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<br />002391 <br /> <br />tables. Prior to 1977 single daily measurements for specific conductance were made (daily values <br /> <br />statistic code 000 II). Since that time, specific conductance has been measured at specific intervals <br /> <br />with automated mini-monitor instrumentation; mean daily values are calculated from these data <br /> <br />(daily values statistic code (00003). <br /> <br />Reclamation began its water quality monitoring ofthe Glen Canyon Dam tail water as part of <br /> <br />Phase I of the Glen Canyon Environmental Studies program in August 1988. This program was <br /> <br />begun with measurements of temperature and specific conductance at bi-hourly intervals. As <br /> <br />instrumentation improved, measurement of dissolved oxygen was added in June 1991; pH <br /> <br />measurements began in July. 1995. Monitoring at Lees Ferry was initiated in October 1991. This <br /> <br />monitoring has been conducted with various versions of the Hydrolab? Corporation?s Datasonde <br /> <br />and Recorder submersible multi-parameter data logging instrumentation (Hydro lab, 1994). These <br /> <br />monitors are serviced ona monthly basis. The Grand Canyon Monitoring and Research Center <br /> <br />(GCMRC) currently maintains this program., <br /> <br />c. Chemical Analysis <br /> <br />The Colorado River at Lees Ferry gage (09380000) gage is maintained as part of the USGS <br /> <br />National Stream-Quality Accounting Network. Analysis of a broad range of water quality <br /> <br />parameters and contaminants is conducted on samples collected on a bimonthly basis. <br /> <br />As part ofthe monthly servicing of the tailwater instrumentation maintained by GCMRC, samples <br /> <br />are collected and analyzed for major ionic constituents and nutrient concentration and analyzed <br /> <br />according to standardized procedures (APHA, 1992). Biological samples similar to those collected <br /> <br />at reservoir stations are also collected. <br /> <br />B. Data management <br /> <br />Prior to the mid-1980s all data was stored as hard copy records in binders. Over time, more data <br /> <br />06/02/98 <br /> <br />DRAFT <br /> <br />Page 14 of62 <br />