Diego Garcia Diego Garcia is a tropical , footprint - shaped coral atoll located south of the equator in the central Indian Ocean . It is part of the British Indian Ocean Territory ( BIOT ) . The atoll is approximately east of the coast of Africa ( at Tanzania ) , south - southwest of the southern tip of India ( at Kanyakumari ) and west - northwest of the west coast of Australia ( at Cape Range National Park , Western Australia ) . Diego Garcia lies in the Chagos Archipelago at the southernmost tip of the Chagos - Laccadive Ridge — a vast submarine range in the Indian Ocean , topped by a long chain of coral reefs , atolls , and islands comprising Lakshadweep , Maldives , and the Chagos Archipelago . Local time is year - round ( DST is not observed ) . The United States Navy operates Naval Support Facility ( NSF ) Diego Garcia , a large naval ship and submarine support base , military air base , communications and space - tracking facility , and an anchorage for pre - positioned military supplies for regional operations aboard Military Sealift Command ships in the lagoon . Mauritius sought to regain sovereignty , lost to the UK in 1965 , over the Chagos Archipelago . Between 1968 and 1973 , the Chagossians , then numbering about 2 , 000 people , were expelled by the British government to Mauritius and Seychelles to allow the United States to establish a military base on the island . Today , the exiled Chagossians are still trying to return , claiming that the forced expulsion and dispossession was illegal ( see Depopulation of Diego Garcia ) . History . Pre - history . According to Southern Maldivian oral tradition , traders and fishermen were occasionally lost at sea and got stranded in one of the islands of the Chagos . Eventually they were rescued and brought back home . However , there are no separate names for the different atolls of the Chagos in the Maldivian oral tradition . The island may have been visited during the Austronesia n diaspora around 700 AD , and some say the old Maldivian name for the islands originated from Malagasy . It is also suggested that the Arabs , who reached Lakshadweep and Maldives around 900 AD , may have visited the Chagos , and that Zheng He may have sailed close in 1413 – 1415 , since it is documented on a Ming Dynasty map . European discovery . Portuguese explorers may have been the first Europeans to discover the island of Diego Garcia . The Portuguese navigator Pedro de Mascarenhas may have discovered the island during his voyage of 1512 – 1513 , but there is little corroborative evidence for this ; cartographic analysis points to 1532 or later . Tradition suggests that the island took its name from the Spanish navigator Diego García de Moguer , who discovered the island in the 1500s . Garcia was the explorer who sailed to the Río de la Plata in 1526 , and possibly with Hernando de Soto ' s voyage . García headed a Portuguese expedition in the Indian ocean in 1554 and died before completing the return travel . Some Portuguese scholars believe that Garcia ' s supposed Christian name , " Diego " , was a misnomer or a misreading that came into use towards the end of the 16th century . Although the Cantino planisphere ( 1504 ) and the Ruysch map ( 1507 ) clearly delineate the Maldive Islands , giving them the same names , they do not show any islands to the south which can be identified as the Chagos archipelago . The Sebastian Cabot map ( Antwerp 1544 ) shows a number of islands to the south which may be the Mascarene Islands . The first map which identifies and names " Los Chagos " ( in about the right position ) is that of Pierre Desceliers ( Dieppe 1550 ) , although Diego Garcia is not named . An island called " Don Garcia " appears on the " Theatrum Orbis Terrarum " of Abraham Ortelius ( Antwerp 1570 ) , together with " Dos Compagnos " , slightly to the north . It may be the case that " Don Garcia " was named after Garcia de Noronha , although there no evidence exists to support this supposition . The island is also shown as ' Don Garcia ' on Mercator ' s " Nova et Aucta Orbis Terrae Descriptio ad Usum Navigatium Emendate " ( Duisburg 1569 ) . However , on the " Vera Totius Expeditionis Nauticae Description " of Jodocus Hondius ( London 1589 ) , " Don Garcia " mysteriously changes its name to " I . de Dio Gratia " , while the " I . de Chagues " appears close by . The first map to delineate the island under its present name , Diego Garcia , is the " World Map " of Edward Wright ( London 1599 ) , possibly as a result of misreading Dio ( or simply " D . " ) as Diego , and Gratia as Garcia . The " Nova Totius Terrarum Orbis Geographica " of Henricus Hondius ( Antwerp 1630 ) repeats Wright ' s misreading of the name , which is then proliferated on all subsequent Dutch maps of the period , and to the present day . Settlement of the island . Diego Garcia and the rest of the Chagos islands were uninhabited until the late 18th century . In 1778 the French Governor of Mauritius granted Monsieur Dupuit de la Faye the island of Diego Garcia , and there is evidence of temporary French visits to collect coconuts and fish . Several Frenchmen living in " a dozen huts " abandoned Diego Garcia when the British East India Company attempted to establish a settlement there in April 1786 . The supplies of the 275 settlers were overwhelmed by 250 survivors of the wreck of the British East Indian Ship " ATLAS " in May , and the colony failed in October . Following the departure of the British , the French colony of Mauritius began marooning lepers on Diego Garcia , and in 1793 the French established a coconut plantation using slave labour , which also exported cordage made from coconut fiber , and sea cucumbers , known as a delicacy in the orient . Diego Garcia became a colony of the United Kingdom after the Napoleonic wars as part of the Treaty of Paris ( 1814 ) , and from 1814 to 1965 it was administered from Mauritius . On Diego Garcia , the main plantations were located at East Point , the main settlement on the eastern rim of the atoll ; Minni Minni , north of East Point ; and Pointe Marianne , on the western rim , all located on the lagoon side of the atoll rim . The workers lived at these locations , and at villages scattered around the island . From 1881 through 1888 Diego Garcia was the location of two coaling stations for steam ships crossing the Indian Ocean . In 1882 the French - financed , Mauritian - based Societe Huilere de Diego et Peros ( the " Oilmaking Company of Diego and Peros " ) , consolidated all the plantations in the Chagos under its control . 