It is important that a uniform system of symbols and footnotes be used in the production of daily discharge tabulations. The symbols (and footnotes) used by Environment Canada in the publication of Surface Water Data are set out below together with instructions on their use.
The following has been adapted from the "Manual of Hydrometric Data Computations and Publication Procedures", pages 12 and 13.
(a) "A" - Manual Gauge
Use this symbol during open water periods to identify the use of one or more manual gauge observations to obtain a daily stage at a station where the water stage recorder was temporarily out of operation. Enter this symbol to the right of the daily discharge figure or to the right of the daily stage figure if no discharge data are shown. This symbol will also be used when the chart record is available for only part of a day. During a year when a recorder is installed, the symbol "A" will be used on all days prior to the chart records to identify manual gauge readings. Do not enter this symbol in any monthly or annual summary data, except for the extremes in the annual summary, if applicable. Do not use this symbol during ice periods. However, a footnote will be required if the recording gauge was not in operation in winter periods. Use of this symbol must be accompanied by an appropriate reference in a footnote (i.e., A - Manual gauge). The symbols "B" or "E" have precedence over the symbol "A".
(b) "B" - Ice Conditions
Use this symbol to indicate that ice conditions in the stream have altered the open water stage-discharge relationship. The symbol is entered to the right of the daily discharge figure. This symbol will not be used for water level data. However, if it is required for specific stations, an appropriate explanation should be given in the Station Analysis Form AQU-07. Do not enter this symbol in any monthly or annual summary data except for the extremes in the annual summary, if applicable. Use of this symbol must be accompanied by an appropriate reference in a footnote (i.e., B - Ice conditions). The symbol "B" has precedence over the symbols "A" and "E".
(c) "D" - Dry
Use this symbol to indicate that the stream or lake is "dry" or that there is no water at the gauge. This symbol is used without a footnote in the gauge height column.
(d) "E" - Estimated
Use this symbol whenever the discharge during open water periods was determined by some indirect method, such as interpolation, significant high stage extension, comparison with other streams, or by correlation with meteorological data. If desired, the method of estimate may be given in a footnote. Enter this symbol to the right of the daily discharge or daily water level figure. Do not use this symbol during ice periods. Do not enter this symbol in any monthly or annual summary data except for the extremes in the annual summary, if applicable. Use of this symbol must be accompanied by an appropriate reference in a footnote (i.e., E - Estimated). The symbol "E" has precedence over the symbol "A".
(e) In summary, although only the symbols "A", "B", "D", or "E" will be used, only the symbols "A", "B" or "E" will be accompanied by a footnote in the data compilations or on printouts. For example, footnotes may be used if the symbol applies to one or more periods, or to explain that the recording gauge was not in operation during all or part of the winter period.
(f) The computer printouts for daily discharges and water levels will show a symbol for each day, where applicable.
Although the Station Analysis Form AQU-07 will not be dealt with in this section, the reader should be aware that pertinent facts regarding the open water computations should be noted for eventual inclusion in the station analysis.
For instance, the reasons for the distribution of the gauge and shift corrections, including the stage-shifting; the period of use of stage-discharge tables; etc.
In particular, any deviation from the commonly practiced computation procedure should be tabulated in the station analysis.
This section has covered the derivation of stage-discharge curves and tables from discharge measurements, and the production of discharge data by combining stage data and the stage-discharge relationship. The stage-discharge curve must be determined by a manual process in order to give appropriate weighting to the discharge data. After that, data may be processed manually or by computerized methods.
There are a number of specialized software packages for hydrometric data processing, and some users have adapted more general software such as spreadsheets for this purpose. This section has described techniques as if data were being processed manually, as it is essential that the user be familiar with the rationale. Hydrometric computer packages can expedite data processing, but do not replace the knowledge and skill of a competent hydrometric technician. The judgments required at various stages of the process must be suitably documented, whether manual or computerized processing is used.