NPS pollution is caused when rainfall or snowmelt runs over land or through the ground, picks up pollutants and deposits them into rivers and lakes or introduces them into ground water. NPS pollution also includes adverse changes to animals, vegetation, the shape and flow of streams, and other aquatic systems.
Sources of NPS pollution are the human activities that generate the pollutant of effect on the water resource. NPS pollution is widespread because it can occur any time human activities disturb the land or water. Agriculture, forestry, grazing, septic systems, recreational boating, off-road vehicles, urban runoff, construction, physical changes to stream channels (hydromodification) and habitat degradation are potential sources of NPS pollution. Careless or uniformed management of households, lawns and gardens also contributes to NPS pollution. The four leading sources of NPS pollution in Ohio are: agriculture, hydromodification, mining, and urban runoff.
Causes of NPS pollution are the actual agents that affect water resource quality. The four leading causes of NPS pollution in Ohio are: habitat alteration, organic enrichment/low dissolved oxygen, siltation of stream channels (fine soil particles), and plant nutrients.