Water Quality Assessment of the South Platte River Basin, Colorado , Nebraska, and Wyoming

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SOURCES AND CHARACTERISTICS OF AVAILABLE WATER - QUALITY DATA In late 1991, a telephone survey was conducted to establish the availability of water - quality data in the South Platte River Basin. Information collected included: data availability, format, and storage medium (paper or computer); years of record; constitu- ents analyzed; and methods and frequency of data col- lection. Additionally, during the first South Platte River Basin Liaison Committee meeting (July 1991), members of the Liaison Committee were polled as to the nature and availability of similar water - quality data. The Liaison Committee is composed of representatives from local, State, and national agencies concerned with water resources within the study basin. Organizations contacted as potential sources for water - quality data are listed in table 4. These agencies were asked to provide water - quality data that could be used in an analysis of available nutrient, suspended- sediment, and pesticide data. Data available on magnetic media were requested because of ease of data transfer; data available only on hard copy were not included in this analysis. The available data across the study unit were not ideal for conducting a basin -wide water - quality assess- ment. For example, each agency has sampled for dif- ferent purposes and, accordingly, has analyzed different constituents using different sampling tech- niques and analytical methods. The lack of consistency in these two factors makes it difficult to combine data from different agencies. Additionally, sites with long- term monthly data are rare in the basin and lack neces- sary areal distribution to characterize differences in water quality as it might relate to various land uses. Furthermore, few sites had complete nutrient species analyses, and most sites lacked suspended- sediment and pesticide data. The analysis of available data presented here is not meant to be an exhaustive analysis of all possible data collected within the study unit. The philosophy adopted here is that after evaluating the most easily obtainable data, gaps in space, time, flow regime, and other characteristics will be recognized. Data more dif- ficult to obtain can be used to fill these gaps when the additional information is worth the extra effort. Other agencies' data were used when their data collection and laboratory analysis methods were documented and appropriate. Data - Selection Criteria and Screening Procedures The data set of available water - quality data was refined by selecting constituents of interest and a time period of interest. Nutrient constituents selected were: total nitrogen, total organic nitrogen plus ammonia (for surface -water sites), dissolved organic nitrogen plus ammonia (for ground -water sites), dissolved ammonia, dissolved nitrite, dissolved nitrite plus nitrate, dis- solved phosphorus, dissolved orthophosphate, and total phosphorus. All nitrogen species are reported as nitro- gen, and all phosphorus species are reported as phos- phorus. Suspended- sediment constituents selected were: suspended- sediment concentration and sus- pended- sediment particle size distribution. Pesticide constituents selected consisted of the following com- Table 4. Organizations contacted as potential sources of water - quality data in the South Platte River Basin Organizations Central Colorado Water Conservancy District Colorado Division of Wildlife Colorado Department of Health, Water Quality Control Division Colorado State Engineer Office Colorado State University Colorado Water Resources Research Institute Denver Regional Council of Governments Denver Water Department Lower South Platte Water Conservancy District Metro Wastewater Reclamation District Northern Colorado Water Conservancy District Northern Front Range Water Quality Planning Association Twin Platte Natural Resources District Urban Drainage and Flood Control District U.S. Army Corps of Engineers U.S. Bureau of Land Management U.S. Bureau of Reclamation U.S. Department of Agriculture, Soil Conservation Service U.S. Environmental Protection Agency U.S. Fish and Wildlife Service, Division of Environmental Contaminants U.S. Forest Service 18 Water- Quality Assessment of the South Platte River Basin, Colorado, Nebraska, and Wyoming -- Analysis of Available Nutrient, Suspended - Sediment, and Pesticide Data, Water Years 1980 -92