CONTENTS

中　　文

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PREFACE

Due to rapid economic growth in recent Years, the demands of water for agricu IturaI and industrial uses, as well as Public water supplies In Taiwan, have drastically increased each year. To utilize water resources and meet the requirements of social and economic development, the Uater Resources PlanninO Commission has followed the idea of the " Comprehensive Development Programs in Taiwan", then divided the entire Taiwan area into North Central South and East water resources regions. Each reoion is considered as an integral unit to obtain reasonable distribution of water resources through effective Planning and employment.

Hydroloflical data are the basic requirement for water resources management and development. For Years, hYdrometric stations on the river basins in Taiwan have been organized to form the Taiwan HydrometeoroloflicaI Network by the Commission. Through the Network, the standardization of observation methods.and record1n9 systems has gradually unified. The water data storage and retrieval system was established to Provide more information for the Public by the Commission.

The very first volume of "Hydrological Year Book of Taiwan, Republic of Chinas 1970" covering the data collected from the establishment of each station up to 1970, was Published in 1972. Since then, the Year Book has been published annually. Compilations of these Publications have been improved gradually.

In addition to compile the water quality data collected by other agencies, the river water quality data of Tachia River, Choshui River, Tai-power’s hydrological staions, and the groundwater quality data of Taipei basin and Kaoping area, which were sampled and analyzed by the laboratory personnels of Water Resources Planning Commission were added in this 1991 Hydrological Year Book. These water quality data can be essential to water resources planning.

It was a dry year in 1991. The average annual rainfall was only 2,116 mm, which was 16％ less than the long-term (1949-1990) average annual rainfall of 2,515 mm. After November of 1990, the scarcity of rainfall had caused drought in the spring of 1991. The total stream runoff was 53.1 billion cubic meters, which was 21％less than the long-term ( 1949-1990) average annual streamflow of 66.8 billion cubic meters There were three typhoons ravaged Taiwan area, and serious damages were reported in the east and south regions.

This volume of Year Book of 1991 is now completed and will be distributed to various governmental and private agencies. Suggestions for improving the Year Book are welcome and appreciated.

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Director General

October, 1991