WSP04550 - Laserfiche WebLink

Home Browse Search

~SGS Concentrations of nitrogen and phosphorus were measured during the summer of 1985 at multiple locations and depths in the reservoir. Total-nitrogen concentrations at Pueblo Reservoir ranged from less than 0.2 to 1.2 mg/L and had an average concentration of 0.6 mg/L. The predominant nitrogen form was organic nitrogen, which, as in the Arkansas River, comprised about 60 percent of the total nitrogen. The average total-inorganic-nitrogen concentration near the reservoir surface was about 0.2 mg/L; near the reservoir bottom, the average concentration was about 0.3 mg/L. Concentrations of total phosphorus ranged from less than 0.01 to 0.05 mg/L near the reservoir surface and ranged from less than 0.01 to 0.22 mg/L near the reservoir bottom. Concentrations of total phosphorus were largest near the reservoir bottom. Concentrations of major ions in samples collected near the reservoir bottom at transect 2 varied greatly during the summer of 1985, whereas the concentrations of the ions changed very little in samples collected near the reservoir surface at transect 7 (nearest the dam) during the summer of 1985. Variations in ion concentrations were consistent with changes in specific conductance that occurred with depth and demonstrate the effects of chemical stratification and inflow on concentrations of specific ions. Dissolved- solids concentrations at the Arkansas River at Portland, as indicated by specific-conductance measurements, usually are largest from January to March and smallest during June and July. Concentrations of most trace elements generally were small and were less than the established water-quality standards for Pueblo Reservoir. However, in 1985, concentrations of total iron occasionally exceeded the aquatic-life standard (1,000 ~g/L) near the reservoir bottom at transect 2, and dissolved- manganese concentrations exceeded the standard for public water supply near the reservoir bottom at transect 2. Trace elements that occurred in the largest concentrations at the Arkansas River at Portland are barium, iron, manganese, strontium, and zinc. Trace elements primarily occur in association with suspended material. Diatoms, green algae, blue-green algae, and cryptomonads comprised the majority of the phytoplankton in Pueblo Reservoir in the summer and fall of 1985. The maximum average concentration of phytoplankton was 41,000 cells/mL and occurred in July. Blue-green algae dominated from June to September; diatoms dominated in October. The average concentrations of phytoplankton drastically decreased from July to October. Zooplankton densities ranged from a few thousand organisms/m3 at transects 1 and 2 to about 80,000 organisms/m3 at transect 5 during August. A list of potential inbasin contaminants and transportation-related contaminants was compiled and included in the section in the back of the report titled "Supplemental Information Related to Potential Contaminants to Pueblo Reservoir." Currently (1986), the greatest threat of contamination in the upper Arkansas River basin probably is from metal mines that discharge to the streams in the vicinity of Leadville. Flammable liquids, combustible liquids, and flammable gases accounted for 71 percent of the hazardous mater- ials and 71 percent of the loads terminated in Colorado. Flammable liquids, combustible liquids, corrosives, oxidizers, and petroleum materials frequently are transported by rail. Depending on the specific compounds, location, and quantity of material spilled, a spill could pose a threat to the quality of water in Pueblo Reservoir. 48