According to the USGS source, nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but their overabundance in water can cause a number of adverse health and ecological effects. Nitrogen, in the forms of nitrate, nitrite, or ammonium, is a nutrient needed for plant growth. About 78% of the air that we breathe is composed of nitrogen gas, and in some areas of the United States, particularly the northeast, certain forms of nitrogen are commonly deposited in acid rain.

Although nitrogen is naturally abundant, it is also introduced through sewage and fertilizers. Chemical fertilizers or animal manure are commonly applied to crops to add nutrients, but may be difficult or expensive to retain on site. Unless specialized structures have been built on the farms, heavy rains can generate runoff containing these materials into nearby streams and lakes. Wastewater-treatment facilities that do not specifically remove nitrogen can also lead to excess levels of nitrogen in surface or groundwater.

Nitrate can get into water directly as the result of fertilizer runoff. Some nitrate enters water from the atmosphere, which carries nitrogen-containing compounds derived from automobiles and other sources. More than 3 million tons of nitrogen are deposited in the United States each year from the atmosphere, derived either naturally from chemical reactions or from the combustion of fossil fuels, such as coal and gasoline. Nitrate can also be formed in water bodies through the oxidation of other forms of nitrogen, including nitrite, ammonia, and organic nitrogen compounds such as amino acids. Ammonia and organic nitrogen can enter water through sewage effluent and runoff from land where manure has been applied or stored.

Excess nitrogen can overstimulate the growth of aquatic plants and algae, in turn, clogging water intakes, using up dissolved oxygen, and blocking light to deeper waters. Lake and reservoir eutrophication can occur, which produces unsightly algae scums on the water surface, can occasionally result in fish kills, and can even kill a lake by depriving it of oxygen. The respiration efficiency of fish and aquatic invertebrates can be affected, leading to a decrease in animal and plant diversity, and affects our use of the water for fishing, swimming, and boating.

All water quality data is provided by the Nevada Division of Environmental Protection. Learn more at https://ndep.nv.gov. 

The Nevada Division of Environmental Protection (NDEP) oversees compliance with the Federal Clean Water Act and conducts periodic, comprehensive water quality analysis to identify impaired waterbodies and create a priority list for which plans are needed to restore water quality.  

*Note that samples are not collected every month each year, and include storm, flood and drought years.