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streamflow records were reviewed for spatial coverage throughout Division 1 and Water <br />District 47, period of available records, completeness of available records, and data reliability. <br />3.2.2.1 Spatial Coverage. There are 302 gaging stations in the South Platte and North <br />Platte River basins; 267 in the South Platte and 35 in the North Platte River basin (including six <br />gaging stations in the Laramie River Basin). Stations are located on river mainstems and <br />tributaries throughout Division 1 and Water District 47 and this spatial coverage is adequate for <br />water resources planning purposes. However, the Division 1 Engineer has indicated the spatial <br />coverage is less than ideal for water rights administration needs on the lower South Platte River, <br />the Cache la Poudre River, and Boulder Creek. <br />3.2.2.2 Period of Records. At least 85 streamflow gages in the South Platte River basin <br />have records extending to 2000, indicating the gages are currently active. Only four streamflow <br />gages in the North Platte River basin (including two in the Laramie River basin) are currently <br />active. Many of the gages have relatively short periods of records and are located on small <br />tributaries to the mainstem rivers in the basin. Out of the total of 302 gages in both the South <br />Platte and North Platte River basins, 29 gages do not have any records after 1949. <br />3.2.2.3 Completeness of Records. For the period of record at each gage, Table B-1 lists <br />the percentage of daily data that are missing. Of the 302 gages, about 45 are streamflow gages <br />with less than 10 percent missing records for 1950-2000. Approximately 65 streamflow gages <br />have less than 30 percent missing records. Assuming a study period of 1950 to the present, <br />missing daily and monthly data would need to be estimated to provide complete data sets. <br />3.2.2.4 Reliability of Records. The measurement procedures and preparation of the <br />records are established and accepted in the water community. The records published by the <br />USGS indicate the accuracy of the record by "poor," "fair," "good," and "excellent." Each <br />qualitative description relates to a statistical degree of accuracy. Reliability is generally <br />considered adequate for modeling purposes; however, the Division 1 Engineer has indicated that <br />three administrative gages on the lower South Platte mainstem (located at Julesburg Balzac, and <br />Kersey) are not hydraulically stable and require extensive care to improve reliability. <br />3.2.3 Additional Data Required <br />As with any water resource study, additional streamflow information is always useful. <br />A complete record of monthly and daily streamflows covering the study period of record and <br />adequately defining the flows over the study basin would be needed for an accurate water <br />resources modeling effort. Evaluation of additional data to support water resources investigations <br />should consider both the cost of additional data collection and the accuracy improvement from <br />the additional data. Potential streamflow-related data collection activities for the SPDSS are <br />discussed below and summarized in Table 3-1 at the end of this chapter. <br />3.2.3.1 Fill Missing Records for Key Streamflow Gages. Based on the review of data <br />in Table B-1 and interviews with water users, it has been determined that the available spatial <br />coverage of streamflow gages is adequate for development of models of the surface and <br />p:data\gen\spdss~final report\chapter 3.doc 3-3 <br />October 31, 2001 <br />