report and released a final version (2019), titled Evaluation of Recommended Revisions to Bulletin 17B (Cohn et al., 2019). The original draft report was submitted to the Subcommittee on Hydrology in August 2013, as part of the basis for the recommended revisions to Bulletin 17B. The report was revised in April 2014 to include additional PILF censoring at the 25th percentile. This final report incorporates comments from HFAWG members and from USGS peer reviewers.   

The Evaluation report results demonstrate that flood quantile estimators proposed as a revision of Bulletin 17B:

Some figures from the Evaluation Report

Presentations and outreach, on issues related to the Bulletin 17B revisions, are listed here. This list generally includes technical presentations on EMA, plotting positions, low outliers, applications, etc. See the HFAWG Minutes page for presentations and topics of discussion at HFAWG meetings.

For those presentations given at conferences, where a paper was published (such as at ASCE EWRI), see the list in the References and Documents section for a full citation. Links are provided to download papers if they available.

1995

1996

1997

1998

2000

2007

2008

2009

2010

2013

2014

2015

2016

2017

2018

2019

Flood Frequency Software

Flood frequency software that implements the Bulletin 17C recommended methods -  EMA/LP3 with interval data, historical/paleoflood data, MGBT for low outliers, regional skew weighting, confidence limits, etc., is available from USACE and USGS. 

Tim Cohn (USGS) was the principal author of the core EMA routines used in the software. Several HFAWG members and collaborators have been heavily involved in testing, research, and development of the software.

There are several software packages available that may be used to apply the recommended Bulletin 17C methods.

A USACE version of PeakfqSA, that includes extreme quantiles for dam safety and nuclear facilities is available (includes Fortran source code, compile instructions, executables, examples, manual) by John England. It is a stand-alone (console) version of EMA/LP3 available for Linux, MS Windows 7/10, and Macbook (High Sierra, Version 10.13.4). It is based on the last version of PeakfqSA  written by Tim Cohn. The manual is a bit dated and will eventually be revised. A public repository for PeakfqSA on GitHub is under development. 

The USGS has released PeakFQ version 7.3 that implements the recommended methods in Bulletin 17C,  including EMA, interval data, MGBT, and new confidence intervals. This software works on Microsoft Windows 7/8/10.

The U.S. Army Corps of Engineers Hydrologic Engineering Center has revised the HEC-SSP software to include Bulletin 17C methods. Most recently, HEC-SSP version 2.2 has been released in June 2019. The software includes Bulletin 17C examples, volume frequency with EMA, and other features.

Reclamation has used flood frequency with EMA/LP3 for many site-specific studies since the late 1990s. This software has been called "EMA" (England, 1999) and "EMFREQ" (England, 2000), and relies on much of the EMA routines developed by Tim Cohn. EMFREQ version 1.2 (2007, WinXP) has seen extensive use and application with historical and paleoflood data for dam safety applications (see Applications). The software contained the single GBT low outlier test and confidence intervals from Cohn et al. (2001). It is mentioned here only for reference and history and is no longer supported, because the software does not include all the Bulletin 17C revisions, including MGBT and improved confidence intervals. The Reclamation EMA user manual (England, 1999) does not currently describe all the features in that version.

Training

A technical workshop on Bulletin 17C was held at the SEDHYD 2019 conference on June 24, 2019. The Technical Workshop agenda is available here. The Bulletin17C SEDHYD workshop presentations are available here.

A technical workshop on Bulletin 17C was held at the ASCE EWRI 2018 conference on Thursday June 7, 2018. The Technical Workshop agenda is available here. A Quiz on EMA Flow Intervals and Perception Thresholds (courtesy of Andrea Veilleux, USGS) was covered at the workshop and is available here.

The EWRI 2018 Bulletin 17C Workshop agenda and presentations are available here

HEC-SSP beta version 2.20.249 that was used in the workshop is available here.

Details on the EWRI 2018 conference and technical workshops are at http://www.ewricongress.org/.

A short course on Bulletin 17C was held at the ASCE EWRI 2016 conference on Thursday May 26, 2016. 

