近年昆明市茨坝—岗头村富水块段地下水位持续下降原因分析

Analysis on the reasons for continuous declination of groundwater table in the Ciba-Gangtou village water-rich block in Kunming in recent years

茨坝—岗头村富水块段位于蛇山断裂东侧盘龙江谷地,东以黑龙潭东支断裂、玄武岩为隔水边界,南以陡坡寺组泥质粉砂岩为隔水边界,面积16.07 km2.富水块段岩溶含水层主要以二叠系和石炭系的灰岩、白云岩为主,埋深2.5～173.92 m.块段内岩溶地下水由北向南,由西向东径流,于山前缓坡边缘以泉排泄,部分向深部径流,形成承压区.为弄清近年富水块段岩溶地下水位持续下降的原因,在查明富水块段水文地质条件的基础上,对比分析了该富水块段近3年（20092011年）降雨量与多年平均降雨量及其地下水补给、开采减少量和地下水位的变幅.结果表明,降雨量偏少是导致地下水补给量减少,进而造成茨坝—岗头村富水块段在关闭部分开采井及减少开采量后,地下水位仍然持续下降的主要原因.

The Ciba-Gangtou village water-rich block,16.07 km2 in area,is located in the Panlongjiang river valley on the east of Sheshan fault in northern suburb of Kunming.There are some famous karst springs such as the Heilongtan,the Lanlongtan and the Bailongtan.The karst aquifer of the water-rich block mainly composed of limestone and dolomite in the Permian and Carboniferous systems covered on the top by quaternary proluvial and alluvial gravel layers of 2.5-173.92 m in thickness.It takes east Heilongtan branch fault and basalt as the impermeable boundary to the east and the Douposi group argillaceous siltstone as the impermeable boundary to the south.Groundwater flows from north to south and from west to east,some of the groundwater discharges by the spring on the gentle slope piedmont edge and some runs deep down,forming the confined area.The rainfall decreased in recent years,leading to drought in Kunming,where the waterrich block is located.In particular for the continuing drought during 2009-2011,the karst groundwater table declines continuously in the water-rich block affecting greatly the production and livelihood there.In order to clarify the reasons for the declining groundwater table,this paper analysis the decrease of rainfall,comparing to the average rainfall,and the decrease of groundwater recharge and extraction,as well as amplitude of groundwater table in the water-rich block during 2009-2011,based on ascertaining hydrogeological condition.The results show that the reduction of the annual rainfall compared to normal amounts leads to the reduction of groundwater recharge,which is the main reason for the declining trend of groundwater table after reducing exploitation continuously and closing of the wells in the Ciba-Gangtou village water-rich block.This understanding to the drought in Yunnan and rational exploitation of karst groundwater is of some guiding significance.