Benthic Monitoring in Virginia
What proportion of water quality monitoring stations are evaluated for benthic health?
There are 7,952 water quality monitoring stations in the commonwealth. The are well-distributed throughout the region. Of these, 1,990 (25%) are monitored for benthic health.
What proportion of water quality monitoring stations are evaluated for benthic health?
There are 7,952 water quality monitoring stations in the commonwealth. The are well-distributed throughout the region. Of these, 1,990 (25%) are monitored for benthic health.
What proportion are impaired for benthic health?
Of the stations evaluated for benthic health, 24% are impaired, 41% are not impaired, and 35% are not yet determined (data are insufficient to determine the impairment status).
Of the stations evaluated for benthic health, 24% are impaired, 41% are not impaired, and 35% are not yet determined (data are insufficient to determine the impairment status).
How often is sediment chemistry measured along with benthic health?
Sediment is collected for chemical analysis (metals and/or organic constituents) at 12% of water quality monitoring stations. Half of these stations are also monitored for benthic health.
Sediment is collected for chemical analysis (metals and/or organic constituents) at 12% of water quality monitoring stations. Half of these stations are also monitored for benthic health.
A Focus on Benthic Impairments in the Southwest Regional Office District
Water quality monitoring in the Southwest Regional Office District of Virginia includes the assessment of 820 monitoring stations. Of these, 314 (38%) are monitored for benthic health. This is a higher percentage of stations monitored for benthic health than the state-wide average of 25%.
Of the benthic monitoring stations in in the southwest region, 26% are impaired. Sediment chemical data (metals and/or organic constituents) were collected at 40% of these impaired stations.
What is the cause of the impairments (the "stressor") based on current studies?
Impaired waters are investigated further within watersheds. The blue regions in the figure below indicate watersheds for which a TMDL document has been prepared. These include TMDLs based on benthic impairments and TMDLs based on other types of impairments (e.g., physical or chemical impairments). As indicated on the map, not all benthic impaired locations have had TMDL documents completed at this point (14 impaired stations do not have TMDLs). In addition, TMDL documents can encompass multiple monitoring stations located on connected waters (from 1-7 monitoring stations are included in the completed TMDLs).
Impaired waters are investigated further within watersheds. The blue regions in the figure below indicate watersheds for which a TMDL document has been prepared. These include TMDLs based on benthic impairments and TMDLs based on other types of impairments (e.g., physical or chemical impairments). As indicated on the map, not all benthic impaired locations have had TMDL documents completed at this point (14 impaired stations do not have TMDLs). In addition, TMDL documents can encompass multiple monitoring stations located on connected waters (from 1-7 monitoring stations are included in the completed TMDLs).
As of May 2014, 16 TMDL documents have been developed for benthic impairments in the Southwest region. These documents were downloaded from the VDEQ website and investigated further. The documents include a stressor analysis, which identifies the likely cause of the impairments. Fifteen of the 16 impairments have been attributed to some form of sediment loading (8 "sediment" impairments, 3 total suspended solids (TSS), and 4 total dissolved solids (TDS)). One impairment was attributed to elevated chloride levels in the water. As such, sediment in some form is identified as the key stressor in the vast majority of benthic impairments in Southwest Virginia.
What is the status of TMDL development?
As stated above, in the Southwest region, 14 impaired monitoring stations do not yet have TMDL reports.
What is the status of TMDL development?
As stated above, in the Southwest region, 14 impaired monitoring stations do not yet have TMDL reports.