Assessment & Monitoring > NWCA

National Wetland Condition Assessment (NWCA)

In 2011, EPA conducted field sampling for the first-ever National Wetland Condition Assessment (NWCA). Numerous state agencies, tribes, and cooperators participated in the survey, including CNHP. The purpose of NWCA was to assess the condition of the Nation’s wetlands by collecting data from over 1,100 wetlands within the lower 48 states.

Data were collected on vegetation, soils, water quality, hydrology, and buffers within each targeted wetland. The survey employed a probabilistic random survey design that will allow the results to be extrapolated to all wetlands within the contiguous U.S. The target population for NWCA included all tidal and nontidal wetlands of the contiguous U.S. with rooted vegetation and, when present, open water less than one meter deep. Certain farmed wetlands not currently in crop production were also sampled.


CNHP was contracted to carry out all site evaluation and field sampling for Colorado and Wyoming, due to its experience conducting wetland condition assessment projects. Out of 900 randomly selected wetlands across the country, twelve were located in Colorado and nine in Wyoming. Two random sites from each state were sampled twice to determine intra-annual variability. In addition to the random sites, CNHP sampled four reference sites in Colorado, one in Wyoming, and one in Utah. Reference sites were handpicked wetlands known to be in good condition. Data from reference sites will help set condition thresholds for the randomly selected sites.

EPA provided field training in May 2011 and all members of the CNHP field team participated. Field work took place between June and September 2011 and followed EPA protocols. All field samples were shipped to cooperating laboratories for analysis and all data have been submitted to the EPA for processing. Data analysis will take place in 2012–2013, with a final report by 2014.

For more information on the NWCA, see the EPA’s NWCA website.