地下水环境对灌区渠系节水改造响应机理的热示踪研究

The improvement of agricultural water use efficiency is imperative in China because water supply and demand here have become increasingly prominent. Seventy-five percentage of the total irrigation water is deliveried by open canal, which cause 33% of irrigation water loss through seepage. The water-saving renovation project of canal system is carried out recently with the expectation of sustanible water resource utilization. The new strategy has changed the hydrologic cycle in agricultural area thus cause unignored groundwater environmental change. Research will be carried out to determine the seepage rate of the channel, to investigation the dynamic process between the the cannel water and the groundwater and to recover the mechanism of water, heat, salt and associated processes considering different channel lining in this research project. Heat tracing techniques, combined with field trails, sentinel surveillance and laboratory experiments will be used in this study. Several results are expected: i) the mechanism for the response of shallow groundwater dynamics to canal lining and their environmental dynamics; ii) modeling the groundwater dynamic process and analysing the the channel seepage rate with only temprature dada; iii) new methods for the assessment of soil and water enviroment in agricultural area under diffrent lining conditions. The output will also provide provide theoretical basis and technical support in the canal irrigation management, groundwater development and soil and water enviroment assessment to the arid irrigation region in north China.

我国水资源供需矛盾日益突出，提高农业水资源利用效率刻不容缓。我国农田灌溉用水的75%以上采用明渠输水，渗漏损失占农业总用水量的33%，在此背景下实施的渠系节水改造工程，改变了灌区多年形成的水文循环，还会对地下水环境产生不可忽略的影响。本研究以灌区渠系节水改造对地下水环境影响为研究背景，以渠道渗漏土壤水动态及水、热、盐伴生机理为理论基础，利用热、盐示踪技术开展野外监测、原位示踪和室内模拟试验，定量描述渗漏条件下饱和/非饱和土壤中水分动态同热/盐迁移转化的伴生规律。建立基于动力学理论的点、线、面三级嵌套自适应模型，探讨采用温度资料模拟渗漏量、地下水位和水盐动态的数值方法，运用模型研究地下水及水土环境对渠系节水改造的响应机制；创新不同衬砌条件下渠道渗漏对灌区水土环境影响的评价新方法。研究成果可为我国北方旱区渠系节水改造后的灌溉管理、地下水资源开发利用以及水土环境的评估提供理论依据和技术支撑。

我国农田灌溉用水的75%以上采用明渠输水的方式，其中渗漏损失约占农业用水量的33%，在此背景下在此背景下实施的渠系节水改造工程，改变了灌区多年形成的水文循环，还会对地下水环境产生不可忽略的影响。本研究以灌区渠系节水改造对地下水环境影响为研究背景开展了以下研究：（1）在室内开展饱和条件下均质、非均质多孔介质的热示踪试验及模拟研究，定量描述非均质性介质中水热迁移过程的特征和规律。（2）开展土壤入渗条件下的室内水热迁移试验及模拟研究，定量分析一维入渗条件下饱和/非饱和土壤的水热运移规律。（3）以渠道渗漏土壤水动态及水、热、盐伴生机理为理论基础，利用热、盐示踪技术开展野外监测、原位示踪和室内模拟试验，定量描述渠系渗漏条件下饱和/非饱和土壤中水分动态同热/盐迁移转化的伴生规律。（4）开展河道回补地下水过程的试验和模拟研究，通过分析温度对再生水中NO3-N浓度的影响，探究以河岸渗滤系统为背景的二维水氮运移规律。以上研究成果可为我国北方旱区渠系节水改造后的灌溉管理、地下水资源开发利用以及水土环境的评估提供理论依据和技术支撑。