Proposed nutrient criteria for water supply lakes and reservoirs

Abstract

Nutrient enrichment of lakes and reservoirs used for a potable water supply can lead to a broad array of adverse effects ranging from operational problems to potential increases in certain human health–related risks. Human health risks that may be exacerbated by nutrient enrichment stem from increases in disinfection by‐products, cyanotoxins, and arsenic. New York state is developing numeric nutrient criteria for the protection of water supply lakes and reservoirs by establishing relationships between nutrients, algal abundance, dissolved organic carbon, and trihalomethanes, and then targeting established regulatory endpoints to set appropriate numeric nutrient criteria thresholds. This approach represents a much‐needed bridge between the Safe Drinking Water Act and the Clean Water Act by defining source water protection goals. Findings to date from the investigation of 21 systems indicate that a mean chlorophyll a threshold of 4–6 μg/L would likely be protective of potable water supply lakes and reservoirs.