ESOP 1996 USGS Stream Flow Dataset 1.0 General Description The United States Geological Survey (USGS) stream flow dataset is one of various hydrological datasets provided for the GEWEX Continental-Scale International Project (GCIP) Enhanced Seasonal Observing Period (ESOP) 1996 project. This dataset contains stream flow data from 821 USGS stations in the ESOP 1996 domain. This dataset covers the complete ESOP 1996 time period (01 April 1996 through 30 September 1996) and for the ESOP 1996 domain. The ESOP 1996 domain is approximately 91W to 107W longitude and 31N to 40N latitude. No additional quality control was performed by the University Corporation for Atmospheric Research/Joint Office for Science Support (JOSS). 2.0 Detailed Data Description The data collected at USGS gaging stations consist of records of stage and measurements of discharge of streams or canals, and stage, surface area, and contents of lakes or reservoirs. This dataset contains only the USGS stream flow data. For USGS stream-gaging stations, the daily mean discharge is computed from gage heights and rating tables. These rating tables are prepared from stage-discharge-relation curves and give the discharge for any stage. If extensions to the rating curves are necessary to express discharge greater than measured, they are made on the basis of indirect measurements of peak discharge, step-backwater techniques, velocity-area studies, and logarithmic plotting. If the stage-discharge relation is subject to change because of frequent or continual change in the physical features that form the control, the daily mean discharge is computed by the shifting-control method, in which correction factors based on individual discharge measurements and notes by engineers and observers are used in applying the gage heights to the rating tables. If the stage-discharge relation for a station is temporarily changed by the presence of aquatic growth or debris on the control, the daily mean discharge is computed by what is basically the shifting-control method. At some USGS gaging stations, acoustic velocity meter (AVM) systems are used to compute discharge. The AVM system measures the stream's velocity at one or more paths in the cross section. Coefficients are developed to relate this path velocity to the mean velocity in the cross section. Because the AVM sensors are fixed in positions, the adjustment coefficients generally vary with stage. Cross-sectional area curves are developed to relate stage to cross section area. Discharge is computed by multiplying path velocity by the appropriate stage related coefficient and area. Changing stage, backwater from reservoirs, tributary streams, or other sources, and ice in the winter affect the stage-discharge relation. Special methods, such as using comparable records of discharge for other stations, are then used to compute discharge. If no gage-height record can be obtained from a gaging station due to failed equipment, etc., daily discharge values are estimated using various means. These methods are discussed in the "U.S. Geological Survey Water-Data Report MO-94-1". Further information regarding the stream flow data description can be found in the USGS Water Resources Data publications (by state) for water year 1996. These documents are available from the National Technical Information Service, Springfield, VA. 2.1 Detailed Format Description The USGS stream flow dataset contains three metadata parameters and three data parameters. The metadata parameters identify the network, station, and time at which the data was collected. Each record contains one month's data. The three data parameters (stream flow, stage, and hour of observation) are repeated once for each UTC day (0000 to 2300). All records contain data for 31 days regardless of the actual number of days in a month. Months with less than 31 days are padded with missing values (e.g., -999.99). The stream flow values are reported in cubic meters per second and are 24 hour averages. There are no stage values in this dataset, so the stage values are shown as missing. The hour of observation is the beginning UTC hour for the 24 hour period for which the stream flow value is valid. Table 1 below details the data parameters in each record. For further details on the data format, see Showen (1980). Table 1 Parameters Units Date of Observation UTC Year/month Network Identifier Abbreviation of platform name Station Identifier Network Dependent Stream flow (24hr ave) Cubic meters per second Stage Meters (always -999.99 for USGS) Hour of Observation Beginning UTC hour for 24 hour period for which stream flow and stage values are valid. 2.2 Data Remarks There are no stage values in this dataset. 3.0 Quality Control Processing No additional quality control (QC) was performed on this dataset by the UCAR/Office of Field Project Support (UCAR/JOSS). 4.0 References Reed, H.L., Perkins, T.J. and Gray Jr., G.L., 1994: Water Resources Data Missouri Water Year 1994, U.S. Geological Survey Water- Data Report MO-94-1, National Technical Information Service, Springfield, Virginia, 338pp. Showen, C.R., 1980; Data Formats For U.S. Geological Survey Computer Files Containing Daily Values for Water Parameters. U.S. Geological Survey, Open-File Report 76-563 (Revised), Reston, Virginia, 20pp.