20th century . In 1914 the island was visited by the German light cruiser SMS " Emden " half - way through its historic commerce raiding cruise during the first months of World War I . In 1942 the British established RAF Station Diego Garcio as an advanced flying boat unit at the East Point Plantation , staffed and equipped from No 205 and No 240 Squadrons , then stationed on Ceylon . Both Catalina and Sunderland aircraft were flown during the course of World War II in search of Japanese and German submarines and surface raiders . Following the conclusion of hostilities , the station was closed on 30 April 1946 . In 1962 the Chagos Agalega Company of the British colony of Seychelles purchased the Societe Huiliere de Diego et Peros and moved company headquarters to Seychelles . In the early 1960s , the UK was withdrawing its military presence from the Indian Ocean area , not including the base at RAF Gan to the north of Diego Garcia in the Maldives ( which remained open until 1976 ) , and agreed to permit the United States to establish a Naval Communication Station on one of its island territories there . The United States requested an unpopulated island belonging to the UK to avoid political difficulties with newly independent countries , and ultimately the UK and United States agreed that Diego Garcia was a suitable location . Purchase by the United Kingdom . To accomplish the UK / United States mutual defense strategy , in November 1965 , the UK purchased the Chagos Archipelago , which includes Diego Garcia , from the then self - governing colony of Mauritius for £3 million to create the British Indian Ocean Territory ( BIOT ) , with the intent of ultimately closing the plantations to provide the uninhabited British territory from which the United States would conduct its military activities in the region . In April 1966 the British Government bought the entire assets of the Chagos Agalega Company in the BIOT for £600 , 000 and administered them as a government enterprise while awaiting United States funding of the proposed facilities , with an interim objective of paying for the administrative expenses of the new territory . However , the plantations , both under their previous private ownership and under government administration , proved consistently unprofitable due to the introduction of new oils and lubricants in the international marketplace , and the establishment of vast coconut plantations in the East Indies and the Philippines . On 30 December 1966 , the United States and the UK executed an agreement through an Exchange of Notes which permit the United States to use the BIOT for defense purposes for 50 years ( through December 2016 ) , followed by a 20 - year optional extension ( to 2036 ) to which both parties must agree by December 2014 . No monetary payment was made from the United States to the UK as part of this agreement or any subsequent amendment . Rather , the United Kingdom received a US $ 14 million discount from the United States on the acquisition of submarine - launched ballistic missile system Polaris missiles per a now - declassified addendum to the 1966 agreement . Arrival of the United States Navy . In March 1971 , United States Naval construction battalions ( Seabees ) arrived on Diego Garcia to begin the construction of the Communications Station and an airfield . To satisfy the terms of an agreement between the UK and the United States for an uninhabited island , the plantation on Diego Garcia was closed in October of that year . The plantation workers and their families were relocated to the plantations on Peros Bahnos and Salomon atolls to the northwest ; those who requested were transported to the Seychelles or Mauritius . In 1972 , the UK decided to close the plantations throughout the Chagos , including those on Peros Banhos and the Salomon Islands , and deported the Ilois to their ancestral homes on either the Seychelles or Mauritius . The then - independent Mauritian government refused to accept the islanders without payment , and in 1974 , the UK gave the Mauritian government an additional ₤650 , 000 to resettle the islanders . By 1973 , construction of the Naval Communications Station ( NAVCOMMSTA ) was completed . In the early 1970s , setbacks to United States military capabilities in the region including the fall of Saigon , victory of the Khmer Rouge in Cambodia , the closure of the Peshawar Air Station listening post in Pakistan and Kagnew Station in Ethiopia , the Mayaguez incident , and the build - up of Soviet Naval presence in Aden and a Soviet airbase at Berbera , Somalia , caused the United States to request , and the UK to approve , permission to build a fleet anchorage and enlarged airfield on Diego Garcia , and the Seabees doubled the number of workers constructing these facilities . Following the fall of the Shah of Iran and the Iran Hostage Crisis in 1979 – 1980 , the West became concerned with ensuring the flow of oil from the Persian Gulf through the Strait of Hormuz , and the United States received permission for a $ 400 million expansion of the military facilities on Diego Garcia consisting of two parallel runways , expansive parking aprons for heavy bombers , 20 new anchorages in the lagoon , a deep water pier , port facilities for the largest naval vessels in the American or British fleet , aircraft hangars , maintenance buildings and an air terminal , a fuel storage area , and billeting and messing facilities for thousands of sailors and support personnel . Naval support facility established . On 1 October 1977 , Naval Support Facility , Diego Garcia , was established as the senior United States Navy command on the island . At the time the NAVCOMMSTA was the primary tenant , but as the new major facilities were completed , most notably the expanded anchorage and mooring area and the extended airfield , other tenants were commissioned . In 1980 , the United States Navy established the Near - Term Prepositioned Force of 16 ships . Then NTPF became the Afloat Prepositioning Force ( AFP ) and eventually Maritime Prepositioning ship Squadron Two ( MPSRON 2 ) consisting of 20 deep - water pre - positioned logistics ships anchored in the lagoon . In 1981 , the Naval Air Facility was commissioned . It was decommissioned in 1987 and its responsibilities returned to the NSF . In 1982 , Construction activities were transferred from the Seabees to a consortium of civilian contractors , and the majority of the projects were completed by 1988 . On 26 March 1982 , Barbara Shuping and five other women were assigned to the NSF . Prior to this assignment , no women had lived on island since those on the plantation in 1971 . In 1985 , the new port facilities were completed , and the USS " Saratoga " ( CV - 60 ) was the first aircraft carrier to tie up . Strategic Air Command began deploying Boeing B - 52 Stratofortress bombers and aerial refueling aircraft to the newly completed airfield facilities in 1987 . Following the