旱涝急转发生机理与减灾方法研究

The disasters of drought and water logging are often taken as two kinds of individual disasters separately in the current research work. However, this can not match with the truth that drought disaster and water logging disaster appear alternatively in some regions of China within short time, and the phenomenon of “heavy rain heavy disaster, light rain light disaster, no rain drought disaster” in parts of China. In addition, the current study method can not explain the disaster-causing factors of drought and water logging, the evolving law of disaster-pregnant environment and the response law of hazard bearing bodies in theory. For satisfying the urgent practical need to govern the disasters of droughts-floods abrupt alternation, a new theory system is required to propose for studying the whole process and the whole cycle of drought and water logging disasters. For the complex process of droughts-floods abrupt alternation, the interdisciplinary approaches are adopted in this program to analyze the influence mechanism of droughts-floods alternation on crop physiology and final yield. A hydrology model for irrigation districts will be built to consider the alternation of infiltration mechanism under the conditions with or without water accumulation and to consider the change of flow direction during the process of droughts-floods abrupt alternation. In this program, the nonlinear dynamic statistic prediction model for drought and water logging disasters will be also constructed to forecast the long-term change trend of droughts-floods abrupt alternation under different climate scenarios. This prediction model will be based on climatology and dynamics mechanism. This program will help us reveal the happening, developing and evolving law of droughts-floods alternation and its regulation, which will fill the gap of theory and method on the whole process and the whole cycle of drought and water logging disasters and open up new ways for treating drought and water logging disasters.

现有的旱、涝灾害研究基本是将旱、涝作为独立灾害过程来开展的，它与我国部分地区发生的“大雨大灾、小雨小灾、无雨旱灾”旱涝交替以及气候主导的旱涝急转现象极不相称，它在理论上难以解释旱涝交替过程中的致灾因子、孕灾环境的演变规律以及承灾体的响应规律，在实践上不能满足旱涝急转灾害治理的客观需求，迫切需要提出新的面向旱涝全过程、全周期的灾害治理理论体系。申请项目以旱涝交替过程为研究对象，采用多学科交叉的方法，分析旱涝交替胁迫对作物水分生理与最终产量形成的影响机制，研究旱涝急转过程中积水入渗与非积水入渗交替出现、水流方向变化的条件下的灌区水文模型，建立具有天气气候学意义和动力学机制的非线性动力统计旱涝灾害预报模式，预测未来不同气候情景下旱涝急转长期变化情势。项目的开展将揭示旱涝交替过程的发生、发展、演变规律与调控规律，填补旱涝全过程、全周期研究理论与方法的空白，同时开辟旱涝灾害治理的新途径

提出了一个日尺度旱涝急转指数DWAAI指标，建立了诱发长江中下游流域夏季旱涝急转事件的概念性模型，揭示了前期热带东太平洋海温异常偏低和北极海冰密集度异常偏低共同强迫对大气环流的影响可能是造成长江中下游流域发生旱涝急转事件的主要原因。研究发现：长江流域内发生旱涝急转事件的区域范围越来越广，事件频率和强度均具有逐年增长趋势。旱涝急转事件与事件发生前Nino 3.4 区域海温持续异常偏低存在一定关系。.提出了计算交替积水条件下降雨入渗补给量的计算模型，安徽蚌埠五道沟水文实验站资料检验表明：降雨入渗补给量模拟结果相对误差均小于17%，Nash-Sutcliffe系数大于0.71，表明模型具有较好的模拟旱涝急转条件下的内涝积水过程的能力。.项目进行了为期5年的水稻旱涝急转测坑试验结果表明：与单旱组相比产量削减程度增加30%以上，总粒数损失增加33.9%～35.2%，与单涝组对比，单涝组产量补偿113.0%。旱涝急转过程中株高的二次抑制、净光合速率峰值、日平均净光合速率的降低是重要原因。区域尺度上基于遥感高精度反演的县级区域作物种植结构图和作物产量分析表明：湖北省监利县2009年至2016年水稻产量与旱涝程度关系显示南方地区水稻对旱灾的耐受力比涝灾的耐受力相对强一些。.项目对汉江流域未来RCP4.5、RCP8.5情景下旱涝急转情势进行了预测，干旱事件频率呈逐渐减小趋势，到2050s发生频率降至最小，洪涝事件频率呈逐渐增大趋势，到2050s增至最大，2021~2050年汉江流域两种气候情景下干旱事件发生的频率（达到35%左右）均大于洪涝事件发生的频率（为19%左右），干旱事件的威胁性更大。项目提出了旱涝急转条件下一种新的基于分区的限制供水规则，徐家河水库供水调度的实例研究表明了新的限制供水规则具有一定的合理性和有效性。