Water pollution comes from a wide variety of both highly and sparsely populated areas, active and in-active industries, and even the occasional accidents. While it is impossible to list all the sources and problems of water quality, below we focus on the largest known contributors that have yet to be tackled.
Worldwide, excessive amounts of nutrients (eutrophication) have been identified as the most widespread, costly, and challenging contributor to water quality issues. Primarily, these nutrients are nitrogen and phosphorus, which occur naturally in nature, but excessive amounts enter our waterway from agriculture, storm water, waste water, and residential areas. However, agriculture is the primary source (48% of water stream and river pollution in the United States; and 50-80% of nitrogen comes from agriculture in the EU).
Nutrient water pollution causes an increase in the growth and presence of both good and bad algae. While some algae blooms of ‘good’ algae can actually increase the amount of available food for aquatic species, there are a small percentage of algae that produce powerful toxins that can kill plants and animals. Regardless of the good or the bad, both cause ugly scenarios when large amounts of the algae die and decompose because it reduces the amount of oxygen in the water which causes animals to have to leave or die. Algae blooms occur both in freshwater and marine environments, and are occurring at an alarming rate around the world.
Agriculture practices of fertilizing and managing manure are the two biggest contributions to nutrient pollution. Through excessive and uniform fertilizer application, much of the nutrients are not fully absorbed by the soil before heavy irrigation or storm events cause surface water runoff. Further, because agriculture clears the land of natural vegetation and often is located next to rivers, lakes, and/or irrigation ditches, the surface water quickly flows off the land and enters the water.
Manure management is a big concern, because large spills into rivers seem to happen every month, and world wide total several millions of gallons of manure in our rivers, lakes, and oceans. On large livestock farms, special lagoons are often constructed to house large amounts of manure and urine. However, during heavy rainfall these lagoons can overflow, and often mechanical issues or faulty construction can cause massive leaks. Historic spills include:
- 3 million gallons into the Black River in 2005, which killed approximately 250,000 fish
- 1 million gallons spilled into wetland and Little Eau Pleine River in 2014
- 2-mile long stream of manure flowed into Castle Rock Creek in 2016, which has killed approximately 50 fish.
In cities and populated areas, storm water runoff is a primary cause of urban flooding and water pollution. In the United States, it has been estimated that 10 trillion gallons of polluted water enters rivers, lakes, and coastal waters every year. Some of this pollution is raw sewage, where in rain events cause combined sewage overflows (CSO) systems to release raw sewage into waterways. In the United States, there are nearly 800 communities that have CSOs and continue to spill unknown amounts of raw sewage into our waterways. In fact, sewage in rivers accounts for the following nitrogen contributions: United States 12%, Western Europe 25%, and China 33% (Millennium Ecosystems Assessment, 2005).
Further, a recent pollution of interest are pharmaceuticals entering waterways. In many countries where prescription drug consumption is high, there is no doubt that these chemicals have entered into the water systems. However, the effects of these chemicals on the ecosystems and aquatic species is not well known at this time. Further, it is not well know how much of these chemicals are in our drinking water, as most water treatment plants do not test for, nor have the capability to remove these chemicals.
Industrial waste products occasionally enter waterways through accidental discharges or slowly and consistently from unregulated abandoned mines. Accidental spills can result from vehicle accidents along roads that border highways, factory accidents, or natural disasters causing the discharge of chemicals.
Abandoned mines left inactive for many years, decades, and even centuries still remain a threat to water quality. In Britain, thousands of mines are abandoned and threaten surface and ground water. England and Wales, 9% of the rivers are failing to meet the Water Framework Directive's targets due to abandoned mines (Abandoned mines and the water environment). In the U.S. there are an estimated 500,000 abandoned mines, and in Colorado, there are 7,300 abandoned mines, which at least 230 are known to be leaking heavy metals into nearby rivers. Abandoned mines and other industrial spills release pollutants like mercury, cyanide, zinc, lead, copper, and cadmium cause significant damage. A recent example is the August 2015 Animas Mine Disaster in Colorado, which released large amounts of arsenic, lead, copper, and cadmium. These chemicals have both short and long-term effects on animals both from direct and indirect (e.g. food chain) exposure.
Temperature and Suspended Matter
Temperature pollution occurs when industries use river water to power or cool machinery. When the water is discharged back to the river, the elevated temperature causes two problems. First, aquatic species are sensitive to temperature, and often will not reproduce in unfavorable temperatures . Secondly, the elevated temperature reduces dissolve oxygen, and thus reduces the sustainability to support the aquatic life.
Suspended solid matter that enters waterways also reduces the ability to support a rich aquatic life. With elevated suspended soil amounts, the water’s turbidity increases and prevents photosynthesis from occurring and reduces the amount of aquatic vegetation, which other aquatic life depend upon for food and shelter. Examples of large amounts of suspended solids are from high amounts of bank erosion, increased erosion from point-source pollution discharges, and runoff from areas deforested or recent fire.