Iraqi invasion of Kuwait in August 1990 , three ships of COMPSRON 2 sortied , delivering a Marine Expeditionary Brigade to Saudi Arabia for participation in the Gulf War . Other COMPSRON 2 ships offloaded the munitions , bombs , and fuel on Diego Garcia that were required for the American bomber fleet that deployed to airfield . Subsequently , B - 52G bombers flew more than 200 17 - hour bombing missions over 44 days and dropped more than of bombs on Iraqi forces in Iraq and Kuwait . One of the B - 52s crashed from mechanical failures just north of the island with the loss of three of its six - man crew . Beginning on 7 October 2001 , the United States again commenced military operations from Diego Garcia using B - 1 , B - 2 , and B - 52 bombers to attack enemy targets in Afghanistan following the attacks on New York City and the Pentagon . A B - 1 bomber was lost on 12 December 2001 to mechanical failures just after take off from the island , but the crew survived and was rescued by the USS " Russell " ( DDG - 59 ) . Combat operations resumed in the spring of 2003 , with MPSRON TWO sortieing to the Persian Gulf for Operation Iraqi Freedom , and bombing operations began again , this time against Iraq . Bomber operations ceased from Diego Garcia on 15 August 2006 . Protection from industry . In 2004 , the UK applied for , and received , Ramsar Site status for the lagoon and other waters of Diego Garcia . On 1 April 2010 , the UK Cabinet declared the Chagos Archipelago a Marine Protected Area ( MPA ) and prohibited all extractive industry , including fishing and oil and gas exploration . It is unclear whether Diego Garcia is included in the MPA . Inhabitants . Diego Garcia had no permanent inhabitants when discovered by the Spanish explorer Diego García de Moguer in the 16th century and remained so until settled as a French colony in 1793 . French settlement . Most inhabitants of Diego Garcia through the period from 1793 to 1971 were plantation workers , but also included Franco - Mauritian managers , Indo - Mauritian administrators , Mauritian and Seychellois contract employees , and in the late 19th Century , Chinese and Somali employees . A distinct Creole culture called the Ilois , which means " Islanders " in French Creole , evolved from these workers . The Ilois , now called Chagos Islanders or Chagossians since the late 1990s , were descended primarily from slaves brought to the island from Madagascar by the French between 1793 and 1810 , and Malay slaves from the slave market on Pulo Nyas , an island off the northwest coast of Sumatra , from around 1820 until the slave trade ended following the Slavery Abolition Act of 1833 . The Ilois also evolved a French - based Creole dialect now called Chagossian Creole . Throughout their recorded history , the plantations of the Chagos Archipelago had a population of approximately 1 , 000 individuals , about two - thirds of whom lived on Diego Garcia . A peak population of 1 , 142 on all islands was recorded in 1953 . The primary industry throughout the island ' s colonial period consisted of coconut plantations producing copra and / or coconut oil , until closure of the plantations and relocation of the inhabitants in October 1971 . For a brief period in the 1880s it served as a coaling station for steamships transiting the Indian Ocean from the Suez Canal to Australia . Deportation of 1971 . All the inhabitants of Diego Garcia were involuntarily relocated to other islands in the Chagos Archipelago or to Mauritius or Seychelles by 1971 to satisfy the requirements of a UK / United States Exchange of Notes signed in 1966 to depopulate the island when the United States constructed a base upon it . No current agreement exists on how many of the evacuees met the criteria to be an Ilois , and thus be an indigenous person at the time of their removal , but the UK and Mauritian governments agreed in 1972 that 426 families , numbering 1 , 151 individuals were due compensation payments as exiled Ilois . The total number of people certified as Ilois by the Mauritian Government ' s Ilois Trust Fund Board in 1982 was 1 , 579 . This involuntary relocation decision remains in litigation as of 2010 . After 1971 . Between 1971 and 2001 , the only residents on Diego Garcia were UK and United States military personnel and civilian employees of those countries . These included contract employees from the Philippines and Mauritius , including some Ilois . During the combat operations from the atoll against Afghanistan ( 2001 – 2006 ) and Iraq ( 2003 – 2006 ) , a number of allied militaries were based on the island including Australian , Japanese and the Republic of Korea . According to David Vine , " Today , at any given time , 3 , 000 to 5 , 000 U . S . troops and civilian support staff live on the island . " The inhabitants today do not rely on the island and the surrounding waters for sustenance . Although some recreational fishing for consumption is permitted , all other food is shipped in by sea or air . Politics . Diego Garcia is the largest and only inhabited island in the British Indian Ocean Territory , an Overseas territory of the United Kingdom , and , usually abbreviated as " BIOT " . The Government of the BIOT consists of Commissioner appointed by the Queen . The Commissioner is assisted by an Administrator and small staff , and is based in London and resident in the Foreign and Commonwealth Office . Originally colonized by the French , Diego Garcia was ceded , along with the rest of the Chagos Archipelago , to the United Kingdom in the Treaty of Paris ( 1814 ) at the conclusion of a portion of the Napoleonic Wars . Diego Garcia and the Chagos Archipelago were administered by the colonial government on the island of Mauritius until 1965 , when the United Kingdom purchased them from the self - governing government of Mauritius for £3 million , and declared them to be a separate British Overseas Territory . The BIOT administration was moved to Seychelles following the independence of Mauritius in 1968 until the independence of Seychelles in 1976 , and to a desk in the Foreign and Commonwealth Office in London since . Military administration . UK represents the Territory internationally . A local government as normally envisioned does not exist . Rather , the administration is represented in the Territory by the Officer commanding British Forces on Diego Garcia , the " Brit Rep " . Laws and regulations are promulgated by the Commissioner and enforced in the BIOT by Brit Rep . Of major concern to the BIOT administration is the relationship with the United States military forces resident on Diego Garcia . An annual meeting called " The Pol - Mil Talks " ( for Political - Military ) of all concerned is held at the Foreign and Commonwealth Office