Effects of Nonpoint Source Pollution

The effects of nonpoint source pollution varies according to the specific pollutant. The examples given below are not an exhaustive list; more examples can be found on the Louisiana Nonpoint Source Pollution Program web site.

• Run-off from erosion-prone areas (such as constructions sites and poorly-managed agricultural lands) can deposit excess amounts of sediment into nearby receiving water, reducing the clarity of water. Cloudy water limits the ability of plants to produce oxygen, consequently impacting fish and other local wildlife. Sediment can also smother lake and ocean bottom organisms. When sediment fills in waterways, it hinders navigation and increases flooding.
• Fertilizers washed away from agriculture lands and residential areas can cause algal blooms in ponds, lakes, and other bodies of water. This removes oxygen from the water, vastly reducing local populations of fish. Excess nutrients cause excessive plant growth, disrupting natural nutrient cycles, again resulting in a decline in the number of desirable fish species.
• Improperly managed animal wastes from livestock and improperly-sited septic tank systems can produce dangerously high levels of fecal coliform bacteria and other harmful microorganisms. This can lead to diseases such as infectious hepatitis, typhoid fever, dysentery, and other forms of diarrhea, rendering streams, rivers, bayous, lakes, and other bodies of water unfit for human use (such as fishing, swimming, water skiing, etc.).
• Crop debris is a major organic pollutant resulting from agricultural activities. During decomposition, it removes oxygen from receiving waters which can result in stress or death among fish and other aquatic species.
• Herbicides, pesticides, and other toxic agents that have been washed into rivers, streams, lakes, bayous, and other bodies of water can collect in local plants and animals. As a result, local wildlife becomes unfit for human consumption, which reduces opportunities for hunting and fishing. In addition, soluble pesticides and herbicides can reach ground water, rendering it unsafe for drinking or necessitating expensive cleanup.
• Chemicals (including excessive concentrations of salts and minerals), petroleum products, and heavy metals all contaminate receiving water, rendering water unfit for human and animal consumption and impairing the growth of plants. It can also reduce or restrict the water's value for industrial and municipal use, irrigation, and propagation of fish and wildlife. Water purification and treatment systems become more expensive to operate. Excessive salts can adversely alter the permeability of soils.
• Louisiana's coastal marshlands are some of the most productive soil, water, and plant resources existing in the United States of America. However, saltwater intrusion converts approximately 88 acres (356,136 square meters) of marshlands to open water each day. This annual loss of 32,000 acres (129.5 square kilometers) of marshland accelerates each year. Intrusion of saltwater causes the loss of fresh and intermediate vegetation, which results in rapid erosion of marsh soils and the ultimate conversion to open water.