Aquatic Resources Delineation Overview

An Aquatic Resources Delineation is a process used by the Corp of engineers to identify, classify, and map the boundaries of aquatic resources, such as wetlands, streams, rivers, lakes, and ponds, within a specific area. This delineation is crucial for understanding the extent and types of aquatic resources present in a location, which can include both natural and man-made water bodies. The purpose of delineation is to provide a clear and scientifically accurate representation of aquatic resources, which is essential for land-use planning, environmental protection, and regulatory compliance.

Key Steps in Aquatic Resources Delineation:
  • Preliminary Assessment: Initial review of maps, aerial photographs, and other resources to identify potential aquatic features.
  • Field Investigation: On-site examination to verify and map the boundaries of aquatic resources. This involves identifying soil types, hydrology, and vegetation that indicate the presence of aquatic resources.
  • Mapping and Reporting: The results of the field investigation are documented in detailed maps and reports, which describe the location, size, and type of aquatic resources identified.
Relation to the Clean Water Act (CWA):

The Clean Water Act (CWA) is a key piece of U.S. legislation aimed at regulating the discharge of pollutants into the waters of the United States and protecting the nation's water resources. The CWA's primary goal is to restore and maintain the integrity of the nation's waters, including rivers, lakes, streams, wetlands, and coastal areas.

Aquatic Resources Delineation is directly related to the CWA because:

  • Jurisdictional Determination: The CWA requires that certain waters, known as "waters of the United States" (WOTUS), be protected from unregulated discharge of pollutants. Delineation helps determine which aquatic resources fall under federal jurisdiction by identifying WOTUS.
  • Permitting Process: Before any land development or construction activities can occur, developers must obtain permits if their projects may impact WOTUS. The delineation process is essential in determining whether a permit is needed under Section 404 of the CWA, which regulates the discharge of dredged or fill material into WOTUS.
  • Environmental Protection: Accurate delineation ensures that aquatic resources are properly identified and protected according to CWA regulations. It helps avoid unintentional impacts on these resources, ensuring that they remain viable and healthy.

In summary, Aquatic Resources Delineation is a critical process that supports the implementation and enforcement of the Clean Water Act by identifying and protecting important water resources within the United States.

Questions regarding Aquatic Resource Delineations please contact your local regulatory office.

The District encourages applicants to use consultants to conduct preliminary wetland delineations, especially for large and/or complex areas.

Delineations, which meet our minimum standards may then be submitted to the District for review and verification.

Ordinary High Water Mark (OHWM) Delineation

The ordinary high water mark (OHWM) defines the lateral extent of nontidal aquatic features in the absence of adjacent wetlands in the United States. The federal regulatory definition of the OHWM, 33 CFR 328.3(c)(7), states the OHWM is “that line on the shore established by the fluctuations of water and indicated by physical characteristics such as [a] clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas.”

The National OHWM Field Delineation Manual for rivers and streams: Final Version can be accessed and downloaded through the engineer Research & Development Center (ERDC) website by clicking here. This is the first manual to present a methodology for nationwide identification and delineation of the OHWM. A two-page data sheet and field procedure outline a weight-of-evidence (WoE) methodology to organize and evaluate observations at stream sites. This manual presents a consistent, science-based method for delineating the OHWM in streams. It also describes regional differences and challenges in identifying the OHWM at sites disturbed by human-induced or natural changes and illustrates how to use remote data to structure field inquiries and interpret field evidence using the principles of fluvial science. The manual demonstrates that, in many landscape settings, the OHWM may be located near the bankfull elevation.

OHWM Regional Supplements
Nationwide:
Arid West:
Western Mountains, Valleys and Coast supplements:

Rapid Ordinary High Water Mark (OHWM) Identification Data Sheet (September 2024)


Assessing Stream Duration

Regional Stream flow Duration Assessment Methods (SDAMs) -

The U.S. Army Corps of Engineers (Corps) Albuquerque, Chicago, Detroit, Fort Worth, Galveston, Kansas City, Los Angeles, Omaha, Rock Island, Sacramento, San Francisco, St. Louis, St. Paul, and Tulsa Districts, and the U.S. Environmental Protection Agency (EPA), Regions 5, 6, 7, 8, and 9 jointly announce the availability of the Regional Streamflow Duration Assessment Methods (Regional SDAMs) for the Arid West, Western Mountains and Great Plains. The methods are rapid assessment tools for distinguishing between ephemeral, intermittent, and perennial streamflow at the reach scale for the Arid West, Western Mountains and Great Plains regions.  For background information, SDAM development, instructions/training materials for completed SDAMs,  and field form information please visit  EPA's SDAM webpage .

NOTE - SDAMs are region specific, please download and view the map of SDAM regions 

Regional SDAM manuals and data forms:

Wetland Delineation

Wetland delineation is fundamental to Corps of Engineers (Corps) and Environmental Protection Agency (EPA) regulatory responsibilities under Section 404 of the Clean Water Act (CWA).  Wetland delineation consists of standardized procedures that are used to determine if a wetland is present on a site and, if so, to establish its boundaries in the field.  In combination with current regulations and policies, delineation methods help to define the area of Federal responsibility under the Act, within which the agencies attempt to minimize the impacts of proposed projects to the physical, chemical, and biological integrity of the Nation’s waters.

