In response to US Coast Guard regulations, a variety of ballast water management approaches have been developed to decrease the likelihood that ballast water discharged by ships will introduce non-indigenous species (NIS) to the unique marine bioregions of United States and elsewhere. The most obvious strategy is for ships to not release their ballast water (and the organisms it contains) to ports and coastal waters, when possible. Ships arriving to US ports may also use water sourced from a US Public Water System in ballast water tanks, which should be free of any organisms. Until recently, for those ships that must release ballast at port but which are not carrying US public water in their tanks, the most widespread ballast water management approach has been open-ocean exchange, whereby ships exchange coastal ballast water with open-ocean water to reduce the number of coastal biota introduced to next port of call. Open-ocean exchange requires pumping coast water out of a tank and refilling with oceanic water (empty/refill exchange), or via the flow-through exchange where several tank volumes of oceanic water are pumped continually into a ballast water tank to displace the coastal water and biota into the open ocean. Open-ocean ballast water exchange creates a habitat mismatch whereby oceanic organisms rather than coastal organisms are released in next port of call.
While these methods of ballast water management reduce the risk of introducing a non-indigenous species, they do fully not eliminate risk. However, ballast water treatment systems are now being developed and used to treat ballast water in the US and elsewhere, typically onboard ships. These technologies allow the ballast water to be treated upon entering and/or before exiting the ballast water tank to reduce the number of viable organisms that are ultimately released to the environment. Ballast water treatment operations may be carried out at port or while underway, thereby eliminating the need for ballast water water exchanges while further reducing risk of NIS introductions. In 2012, the US Coast Guard adopted a a set of discharge standards as specified in 33 CFR § 151.2030(d) that specifies the concentrations and types of marine biota that can be legally discharged per volume of ballast water. As such, onboard ballast water technologies are a rapidly growing industry and have been increasingly adopted for ballast water management of water discharged into US waters.
This section presents and quantifies discharged ballast water volumes reported to the NBIC, including whether the water was managed prior to discharge into US territorial waters. ALL options to actively manage BW discharge are those specified in 33 CFR 151.2025:
- Ballast Water Exchange
- Ballast Water Treatment
- Use water from a US Public Water System
- Discharge to a facility or ship for treatment
Because federal and state regulatory requirements may differ to some extent depending on where ships are operating and on the origin of their ballast water, it is important to evaluate overseas and coastwise discharge independently when analyzing all types of ballast water management simultaneously.
Note: All data available in graphs and tables extend through the last complete month and are refreshed monthly. Because ballast water management reports may be amended, corrected or changed during quality control processes, particularly within the 20 days from arrival date for the last complete month, this may result in updates that will register when the data are next refreshed. All data are subject to change and use of any of the NBIC data implies agreement with the NBIC Data Use Agreement policy. Cite our data.
Temporal Patterns of BW Management
At the national scale, three of the most significant BW Management (BWM) observations are:
- For overseas ballast water the vast majority of discharge is managed and the proportion of unmanaged discharge has been decreasing through time.
- Coastwise ballast water discharge has largely been unmanaged. As the discharge standard is phased in, more vessels will be required to treat their ballast water.
- Since 2015 there has been a major increase in the volume of treated ballast water discharge, which now surpasses other forms of ballast water management.
Monthly Ballast Water Management by Coastal Region and State
This interactive figure presents the total reported discharge volumes of either overseas ballast water or coastwise ballast water by the type of BW Management for each month since 2005. To tailor your query and figure, use the data filters located just below the chart. Select 'All Coasts' or 'All States' to view the national total; alternatively, you can select any coastal region or state to view temporal changes in discharge for that region. Select whether you are interested in ballast water that is of overseas or coastwise origin, and whether you would like to see ballast water trends across all commercial ship types by leaving the filter item 'Ship Type' blank, or filter for a specific type of ship using the drop down menu for 'Ship Type'. You can zoom and pan interactively in the figure or you can use the filter to select a specific time period. To select a date range in the chart, hold down the left mouse button and drag the arrow across the graph. To pan across the graph, hold down the 'shift' key while dragging the arrow across the graph. Click the categories in the legend to turn off or on data that shown in the graph for that category. The figure and data can be exported using the 'Export Chart' menu in the upper right corner of the figure.
Management: Coast and Ship Type
| Coast | Date | BW Type | Ship Type | BW Exchange | BW Treatment | Public Water Source | Facility | None |
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Management: State and Ship Type
| State | Date | BW Type | Ship Type | BW Exchange | BW Treatment | Public Water Source | Facility | None |
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