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

Section 2: Rainfall Analysis

Page 54

Stochastic Model of Daily Precipitation using the Time Series Methodology

Silvia Vega,
University of Yucatan, Mexico

S. Gaona V.
Universidad Nacional Autonoma de Mexico

Introduction

The Yucatan Peninsula, situated in the eastern part of the Mexican Republic (Fig. 1), has geological conditions that necessitate the proper management of its water resources. The aquifer of this peninsula is of the calcareous type (Lesser 1976). Here, the limestone in the study area is covered in some places by just a few centimeters of soil (Gaona, Gordillo, and Villasuso 1980). The area is relatively flat, and there are no rivers and lakes. For this reason, groundwater and precipitation are the only sources of water that can be considered.

In this region, the groundwater has a high content of carbonates and is frequently contaminated by injections of municipal and industrial wastes that infiltrate to the groundwater table. It is for this reason that we consider precipitation as the most viable way to obtain potable water for human consumption. Although rainfall catchment was a very common source of water in the past, the actual design of an adequate system for catchment storage and the management of pluvial water requires more scientific studies.

The first of these studies consists in the development of a statistical model of rainfall by using historical data to plan the tank volume and their catchment areas.

Presented here is the statistical analysis of the data and the way in which it will be used to design the cistern, including the results.

The data consist of the daily rainfall-depth measurements corresponding to the past twenty-five years from one of the forty meteorological stations that exist in the Yucatan Peninsula-that which is situated in the city of Merida. A microprocessor Radio-Shack TRS-80 model was used for the analysis, which was done on a daily basis, to obtain results that can be used in other areas even though it was not necessary for our purpose.

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