EWRI 2016 Short course material - presentations, references, and documents that were provided to participants is available here (63 Mb file). HEC-SSP beta software and Bulletin 17C examples used in the EWRI 2016 Short Course are available here

Flood frequency concepts that are included in Bulletin 17C (EMA, interval data, PILFs, confidence intervals, etc.) are currently part of USGS Flood Frequency training classes. USGS also conducts periodic webinars on the PeakFQ software. Contact Chief, Analysis and Prediction Branch, USGS for details. The US Army Corps of Engineers, Risk Management Center periodically offers training on hydrologic hazards, including flood frequency with EMA/LP3. Please contact me for details. The USACE Hydrologic Engineering Center also offers training in flood frequency.

Other training courses, short courses, seminars, and webinars on Bulletin 17C and software are under development by USACE and USGS.

Additional information on training courses will be posted here, as it becomes available.

EMA/LP3 Software

(click images to enlarge)

References and documents relevant to Bulletin 17C are listed here, with links to obtain the document (if available). These documents are provided for research purposes of the HFAWG.

Blainey, J.B. (2000) Monte Carlo simulation of paleofloods: information content of paleoflood data in flood-frequency analysis, M.S. Thesis, Department of Hydrology and Water Resources, University of Arizona, Tucson, 93 p.

Blainey, J.B., Webb, R.H., Moss, M.E., and Baker, V.R. (2002) Bias and information content of paleoflood data in flood frequency analysis, in House, P.K., Webb, R.H., Baker, V.R., and Levish, D.R., eds., Ancient Floods, Modern Hazards: Principles and Applications of Paleoflood Hydrology, American Geophysical Union, Washington, D.C., p. 161-174.

Bureau of Reclamation (2002) Flood Hazard Analysis - Folsom Dam, Central Valley Project, California. Bureau of Reclamation, Denver, CO, January, 128 p. and 4 appendices

Chowdhury, J.U. and J.R. Stedinger (1991) Confidence Intervals for Design Floods with Estimated Skew Coefficient. Journal of Hydraulic Engineering, 117(7), pp. 811-831.

Cohn, T.A., W.L. Lane, and W.G. Baier (1997) An algorithm for computing moments-based flood quantile estimates when historical information is available, Water Resour. Res., 33(9), 2089–2096.

Cohn, T.A., W.L. Lane, and J.R. Stedinger (2001) Confidence Intervals for EMA Flood Quantile Estimates, Water Resources Research, 37(6), 1695-1706.

Cohn, T.A., Barth, N.A., England, J.F. Jr., Faber, B., Mason, R.R. and Stedinger, J.R. (2019) Evaluation of Recommended Revision to Bulletin 17B. USGS Open File Report 2017-1064, 141 p.

Cohn, T.A., England, J.F. Jr., Berenbrock, C., Mason, R.R., Stedinger, J.R., and Lamontagne, J.R. (2013b) A Generalized Grubbs-Beck Test Statistic for Detecting Multiple Potentially-Influential Low Outliers in Flood Series, Water Resour. Res., vol 49, doi:10.1002/wrcr.20392, pp. 5047-5058.

Curtis, J. A. and Whitney, J. W. (2003) Geomorphic and hydrologic assessment of erosion hazards at the Norman municipal landfill, Canadian River floodplain, Central Oklahoma, Environmental and Engineering Geoscience 9(3),doi:10.2113/9.3.241, pp. 241-252.

Eash, D.A., Barnes, K.K., and Veilleux, A.G., 2013, Methods for estimating annual exceedance-probability discharges for streams in Iowa, based on data through water year 2010: U.S. Geological Survey Scientific Investigations Report 2013-5086, 63 p. with appendix.

England, J.F. Jr. (1998) Assessment of Historical and Paleoflood Information in Flood Frequency Analysis. M.S. Thesis, Department of Civil Engineering, Colorado State University, Fort Collins, CO, 292 p.

England, J.F. Jr. (1999) Draft User’s manual for program EMA, At-Site Flood Frequency Analysis with Historical/Paleohydrologic Data. Bureau of Reclamation, Denver, CO, July, 52 p.