in London to resolve pertinent issues . These resolutions are formalized by an " Exchange of Notes " , or , since 2001 , an " Exchange of Letters " . Transnational political issues . There are two transnational political issues which affect Diego Garcia and the BIOT , through the British government . As these issues affect the BIOT as a whole , not just the island of Diego Garcia , they are more appropriately and completely addressed in the Wikipedia articles British Indian Ocean Territory and Depopulation of Diego Garcia . Prison site allegations . In June 2004 , the British Foreign Secretary Jack Straw stated that United States authorities had repeatedly assured him that no detainees had passed in transit through Diego Garcia or were disembarked there . In October 2007 the all - party Foreign Affairs Committee of the British Parliament announced that it would launch an investigation of continued allegations of a prison camp on Diego Garcia , which it claimed were twice confirmed by comments made by Retired United States Army General Barry McCaffrey . On July 31 , 2008 , an unnamed former White House official alleged that the United States had imprisoned and interrogated at least one suspect on Diego Garcia during 2002 and possibly 2003 . Manfred Nowak , one of five of the United Nations Special Rapporteur on torture , says that credible evidence exists supporting allegations that ships serving as black sites have used Diego Garcia as a base . The human rights group Reprieve alleges that United States - operated ships moored outside the territorial waters of Diego Garcia were used to incarcerate and torture detainees . Rendition flight refuelling admission . Diego Garcia is rumoured to have been one of the locations of the CIA ' s black sites . Several groups claim that the military base on Diego Garcia has been used by the United States government for transport of prisoners involved in the controversial extraordinary rendition program , an allegation formally reported to the Council of Europe in June 2007 . On February 21 , 2008 , British Foreign Secretary David Miliband admitted that two United States extraordinary rendition flights refuelled on Diego Garcia in 2002 . No reference was made to whether prisoners were on board the aircraft at the time . Khalid Sheikh Mohammed is one of the " high - value detainees " suspected to have been held in Diego Garcia . WikiLeaks CableGate disclosures ( 2010 ) . According to Wikileaks CableGate documents ( reference ID " 09LONDON1156 " ) , in a calculated move planned in 2009 , the UK proposed that the BIOT become a " marine reserve " with the aim of preventing the former inhabitants from returning to their lands . A summary of the diplomatic cable is as follows : Geography . Diego Garcia is the largest land mass in the Chagos Archipelago ( which includes Peros Banhos , the Salomon Islands , the Three Brothers , the Egmont Islands and the Great Chagos Bank ) , being an atoll occupying approximately , of which is dry land . The continuous portion of the atoll rim stretches from one end to the other , enclosing a lagoon long and up to wide , with a pass opening at the north . There are three small islands located in the pass . The island consists of the largest continuous atolls in the world . The dryland rim varies in width from a few hundred metres to 2 . 4 km . Typical of coral atolls , it has a maximum elevation on some dunes on the ocean side of the rim of nine metres ( 30 ft ) above mean low water . The rim nearly encloses a lagoon about long and up to wide . The atoll forms a nearly complete rim of land around a lagoon , enclosing 90 percent of its perimeter , with an opening only in the north . The main island is the largest of about 60 islands which form the Chagos Archipelago . Besides the main island , there are three small islets at the mouth of the lagoon : " West Island " ( 3 . 4 ha / 8 . 4 acres ) ; " Middle Island " ( 6 ha / 14 . 8 acres ) ; and " East Island " ( 11 . 75 ha / 29 acres ) . A fourth island shown on some maps , " Anniversary Island " one km ( 1 , 100 yards ) southwest of Middle Island , appears as just a sand bar on satellite images . Both Middle Island and Anniversary Island are part of the " Spur Reef " complex . The total area of the atoll is approximately . The lagoon area is approximately with depths ranging down to about 25 m ( 80 feet ) . The total land area ( excluding peripheral reefs ) is approximately . The coral reef surrounding the seaward side of the atoll is generally broad , flat , and shallow at about 1 m ( 3 feet ) below mean sea level in most locations and varying from 100 to 200 m ( 300 to 650 feet ) in width . This fringing seaward reef shelf comprises an area of approximately . At the outer edge of the reef shelf , the bottom slopes very steeply into deep water , at some locations dropping to more than within 1 km ( 0 . 6 miles ) of the shore . In the lagoon , numerous coral heads present hazards to navigation . The shallow reef shelf surrounding the island on the ocean side offers no ocean - side anchorage . The channel and anchorage areas in the northern half of the lagoon are dredge d , along with the pre - 1971 ship turning basin . Significant salt - water wetlands called barachois exist in the southern half of the lagoon . These are small lagoons off of the main lagoon , filled with seawater at high tide and dry at low tide . Scientific expeditions in 1996 and 2006 described the lagoon and surrounding waters of Diego Garcia , along with the rest of the Chagos Archipelago , as " exceptionally unpolluted " and " pristine " . There are no endemic species of plants , birds , amphibians , reptiles , mollusks , crustaceans , or mammals on Diego Garcia or in the surrounding waters . There are several endemic fish and aquatic invertebrates . All plants , wildlife , and aquatic species are protected to one degree or another . In addition , much of the lagoon waters are protected wetlands as a designated Ramsar site , and large parts of the island are nature preserves . Diego Garcia is frequently subject to earthquakes caused by tectonic plate movement along the Carlsberg Ridge located just to the west of the island . One was recorded in 1812 ; one measuring 7 . 6 on the Richter Scale hit on November 30 , 1983 , at 21 : 46 local time and lasted 142 seconds , resulting in a small tsunami which raised wave height in the lagoon to 1 . 5 metres ( 5 ft ) , and another on December 2 , 2002 , an earthquake measuring 4 . 