Managing hydrologic extremes due to climate variability is an essential mission of water management agencies. Climate change requires water resources managers to move from an equilibrium - or stationary - paradigm to one of constant evolution that recognizes the dynamic nature of physical and socioeconomic processes.
USACE infrastructure, operations, safety and maintenance programs are facing growing stresses caused by aging infrastructure, hydrologic nonstationarity, urban growth, coastal development, evolving navigation and shipping practices, changing agricultural practices, and increasing recognition of the need for ecosystem restoration. USACE must ensure that its systems and projects will remain adaptable and sustainable over time even if the frequency and severity of extreme hydrologic events may change.
Hydrological tools and methods supporting climate change adaptation planning and implementation is a major focus of Brekke et al. (2009) and subsequent discussions by the interagency Climate Change and Water Working Group (USACE 2011). The team will develop processes, methods and guidance for hydrology used in climate change impact assessments and adaptation planning and design.
Hydrological Methods for Nonstationary Cases
The initial focus is on hydrological methods for nonstationary cases. The Climate and Global Change team supported a January 2010 interagency and international expert workshop supported by the IPET/HPDC Lessons Learned Implementation Team (formerly Actions for Change Theme 1). The workshop, "Nonstationarity, Hydrologic Frequency Analysis, and Water Management" addressed whether assumptions of stationarity are valid, use of different statistical models in nonstationarity conditions, trend analyses, how to use the output from global climate models (GCM), and how to treat uncertainty in planning, design, and operations. This workshop also resulted in a special collection of journal papers in the Journal of the American Water Resources Association, June 2011, Volume 47, Issue 3. The Featured Collection on "Nonstationarity, Hydrologic Frequency Analysis, and Water Management" included 13 papers on the topic by national and international experts. An interagency and expert group is currently working on the development of an annotated bibliography of nonstationarity that can support further guidance on the topic.
Selection of Approach to Develop Climate Information
This Climate Change and Water Working Group (CCAWWG) workshop reflects the needs of CCAWWG agencies, who are now planning climate adaptation strategies and policies that will ensure effective and efficient use of Federal water resources on temporal scales from the near (5-10 years) to long term (10-50 years or longer). To do so, the CCAWWG agencies need to rely on good practice guidelines to assess the large and varied portfolio of possible approaches for producing and using actionable climate science for water resource adaptation questions. Adding to the complexity is that each method or analytical technique in this portfolio brings uncertainties and particular deficiencies, some of which are large or only partly characterized and poorly quantified.
In an effort to better define these user needs, USACE, along with Reclamation, has published a report in support of CCAWWG that discusses information and tool gaps needed for longer-term water resources planning and management. A related report, prepared by USACE, Reclamation, and the National Weather Service, discusses information and tool gaps needed for longer-term water resources planning and management. Both reports can be found on the CCAWWG website.
USACE has presented an example of one methodology (pps, 12.32 MB) to select from among climate change scenarios and projections.The approach provides one method of examining global climate models (GCMs) used by the World Meteorological Organization (WMO) Coupled Model Intercomparison Project (CMIP). This method selects five representative climate change scenarios: hotter and wetter, warmer and wetter, warmer and drier, hotter and drier, and central tendency. While the approach detailed in the brief is plausible, USACE is developing new data and methods to move to a more objective technique for determining climate change scenarios and projections.
Appropriate Uses of Paleoflood Information
Engineering Technical Letter ETL 1100-2-2, "Appropriate Application of Paleoflood Information for Hydrology and Hydraulics Decisions," establishes guidance for the appropriate use of paleoflood analyses and information to support USACE hydrology and hydraulics (H&H) decision making. Paleohydrology describes the evidence of the movement of water and sediment in stream channels before the time of continuous hydrologic records or direct measurements. The utility of paleoflood information should be considered with respect to the H&H decision at hand, including both the policy and the technical requirements of that decision.
Utilizing paleoflood data for supporting the decisions of USACE H&H practitioners is the subject of an investigation and report that synthesizes relevant literature and scientific findings related to USACE H&H assessments. Appropriate Application of Paleoflood Information for the Hydrology and Hydraulics Decisions of the U.S. Army Corps of Engineers (pdf, 2.62 MB) investigates utilization of geologically obtained and hydrologically transformed paleoflood data in both the relatively recent past (50-500 years) to the very distant past (500-10,000 years).
The main conclusions of the report are that the utility of paleoflood information should be considered with respect to the H&H decision at hand for situations where paleoflood data is potentially useful to H&H decisions, the resources necessary to conduct the investigation should be weighed against the underlying uncertainties and assumptions; paleofloods can provide direct and useful information about stage histories and can be used, given cautions, to estimate discrete event discharge values; and paleoflood information is less useful if it is meant to inform a portfolio of projects or compare locations across a wide geographic region that has varied terrain and geological contexts. The report is part of a larger effort to explore processes, methods and guidance for hydrology used in climate change impact assessments and adaptation planning and design. More information…
Climate and Hydrology Projection Data and Guidance
USACE, in conjunction with Lawrence Livermore National Laboratory (LLNL), Bureau of Reclamation, U.S. Geological Survey, Climate Central, Scripps Oceanographic Institute, and Santa Clara University, has produced downscaled climate projection data and hydrologic simulations. The data are housed in the publicly accessible Downscaled Climate and Hydrology Projections archive, hosted by LLNL, which is meant to provide access to climate and hydrologic projections at spatial and temporal scales relevant to watershed or basin-scale water resources management decisions
It is important to understand how and why the data were developed, the file-naming convention, and other aspects of the archive to properly extract and use the derived data. At a minimum, the user should view two videos introducing the archive, including "An Introduction to the Downscaled Climate and Hydrology Projections Website ," and complete the MetEd lesson "Preparing Hydro-climate Inputs for Climate Change in Water Resources Planning." This lesson provides necessary background information needed to use the projections site effectively to retrieve climate and hydrology projections data for impacts analysis.
- In the first video, Dr. Subhrendu Gangopadhyay, hydrologic engineer at the Bureau of Reclamation's Technical Service Center in Denver, introduces the website and provides an overview of the lesson.
- In the second video, Dr. Gangopadhyay steps through the process of retrieving projections data using the website.
You are also encouraged to register for additional online classes developed as part of the Climate Change and Water Working Group's interagency collaboration on climate hydrology training at MetEd for further guidance and instructions using climate projection data.
A consortium of partners including the U.S Army Corps of Engineers the Lawrence Livermore National Laboratory (LLNL), the Bureau of Reclamation, the U.S. Geological Survey, Climate Central, Scripps Oceanographic Institute, the National Science Foundation/National Center for Atmospheric Research, and Santa Clara University have produced and archived global climate model outputs temporally and spatially downscaled by several different methods as well as a smaller range of hydrologic outputs from models forced by those projected climatologies. The outputs are available from the publically accessible website, Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections hosted by LLNL. The archive also has other documents (pdf, 469 KB) describing the outputs and the archive and methods change history.
In addition to the archive, the agencies have developed two training videos: An Introduction to the Climate and Hydrology Projections Website and Training and A Tour of Climate and Hydrology Projections Archive Site as well as an online course, Preparing Hydro-climate Inputs for Climate Change in Water Resources Planning. These resources help users select and retrieve the climate and hydrology projection outputs for studies and additional research.