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

Section 3: Design, Cost, And Policy

Page 164

Adjusting Operation Policy for a Rain Water Cistern System

Andrew Lo & Yu-Si Fok
University of Hawaii at Manoa, USA

Introduction

Rain water cistern systems have long been a water supply source in many countries. In some rural areas where municipal water is limited or unavailable, rain water for domestic use is caught on roofs and stored in water tanks. To design an efficient catchment system, adequate catchment area and cistern capacity in relation to water demand are factors that have to be carefully selected and designed to suit the rainfall pattern of the design area. If the average rainfall could be daily obtained, only enough catchment and storage would be needed to satisfy respectively the daily water demand and peak loads. However, there are many areas with frequent droughts that can last for months. Severe water shortage problems emerge even with extremely large catchment and storage. To alleviate such problems, the operating rule of the catchment system must be modified. Appropriate water use reduction imposed prior to the onset of dry weather may save enough water to last through the drought.

The following sections describe a linear and a non-linear reduction strategy, and their performance is compared to the classical unadjusted operating policy.' Conclusions are then drawn in relation to the proper form of rain water cistern system operation policy.

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