河水温度对干旱区宽浅型河床渗透系数影响的定量研究

River water temperature exerted an important influence on variability of streambed hydraulic conductivity, especially in arid areas where the daily and annual temperature varies greatly. However, it is still not clear at present how the influence does in the arid broad-shallow rivers, which exhibits intermittent river flow (drying and wetting alternation) and seasonal freeze thawing. This project intends to carry out investigation on the typical riverbed cross-section of Donghe River in Ejina. Temperatures and water levels will be automatically and simultaneously monitored at continuous step for river-aquifer systems. A set of streambed hydraulic conductivity values (under the effect of continuous changes in water temperature) will be estimated via numerical solutions of coupled water flow and heat transport model. The variation of river temperature and streambed hydraulic conductivity under the different river water flow conditions will be analyzed.Meanwhile, the streambed hydraulic conductivity values will be estimated using grain-size distribution method (free from the effect of water temperature) and standpipe method (at certain water temperature). Comparison of the streambed hydraulic conductivity values derived from different methods under different temperature scales will be analyzed, and it is expected to reveal the effect of river water temperature on the streambed hydraulic conductivity. Results of this research are expected to contribute a better understanding of the interaction processes between river water and groundwater in arid areas, and also provide a basis for quantifying surface water-groundwater exchanges.

河水温度是引起河床渗透系数动态变化的关键因素之一，尤其在昼夜及年内温差显著的干旱区。但对于间歇性过水（干湿交替）和季节性冻融的干旱区宽浅型河流，其河水温度变化规律及其对河床渗透系数的影响机制目前尚不十分清楚。本项目拟以额济纳东河为研究对象，选取典型河床断面，开展河流-含水层系统温度与水位的同步高频连续观测，并通过数值求解水热耦合运移方程计算获取河床渗透系数的时间序列数据（连续变化温度影响），探讨在不同河流水文条件下的河水温度与河床渗透系数变化规律。结合河床沉积物颗粒级配分析（不考虑温度影响）与原位竖管渗透实验（某一时刻温度影响）所获得的河床渗透系数值，通过对比分析定量揭示河水温度对河床渗透系数的影响。研究成果将深化对干旱区河水与地下水转化机理的认识，并为河流补给地下水的定量研究奠定基础。

本项目以河水温度对干旱区河床渗透性能影响的定量研究为核心，按计划在黑河下游额济纳东河布设了河流-含水层系统温度与水位同步连续观测（1次/1小时）系统，开展了点尺度的河床渗透系数野外原位测定与室内分析实验，构建了基于水位与温度同步观测的河流-含水层系统水热运移模型。通过开展上述研究，揭示了河道干湿变化与季节冻融过程中的河床温度变化规律；发展了基于野外竖管渗透实验的河床渗透系数计算方法；识别了影响干旱区间歇性河流河床渗透系数的主要因素；重建了研究期间河床渗透系数随河水温度变化的时间序列，并模拟分析了河水温度变化对河道渗漏速率的影响。研究成果深化了对干旱区河床渗透性能时空变异及河水与地下水转化的认识。在本项目资助下，发表了SCI学术论文4篇和北大中文核心期刊论文1篇，参加国际学术会议4次，完成了预期研究计划与目标。