England, J.F. Jr. (2000) A Simple Moments-Based Estimator That Utilizes Historical And Paleohydrologic Information, American Society of Civil Engineers, Joint Conference on Water Resources Engineering and Water Resources Planning and Management July 30 - August 2, 2000, Minneapolis, MN, 10 p.

England, J.F. Jr. and Collins, C.D. (2004) Flood Frequency and Hydrographs, Brantley Dam, New Mexico. Bureau of Reclamation, Denver, CO, December, 11 p. and appendices.

England, J.F. Jr. and Cohn, T.A. (2007) Scientific and Practical Considerations Related to Revising Bulletin 17B: The Case for Improved Treatment of Historical Information and Low Outliers, American Society of Civil Engineers, EWRI World Water & Environmental Resources Congress, May 15-19, 2007, Tampa, FL, 9 p.

England, J.F. Jr. and Cohn, T.A. (2008) Bulletin 17B Flood Frequency Revisions: Practical Software and Test Comparison Results, American Society of Civil Engineers, EWRI World Water & Environmental Resources Congress, May 13-16, 2008, Honolulu, HI, 11 p.

England, J.F. Jr., Salas, J.D., and Jarrett, R.D. (1998) A Comparison of Moments-based Estimators for Flood Frequency Analysis That Incorporate Historical Information. Proceedings, First Federal Interagency Hydrologic Modeling Conference, Las Vegas, NV, by the Subcommittee on Hydrology of the Interagency Committee on Water Data, pp. 4-37 - 4-44.

England, J.F. Jr., Salas, J.D., and Jarrett, R.D. (2003a) Comparisons of two moments-based estimators that utilize historical and paleoflood data for the log-Pearson Type III distribution. Water Resour. Res. 39 (9), pp. SWC-5-1 – SWC-5-16, doi:10.1029/2002WR001791.

England, J.F. Jr., Jarrett, R.D., and Salas, J.D. (2003b) Data-based comparisons of moments estimators that use historical and paleoflood data. J. Hydrol. 278 (1-4), doi:10.1016/S0022-1694(03)00141-0, pp. 170-194.

England, J.F. Jr., Klawon, J.E., Klinger, R.E. and Bauer, T.R. (2006) Flood Hazard Study, Pueblo Dam, Colorado, Final Report, Bureau of Reclamation, Denver, CO, June, 160 p. and seven appendices.

England, J.F. Jr., Cohn, T.A., Faber, B.A., Stedinger, J.R., Thomas, W.O., and Mason, R.R. (2013) Revisions Recommended to Bulletin 17B – US National Flood Frequency Guidelines, Abstract H51Q-03, presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec.

Godaire, J.E., and Bauer, T.R., 2012, Paleoflood study, North Fork Red River basin near Altus dam, Oklahoma: U.S. Department of Interior, Bureau of Reclamation, Denver, Colo., 55 p.

Godaire, J.E., and Bauer, T.R., 2013, Paleoflood study on the Rio Chama near El Vado dam, New Mexico: U.S. Department of Interior, Bureau of Reclamation, Denver, Colo., 58 p.

Godaire, J.E., Bauer, T.R., and Klinger, R.E., 2012, Paleoflood study, San Joaquin River near Friant dam, California: U.S. Department of Interior, Bureau of Reclamation, Denver, Colo., 60 p.

Gotvald, A.J., Barth, N.A., Veilleux, A.G., and Parrett, Charles (2012) Methods for determining magnitude and frequency of floods in California, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2012–5113, 38 p., 1 pl

Griffis, V. W. (2003) Evaluation of log-Pearson type 3 flood frequency analysis methods addressing regional skew and low outliers, M.S. thesis, Dept. of Civil and Environ. Eng., Cornell Univ., Ithaca, N.Y.

Griffis, V. W. (2008) EMA with historical information, low outliers, and regional skew, in proceedings World Water & Environmental Resources Congress 2008, Editors R. W. Babcock and R. Walton, American Society of Civil Engineers, Reston, Virginia.