6 on the Richter Scale struck the island at 12 : 21 a . m . In December 2004 , a tsunami generated near Indonesia caused minor shoreline erosion on Barton Point ( the northeast point of the atoll of Diego Garcia ) . Oceanography . Diego Garcia lies within the influence of the South Equatorial current year - round . The surface currents of the Indian Ocean also have a monsoonal regime associated with the Asian Monsoonal wind regime . Sea surface temperatures are in the range of 80 - 84 °F / 26 - 28 °C year - round . Fresh water supply . Diego Garcia is the above - water rim of a coral atoll composed of Holocene coral rubble and sand to the depth of about 36 metres ( 120 ft ) , overlaying Pleistocene limestone deposited at the then - sea level on top of a seamount rising approximately 1 , 800 metres ( 6 , 000 ft ) from the floor of the Indian Ocean . The Holocene sediments are porous and completely saturated with sea water . Any rain falling on the above - water rim quickly percolates through the surface sand and encounters the salt water underneath . Diego Garcia is of sufficient width to minimise tidal fluctuations in the aquifer , and the rainfall ( in excess of 102 . 5 inches / 260 cm per year on average ) is sufficient in amount and periodicity for the fresh water to form a series of convex , fresh - water , Ghyben - Herzberg lenses floating on the heavier salt water in the saturated sediments . The horizontal structure of each lens is influenced by variations in the type and porosity of the sub - surface deposits , which on Diego Garcia are minor . At depth , the lens is globular ; near the surface it generally conforms to the shape of the island . When a Ghyben - Herzberg lens is fully formed , its floating nature will push a freshwater head above mean sea level , and if the island is wide enough , the depth of the lens below mean sea level will be 40 times the height of the water table above sea level . On Diego Garcia this equates to a maximum depth of 20 metres . However , the actual size and depth of each lens is dependent on the width and shape of the island at that point , the permeability of the aquifer , and the equilibrium between recharging rainfall and losses to evaporation to the atmosphere , transpiration by plants , tidal advection , and human use . In the plantation period , shallow wells , supplemented by rainwater collected in cisterns , provided sufficient water for the pastoral life style of the small population . On Diego Garcia today , the military base uses over 100 shallow " horizontal " wells to produce over 560 , 000 liters per day from the " Cantonment " lens on the northwest arm of the island - sufficient water for western - style usage for a population of 3 , 500 . It is estimated that this 3 . 7 km lens holds 19 million m of fresh water and has an average daily recharge from rainfall of over 10 , 000 m , of which 40 % remains in the lens and 60 % is lost through evapotranspiration . Extracting fresh water from a lens for human consumption requires careful calculation of the sustainable yield of the lens by season because each lens is susceptible to corruption by salt - water intrusion caused by overuse or drought . In addition , overwash by tsunamis and tropical storms has corrupted lenses in the Maldives and several Pacific islands . Vertical wells can cause salt upconing into the lens , and over - extraction will reduce fresh water pressure resulting in lateral intrusion by seawater . Because the porosity of the surface soil results in virtually zero runoff , lenses are easily polluted by fecal waste , burials , and chemical spills . Corruption of a lens can take years to " flush out " and reform , depending on the ratio of recharge to losses . There are a few natural depressions on the atoll rim that capture the abundant rainfall to form areas of fresh - water wetlands . Two are of significance to island wildlife and to recharge their respective fresh - water lenses . One of these is centered on the northwest point of the atoll , another is found near the Point Marianne Cemetery on the southeast end of the airfield . Other , smaller freshwater wetlands are found along the east side of the runway , and in the vicinity of the receiver antenna field on the northwest arm of the atoll . There are also several man - made fresh - water ponds resulting from excavations made during construction of the airfield and road on the western half of the atoll rim . These fill from rainfall and from extending into the Ghyben - Herzberg lenses found on this island . Climate . Precipitation : All precipitation falls as rain , characterised by air - mass type showers . Annual rainfall averages 2213 mm , with the heaviest precipitation from May to December . February is the driest month with 18 mm of rain , and August the wettest month , averaging 298 mm of rain . Temperatures : The surrounding sea surface temperature is the primary climatic control and temperatures are generally uniform throughout the year , with an average maximum of by day during March and April , and in July through September . Diurnal variation is approximately , falling to the low 27 °C ( 82 °F ) by night . Humidity is high throughout the year . The almost constant breeze keeps conditions reasonably comfortable . Winds : From December through March , winds are generally westerly at approximately . During April and May winds are light and variable , ultimately backing to an east - southeasterly direction . From June through September the influence of the Southeast trades is felt , with speeds of 10 - 15 knots . During October and November winds again go through a period of light and variable conditions veering to a westerly direction with the onset of summer in the Southern Hemisphere . Thunderstorms : Activity is generally noticed during the afternoon and evenings during the summer months ( December through March ) and when the Intertropical Convergence Zone is in the vicinity of the island . Diego Garcia is at minimum risk from tropical cyclones due to its proximity to the equator where the coriolis parameter required to organize circulation of the upper atmosphere is minimal . Low - intensity storms have hit the island , including in 1901 , which blew over 1 , 500 coconut trees , on September 16 , 1944 which caused the wreck of a Royal Air Force PBY Catalina , September 1990 which demolished the tent city then being constructed for United States Air Force bomber crews during Operation Desert Storm , and on July 22 , 2007 , when winds exceeded and over of rain fell in 24 hours . The island was somewhat affected by the tsunami caused by the 2004 Indian Ocean earthquake . Service personnel on the western arm of the island reported only a minor increase in wave activity . The island was protected to a large degree by its favourable ocean topography . About 80 km ( 50 mi ) east of the atoll lies the 650 km ( 400 - mile ) long Chagos Trench , an underwater canyon plunging more than 4 , 900 m ( 16 , 000 ft ) . The depth of the trench and its grade to the atoll ' s slope and