Stream Nutrient Levels Assessment (OI3798)

The metric is intended to capture whether the organization has measured nitrogen and phosphorus levels in streams or rivers on land it manages. Nitrogen and phosphorus levels are key determinants of stream health. Although nitrogen and phosphorus are crucial for life on Earth, agricultural fertilization, cattle breeding, and industrial emissions can oversaturate ecosystems with these elements, which leads to habitat degradation by eutrophication.

Organizations should measure nutrients, including phosphorus and nitrogen, immediately downstream of controlled land—as reported by Land Directly Controlled: Total (OI5408), Land Indirectly Controlled: Total (PI3789), and related submetrics—and preferably at both base and storm flows. Guidance on measuring nitrogen and phosphorus concentrations can be found at EPA’s Total Nitrogen (https://www.epa.gov/sites/production/files/2015-09/documents/totalnitrogen.pdf) and Phosphorus (https://archive.epa.gov/water/archive/web/html/vms56.html) pages.

Organizations are encouraged to footnote summary statistics of these data and should consult national, sub-national, or tribal standards to determine whether measured nutrient levels are within environmentally sustainable levels, as local and international water quality legislation often specify limits and target values for nutrient levels in water.