The National Park Service initiated a Level 1 Water-Quality Inventory program to provide water-quality data to park managers so informed natural resource management decisions could be made. Level 1 water-quality data were collected by the U.S. Geological Survey Arizona Water Science Center at 57 sites in 13 National Park units located in the Southern Colorado Plateau Inventory and Monitoring network in water years 2005 and 2006. These data describe the current water-quality at selected sites within the park units and provide information for monitoring future trends. Water samples were collected three times at each type of site including wells, springs, seeps, tinajas, rivers, a lake, and an irrigation ditch. Field measurements were taken at each site and they included pH, specific conductance, temperature, barometric pressure, dissolved oxygen, alkalinity, turbidity, and discharge rates where applicable. Water samples collected were sent to the U.S. Geological Survey National Water Quality Laboratory and analyzed for major ions, trace elements, and nutrients. The National Water Quality Laboratory also analyzed selected samples for mercury and petroleum hydrocarbons. Additional samples at selected sites were collected and analyzed for cyanide, radiochemistry, and suspended sediment by U.S. Geological Survey contract labs. Fecal-indicator bacteria (Escherichia coli) were sampled for at selected sites as another indicator of water quality. Quality control for this study was achieved through proper training of field personnel, use of standard U.S. Geological Survey field and laboratory protocols, collection of sample blanks and replicates, and a thorough review of the water-quality analyses. Measured field pH ranged from 6.0 to 8.8, within normal range for springs and rivers, at most sites. Concentrations of dissolved solids ranged from 48 to 8,680 mg/L and the majority of samples had concentrations of dissolved solids below 900 mg/L. Trace-element concentrations at most sites were at or near the laboratory reporting levels. The highest overall trace-element concentrations were found at U.S. Highway 160 Spring near Park Entrance to Mesa Verde National Park. Concentrations of uranium in samples at all sites ranged from below the detection limit to 55.7 ?g/L. Water samples from selected sites were analyzed for total petroleum hydrocarbons and concentrations of total petroleum hydrocarbons were at or above the laboratory detection limit in samples at six National Park units. Ten sites were sampled for Escherichia coli and positive counts were found at 9 out of the ten sites, the highest colony counts were found at Chinle Creek at Chinle, AZ in Canyon de Chelly National Monument. Measured concentrations of dissolved ammonia, nitrite, and nitrate were at or near laboratory reporting levels at most sites; nitrate concentrations ranged from below the reporting limit (0.047 mg/L) to 9.77 mg/L. Samples that were analyzed for mercury had concentrations below or at the laboratory reporting level. Concentrations of cyanide were less than the laboratory reporting level for all samples except two, Spruce Tree House Spring in Mesa Verde National Park and Pine Tree Canyon Tinaja in Canyon de Chelly National Monument, which had average concentrations of .042 and .011 ?g/L respectively. Gross alpha/beta radioactivity counts were below the U.S. Environmental Protection Agency maximum contaminant level except for samples from Casa Chiquita Well  Middle at Chaco Culture National Historical Park which averaged 35 pCi/L. Suspended-sediment concentrations were variable and ranged from 10 to 150,000 mg/L.