shelf shore makes it more difficult for substantial tsunami waves to build before passing the atoll from the east . In addition , near shore coral reefs and an algal platform may have dissipated much of the waves ' impact . A biological survey conducted in early 2005 indicated erosional effects of the tsunami wave on Diego Garcia and other islands of the Chagos Archipelago . One stretch of shoreline was found to have been breached by the tsunami wave , representing approximately 10 percent of the eastern arm . A biological survey by the Chagos Conservation Trust reported that the resulting inundation additionally washed away shoreline shrubs and small to medium - size coconut palms . Vegetation . The first botanical observations of the island were made by Hume in 1883 , when the coconut plantations had been in operation for a full century . Subsequent studies and collections during the plantation era were made in 1885 , 1905 , 1939 , and 1967 . Thus , very little of the nature of the pre - contact vegetation is known . The 1967 survey , published by The Smithsonian is used as the most authoritative baseline for more recent research . These studies indicate the vegetation of the island may be changing rapidly . For example , J . M . W . Topp collected data annually between 1993 and 2003 and found that on the average three new plant species arrived each year , mainly on Diego Garcia . His research added fully a third more species to Stoddart . Topp and Martin Hamilton of Kew Gardens compiled the most recent checklist of vegetation in 2009 , which can be found at this footnote . In 1967 , Stoddart described the land area of Diego Garcia as having a littoral hedge of " Scaevola taccada " , while inland , " Cocos nucifera " ( Coconut ) was the most dominant tree , covering most of the island . The substory was either managed and park - like , with understory less than 0 . 5 metres in height , or consisted of what he called " Cocos Bon - Dieu " – an intermediate story of juvenile trees and a luxuriant ground layer of self - sown seedlings – causing those areas to be relatively impenetrable . There are also areas of remnant tropical hardwood forest at the sites of the plantation - era villages , as well as " Casuarina equisetifolia " ( Iron Wood Pines ) woodlands . In 1997 , the United States Navy contracted a vegetation survey that identified about 280 species of terrestrial vascular plant s on Diego Garcia . None of these was endemic , and another survey in 2005 identified just 36 species as " native " , meaning arriving without the assistance of humans , and found elsewhere in the world . No terrestrial plant species are of any conservation - related concern at present . Of the 36 native vascular plants on Diego Garcia , there are 12 trees , five shrub s , seven dicotyledon herbs , three grasses , four vine s , and five fern s . The 12 tree species are : " Barringtonia asiatica " ( Fish - poison Tree ) , " Calophyllum inophyllum " ( Alexandrian Laurel ) , " Cocos nucifera " , " Cordia subcordata " , " Guettarda speciosa " , " Intsia bijuga " , " Hernandia sonora " , " Morinda citrifolia " , " Neisosperma oppositifolium " , " Pisonia grandis " , " Terminalia catappa " , and " Heliotropium foertherianum " . Another three tree species are common , and may be native , but they may also have been introduced by humans : " Casuarina equisetifolia " , " Hibiscus tiliaceus " , and " Pipturus argenteus " . The five native shrubs are : " Caesalpinia bonduc " , " Pemphis acidula " , " Premna serratifolia " , " Scaevola taccada " ( often mispronounced " Scaveola " ) , and " Suriana maritima " . There are also 134 species of plants classified as " weedy " or " naturalised alien species " , being those unintentionally introduced by man , or intentionally introduced as ornamentals or crop plants which have now " gone native " , including 32 new species recorded since 1995 , indicating a very rapid rate of introduction . The remainder of the species list consists of cultivated food or ornamental species , grown in restricted environments such as a planter ' s pot . In 2004 , there were 10 recognised plant communities on the atoll rim : 1 . Calophyllum Forest , dominated by " Calophyllum inophyllum " , with trunks that can grow in excess of 2 metres in diameter . This forest often contains other species such as " Hernandia sonora " , " Cocos nucifera " and " Guettarda speciosa " with a " Premna obtusifolia " edge . When found on the beaches , " Calophyllum " often extends over the lagoon water and supports nesting red - footed boobies , as does " Barringtonia asiatica " . Found mostly on the eastern arm of the atoll . 2 . Cocos Forest , essentially monotypic ( " Cocos bon Dieu " ) , with the understory consisting of Cocos seedlings . 3 . Cocos - Hernandia Forest , dominated by two canopy species - " Cocos nucifera " and " Hernandia sonora " . 4 . Cocos - Guettarda Forest , dominated by the canopy species " Cocos nucifera " and " Guettarda speciosa " . The understory consists of a mix of " Neisosperma oppositifolium " , with " Scaevola taccada " and " Tournefortia argentea " on the beach edge . 5 . Hernandia Forest , dominated at the canopy level by " Hernandia sonora " . The most representative areas of this forest type are on the eastern , undeveloped part of the atoll . " Calophyllum inophyllum " and " Cocos nucifera " are often present . Understory species in this forest are often " Morinda citrifolia " , Cocos seedlings and " Asplenium nidus " ( bird ' s nest fern ) , and occasionally , " Neisosperma oppositifolium " and " Guettarda speciosa " . 6 . Premna shrubland , occurring generally between marshy areas and forested areas . The most conspicuous vegetation is primarily " Premna obtusifolia " , with " Casuarina equisetifolia " and " Scaevola taccada " on the margins . The dense groundcover consists of species such as " Fimbristylis cymosa " , " Ipomoea pes - caprae " ( Beach Morning Glory ) and " Triumfetta procumbens " . Premna shrubland appears mostly adjacent to the developed areas of the atoll , particularly in the well fields . 7 . Littoral Scrub lines almost the entire seashore and lagoon shore of the island . It is dominated by " Scaevola taccada " , but it also contains scattered coconut trees , " Guettarda speciosa " and " Pisonia grandis " . On the seaward side , it also contains " Tournefortia argentea " and " Suriana maritima " . On the lagoon side , it may also contain " Lepturus repens " , " Triumfetta procumbens " and " Cyperus ligularis " . There are also large pockets of " Barringtonia asiatica " on the eastern edge of the lagoon . 8 . Maintained areas of grass and sedges routinely mowed . Aerial photographs of the island clearly display large areas of grasslands and park - like savanna upon which the United States military has constructed large outdoor facilities such as antenna fields and the airport . 