Ground-Water Resources of the Republic of El Salvador Central America By A. N. SAYRE and G. C. TAYLOR, JR. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1079-D Geologic and hydrologic studies of water supply as a part of the program of the Health and Sanitation Division of El Salvador UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1951 i i UNITED STATES DEPARTMENT OF THE INTERIOR Oscar L. Chapman, Secretary I . GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $1.00 (paper cover) CONTENTS Page Abstract_______________________________________________________ 155 Introduction- __ ____________________-_____________-___-,____-.-__-_ 157 Scope and purpose of the investigation________________________ 157 Acknowledgments___ _ _________'_________--________-_--__-____ 157 Historical sketch____________________________________________ 158 Geographic sketch.____________________________________________ 158 Climate_______________._____________________ 159 Physiography___________________________________________________ 162 General features.______-________-_-______---________-_----_-__- 162 Physiographic districts______________________________________ 162 Central highlands__________________________________ 163 Western plateau__-_________-_________-_________-_-_-_____- 168 Eastern uplands..__________-_-___-_-_----__________--____- 169 Northern highlands________________________________________ 169 Coastal plain___________________________________________ 169 Geology__________________________________________ 170 Sequence and general features of the rocks._______________________ 170 Summary of the geologic history______________.__________________ 170 Physical character and water-bearing properties of the strata________ 173 Quaternary system______________________________________ 173- Recent series_______________________________________ 173 Beach and estuarine deposits______________________ 173 Landslides, talus, and alluvial fans_________________ 174 Younger alluvium_________________________________ 175 Younger Quaternary lavas and pyroclastic deposits _____ 176 Pleistocene series______________________________________ 177 Older alluvium__________________________________ 177 Older Quaternary lavas and pyroclastic deposits ________ 178 Lake beds____._______________________ 179 Tertiary system________________________________________ 181 Late Tertiary (?) pyroclastic deposits and lavas_________ 181 Early (?) Tertiary volcanic rocks and related sedimentary rocks__________.______________________ 183 Cretaceous and Jurassic systems___________________________ 185 Lower Cretaceous and Upper Jurassic series_____________ 185 Metapdn formation________________________________ 185 Ground water _____________________________________________________ 18& Introduction._________________________________________________ 186- Ground-water resources by departments________-___---___---_____ 187 Departamento de Ahuachapdn_______________________________ 187 General features.._____________________________________ 187 Ground-water conditions___.______._____________________ 188 Local supplies_________________________________________ 189 Ahuachapdn __ ___________________________________ 1891 Atiquizaya___ _ __________________________________ 189- in IV CONTENTS Ground Water Continued Ground-water resources by departments Continued Page Departamento de Cabanas________________________________ 190 General features_____________________________________ 190 Local supplies_________________________________________ 191 Sensuntepeque ____________________________________ 191 Departamento de Chalatenango.____________________________ 191 Departamento de Cuscatl£n________________________________ 192 General features_______________________________________ 192 Ground-water conditions._______________________________ 193 Local supplies____________'_____________________________ 194 Cojutepeque ______________________________________ 194 El Carmen______________________________________ 194 San Rafael Cedros_______________________.______ T ___ 194 Departamento de La Libertad_____________________________ 195, General features_--_----_------___---_____________--_-_ 195 Ground-water conditions.______________________________ 195 Local supplies-________-___--_______-____-__-______--_. 197 Antiguo Cuscatl£n_________________________________ 197 Quezaltepeque_ ________-_____-___-_---_________-_- 197 Nueva San Salvador (Santa Tecla)__________________ 197 Departamento de La Paz______-_____________________-______ 198 General features..__________________________'___________ 198( Ground-water conditions.