1st International Conference on Rain Water Cistern Systems
Honolulu, Hawaii, USA - June 1982

Section 2: Rainfall Analysis

Page 77

General Methodology for the Characterization of Rainfall Time Distribution

Van-Thanh-Van Nguyen
University of Quebec, Canada

Introduction

Information on variations in rainfall time characteristics is always necessary in various types of hydrologic studies concerning the planning, design and operation of water resources systems.. Most previous research on the time distribution of rainfall usually involved the study o temporal distributions of "rainfall exteriors" characteristics, such as total event depth, total event duration and time between events, but very few studies deal with the time distribution of rainfall within each individual vent or the temporal pattern of each event.

The objective of this study is to provide basic information on the variability of temporal patterns based on the probabilistic characteristics of an actual rainfall record. Information concerning the nature of the temporal distribution of rainfall within a rainfall event is usually presented as a mass curve of accumulated depth as a function of time. The purpose here is to ascertain the probability distributions of rainfall accumulated at the end each time unit within such a total rainfall event representation.

First, a general theoretical model will be proposed, and then a numerical application will be presented by using a 32-year record of daily rainfall at Dorval Airport on Montreal Island (Canada). In the numerical example, the daily precipitation is selected because relatively long and reliable records are readily available and such data are frequently sufficient for many practical problems. The model, however, might be used for hourly rainfall (Nguyen and Rouselle 1981) and for rainfall durations of one ay or longer.

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