The Corps of Engineers defined and developed methods of identifying wetlands in the January 1987, Corps of Engineers Wetlands Delineation Manual (Corps Manual). The Manual was prepared by the Environ-mental Laboratory (EL) of the U.S. Army Engineer Waterways Experiment Station (WES), Vicksburg, Mississippi. The work was sponsored by Headquarters, U.S. Army Corps of Engineers (HQUSACE), through the Wetlands Research Program. Since the manuals issuance, the use and interpretation of the Manual has been clarified and updated through a series of guidance documents and memoranda from USACE Head Quarters.

The purpose of this manual is to provide users with guidelines and methods to determine whether an area is a wetland. The manual describes technical guidelines and methods using a multiparameter approach to identify and delineate wetlands for purposes of Section 404 of the Clean Water Act.

Specific objectives of the manual are:
  1. Present technical guidelines for identifying wetlands and distinguishing them from aquatic habitats and other non wetlands.
  2. Provide methods for applying the technical guidelines.

  3. Provide supporting information useful in applying the technical guidelines.

Wetland Defined

The following definition, diagnostic environmental characteristics, and technical approach comprise a guideline for the identification and delineation of wetlands;

  1. The Corps of Engineers (Federal Register 1982) and the EPA (Federal Register 1980) jointly define wetlands as: "Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas."

  2. Wetlands have the following general diagnostic environmental characteristics:
    1. Vegetation. The prevalent vegetation consists of macrophytes that are typically adapted to areas having hydrologic and soil conditions described in a above. Hydrophytic species, due to morphological, physiological, and/or reproductive adaptation(s), have the ability to grow, effectively compete, reproduce, and/or persist in anaerobic soil conditions. Indicators of vegetation associated with wetlands1are listed in paragraph 35 of the manual.
    2. Soil. Soils are present and have been classified as hydric, or they possess characteristics that are associated with reducing soil conditions. Indicators of soils developed under reducing conditions are listed in paragraphs 44 and 45 of the manual.
    3. Hydrology. The area is inundated either permanently or periodically at mean water depths <6.6-feet, or the soil is saturated to the surface at some time during the growing season of the prevalent vegetation. Indicators of hydrologic conditions that occur in wet-2lands are listed in paragraph 49.

  3. Technical approach for the identification and delineation of wetlands. Except in certain situations defined in this manual, evidence of a mini-mum of one positive wetland indicator from each parameter (hydrology, soil, and vegetation) must be found in order to make a positive wetland determination.

The Manual was further refined by the U.S. Army Engineer Research and Development Center (ERDC) at the request of Headquarters, U.S. Army Corps of Engineers (USACE), with funding provided through the Wetlands Regulatory Assistance Program (WRAP) to create a series of Regional Supplements.  these supplements are intended to provide technical guidance and procedures for identifying and delineating wetlands that may be subject to regulatory jurisdiction under Section 404 of the Clean Water Act or Section 10 of the Rivers and Harbors Act. The development of Regional Supplements is part of a nationwide effort to address regional wetland characteristics and improve the accuracy and efficiency of wetland-delineation procedures.  Below is the map of locations and general extent of the different Regional Supplements.

Map the United states including Alaska and Hawaii detailing the areas or regions to apply the specifc  Wetland Delineation regional Supplement. Lime green indicates the use of the "Western Mountains, Valleys and Coast" supplement; the area in yellow indicates the use of the "Great Plains" supplement; the area in Pink indicates the use of the "Arid West" Suplement. these three supplements are the only supplements that can be applied in the SPA, regulatory division Area of Responcibility.

Wetland Regional Supplements applicable to Albuquerque District Area of Responsibility and Supporting Information


 This supplement is applicable to the Arid West Region, which consists of all or portions  of 12 states: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Texas, Utah, Washington, and Wyoming. It is designed for use with the current version of the Corps Manual (Environmental Laboratory 1987) and all subsequent versions. Where differences in the two documents occur, this Regional Supplement takes precedence over the Corps Manual for applications in the Region. 

Arid West guide and wetland data collection sheets:

Additional information regarding the Arid West Regional Supplement can be found on the USACE Headquarters website.


This supplement is applicable to the Western Mountains, Valleys, and Coast (WMVC) Region, which consists of portions of 12 states: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, and Wyoming. It is designed for use with the current version of the Corps Manual (Environmental Laboratory 1987) and all subsequent versions. Where differences in the two documents occur, this Regional Supplement takes precedence over the Corps Manual for applications in the WMVC Region. 

WMVC regional guide and wetland data collection sheets:

Additional information regarding the WMVC Regional Supplement can be found on the USACE Headquarters website.

 

 

 

 


This supplement is applicable to the Great Plains Region, which consists of all or portions of 11 states:  Colorado, Kansas, Minnesota, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. It is designed for use with the current version of the Corps Manual (Environmental Laboratory 1987) and all subsequent versions. Where differences in the two documents occur, this Regional Supplement takes precedence over the Corps Manual for applications in the WMVC Region. 

Great Plains regional guide and wetland data collection sheets:

Additional information regarding the AW Regional Supplement can be found on the USACE Headquarters website.

Additional resources in support to wetlands delineations can be found on the the USACE Headquarters Regional Supplements to the Corps Delineation Manual website.

Publications & Other Resources used in Aquatic Resource Delineations

The following publications and other technical resources are useful tools in land management involving wetlands:

National Wetland Plant List

National Wetland Inventory

ERDC Wetlands Publications

Moist-Soil Impoundments for Wetland Wildlife