1.   Purpose and objectives

     This material on the statistical analysis of water level and discharge data was prepared for use in training courses.

2.   Description

     The main subjects covered in the manual are:

     - Network design and hydrological observations: A short introduction 
       to essential aspects of planning networks and the management of 
       basic hydrological data.

     - Plausibility of hydrological data: All measured hydrological data or 
       the values derived therefrom contain errors. Quality control tests 
       for the examination of possible errors in hydrological data are 
       recommended.

     - Theoretical probability distributions: This chapter covers the 
       concept of distribution functions, moment and quantiles, empirical 
       distributions, plotting positions, partial series, and distribution 
       functions, including the Gaussian or normal distribution, log 
       normal, Pearson type III, log Pearson III and Gumbel.

     - Correlation and regression analysis: Theoretical considerations are 
       useful to indicate the existence of correlation between hydrological 
       variables. The problem is then to determine the type and degree of 
       correlation.

     - Flood and low flow events: Definitions of flood and low water 
       characteristics are described and the requirements and procedures 
       for their evaluation are indicated.

     - Time series analysis: The main objective of time series analysis in 
       hydrology is to disaggregate the trend, the periodic and the 
       stochastic elements from a measured hydrograph. The methods of time 
       series analysis are also used to evaluate the accuracy estimates of 
       statistical parameters and to determine whether a time series is 
       sufficiently long.

     - Further chapters deal with auto- and cross-correlation, spectrum 
       analysis, cross spectrum and coherence. The linear cross-correlation 
       analysis yields information on the degree of the linear relationship 
       and on the kind of agreement of variations in two time series.

     The annex contains examples of the main statistical procedures mentioned.

3.   Input

     Not applicable.

4.   Output

     Not applicable.

5.   Operational requirements and restrictions

     Users should be well acquainted with basic mathematics and hydrology.

6.   Form of presentation

     Manual in English.

7.   Operational experience

     The material has been presented at various workshops.

8.   Originator and technical support

     Dr. Hofius, Dr. Liebscher, Bundesanstalt für Gewässerkunde, Koblenz, and Dr Löken, Niedersächsisches Landesamt für Wasserwirtschaft, Hildesheim.

9.   Availability

     From the HOMS National Reference Centre of the Federal Republic of Germany.

10.  Conditions on use

     Free of charge.