Ground-Water Resources of Cambodia GEOLOGICAL SURVEY WATER-SUPPLY PAPER I608-P Prepared in cooperation with the ^<ryr>s. Government of Cambodia under the t auspices of the United States Agency rf for International Development \ Ground-Water Resources of Cambodia By W. C. RASMUSSEN and G. M. BRADFORD CONTRIBUTIONS TO THE HYDROLOGY OF ASIA AND OCEANIA GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1608-P Prepared in cooperation with the Government of Cambodia under the auspices of the United States Agency for International Development UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1977 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data Rasmussen, William Charles, 1917-73 Ground-water resources of Cambodia. (Geological Survey water-supply paper; 1608-P: Contributions to the hydrology of Asia and Oceania) "Prepared in cooperation with the Govern­ ment of Cambodia under the auspices of the United States Agency for International Development." 1. Water, Underground Cambodia. I. Bradford, G. M., joint author. II. Cambodia. III. United States. Agency for International Development. IV. Title. V. Series: United States. Geological Survey. Water-supply paper ; 1608-P. VI. Series: Contributions to the hydrology of Asia and Oceania. TC801.U2 no. 1608-P [GB1144.C3] 627'.08s [553'.79'09596] 74-20781 For sale by the Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, Arlington, VA 22202 CONTENTS Page Abstract __________________________________________ PI Introduction __________________________________ 2 Purpose and scope of report ____________________ 2 Maps and nomenclature ___________________________________ 2 Base maps ___________________________ 2 National and administrative division boundaries ______ 3 Acknowledgments ________________________ 3 Previous investigations __________________________________ 4 Description of area ______________________________________ 5 Climate ____________________________________ 9 Ground-water terms and concepts __________________________ 11 Ground-water resources by khets ______________________ 16 Environs of Phnom Penh ___________________ 16 Khet Kandal _________________________________ 21 Srok Ponhea Loe ____________________________ 26 Srok Phnum Penh ____________________________- 26 Srok Kandal Stdeng _________________________ 27 Srok Kien Svay and Srok Leuk Dek ________________ 28 Khet Takev ___________________________________ 28 Khet Kampot and Keb ___________________________ 32 Khet Prey Veng ________________________________ 35 Khet Svay Rieng ______________________________ 38 Khet Kampong Cham ________________________ 47 Khet Kracheh _____________________________________ 55 Khet Mondol Kiri ______________________________ 58 Khet Rotanokiri _______________________________ 59 Khet StSeng Treng _____________________________ 60 Khet Kampong Thum ________________________ 60 Srok Barayn ____________________________ 63 Srok Santuk _____________________________ 68 Srok Kampong Svay __________________________ 78 Srok Stoung ________________________________ 78 Khet Preah Vihear ____________________________ 90 Khet Siemreab _______________________________ 96 Khet Batdambang _____________________________ 104 Khet PouthTsat _______________________________ 106 Khet Kampong Chhnang ___________________________ 107 Khet Kampong Spoe ____________ _______________ 108 Khet Kaoh Kong ______________________________ 117 Future developments of ground water ________________ 120 References ________________________________________________ 121 in IV CONTENTS ILLUSTRATIONS Page PLATE 1. Geologic map of Cambodia showing location of lithologic sections _____________________________________ In pocket 2. Map showing location of wells in Cambodia _________ In pocket 3. Lithologic sections of selected areas in Cambodia ____ In pocket FIGURE 1. Khet map of Cambodia _____________--_____---____----- P6 2. Physiographic profiles _____________________ ________ 3. Graphs showing variations in annual rainfall and hydro- meteorologic features at Phnom Penh _______________ 9 4. Diagram of water table and artesian wells ___ _________ 12 5. Graph showing water utilization of a hand-pumped well ___ 20 TABLES Page TABLE 1. Summary of wells drilled 1960-63 _______________ P4 2. Average monthly precipitation in Cambodia ___ ___ 10 3. Records of wells in the Environs of Phnom Penh _______ 18 4. Records of wells in Khet Kandal _____________________ 22 5. Records of wells in Khet Takev _________________ 30 6. Records of wells in Khet Kampot and Keb ______________ 33 7. Selected well logs in Khet Kampot and Keb ________ _ 36 8. Records of wells in Khet Prey Veng __________________ 37 9. Records of wells in Khet Svay Rieng ______ _ ___ 38 10. Records of wells in Khet