Benefits of Wetlands

  1. They improve the quality of our water by filtering sediments and removing contaminants.
  2. They serve as spawning sites and nursery areas for fish and other aquatic life.
  3. They support downstream aquatic systems, including commercial and sport fisheries, by producing food and organic material that is flushed out of the wetlands and into streams during high flows.
  4. They reduce flood damage to crops and Wetlands help improve water quality storing flood water and releasing it slowly, like a giant sponge.
  5. They are breeding, feeding, and wintering habitat for hundreds of wildlife species including: waterfowl, shorebirds, muskrats, turtles, frogs, and salamanders.
  6. They support many endangered species of animals and plants.
  7. They protect shorelines from erosion due to waves and currents.
  8. They provide recreational opportunities, such as hunting, fishing, boating, and wildlife watching.

What is a Wetland?

A wetland is an area that is covered by shallow water or has waterlogged soils for long periods during the growing season in most years.  Prolonged saturation with water leads to chemical changes in wetland soils, which in turn affect the kinds of plants that can grow in wetlands.  Therefore, wetland vegetation often looks quite different from that of the surrounding non-wetland areas.

Wetlands are known by many different names, some of which are specific to particular regions of the country. Wetlands that are dominated by trees and shrubs are commonly called swamps.  Swamp forests associated with rivers and streams in the Southeast are locally known as bottomland hardwoods. Wetlands that consist of herbaceous vegetation, such as sedges, cattails, and bulrushes, are known as marshes. Marshes are highly variable and include fens, sloughs, potholes, and wet meadows. Bogs are generally dominated by sphagnum moss, which, when it dies, builds up in thick layers of peat. Extensive bogs in Canada and Alaska are called muskegs.

The information presented here will help you to determine whether you have a wetland on your property. If you intend to place fill material in a wetland or in an area that might be a wetland, contact the local District Office of the U. S. Army Corps of Engineers  Corps) for assistance in determining if a permit is required.

How are wetlands recognized?

The term "wetland" encompasses a variety of conditions and degrees of wetness. Some wetlands are very easy to recognize because the water sits on the land's surface for much of the year. Other wetlands exist due to saturation of the soil by groundwater and can be difficult to identify. Wetlands do not need to be wet year-round. In fact, due to seasonal variations in rainfall and other environmental conditions, most wetlands lack both surface water and waterlogged soils during at least part of the growing season each year.

One clue that a tract of land may contain wetlands is its topography or position in the landscape. Wetlands occur in areas where water naturally flows or accumulates, such as in the floodplains of streams and rivers, along smaller creeks and washes, in low spots or depressions in flat or rolling landscapes, around seeps and springs, along the fringes of ponds and lakes, and in coastal areas affected by tides. 

Even in fairly obvious wetland situations, it may be difficult to determine where the wetland ends and the upland begins. Therefore, identification of wetland boundaries, a procedure called wetland delineation, is a task best left to a qualified wetland consultant or Corps District personnel.  The Corps uses delineation manuals to determine wetland boundaries.  Wetlands are delineated by carefully examining a site for the presence of wetland indicators - vegetation, soil, and hydrology.

For more information, please see our brochure on Recognizing Wetlands.

The district engineer must determine the compensatory mitigation to be required in a DA permit, based on what is practicable and capable of compensating for the aquatic resource functions that will be lost as a result of the permitted activity. The purpose of a functional assessment is to evaluate current wetland functions and predict potential changes to a wetland's functions that may result from proposed activities. A wetland is compared to similar wetlands that are relatively unaltered. For more information, please see iHGM functional assessments.

Jurisdictional Determinations

Jurisdictional Determination means a written USACE determination that a wetland and/or waterbody is subject to regulatory jurisdiction under Section 404 of the Clean Water Act (33 U.S.C. 1344) or a written determination that a waterbody is subject to regulatory jurisdiction under Section 9 or 10 of the Rivers and Harbors Act of 1899 (33 U.S.C. 401 et seq.). The basis of the jurisdictional determination is also included on the forms. Basis of jurisdictional determination is a summary of the indicators that support the Corps approved jurisdictional determination.

Please mail in your request for a jurisdictional determination to:
Galveston District Regulatory Division 
USACE Galveston District
2000 Fort Point Road
Galveston, TX 77550


Antecedent Precipitation Tool (APT)

6 July 2023 - Download the new version 2.0.0 of the Antecedent Precipitation Tool (APT) 
This new version of the APT contains additional functionalities, to include the incorporation of a newly developed gridded daily precipitation dataset from the National Oceanic and Atmospheric Administration, National Centers for Environmental Information. This new data- the U.S. Climate Gridded Dataset-Daily (nClimGrid-Daily) precipitation dataset- will be useful for instances in which there are not enough suitable weather stations to perform the APT analysis due to poor weather station coverage or instances in which multiple nearby weather stations are missing the same periods of precipitation. This dataset may also be useful when the primary station is further away from the observation point than the dimensions of the grid cell (e.g., if the primary station is 40 miles from the observation point). 

