Gatun Dam The Gatun Dam spillway in full discharge during the rainy season ( April through December ) . The Gatun Dam is a large earthen dam across the Chagres River in Panama , near the town of Gatun . The dam , constructed between 1907 and 1913 , is a crucial element of the Panama Canal ; it impounds the artificial Gatun Lake , which in turn carries ships for 33 km ( 20 statute miles ) of their transit across the Isthmus of Panama . In addition , a hydro-electric generating station at the dam generates electricity which is used to operate the locks and other equipment in the canal . Construction of the dam was a great engineering achievement , eclipsed only by the parallel excavation of the Gaillard Cut ; at the time of completion , the dam was the largest earth dam in the world , and Lake Gatun was the largest artificial lake in the world . Description The dam is situated in the valley of the Chagres River , about 10 km ( 6 miles ) from its mouth in the Caribbean Sea . The hills bordering the valley of the Chagres form a gap just over 2 km ( 1.4 miles ) wide at this point , with a natural rocky hill in the centre of the gap . The gap is filled by an earth dam , 640 metres ( 2 , 100 ft ) thick at the base , 2 , 300 metres ( 7 , 500 ft ) long along the top , 121 metres ( 398 ft ) thick at the water level , and 30 metres ( 100 ft ) thick at the top , which is 9 metres ( 30 ft ) above the normal lake level . The spillway for the dam is constructed on the central hill ; it consists of a semi-circular concrete dam , which regulates the flow of water down a concrete channel built into the back slope of the hill . The spillway dam itself measures 225 metres ( 740 ft ) along the top ; its crest is at 16 feet below the normal lake level . The spillway is designed so that water pouring over the semi-circular dam converges at the bottom from opposite directions and neutralises its own force , thus minimising erosion below . The spillway dam is topped by 14 gates , supported by concrete piers and each 14 metres ( 45 ft ) wide by 6 metres ( 20 ft ) high . These gates , which are electrically operated , are raised or lowered to control the flow of water ; with the lake level at 26.5 metres ( 87 ft ) , its planned maximum level , the capacity of the spillway is 4 , 100 m³ ( 145 , 000 ft³ ) per second , more than the maximum flow of the Chagres River . In addition to this , the culverts in the locks can dispose of 1 , 400 m³ ( 50 , 000 ft³ ) per second . Gatun Lake has an area of 425 km² ( 164 square miles ) at its normal level ; it stores 5.2 cubic kilometres ( 4 , 200 , 000 acre-feet ) of water , which is about as much as the Chagres River brings down in an average year . Power Generation The dam incorporates a hydro-electric generating station , which is situated on the east side of the spillway discharge channel . This uses water from the lake to drive a number of turbine - generators ; as first commissioned , three generators were installed , producing a total of 6 megawatts of electricity . The power generated is used for the operation of the lock and spillway machinery , and for the lighting of the locks and the canal villages . Construction This map from the construction era illustrates the area around the dam and locks , which are shown superposed over the previous French excavations . As described in History of the Panama Canal , the canal effort was began by a French team , who planned to construct a sea-level canal linking the two coasts ; this would not have required the dam to be built . When the United States took over this effort on 4 May , 1904 , some time was spent in preparation and planning before the work got up to full speed , and it was not until 1906 that a lock-based canal was decided upon . Even before this decision was made , Major George Washington Goethals , the chief engineer for the bulk of the construction effort , had already carried out an investigation into the suitability of the land at Gatun for the building of a large dam . Extensive test borings were made to determine the suitability of the land , and pressure tests were carried out on the material to be used in construction to determine its durability . The Gatun location was in most ways ideal for a dam ; the hills enclosing the Chagres open very wide around the area that is now the lake , then close in to a relatively narrow gap with a natural rock-based hill in the centre . This allows a relatively small dam to enclose a huge body of water , which both provides passage for ships across much of the isthmus , and provides a reservoir of water with which to operate the locks . The central hill was the ideal solid base for the construction of the concrete spillway and its dam , the main part of the dam being earth . The only problem was the huge scale of the dam required . The dam was constructed by creating two parallel walls of stone , 366 metres ( 1200 ft ) apart , using material excavated from Culebra and the lock site . Between these walls an impervious core was created , using a hydraulic fill technique ; this was facilitated by the soft clay present in the valley below . Dredges were used to excavate this clay and pump it up into a pond between the outer walls of the dam ; the material was allowed to settle out , and the water was drawn off and pumped back downstream . Thus , a solid core of natural cement was constructed within the dam . After the dam was built to its desired height , the entire up-stream side was armoured by placing large boulders on the face , particularly where there is strong wave action , to break the force of the waves . The dam contains some 17 , 000 , 000 m³ ( 22 , 000 , 000 cubic yards ) of material , and weighs some 27 , 000 , 000 tonnes ( 30 , 000 , 000 short tons ) . It covers 1.17 km² ( 288 acres ) of ground , and contains enough earth and rock to build a wall 1½ metres high and 29 cm thick ( or four foot eight inches high and a foot thick ) around the earth at the equator . References History Of The Panama Canal , by Ira E. Bennett The Panama Canal , by Colonel George W. Goethals   v · d · e   The Panama Canal Overview  • History  • Health Measures  • Panama Railway  • Gaillard Cut  • Gatun Dam  • Chagres River  • Gatun Lake  • The Locks  • Panamax  • Bridge of the Americas  • Centennial Bridge  • Panama Canal Authority  • The Canal Zone  • Expansion project Categories : Panama Canal | Geotechnical engineering | Dams in Panama | Historic civil engineering landmarks In other languages : Français 