Water Quality

Water has been called the universal solvent. It dissolves many naturally-occurring minerals and is a ready receptor of human-caused pollutants. The mineral content of water, measured as total dissolved solids or TDS, progressively increases as rainfall and snowmelt coalesce into streams and rivers, accumulate and evaporate in reservoirs, and seep beneath the surface. For example, a pristine mountain stream in the Verde River basin may contain 80 parts per million (ppm) of TDS while the Verde River itself during spring runoff carries 150 to 250 ppm of TDS. Colorado River water delivered to Phoenix by the Central Arizona Project contains about 650 ppm.

Groundwater varies widely in TDS content depending on quality of recharge, soluble minerals in the aquifer material, and length of time the water remains in the aquifer. For example, public drinking water wells in the Phoenix area yield groundwater with an average TDS contents of 500 ppm, while wells in Tucson average 265 ppm. Many areas in Arizona relying on groundwater exceed the recommended aesthetic drinking water guideline of 500 ppm.
Human activities have polluted both surface waters and groundwater. Surface water quality is especially harmed by nutrients such as nitrogen and phosphorus compounds discharged by wastewater treatment plants and from dispersed nonpoint sources such as farms and feedlots. Urban runoff, timber cuts and acidity and metals from mining operations have polluted some surface waters.
Groundwater in many areas of Arizona is unsuitable for drinking because nitrate levels exceed the federal drinking water standard. Nitrate pollution can be caused by agricultural fertilizers, wastewater treatment plant discharges, industrial wastes and seepage from septic tanks. Discharges from industrial dump sites, waste lagoons and landfills can cause groundwater contamination by volatile organic compounds (VOCs), usually from disposal of industrial solvents. These point sources of pollution typically cause long, narrow contaminant plumes in groundwater, similar in shape to smokestack emissions.
Anyone discharging to surface waters must meet U.S. Environmental Protection Agency water quality standards. All groundwater is protected to drinking water standards by the 1986 Arizona Environmental Quality Act. To obtain a required Aquifer Protection Permit from the Arizona Department of Environmental Quality, dischargers must demonstrate that no water quality standard will be violated. For waters already polluted, state and federal "Superfund" programs aim to find responsible parties and initiate cleanup.

Issues Summary


	Water Quality Water has been called the universal solvent. It dissolves many naturally-occurring minerals and is a ready receptor of human-caused pollutants. The mineral content of water, measured as total dissolved solids or TDS, progressively increases as rainfall and snowmelt coalesce into streams and rivers, accumulate and evaporate in reservoirs, and seep beneath the surface. For example, a pristine mountain stream in the Verde River basin may contain 80 parts per million (ppm) of TDS while the Verde River itself during spring runoff carries 150 to 250 ppm of TDS. Colorado River water delivered to Phoenix by the Central Arizona Project contains about 650 ppm. Groundwater varies widely in TDS content depending on quality of recharge, soluble minerals in the aquifer material, and length of time the water remains in the aquifer. For example, public drinking water wells in the Phoenix area yield groundwater with an average TDS contents of 500 ppm, while wells in Tucson average 265 ppm. Many areas in Arizona relying on groundwater exceed the recommended aesthetic drinking water guideline of 500 ppm. Human activities have polluted both surface waters and groundwater. Surface water quality is especially harmed by nutrients such as nitrogen and phosphorus compounds discharged by wastewater treatment plants and from dispersed nonpoint sources such as farms and feedlots. Urban runoff, timber cuts and acidity and metals from mining operations have polluted some surface waters. Groundwater in many areas of Arizona is unsuitable for drinking because nitrate levels exceed the federal drinking water standard. Nitrate pollution can be caused by agricultural fertilizers, wastewater treatment plant discharges, industrial wastes and seepage from septic tanks. Discharges from industrial dump sites, waste lagoons and landfills can cause groundwater contamination by volatile organic compounds (VOCs), usually from disposal of industrial solvents. These point sources of pollution typically cause long, narrow contaminant plumes in groundwater, similar in shape to smokestack emissions. Anyone discharging to surface waters must meet U.S. Environmental Protection Agency water quality standards. All groundwater is protected to drinking water standards by the 1986 Arizona Environmental Quality Act. To obtain a required Aquifer Protection Permit from the Arizona Department of Environmental Quality, dischargers must demonstrate that no water quality standard will be violated. For waters already polluted, state and federal "Superfund" programs aim to find responsible parties and initiate cleanup. Issues Summary
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