9 . Mixed Native Forest , with no dominant canopy species . 10 . Marshes divided into three different types : Cattail ( " Typha domingensis " ) , wetland , and mixed species . Cattail marshes contained almost entirely cattails . These areas are often man - made reservoirs or drainages that have been almost entirely monotypic . Wetlands were based upon vegetation that occurred in the area with fresh water . Mixed species marshes were highly variable and usually had no standing water . Wildlife . All the terrestrial and aquatic fauna of Diego Garcia are protected , with the exception of certain game fish , rats and cats ; hefty fines are levied against violators . The island is a haven for several types of crustacean ; " warrior crabs " ( " Cardisoma carnifex " ) overrun the jungle at night . The extremely large coconut crab or robber crab ( " Birgus latro " ) is found here in large numbers . Because of the protections provided the species on this atoll , and the isolation of the east rim of the atoll , the species is recorded in greater densities there than anywhere else in its range ( 339 crabs / ha ) . There are no native mammal species on Diego Garcia , and no record of bat s . Other than rats ( " Rattus rattus " ) , all " wild " mammal species are feral descendants of domesticated species . During the plantation era , Diego Garcia was home to large herds of Sicilian Donkeys ( " Equus asinus " ) , dozens of horses ( " Equus caballus " ) , hundreds of dogs ( " Canis familiaris " ) and house cats ( " Felis catus " ) . In 1971 , the BIOT Commissioner ordered the extermination of feral dogs following the departure of the last plantation workers , and the program continued through 1975 , when the last feral dog was observed and shot . Donkeys , which numbered over 400 in 1972 , were down to just 20 individuals in 2005 . The last horse was observed in 1995 , and by 2005 , just two cats were thought to have survived an island - wide eradication program . The total bird list for the Chagos Archipelago , including Diego Garcia , consists of 91 species , with large breeding populations of 16 species . Although there are no endemic birds , there are internationally important seabird colonies . Diego Garcia ' s seabird community includes thriving populations of species which are rapidly declining in other parts of the Indian Ocean . Large nesting colonies of Brown Noddies ( " Anous stolidous " ) , Bridled terns ( " Sterna anaethetus " ) , the Lesser Noddy ( " Anous tenuirostris " ) , Red - footed Booby ( " Sula sula " ) and Lesser Frigate Birds ( " Fregata ariel " ) , exist on Diego Garcia . Other nesting native birds include Red - tailed Tropicbirds ( " Phaethon rubricauda " ) , Wedge - Tailed Shearwaters ( " Puffinus pacificus " ) , Audubon ' s Shearwater ( " Puffinus iherminierii " ) , Black - Naped Terns ( " Sterna sumatrana " ) , White ( or Fairy ) Terns ( " Gygis alba " ) , Striated Herons ( " Butorides striatus " ) , and White - breasted Waterhens ( " Amaurornis phoenicurus " ) , The 680 ha Barton Point Nature Reserve was identified as an Important Bird Area for its large breeding colony of Red - footed Boobies . The island hosts introduced bird species from many different regions , including Cattle Egrets ( " Bubulcus ibis " ) , Indian Barred Ground Dove , also called the Zebra Dove ( " Geopelia striata " ) , Turtle Dove ( " Streptopleia picturata " ) , Indian Mynah ( " Acridotheres tristis " ) , Madagascar Fody ( " Foudia madagascariensis " ) , and chickens ( " Gallus gallus " ) . There are currently three lizards and one toad known to inhabit Diego Garcia , and possibly one snake . All are believed to have been introduced by human activity . The House Gecko ( " Hemidactylus frenatus " ) , the Mourning Gecko ( " Lepidodactylus lugubris " ) , the Garden Lizard ( an agamid ) ( " Calotes versicolor " ) and the Cane Toad ( " Bufo marinus " ) . There may also be a viable population of a type of Blind Snake from the family Typhlopidae , probably the Brahminy Blind Snake ( " Ramphotyphlops braminus " ) . This snake feeds on the larvae , eggs and pupae of ant s and termite s , and is about the size of a large earthworm . Diego Garcia provides suitable foraging and nesting habitat for both the Hawksbill Turtle ( " Eretmochelys imbricata " ) and the Green Turtle ( " Chelonia mydas " ) . Juvenile Hawksbills are quite common in the lagoon and at Barachois Sylvane ( also known as Turtle Cove ) in the southern part of the lagoon . Adult Hawksbills and Greens are common in the surrounding seas and nest regularly on the ocean - side beaches of the atoll . Hawksbills have been observed nesting during June and July , and from November to March . Greens are have been observed nesting in every month ; the average female lays three clutches per season , each having an average clutch size of 113 eggs . Diurnal nesting is common in both species . It is estimated that 300 - 700 Hawksbills and 400 - 800 Greens nest in the Chagos . There are four reptiles and six cetaceans that are endangered and may or may not be found on or around Diego Garcia : . Hawksbill Turtle ( " Eretmocheyls imbricata " ) - KNOWN ; Leatherback Turtle ( " Dermochelys coriacea " ) - POSSIBLE ; Green Turtle ( " Chelonia mydas " ) - KNOWN ; Olive Ridley Turtle ( " Lepidochelys oliveacea " ) - POSSIBLE ; Sperm Whale ( " Physeter macrocephalus " ) - POSSIBLE ; sei whale ( " Balaeonoptera borealis " ) - POSSIBLE ; finback whale ( " Balaeonoptera physalus " ) - POSSIBLE ; Bryde ' s whale ( " Balaeonoptera edeni " ) - POSSIBLE ; blue whale ( " Balaeonoptera musculus " ) - POSSIBLE ; humpback whale ( " Megaptera novaeangliae " ) - POSSIBLE . United States military activities . During the Cold War era , the United States was keen to establish a military base in the Indian Ocean to counter Soviet influence in the region and protect the sea - lanes for oil transportation from the Middle East . The United States saw the island as a strategically important one . The value has been proven many times , with the island providing a " fixed aircraft carrier " for the United States during the Iranian revolution , the Iraqi invasion of Kuwait , Operation Enduring Freedom , and Operation Iraqi Freedom . The United States military facilities on Diego Garcia have been known informally as Camp Justice and , after renaming in July 2006 , as Camp Thunder Cove . Formally , the base is known as Naval Support Facility Diego Garcia ( the U . S . activity ) or Permanent Joint Operating Base ( PJOB ) Diego Garcia ( the UK ' s term ) . United States military activities in Diego Garcia have caused friction between India and the United