USACE is also announcing the release of a new user guide for APT 2.0.0. This publication serves as both a user guide and the technical documentation for the APT, including its inputs, outputs, analyses, common errors, and troubleshooting tips.  All users should download the new version of the APT (version 2.0.0) from GitHub at the following location: 

The changes from version 1.0.23 to version 2.0.0 include:
  • Full integration of the NOAA U.S. Daily Gridded Precipitation Data (nClimGrid-Daily) and it’s associated station count data.
  • Updated user and technical guide to reflect incorporation of the nClimGrid-Daily data into the APT.
  • Addressed issue with batch processing that was limiting the use of appropriate station data during station-based APT analyses.
  • Addressed issue with sizing of station table in pdf outputs when using large numbers of stations in a station-based APT analysis.
  • Addressed issue with interpolation algorithm that fills data gaps in a station-based APT analysis.
  • Updated the URL to access WebWIMP data.

To report additional issues with the APT, please email

16 March 2023 - Download the new version 1.0.23 of the Antecedent Precipitation Tool (APT) 

A recent change to the U.S. Geological Survey (USGS) server housing the elevation data required by the Antecedent Precipitation Tool’s (APT) weather station selection criteria caused the APT to become inoperable. The U.S. Army Corps of Engineers (USACE) has released a new version of the APT which remedies this issue. All users should download the new version of the APT (version 1.0.23) from GitHub at the following location:

This new version includes or incorporates the following:
  • Pointed USGS EPQS query to new API service
  • Fixed bug that allowed GHCN-Daily stations with less than 75% of antecedent conditions to be chosen as primary station
  • Added warning if observation point does not fall within watershed boundary
  • Update U.S. boundary to 2021 census dataset
  • Migrated codebase to Python 3.8

Additional functionalities, to include the incorporation of gridded precipitation data within the APT, will soon be released with an updated APT user guide.  To report additional issues with the APT, please email

February 2022 - Antecedent precipitation Tool (APT) Version 1.0 Technical and User Guide
The Wetlands Regulatory Assistance Program (WRAP) recently published the Technical Note, Antecedent Precipitation Tool (APT) Version 1.0: Technical and User Guide. This document serves as both a user guide and the technical documentation for the APT, including discussions on its inputs, outputs, and analyses. The Technical Note also provides troubleshooting tips to diagnose and address potential errors associated with the APT. The publication is attached and can also be downloaded from the following link:
5 August 2020 - The Corps Antecedent Precipitation Tool (APT) is now available for download from GitHub
The APT is an automation tool that was created by the Corps to rapidly evaluate three climatological parameters, for a given latitude, longitude, and date, to assist in the making and documenting of various determinations required by policy for the execution of U.S. Army Corps of Engineers' Regulatory Program.
The APT is one tool that the Corps may use to determine and document Typical Year conditions (i.e., whether precipitation and other climatic variables are within the normal periodic range (e.g., seasonally, annually) for the geographic area of the applicable aquatic resource based on a rolling thirty-year period).
The APT is available for download at the following location:
Instructions for downloading and installing the tool are included on the GitHub page, and are also provided below:
To install the APT you will need to do the following:
  •  Download the "Antecedent.Precipitation.Tool.7z" file.
  • Use 7zip to extract the 'Antecedent Precipitation Tool' folder to your preferred installation location (right-click the folder, choose 7-Zip, and then Extract Files).
  • This will extract a folder named “Antecedent.Precipitation.Tool”.  This folder IS the program, so put it somewhere out of the way.
  • At this point you may delete the 7zip folder.  However, the extracted “Antecedent.Precipitation.Tool” folder will need to remain on your PC in order for the APT to function.
  • Navigate to the “Antecedent.Precipitation.Tool” folder and Double-click the "Antecedent Precipitation Tool.exe" file.  This will run the installer.
  • Read/Accept the terms of the User License Agreement.
  • A Shortcut will be created on your Desktop and the tool will launch.  Use the desktop shortcut (see attached screen shot) any time you want to run the APT.
  • Note that the APT is configured to automatically update itself as improved versions are released.  Therefore, you will only need to follow this installation process one time, and after that you should use the desktop shortcut any time you want to run the APT.
The Corps is developing additional training materials to support use of the APT, and those materials will generally be released via the APT Help Page.  The APT Help Page can be accessed by clicking APT Help Button, which is an orange question mark icon located in the top right portion of the APT user interface.