Griffis, V.W. and Stedinger, J.R. (2007a) Evolution of flood frequency analysis with Bulletin 17. J. Hydrol. Eng., 12(3), pp. 283–297.

Griffis, V. W. and J. R. Stedinger (2007b) Incorporating climate change and variability into Bulletin 17B LP3 model, Paper 40927-2320, World Environmental & Water Resources Conference - Restoring our Natural Habitat, K.C. Kabbes editor, Tampa, Florida, May 15-18, 2007.

Griffis, V. W., J.R. Stedinger, and T.A. Cohn (2003) Extension of EMA to address regional skew and low outliers, Proceedings World Water & Environmental Resources Congress 2003, June 23-26. Paper # 816. Editors P. Bizier and P. DeBarry, Philadelphia, PA, American Society of Civil Engineers, Reston, Virginia.

Griffis, V.W., J.R. Stedinger, and T.A. Cohn (2004) LP3 Quantile Estimators with Regional Skew Information and Low Outlier Adjustments, Water Resources Research, 40, W07503, doi:1029/2003WR002697.

Harden, T.M., O’Connor, J.E., Driscoll, D.G., and Stamm, J.F. (2011) Flood-frequency analyses from paleoflood investigations for Spring, Rapid, Boxelder, and Elk Creeks, Black Hills, western South Dakota: U.S. Geological Survey Scientific Investigations Report 2011–5131, 136 p.

Hirsch, R.M. and Stedinger, J.R. (1987) Plotting positions for historical floods and their precision. Water Resour. Res. 30(6), pp. 1653-1664.

Hydrologic Frequency Analysis Work Group (HFAWG) (2006) Flood Frequency Research Needs. Memorandum Submitted to Subcommittee on Hydrology, January 16, 3 p.

Hydrologic Frequency Analysis Work Group (HFAWG) (2007) Summary of Gaging Station Data and Testing Methods for the EMA and Bulletin 17B Comparisons. Prepared by Will Thomas, Hydrologic Frequency Analysis Work Group, Subcommittee on Hydrology, revised August 8, 4 p.

Jarrett, R.D. and Tomlinson, E.M. (2000) Regional interdisciplinary paleoflood approach to assess extreme flood potential. Water Resour. Res. 36 (10), DOI: 10.1029/2000WR900098, 2957–2984.

Klinger, R.E., and Bauer, T.R., 2010, Paleoflood study on the South Fork of the Boise River for Anderson Ranch dam, Idaho: U.S. Department of Interior, Bureau of Reclamation, Denver, Colo., 30 p.

Klinger, R.E., and Godaire, J.E., 2002, Development of a paleoflood database for rivers in the western U.S.: U.S. Department of Interior, Bureau of Reclamation, Denver, Colo., 38 p.

Lamontagne, J.R., Stedinger, J.R., Berenbrock, Charles, Veilleux, A.G., Ferris, J.C., and Knifong, D.L. (2012) Development of regional skews for selected flood durations for the Central Valley Region, California, based on data through water year 2008: U.S. Geological Survey Scientific Investigations Report 2012–5130, 60 p.

Lamontagne, J.R., J.R. Stedinger, T.A. Cohn, and N. Barth (2013) Robust National Flood Frequency Guidelines: What is an Outlier?, in World Environmental & Water Resources Conference, Cincinnati, OH, edited by C.L. Patterson, S.D. Struck, and D.J. Murray, ASCE EWRI

Lane, W.L. (1987) Paleohydrologic data and flood frequency estimation. In V.P. Singh (ed.) Regional Flood Frequency Analysis, D. Reidel, pp. 287-298.

Lane, W.L. (1995) Method of moments approach to historical data, informal handout, Bulletin 17B Working Group, Hydrology Subcommittee, Interagency Advisory Committee on Water Data, 2 p.

Lane, W.L. and Cohn, T.A. (1996) Expected moments algorithm for flood frequency analysis. In C.T. Bathala (ed.) North American Water and Environ. Congress 1996, ASCE, Anaheim, California June 22-28, 1996.