Kampong Cham __ ___ _____ 49 11. Records of wells in Khet Kracheh ________________ 57 12. Logs and well records in Khet Stoeng Treng _______ 61 13. Wells in Srok Barayn, Khet Kampong Thum ___________ 64 14. Analyses of water from 4 wells in Srok Barayn ________ 68 15. Records of wells in Srok Santuk, Khet Kampong Thum 69 16. Records of wells in Srok Kampong Svay, Khet Kampong Thum __________________________________ 79 17. Records of wells in Srok Stoung, Khet Kampong Thum __ 89 18. Records of wells in Khet Preah Vihear __ ___ __ __ 91 19. Records of wells in Khet Siemreab _____ ___ 98 20. Specific capacity tests at Siemreab ____ _ ___ 104 21. Water analyses of the city wells at Siemreab, 1961 _____ 104 22. Records of wells in Khet Kampong Chhnang _ ____ __ 109 23. Records of wells in Khet Kampong Spoe _ ______ 113 24. Analyses of water from 3 wells in Khet Kampong Spoe __ 117 25. Records of wells in Khet Kaoh Kong _____ ________ 118 26. Yield, depth, and number of wells recorded in khets of Cambodia through 1963 _____________________ 121 CONTRIBUTIONS TO THE HYDROLOGY OF ASIA AND OCEANIA GROUND-WATER RESOURCES OF CAMBODIA By W. C. RASMUSSEN and G. M. BRADFORD ABSTRACT Cambodia (now the Khmer Republic), in tropical, humid southeast Asia, has an area of 175,630 km2 and a population of about 5 million. 'The Mekong River, one of the world's largest rivers, flows through Cambodia. Also, the Tonle Sap (Grand Lac), a highly productive fresh-water lake, functions as a huge off-channel storage reservoir for flood flow of the Mekong River. Surface- water discharge in streams and rivers of Cambodia is abundant during the wet season, mid-May through mid-November, when 85 percent of the precipi­ tation falls, but is frequently deficient during the remainder of the year. Annual rainfall ranges from 1,370 mm in the central lowlands to more than 5,000 mm in the mountainous highlands. The mean annual temperature for the country is 27.5°C and the evaporation rate is high. During 1960-63, 1,103 holes were drilled in 16 of the 18 khets (provinces), of which 795 or approximately 72 percent, were productive wells at rates ranging from 1.1 to 2,967 1/min. The productive wells ranged in depth from 2 to 209.4 m and were 23.2 m deep on the average. Mr. Rasmussen 2 studied the subsurface geology of Cambodia in considerable detail by examining drillers' logs and constructing nine geologic cross sections. The principal aquifer tapped by drilled wells in Cambodia is the Old Alluvium. In many places, however, dug wells and a few shallow drilled wells obtain water from the Young Alluvium. Sandstone of the Indosinias Formation yields moderate to small quantities of water to wells in a number of places. Also, wells tapping water-bearing basalt have a small to moderate yield. The quality of water is recorded in only a few analyses. The dissolved- solids concentrations appear to be generally low so that the water is usable for most purposes without treatment. Some well waters, however, are high in iron and would have to be aerated and filtered before use. In this report, well records are tabulated, and the geology and hydrology is discussed by khets. The bulk of the available information is on the central lowlands and contiguous low plateaus, as the mountainous areas on the west 1 Geographic names in this report have been verified by the Board on Geographic Names (BGN) of the Geographic Names Division, Defense Mapping Agency, Topographic Com­ mand, Washington, D.C. Names not verified by BGN are shown on the illustrations, and indicated in the text and tables, preceded by a asterisk(*). 2 Mr. Rasmussen was killed in the explosion of a land mine near Saigon, South Vietnam, in May 1973. PI P2 CONTRIBUTIONS TO HYDROLOGY OF ASIA AND OCEANIA and the high plateaus on the east are relatively unexplored with respect to their ground-water availability. No persistent artesian aquifer has been identified nor have any large- potential ground-water sources been found although much of the country yet remains to be explored by test drilling. Well irrigation for garden produce is feasible on a modest scale in many localities throughout Cambodia. It does not seem likely, however, that large-scale irrigation from wells will come about in the future. Ground water may be regarded as a widely available sup­ plemental source to surface water for domestic, small-scale industrial, and irrigation use. INTRODUCTION PURPOSE AND SCOPE OF REPORT The purpose of this report is to describe and evaluate the avail­ ability of ground water in Cambodia (now the Khmer Republic). The description and evaluation are based on test-drilling data and well irecords obtained by the Public Health Division of the United States Agency for International