地下热水的来源与补给机制分析——以重庆北温泉为例

地下热水的来源研究对地下热水资源量评价和可持续开发利用有重要意义。选取重庆市北温泉作为研究对象,采用水化学分析、D、O同位素以及实时在线监测对其热水来源进行了研究。研究认为:重庆市北温泉泉水为中-低温浅层中性地热水,水化学类型为SO4-Ca型,地下热水的δ18O值为-8.48‰~-7.09‰,δD值为-55.46‰~-53.26‰,其补给来源为雨水,补给高程为海拔641~1 206m的岩溶出露区。安装马歇尔槽和CDTP300高分辨率实时在线监测发现:1)地下热水水文地球化学特征在长时间内稳定,体现了稳定的水-岩作用过程;2)北温泉的流量与研究区降雨量呈现出以半年为单位的滞后,雨季偏低,旱季偏高;当场降雨后20d左右,温泉水的水温和电导率微降,水量增加。地下热水的来源为大气降水,其补给除了长时间长距离的含水层稳定补给外,热水上升过程中受地表水和浅层地下水的补给。

Analysis on origin and recharge mechanism of geothermal water-A case study of Beiwenquan hot spring in Chongqing,China

Source research of the hot spring is very important to do the geothermal resources evaluating, and has a guidance for sustainable exploitation and utilization with geothermal resources.Beiwenquan hot springs in Chongqing is selected to be study area,and hydrochemical method,D,O isotope and on-line monitoring system are used to do this study.It is found that,Beiwenquan hot spring in Chongqing is the medium-low temperature,shallow,neutral geothermal water,and the hydrochemical style is SO4-Ca.The value of the δ18 O of Beiwenquan is -8.48‰~-7.09‰,and δD is -55.46‰~-53.26‰.The recharge of this geothermal water is rain water and the recharge area is the karst outcropping area of 641 ~1 206 m altitude.Marshall and CDTP300 slot-line monitoring system are used to do high resolution real-time online monitoring for the North hot springs and found some results.1)The hydrogeochemical features have little change over the long term,which means the hydrochemical features and the water-rock interaction in thermal aquifer is stable.2)However,the discharge and rainfall in the study area is a lag relationship,the discharge of hot spring is almost 6 month delete response on rainfall,the discharge of the hot spring is lower in rainy season,while higher during the dry season.Hydrological features of the hot spring have a certain changes after a rain.About 20 days after rainfall,temperature and electric conductivity will be some decline and the discharge will increase.The origin of these geothermal water is precipitation and its recharge is not only the long-term and long-time geothermal aquifer but also the water supply from the shallow underground water and rain water in the process of thermal water rising.