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Discharge Time-Series <br />Data gaps for discharge-type TS data (stream flow, diversions, reservoir outflows, etc.) will <br />generally be filled by using information from stations directly upstream or downstream. The flow <br />information from an upstream or downstream station will be corrected for time lag and attenuation <br />and used to estimate missing data. Replacement data may also be generated from nearby gages, <br />historical records at the same gage, by applying continuity at a reservoir to estimate flows, and <br />through the application of simple models. <br />If there are no stations directly upstream or downstream from a station with missing data, the data <br />will be stochastically generated using a technique that conserves the station mean, probability <br />density function, and spectral components of the TS. This procedure will be handled on a case-by- <br />case basis. In general, the station statistics will be estimated from available station data, data from <br />other stations, and regional relationships based on physical characteristics. In some cases annual or <br />seasonal data may be available when monthly or daily data are required. In these cases the longer- <br />term data will be disaggregated, preserving the shorter period statistics. <br />Data Comments <br />The replacement of missing data and/or data manipulation requires that modifications to data be <br />clearly spelled out. The user must know how the replacement data were generated, the periods of <br />replacement, and the resulting statistics. Comments that apply to a gage will be stored separately <br />from TS in the station database. It may also be possible that the TS format allows for comments to <br />reside within the TS file. TS that have had data replaced or filled will either be stored separately or <br />flagged. <br />3.0 CONCLUSIONS AND RECOMMENDATIONS <br />At this time emphasis is being placed on identifying the TS that require missing data to be filled and <br />characterizing data gaps within the weather and discharge TS. Once data gaps are identified and <br />characterized, an appropriate technique will be selected to replace missing data as required by the <br />water rights planning and consumptive use models. <br />The replacement of missing data in weather TS will consist primarily of using information from <br />surrounding stations to estimate missing data. If there are no surrounding stations from which to <br />estimate replacement data, specific techniques will be developed to replace data in a manner that <br />preserves the statistical aspects of the TS. <br />The replacement of missing data in discharge TS will consist primarily of using information from <br />either an upstream/downstream station, the historical record at the station, or gage records from <br />nearby stations. If there are no surrounding stations from which to estimate replacement data, <br />specific techniques will be developed to replace data in a manner that conserves mass, continuity, <br />and spectral components of the TS. <br />2 <br />A275 05.10.94 1.05-6 Ritsch, Day <br />