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Table 2

Regulatory approaches used across case studies

Management area	Regulatory approaches
Management area	Setting reduction targets^a	Stormwater management	Wastewater management	Ban on winter manure spreading	Wetland no-net loss policy	Numeric nutrient criteria^b
Murray–Darling basin	•	•				•
Lake Winnipeg Manitoba	•		•	•	•	•
Lake Simcoe	•	•	•		•	•
Prince Edward Island	•				•
Lake Erie	•	•	•	•		•
Lake Taihu	•^b	•	•		•	•^b
Brittany	•	•	•	•	•	•
Lake Léman	•	•	•	•	•	•
Chesapeake Bay watershed	•	•	•	•	^c
Gulf of Mexico Arkansas	•	•	•
Iowa	•	•	•	•
State of Oregon	•			•

Management area	Regulatory approaches
Management area	Setting reduction targets^a	Stormwater management	Wastewater management	Ban on winter manure spreading	Wetland no-net loss policy	Numeric nutrient criteria^b
Murray–Darling basin	•	•				•
Lake Winnipeg Manitoba	•		•	•	•	•
Lake Simcoe	•	•	•		•	•
Prince Edward Island	•				•
Lake Erie	•	•	•	•		•
Lake Taihu	•^b	•	•		•	•^b
Brittany	•	•	•	•	•	•
Lake Léman	•	•	•	•	•	•
Chesapeake Bay watershed	•	•	•	•	^c
Gulf of Mexico Arkansas	•	•	•
Iowa	•	•	•	•
State of Oregon	•			•

^aThis issue is discussed, but we cannot ascertain that reduction targets are required by law.

^bTypically what this means is that the jurisdiction has defined N/P numerical criteria for at least one class of water. With that logic, jurisdiction that uses N/P criteria based on a reduction program (including through TMDLs) do not fit in that category. Implementation details for the whole USA can be found at https://www.epa.gov/nutrient-policy-data/state-progress-toward-developing-numeric-nutrient-water-quality-criteria. One can note that Florida, Minnesota, Missouri, North Carolina, and Oregon are using chlorophyll-a concentrations as a standard that can be used to determine if waters are impaired due to nitrogen and phosphorus pollution. China has a 10 mg/L limit for nitrate (N-NO₃⁻) for both drinking water and surface water standards, but no numerical criteria for phosphorus.

^cAlthough the whole watershed does not have a no-net loss wetland policy, at least Virginia and Maryland do.

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