Levish, D.R., England, J.F. Jr., Klawon, J.E. and O’Connell, D.R.H. (2003) Flood Hazard Analysis for Seminoe and Glendo Dams, Kendrick and North Platte Projects, Wyoming, Final Report, Bureau of Reclamation, Denver, CO, November, 126 p. and two appendices.

National Research Council (NRC) (1999) Improving American River Flood Frequency Analysis, National Academy Press, Washington, D.C., 120 p.

Novembre, N., V. Sankovich, R. Caldwell, J. Niehaus, and J. Wright (2012), Altus Dam Hydrologic Hazard and Reservoir Routing for Corrective Action Study, Bureau of Reclamation, Denver, CO, August 2012.

O'Connell, D.R.H. (1999) FLDFRQ3, Three-parameter maximum likelihood flood-frequency estimation with optional probability regions using parameter grid integration. User’s Guide (Release 1.1) February 24, 1999, Bureau of Reclamation, 19 p.

Olsen, J.R. (2011) Meeting on Flood Frequency Analysis and Bulletin 17B revisions. Memorandum for Record, U.S. Army Corps of Engineers, Institute for Water Resources, Alexandria, VA, 2 p.

Parrett, C., Veilleux, A., Stedinger, J.R., Barth, N.A., Knifong, D.L., and Ferris, J.C. (2011) Regional skew for California, and flood frequency for selected sites in the Sacramento–San Joaquin River Basin, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2010–5260, 94 p.

Stedinger, J.R. and Cohn, T.A. (1986) Flood frequency analysis with historical and paleoflood information. Water Resour. Res. 22(5), pp. 273-286.

Stedinger, J.R., Surani, R., and Therivel, R. (1988) Max user’s guide: A program for flood frequency analysis using systematic-record, historical, botanical, physical paleohydrologic and regional hydrologic information using maximum likelihood techniques. Cornell University, 51 p.

Stedinger, J.R. (1992) Max for flood frequency analysis - or -  maximum likelihood estimators for use with historical data, gaged flow records, and regional information. Cornell University, 10 p.

Stedinger, J.R. and England, J.F. Jr. (2005) Key Documents for Discussion of Evolution of Bulletin 17B and Proposed Changes. Submitted to Hydrologic Frequency Analysis Work Group, Subcommittee on Hydrology, November 3, 9 p.

Stedinger, J.R. and Griffis, V.W. (2008) Flood frequency analysis in the United States: Time to update. Journal of Hydrologic Engineering, ASCE, 13(4):199–204.

Stedinger, J.R. and V.W. Griffis (2011) Getting From Here to Where? Flood Frequency Analysis and Climate. JAWRA Journal of the American Water Resources Association, 47: 506–513. doi: 10.1111/j.1752-1688.2011.00545.x

Stedinger, J.R., W.O. Thomas, T.A. Cohn (2008) Update to Bulletin 17B: Flood Frequency Guidelines in the U.S., Floodplain Management Ass., 2008 Ann. Conference, Paradise Point Resort San Diego, CA, Sept 2-5.

Sutley, D.E., Klinger, R.E., Bauer, T.R. and Godaire, J.E. (2009), Trinity Dam Detailed Hydrologic Hazard Analysis Using the Stochastic Event Flood Model, U.S. Department of Interior, Bureau of Reclamation, Denver, CO

Thomas, W., J. England, T. Cohn, and B. Koper (2008) Recent Developments in Flood Frequency Analysis Including Plans to Update Bulletin 17B. Assoc. of State Flood Plain Managers,  Annual Conference, Reno, NV, May 18-23.

Thomas, W., England, J., Cohn, T. and Steinberger, N (2010) Recent Developments in Flood Frequency Analysis Including Plans to Update Bulletin 17b. Proceedings, Fourth Federal Interagency Hydrologic Modeling Conference, Las Vegas, NV, Jun 28-Jul 1, 2010, 4 p.

Wright, J.M. (2010) Flood Frequency, Middle Rio Grande, New Mexico, U.S. Department of Interior, Bureau of Reclamation, Denver, CO