不合理开采地下水，是导致北海市海水入侵滨海含水层的主要原因。降雨入渗和运河渗漏对地下水补给的减少，对海水入侵起到加速作用。承压含水层顶板弱透水层在海岸带局部存在岩性“天窗”，则有利于海水入侵。重新调整地下水开采布局，恢复运河流经市区的一段渠道，引入市区以外的地表水来解决市区部分供水，是防治北海市海水入侵的主要对策 Unreasonable exploitation of groundwater is the main reason that seawater in Beihai City invaded the coastal aquifer. Rainfall infiltration and canal seepage reduce recharge of groundwater and accelerate seawater intrusion. The confined aquifer roof aquitards exist in the coastal zone lithology “skylight”, it is conducive to seawater intrusion. Re-adjust the layout of groundwater exploitation, restore canal through a section of the urban area, the introduction of surface water outside the urban area to solve part of the urban water supply, prevention and control of sea water intrusion in Beihai City, the main countermeasure