Water quality is defined in terms of the chemical, physical and biological content of water. The water quality of rivers and lakes changes with the seasons and geographic areas, even when there is no pollution present. There is no single measure that constitutes good water quality. For instance, water suitable for drinking can be used for irrigation, but water used for irrigation may not meet drinking water guidelines. The quality of water appropriate for recreational purposes differs from that used for industrial processes.
Many factors affect water quality.
The natural water quality of groundwater in aquifers is related to the quality of recharge water, the mineralogy of soils and aquifer sediments, the residence time in the ground water flow system, and the presence of nearby saline water. Urban stormwater, agricultural runoff, domestic wastewater, industrial wastewater, and hydrologic modifications are the major sources of water pollution in Florida. Other threats include nitrates from dairy and other livestock operations, fertilizers and pesticides in stormwater runoff, toxic chemicals in leachate from hazardous waste sites, and erosion from construction sites, unpaved roads, and farm fields. Septic tank leachate contributes to the degradation of many water bodies by adding nitrate nitrogen, bacteria, viruses, and synthetic organics used in household cleaning products and septic tank cleaners. Industrial activities can increase concentrations of metals and toxic chemicals, add suspended sediment, increase temperature, and lower dissolved oxygen in the water.