中国北方农业灌溉对区域气候和水循环的影响

The large-scale agricultural irrigation (surface water utilization and ground water pumping) can significantly alter the quantity and distribution of water resources, then impact on weather and climate through land–atmosphere feedbacks. The ground water pumping is one of the main approaches for agricultural irrigation in northern China. Therefore, in order to study the climatic effects of irrigation, it is necessary to consider the groundwater changes. Rationally describing the process of human water withdrawal for irrigation in the land surface model is very important for understanding the mechanism of the regional climate and water cycle influenced by human activities. However, the research in this area is still very weak. Based on the existing research, this study plans to develop an agricultural irrigation scheme that including the human groundwater withdraw in the land surface model, and couples it into the regional model, then simulate the physical mechanism of the agricultural irrigation effects on regional climate and water cycle in northern China, and quantitatively evaluated the regional climatic water effects of agricultural irrigation in northern China. The regional climate changes in northern China from present to future under Representative Concentration Pathways 8.5 (RCP8.5) scenario are projected using the global model results and regional model, the possible scenarios of future climate and water cycles lead by agricultural irrigation will be analyzed. These studies will provide scientific advice to water use sustainable development in northern China.

大范围农业灌溉（利用地表水和抽取地下水）可显著改变区域水资源的时空分布，并通过陆气相互作用对天气和气候产生影响。在我国北方，地下水抽取已是农业灌溉取水的主要途径之一。因此，研究灌溉对气候变化的影响有必要考虑地下水的变化，在气候模式中合理描述用于灌溉的人类取用水过程，对深入理解人类活动影响区域气候和水循环变化的机制具有重要意义。然而，这方面的研究仍很薄弱。本研究拟在已有研究的基础上，发展陆面模式中考虑人类取用水过程的农业灌溉参数化方案，并耦合到区域模式中；进一步利用区域模式模拟中国北方农业灌溉对区域气候和区域水循环影响的物理机制，定量评估农业灌溉对区域气候和水循环的贡献。最后，结合全球模式和区域模式模拟结果，对未来增暖背景下中国北方的区域气候进行动力降尺度预估，分析未来在农业灌溉影响下的我国北方区域气候及水循环变化的可能情景，为中国北方地区水资源合理利用及区域的可持续发展提供科学依据。

过去几十年，我国农业灌溉面积迅速扩张，其用水量已达全国总用水量60%，其中75%来自于地下水的开采。在华北，地下水开采是农业灌溉的主要方式，这种大规模的农业灌溉对区域气候和水文过程有什么样的影响？至今缺乏定量的估算和系统的认识。为此，本项目拟利用区域气候模式WRF（Weather Research and Forecasting Model）与新的动态地下水抽取灌溉参数化方案耦合，模拟研究华北地区农业灌溉的区域气候水文效应，定量估算其影响。目的是深入理解农业灌溉对华北地区气候和水文过程的影响，并为中国北方乃至全国农业可持续发展和水资源可持续利用提供科学依据和参考建议。