西南喀斯特地区农业干旱定量监测评价及因旱减产动态预估——以乌江流域为例

The hydro geological conditions in the karst area of southwestern China are unique. The terrain is complex and broken; the soil is shallow; the water storage capacity is poor. And in addition, extreme weather events have frequently occurred during recent years, which has led to a growing degree of agricultural drought and frequency. It seriously threatens agricultural production and food security. It is urgent to carry out agricultural drought monitoring and evaluation and assessing impacts of droughts on crop yields. In this study, we take the Wujiang river basin of Guizhou Province as a study area. Considering the factors of soil moisture and crop moisture requirements of different growth stages, We construct a research method for monitoring and quantitative evaluation of agricultural drought and assessing impacts of droughts on crop yields with physical mechanistic and characteristics of the karst area in southwest China with a daily-scale based on the Soil and Water Integrated Model. This project is intended to be studied from the following. First, we analyze the spatial and temporal distribution of water resources based on the Soil and Water Integrated Model. Secondly, we calculate the agricultural comprehensive drought index based on the output component of the water balance of the Soil and Water Integrated Model and the distributed DNDC model. We build drought monitoring and evaluation model with a daily-scale also. Thirdly, We rebuild the process of agricultural drought events in various historical periods. And we analyze the characteristics of temporal and spatial changes from the perspective of clarifying the mechanistic causes of agricultural drought in the karst area of southwest. Fourthly, not only do we build a distributed DNDC model, and we achieve the prediction for dynamically assessing impacts of droughts on maize yields. We organically connect the drought monitoring evaluation model and the distributed DNDC model also. This study will not only help improve the comprehensive disaster prevention and reduction capabilities of agricultural of the karst area in Southwest China, but also provide information support for the stabilization of grain production.

西南喀斯特地区水文地质条件独特，地形复杂破碎，土壤浅薄、蓄水能力差，生态本底脆弱，加之近年来极端气候事件频发，降水分布不均，导致农业干旱程度和频率日益加大，严重威胁农业生产和粮食安全，急需开展农业干旱监测评价和因旱减产研究。本研究以乌江流域贵州段为研究区，以分布式水文模型SWIM为支撑，综合考虑土壤含水量和作物生长期水分需求等因素，构建物理机制明确、兼具西南喀斯特地区特色的农业干旱定量监测评价及因旱减产动态预估方法。拟从以下几方面进行研究：①分析研究区水资源时空分布格局；②计算综合农业干旱指数，构建日尺度农业干旱监测评价模型并进行验证；③重建历史时期农业干旱事件，定量揭示农业干旱时空演变特征；④构建分布式DNDC模型进行玉米因旱减产的动态预估，并从时空尺度实现和农业干旱监测评价模型有机衔接。本研究有助于提高西南喀斯特地区农业综合防灾减灾能力，为粮食稳产增产提供信息支撑。

农业干旱管理历来是我国抗旱工作重点，发展农业干旱动态灾情评估是区域干旱管理和粮食安全的重大需求。如何准确对干旱发生发展致灾的识别，如何实现粮食因旱减产定量动态预估，对于农业有效防灾减灾具有重要意义。. 本研究围绕乌江流域贵州段玉米干旱发生发展过程动态监测和玉米因旱减产动态预估两大实践需求，主要研究内容：（1）研究区玉米干旱发生发展过程动态监测，包括水文过程模拟、、水量平衡分量（降水、蒸散发、土壤水等）时空分布、气候变化和 LUCC对径流演变的贡献厘定、综合农业干旱指数的构建及验证、干旱发生发展过程逐日动态监测、农业干旱主导性因素的贡献份额厘定；（2）玉米因旱减产动态预估，包括dssat模型适用性评价、玉米产量动态预估以及因旱减产动态预估等内容。. 取得的成果包括：（1）完成了SWIM模型和DSSAT模型在研究区的适用性评价；（2）构建了基于SWIM模型和综合农业干旱指数的农业干旱定量监测评价模型；（3）离厘定了气候变化和LUCC对径流和农业干旱的贡献；（4）分析了降水、蒸散发和土壤水时空变化趋势（5）实现了利用历史气象数据玉米产量动态预估程序构建及产量动态预测；（6）完成了玉米因旱减产动态预估。研究过程中用到诸多空间数据和属性数据，包括气象、土壤、土地利用、遥感影像、水文及玉米生育期实测数据等。. 研究成果对水资源可持续利用及管理有指导参考意义，同时可为研究区玉米实际生产过程中的抗旱管理提供理论依据。