Guide to Hydrological Practices, 6th edition, Volume I - Hydrology.nl

I.2-12
GUIDE TO HYDROLOGICAL PRACTICES
Table I.2.4. Recommended units as appearing in Table I.2.2.
Item Unit Symbol Remarks
1 Centimetre cm ISO
2 Day d ISO
3 Degree Celsius ˚C ISO
4 Gram g ISO
5 Hectare ha
6 Hectopascal hPa ISO
7 Hour h ISO
8 Joule J ISO
9 Kilogramme kg ISO
10 Kilometre km ISO
11 Knot kn, kt
12 Litre l ISO
13 Metre m ISO
14 Microsiemens μS
15 Milligram mg ISO
16 Millimetre mm ISO
17 Minute min ISO
18 Newton N ISO
19 Parts per million ppm
20 Pascal Pa ISO
21 Percentage %
22 Second s ISO
23 Tonne (metric ton) t ISO
24 Year a ISO
25 Bequerel Bq IAEA
to one report. CREX uses many of the principles of
the previous BUFR code, and each message consists
of sections as follows:
Section
number
Name
0 Indicator
section
1 Data
description
section
Contents
CREX
CREX master table number, edition
number, table version number,
data category, then a collection of
descriptors which define the form
and content of data subsets making
the data section and an optional
check digit indicator E
2 Data section A set of data items defined by
section 1
3 Optional
section
4 End section 7777
SUPP followed by additional items
for local use
Further information can be found at http://www.
wmo.int/pages/prog/www/WMOCodes.html.
2.3.3 Accuracy of hydrological
measurements
2.3.3.1 Basic principles
Theoretically, the true values of hydrological elements
cannot be determined by measurements because
errors of measurement cannot be eliminated
completely. The uncertainty in measurement has a
probabilistic character that can be defined as the
interval in which the true value is expected to lie with
a certain probability or confidence level. The width of
the confidence interval is also called error band.
If measurements are independent one from the
other, the uncertainty in the results of measurements
can be estimated by taking at least