地表暖化影响下温度示踪地下水流速方法

为构建温度示踪方法测算地下水流速技术体系,并应用于区域地下水资源评价,基于最小二乘法和垂向一维非稳定流水-热运移方程数值解法,提出地表暖化情形下地下水流速计算方法,并对雷州半岛东北部地下水流速进行测算。结果表明:研究区域地下水补给速度为0.796m/a,入渗以西北部降水和运河渗漏为主;地下水排泄速度为0.269m/a,排泄入海主要发生在东海岛、南三岛和硵州岛附近。温度示踪解析区域地下水流动情况与地下水位分布情况基本一致,观测和计算地温数据具有较强相关性(R^2>0.50)和较低均方根误差(均值0.748),表明提出方法率定得到的地下水流速具有较强的可靠性。参数敏感性分析结果表明,地质体热扩散率和地表温度均对地温计算结果产生较明显的影响,参数的准确率定对利用地温计算地下水流速十分重要。

Temperature Tracing Method for Groundwater Flux Under Surface Warming

In order to construct the technical system of groundwater velocity calculation using heat Abstract:A least square solver was presented for groundwater flux estimation in one-dimensional conduction advection equation solved numerically with MacCormack scheme. This approach was utilized to estimate the groundwater fluxes of the observed borehole under the effect of ground surface temperature (GST) in both rural and urban areas in Leizhou Peninsula, China. The estimated average groundwater recharge rate is 0.796 m/a, while the average discharge rate is 0.269 m/a. The groundwater recharges occur in the north part of the study area; while the discharges occur near Nansan, Donghai and Luzhou Islands, which fit favorably with the local groundwater flow pattern. Relatively high correlations and low RMSE were detected between the observed and computed borehole temperature-depth profiles, indicating that the estimation is reasonable. The sensitivity analysis of surface temperature and thermal diffusivity of geological bodies and GST indicates that the evaluation of subsurface heat island effects is very important for improving the precision of groundwater flux estimation by using borehole temperatures.