State Progress Toward Developing Numeric Nutrient Water Quality Criteria for Nitrogen and Phosphorus
Numeric nutrient criteria are a critical tool for protecting and restoring a waterbody's designated uses related to nitrogen and phosphorus pollution. These criteria enable effective monitoring of a waterbody for attaining its designated uses; facilitate formulation of NPDES discharge permits; and simplify development of total maximum daily loads (TMDLs) for restoring waters not attaining their designated uses (i.e., impaired waters).
The interactive maps and tables below describe progress states are making towards the development of numeric nutrient criteria, the criteria they've developed, and specific details about Clean Water Act adopted criteria, including values and parameters.
States and territories are also conducting additional activities to control nutrient pollution including watershed prioritization, setting goals to reduce nutrient loads, and other work as described in the EPA memo "Working in Partnership with States to Address Phosphorus and Nitrogen Pollution through Use of a Framework for State Nutrient Reductions". However, this particular work is not reflected on this webpage.
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Map - N/P Criteria Progress
The map below shows a national summary of current numeric total nitrogen (TN) and total phosphorus (TP) EPA-approved criteria and those anticipated in the near future based on state-provided information. The information presented in the map is also presented as an interactive table under theTable - Criteria Status & Progress tab.
Click the year of interest to see the relevant development status of TN and TP criteria. To see a summary for a state, move your mouse cursor over the desired state. For all the state's details, click on the state.
Map - Chlorophyll Criteria
The map summarizes current numeric EPA-approved chlorophyll-a criteria. The information presented in the map is also presented as an interactive table under the Table - Criteria Status & Progress tab.
While total nitrogen and total phosphorus criteria are preferable for directly determining TMDLs and NPDES permit discharge limits, chlorophyll-a criteria can be used to determine if waters are impaired due to nitrogen and phosphorus pollution. Chlorophyll-a is a response variable that measures biotic productivity and activity, thus reflecting the nutrient enrichment of the system. Chlorophyll-a concentrations are a direct response to causal variables - total nitrogen and total phosphorus. See Technical Support for Numeric Nutrient Criteria Development.
To see a summary for a particular state, move your mouse cursor over the desired state. For all the state's details, click on the state.
Table - Criteria Status & Progress
The table below shows a national summary of current EPA-approved numeric total nitrogen and total phosphorus criteria adoptions and those anticipated in the near future based on state-provided information. It also shows the status for related EPA-approved criteria such as chlorophyll-a. The information presented below is also presented as interactive maps under the Map - N/P Criteria Progress and Map - Chlorophyll Criteria tabs.
Sort the table by clicking on any desired column. For example, you can sort by state, region, and the level of progress. You can also Change Displayed Table Columns. For an explanation of the table symbols, click Table Legend or "mouseover" one of a states level cells (e.g., "Level 5"). Click the state for complete detailed information.
Table - Numeric Nutrient Criteria
Presented below are numeric nutrient criteria that were extracted from state and territory water quality standards regulations that are EPA-approved or otherwise in effect for Clean Water Act purposes. (See the Water Quality Standards Where You Live website for the state and territory regulations.) The criteria below are also included for each state and territory under the State/Territory Details tab.
To compare criteria, sort the table by clicking on any desired column. You can also filter criteria by state, watertype, parameter, and parameter class.
State/Territory Details
This tab presents detailed information that's available for each state and territory. The information includes a summary of existing EPA-approved N and P criteria, a listing of all available EPA-approved numeric nutrient control criteria, milestone information, and other information. To choose a particular state or territory, use the select box below.
[State]: Summary of Existing Numeric Standards for Nutrients
State Nutrient Control Criteria
Presented below are numeric nutrient criteria that were extracted from EPA-approved water quality standards regulations that are EPA-approved or otherwise in effect for Clean Water Act purposes. Visit the link below for the EPA-approved regulations.
See the Table - Numeric Nutrient Criteria tab to compare the above criteria to those in other states.
Milestone Information - Development of Statewide Numeric N/P Criteria
The milestone information presented below were provided by the state or territory and represents their best estimate for completing key milestones for N and P criteria development. These milestones are updated periodically to reflect milestone completion, revision of milestone dates, and challenges each state has encountered toward criteria development.