States in the past . Various political parties in India repeatedly called for the military base to be dismantled , as they saw the United States naval presence in Diego Garcia as a hindrance to peace in the Indian Ocean . In recent years , relations between India and the United States have improved dramatically . Diego Garcia was the site of several naval exercises between the United States and Indian navies held between 2001 and 2004 . Naval Support Facility Diego Garcia . The Naval Support Facility Diego Garcia provides Base Operating Services to tenant commands located on the island . The command ' s mission is " To provide logistic support to operational forces forward deployed to the Indian Ocean and Persian Gulf AORs in support of national policy objectives . " As of January 2012 , the facility supported the following tenant commands : Additionally , the USS Emory S . Land ( AS - 39 ) is forward deployed to Diego Garcia . United States pre - positioned vessels . The atoll shelters the ships of the United States Marine Pre - positioning Squadron Two . These ships carry equipment and supplies to support a major armed force with tanks , armoured personnel carriers , munitions , fuel , spare parts and even a mobile field hospital . This equipment was used during the Persian Gulf War , when the squadron transported equipment to Saudi Arabia . The ship composition of MPSRON TWO is dynamic . During August 2010 it was composed of : Five of these vessels carry supplies for the US Marine Corps sufficient to support a Marine Air - Ground Task Force for 30 days : USNS " Button " , USNS " Kocak " , USNS " Lopez " , USNS " Stockham " , and USNS " Fisher " . Prior to 2001 , COMPSRON 2 consisted of up to 20 ships , including four Combat Force Ships which provided rapid - response delivery of equipment to ground troops in the United States Army . Three are Lighter aboard ship s ( LASH ) which carry barges called Lighters that contain Army ammunition to be ferried ashore : MV " American Cormorant " , SS " Green Harbour " , ( LASH ) , SS " Green Valley " , ( LASH ) , MV " Jeb Stuart " , ( LASH ) . There were Logistics Vessels to service the rapid delivery requirements of the United States Air Force , United States Navy and Defense Logistics Agency . These included container ships for Air Force munitions , missiles and spare parts ; a 500 - bed hospital ship , and floating storage and offloading unit s assigned to Military Sealift Command supporting the Defense Logistics Agency , and an offshore petroleum discharge system ( OPDS ) tanker ship . Examples of ships are MV " Buffalo Soldier " , MV " Green Ridge " , pre - position tanker USNS " Henry J . Kaiser " , and tanker USNS Potomac ( T - AO - 181 ) . Satellite and communication facilities . Air Force satellite control network station . The United States Air Force operates a remote tracking station on Diego Garcia . Its call sign is " REEF " . This facility became more vital after the closure of the Indian Ocean Station in 1996 . GEODSS Station . The United States Air Force Operates a station of the Ground - based Electro - optical Deep Space Surveillance system on the southern end of the atoll . Global positioning system monitoring station . Diego Garcia is one of the five control bases for the Global Positioning System , operated by the United States military . The United States Air Force also has monitoring stations in Hawaii , Kwajalein , Ascension Island , and Colorado Springs . The stations synchronise and update the atomic clocks on the 24 orbiting satellites that emit the signals used by GPS receivers . HF global station . The United States Air Force operates a High Frequency Global Communications System transceiver site located on the south end of the atoll near the GEODSS station . The transceiver is operated remotely from Joint Base Andrews and locally maintained by NCTS FE personnel . Naval Computer and Telecommunications Station Far East Detachment Diego Garcia . Naval Computer and Telecommunications Station Far East Detachment Diego Garcia operates a detachment in Diego Garcia . This detachment provides base telephone communications , provides base network services ( Local Network Services Center ) , pier connectivity services , an AN / GSC - 39C SHF satellite terminal , operates the Hydroacoustic Data Acquisition System , and performs on - site maintenance for the remotely operated Air Force HF - GCS terminal . Naval Security Group Detachment Diego Garcia . Naval Security Group detachment Diego Garcia was disestablished on September 30 , 2005 . Remaining essential operations were transferred to a contractor . The large AN / AX - 16 High Frequency Radio direction finding Circularly Disposed Antenna Array has been demolished , but the four satellite antenna radome s around the site remain as of 2010 . ETOPS emergency landing site . Diego Garcia may be identified as an ETOPS ( Extended Range Twin Engine Operations ) emergency landing site ( en route alternate ) for flight planning purposes of commercial airliners . This allows twin - engine commercial aircraft ( such as the Airbus A330 , Boeing 767 or Boeing 777 ) to make theoretical nonstop flights between city pairs such as Perth and Dubai ( ) , Hong Kong and Johannesburg ( ) or Singapore and São Paulo ( ) , all while maintaining a suitable diversion airport within 180 minutes ' flying time with one engine inoperable . Space Shuttle . The island was one of 33 emergency landing sites worldwide for the NASA Space Shuttle . None of these facilities were ever used throughout the life of the shuttle program . Cargo service . All consumable food and equipment is brought to Diego Garcia by sea or air , and all non - biodegradable waste is shipped off the island as well . From 1971 to 1973 , United States Navy LSTs provided this service . Beginning in 1973 , civilian ships were contracted to provide these services . From 2004 to 2009 , the U . S . - flagged container ship MV " Baffin Strait " , often referred to as the " DGAR shuttle , " delivered 250 containers every month from Singapore to Diego Garcia . The ship delivered more than 200 , 000 tons of cargo to the island each year . " On the return trip to Singapore , it carried recyclable metals . In 2004 , TransAtlantic Lines outbid Sealift Incorporated for the transport contract between Singapore and Diego Garcia . The route had previously been serviced by Sealift Inc . ' s " MV Sagamore " , manned by members of American Maritime Officers and Seafarers ' International Union . TransAtlantic Lines reportedly won the contract by approximately 10 percent , representing a price difference of about US $ 2 . 7 million . The " Baffin Straits " charter ran from January 10 , 2005 , to September 30 , 2008 , at a daily rate of US $ 12 , 550 .