温度示踪法确定库水-地下水垂向交换速率

Determination of Vertical Exchange Rate between Reservoir Water and Groundwater by Temperature Tracer Method

以青岛市浮山前水库为研究对象,采用DS1922L温度记录器,连续监测(2018年9月5日至17日)3个点位沉积物垂向剖面温度,基于R语言软件模拟沉积物热运移,反求库水-地下水的垂向交换速率,并探讨热弥散度对反求交换速率的影响。模型中的热弥散度往往较难确定,常参考经验值,本文在反演交换速率时,同时反求热弥散度。野外试验期间西北侧与北侧试验点处为地下水补给库水,垂向交换速率分别为0.002 m/h与0.007 m/h;东南侧试验点为库水补给地下水,垂向交换速率为0.12 m/h。当库水补给地下水时,沉积物温度波动较大;地下水补给库水时,沉积物温度波动较小。在反演交换速率时,如果忽略热弥散或参考经验值给定热弥散度,将对反演结果产生影响,但不同试验点的影响程度有差异。若忽略热弥散,对东南侧试验点反演结果影响大;若参考经验值给定热弥散度,当取值不合适时,对北侧试验点反演交换速率的影响比忽略热弥散的影响还要大。因此,在采用热示踪反演垂向交换速率时,宜同时反演确定热弥散度,以提高求解交换速率有效性。

Taking the Fushanqian Reservoir in Qingdao as a research object,the vertical profiles of temperature of the sediments at three sampling sites were continuously monitored using iButton temperature loggers(DS1922 L)from 5 to 17,Sep.2018.The temperature in the sediments was simulated based on R language to determine the vertical exchange rate between surface water and groundwater.The influence of thermal dispersivity coefficient on the determination of vertical exchange rate was also discussed.Thermal dispersivity coefficient is difficult to determine,and it is often determined by reference values.In this paper,thermal dispersivity coefficient is reversed at the same time when the exchange rate is reversed.The results show that reservoir water is recharged by groundwater during the monitoring period at the northwest and north sampling sites,and the vertical exchange rate is 0.002 m/h and 0.007 m/h respectively.The groundwater is recharged by reservoir water at the southeast sampling site,and the vertical exchange rate is 0.12 m/h.The temperature fluctuation of sediment is greater when the groundwater is recharged by reservoir water compared with that when the reservoir water is recharged by groundwater.If thermal dispersivity is ignored or given according to reference values,it will have different effects on the determination of exchange rate at different sampling sites.If thermal dispersivity is ignored,it will have a great influence at the southeast sampling site.If thermal dispersivity coefficient is assigned improperly according to reference values,the influence on the determination of exchange rate at the north sampling site is greater than that of neglecting thermal dispersivity.Therefore,we suggest that the thermal dispersivity coefficient should be determined by inverse modeling to improve the effectiveness of the results of exchange rate.