SBR- Content.pmd - INBO

State of the Basin Report - 2003Sources of contamination are widespread. They include the discharge of untreated or partially-treatedhuman sewage; the practice of combining sewage with storm water drainage; the emptying oroverflowing of septic tanks and cess pits; the use of untreated night soil in agriculture; seepage frompit latrines; defecation in the open; pollution by the waste from intensive livestock operations; andcontamination from people bathing or washing clothes in water courses. These sources affect surfacewater or groundwater, and in some cases, both.Pollutants from industries such as paper mills, textile mills and chemical factories may become athreat in the future as more of these industries are established in the LMB. Problems could occur notonly in larger centres such as Phnom Penh and Vientiane, but also in fast-expanding smaller citiessuch as Ubon Ratchathani, Udon Thani, Khon Kaen and Nong Khai in Northeast Thailand and areasin the Mekong Delta in Viet Nam which have been targeted for development. Increasing pollution ofwater sources by industries in cities and towns may well hinder the already difficult task of extendingbasic water and sanitation services to the urban poor.3.2.2 Contamination of groundwater, including arsenic contaminationDistinction needs to be made between shallowgroundwater that is vulnerable to pollution but easilyaccessed with simple drilling equipment or digging byhand, and deeper, more reliable groundwater. Many ruralcommunities rely, at least in part, on shallowgroundwater. This is vulnerable to contamination fromrun-off, flooding, latrines and other sources of faecalcontamination, and when users draw water.Contamination of groundwater may be made more likelyas a result of poorly installed or badly maintainedboreholes and wells. Mining, manufacturing and leaksfrom underground petrochemical tanks may threatengroundwater quality in future.Contamination of groundwater from natural sources isreceiving much greater attention following the discoveryof high arsenic levels in groundwater in many parts ofSouth and Southeast Asia, with associated impacts onthe health of communities. Both fluoride and arsenicare now increasingly recognised as threats to waterquality. Iron and manganese salts may be as well, butmore for aesthetic than for health reasons.A high frequency of gastro-enteric, wormrelatedand other diseases are linked withcontamination of, or shortage of, domesticwater and poor sanitationBox 4. ArsenicArsenic, in particular, is an increasing concern. As a WHO meeting recognised in 2002 9 , arseniccontamination of groundwater is a very complex problem, not only in terms of its origin,movement and transformation, but also because of its very significant health and social impacts.The areas at most risk in the LMB appear to be along the valley and floodplains of the Mekong/Tonle Sap/Bassac and deltaic areas. Here rock, soil and aquifers may contain historic arsenicrichdeposits washed down from the Himalayas. The precise mechanisms of arsenic release250