Of the six main types of water pollution, Lake Tahoe is affected most seriously by Sediments and Nutrients. The table shows the six pollution types, their major sources, and their effects.
| Class | Examples | Major Sources | Major Effects |
| Nutrients | Nitrogen Phosphorus |
Fertilizers, leaking sewer pipes, animal wastes, soil erosion | Slow, steady increase of single-cell algae reduces the lake’s famed clarity |
| Sediments | Soil, sand, silt, dust, gravel | Erosion of soil by water or wind, road de-icing, storm drains | Carries attached phosphorus into the lake. Suspended sediment reduces water clarity |
| Pathogens | Bacteria, viruses, parasites | Cattle, horses, humans, leaking sewage systems, storm drains | Make water unsafe for human consumption |
| Toxins | Hydrocarbons, heavy metals, petroleum products | Chemical spills, automobile products and emissions, watercraft, street runoff, leaking underground petroleum storage tanks, improper use of pesticides | Harms wildlife and fish, contaminates human drinking water |
| Salinity | Total dissolved solids (TDS), salts | Road de-icers | Accumulates in lakes |
| Thermal Pollution | Increase water temperature | Loss of streamside tree canopy | Water holds less dissolved oxygen; harms aquatic life |
| Excerpted from Home Landscaping Guide for Lake Tahoe and Vicinity, University of Nevada Cooperative Extension | |||
Nutrient pollution occurs when phosphorus and nitrogen enter the lake in dissolved or particulate forms. These chemicals are commonly found in fertilizer. They are literally food for plants, including the algae that is beginning to turn Lake Tahoe green. While fertilizer is good for your landscape plants if your soils are poor, it is bad when it is carried off your property and into roadside ditches or nearby streams. Other sources of nutrient pollution include auto, factory and wood stove emissions, human and animal wastes, and fine sediments, which usually carry phosphorus with them.
Sediments are small and very small particles of eroded soil, including dust and pulverized road sand. When these particles are washed or blown into our streams and into the lake, the larger grains settle to the bottom, but the tiny, fine particles remain suspended in the lake water. Since one of the main sources for phosphorus pollution is sediment, the control of soil erosion in the Tahoe Basin has become a major priority of scientists and agency officials who are trying to prevent further pollution of the lake.
In the $2 million scientific study, the Lake Tahoe Watershed Assessment, water quality researchers blamed the steady loss of Tahoe’s famed water clarity on the combination of fine suspended sediment and equally tiny single celled algae, called phytoplankton, which are also suspended in the lakes water and do not settle out. These algae will continue to grow in Lake Tahoe until we reduce the amounts of nutrients that feed them. Since some nutrients and fine sediments enter the lake through air pollution, our basic strategy to save the lake is to improve air quality in the basin while reducing the soil erosion rate.
While pollution by pathogens and toxins are serious events when they occur, these problems are not widespread. Salinity and thermal pollution are even less often problems for the lake, although road deicing salt can increase lake salinity in areas where road runoff and improperly stored snow can make their way into nearby streams or the lake itself.
The Lake Tahoe Report 008
Air Date: 2003.03.25
Video Segment: Major Types of Pollution
Interviewees: John Cobourn (UNCE), Heather Segale (UNCE)