湄公河（RiverMekong） 　　TheMekongRiver(knowninTibetasDza-chu,ChinaasLancangJiangandThailandasMaeNamKhong),isamajorriverinsoutheasternAsia.Itisthelongestriverintheregion.FromitssourceinChina'sQinghaiProvinceneartheborderwithTibet,theMekongflowsgenerallysoutheasttotheSouthChinaSea,adistanceof4,200km(2,610mi).TheMekongcrossesYunnanProvince,China,andformstheborderbetweenMyanmar(Burma)andLaosandmostoftheborderbetweenLaosandThailand.ItthenflowsacrossCambodiaandsouthernVietnamintoarichdeltabeforeemptyingintotheSouthChinaSea.Intheuppercoursearesteepdescentsandswiftrapids,buttheriverisnavigablesouthofLouangphrabanginLaos. 　　Thenaturalresourcemanagementissuesandprioritiesdifferineachofthecountriesandthelevelofdevelopmentandpopulationsvarysignificantly.Innorth-eastThailand,withover20millionpeople,thewaterresourcesarevirtuallyfullydevelopedandproblemsareemergingassociatedwithsalinisationofarablelandsasresultofover-clearingofnativevegetationandpoorirrigation,soilerosion,anddecliningwaterqualityintheriversandstreams.InLaos,with5millionpeopleandamuchpoorercountryfromaGDPperspective,thewaterresourcesarelargelyundeveloped.Cambodia,with10millionpeople,isrecoveringfromdecadesofwar,andintheMekongdeltasome20millionVietnameseliveonsomeofthemosthighlyproductiveagriculturallandintheworld.