______________________________ 199 Local supplies...._____________________________________ 200 Zacatecoluca_ _____________________________________ 200 Departamento de La Uni6n_________________________________ 200 General features__-______------___-____----_--_-------- 200 Ground-water conditions. ______________________________ 201 Local supplies__________---_---__-_____----_---___-_-_- 201 Santa Rosa____-__--------_____-__-------_-------- 201 Departamento de Morazan_________________________________ 202 General features-______________________________________ 202 Ground-water conditions_______________________________ 202 Local supplies_______----------__---------------_---_-_ 203 Jocoro_ _ __________-__----__--_-_-_-_-_----__---_- 203 San Francisco._________-____I_______________-___-_ 203 Departamento de San Miguel_-__---___-_-__---_-__--__---_- 203 General features__________-----_____--_------_--------- 203 Ground-water conditions.______________________________ 204 Departamento de San Salvador___________________________.__ 204 General features____------_--------_---_---___--------- 204 Ground-water conditions.______________________________ 205 Local supplies_________________________________________ 206 San Salvador._______________________________ 206 Mejicanos ________________________________________ 207 Villa Delgado__-------------------------_-------- 208 San Martin____________________________________ 208 Tonacatepeque_ ___________________________________ 209 Departamento de San Vicente_____________________________ 209 General features.______________________________________ 209 Ground-water conditions.______________________________ 209 Local supplies_________-___^__-___-___-_-___--_-------- 211 Guadalupe_______-____-___________-____-_-----__-_ 211 San Vicente___.____________________ 212 CONTENTS Ground water Continued Ground-water resources by departments Continued page Departamento de Santa Ana ___ ___________________________ 212 General features. ______________________________________ 212 Ground-water conditions_____________________________._ 213 Departamento de Sonsonate_________________--_____________ 215 General features______________________-________________ 215 Ground-water conditions. ______________________________ 215 Local supplies_____-_-__--______-____-__-_--_-____---_- 216 Armenia _ _______________________________________ 216 San Julian _________ . _______ _ _________ __ 217 Departamento de Usulatdn__________________---____-__--__- 217 General features________________________-_________----_ 217 Ground-water conditions__________________-_____--__-__ 217 Local supplies._______--___________________-______-_--__ 220 Alegrfa_-__-_-----_-_-___---_--__------___-------- 220 Jucuapa_ _________________________________________ 220 Usulatan. ____________________________ ____ ___ _ 221 Index _ _ __ _____ _____ ____________ ________ ___ _____ --._ 223 ILLUSTRATIONS Page PLATE 3. Map of the Republic of El Salvador, Central America..-- In pocket FIGURE 7. Index map of Central America showing the location of the Republic of El Salvador.._____________________________ 159 GROUND-WATER RESOURCES OF THE REPUBLIC OF EL SALVADOR, CENTRAL AMERICA By A. N. SATEB and G. C. TAYLOR, JR. ABSTRACT This report is based on an investigation by the writers of the U. S. Geological Survey assigned to the Institute of Inter-American Affairs to determine the ground-water resources of El Salvador, especially with reference to the devel­ opment of ground water for public water supplies and for domestic use. The field work on the investigation was carried on from June 1943 through Feb­ ruary 1944. During this period, studies were made of the water-supply prob­ lems of some 30 towns and cities in the republic. El Salvador, smallest of the five Central American Republics, covers an area of about 13,176 square miles. The climate of the country is the savanna typical of the subequatorial belt of the tropics. There are two seasons, a wet season from June to October, inclusive, and a dry season during the low-sun period. The average annual rainfall over the country as a whole is about 75 inches, most of which occurs in the wet season. Much of the western and central part of El Salvador is an elevated plateau ranging from 1,000 to 2,000 feet above sea level. The eastern part of the country Is largely a hilly upland ranging from 500 to 1,500 feet above sea level. The plateau and upland are moderately dissected by numerous canyons and narrow valleys separated by broad sloping interfluves. Surmounting the plateau and upland are five groups of volcanic peaks which form a discontinuous highland that traverses the country from east to west. The summits of this highland rise from 5,000 to 8,000 feet above sea level. Bordering the shore line is a narrow coastal plain that rises inland to an elevation of about 500 feet. In El Salvador, nonmarine strata