考虑土壤水空间异质性的灌溉模式斑状化区域农业干旱评估

Soil moisture is the only type of water that crops are able to absorb. The media for storing soil moisture are various, and their lithological features are usually different. As a result, the spatial distribution of soil moisture is significantly heterogeneous. Meanwhile, irrigation practices further disturb the near surface soil moisture. Thus these two aspects exacerbate the uncertainty of the mechanism of regional agricultural drought and augment the difficulty of scientific drought management. Currently, it is very urgent to study the spatial heterogeneity of soil moisture so as to deeply understand the mechanism of agricultural drought and to establish an optimized agricultural program considering multiple water allocation strategies with the restrains of the “red lines” for sustainable water resources utilization..The Yongnian of Handan will be selected as the study area, where regional soil moisture monitoring at multiple soil layers will be conducted in order to investigate the spatiotemporal distribution of soil moisture. With the consideration of crop features, the soil moisture storage reservoir method will be adopted to establish the regional agricultural drought index. With the proposed drought index, the physical mechanism of regional agricultural drought will be explored, and the water-cycle-based regional drought model will be established. Meanwhile, the patchy features of soil moisture arising from regional irrigation program will be investigated, and the numerical simulations and evaluations of regional agricultural drought will be conducted under the scenarios of multiple wet years and multiple irrigation programs. Finally, the irrigation program on field scale will be optimized considering the restrains of the “red lines” for sustainable water resources utilization, and the regional irrigation model with the interaction of crop yield and irrigation practices will be developed. The findings of this study will further improve the fundamental theory for agricultural drought in North China Plain and promote the development of rational regional drought models and scientific irrigation models.

土壤水是作物可吸收水分的唯一类型，因其赋存介质及岩性组分不同，在空间上分布具有显著差异，是造成农业干旱成因复杂的主要原因之一，且多种灌溉方式的干预更加剧了区域农业干旱机制的不确定性和灌区科学管理的困难性。目前充分考虑土壤水空间异质性的农业干旱发生机制尚未明晰，红线约束下多元制度优化的灌溉模式尚未构建，亟待深入研究。.本项目以邯郸永年为研究区，开展区域土壤含水量分层监测试验，解析土壤水的时空分布规律；基于土壤水库解析法并考虑作物特性，构建区域农业干旱指标，辨析区域农业干旱发生机制，建立基于水循环的区域干旱模型；精确剖析区域灌溉模式斑块状构成特征，开展不同枯水年与不同灌溉制度组合情景下的区域干旱数值模拟与评估，优化红线约束下的农田尺度灌溉制度，构建干旱/作物产量-制度互馈的区域灌溉模式。该研究成果将完善华北平原农业干旱基础理论，促进区域适用性干旱模型和科学灌溉模式的构建。

土壤水对农作物生长异常关键，准确监测与评价土壤水对辨析农业干旱发生和发展过程尤为重要。河北省永年区是典型的冬小麦、夏玉米轮作区域，具有典型的斑状化、动态化的土壤下垫面分布特征，土壤水空间分布复杂。本项目借助土壤墒情试验、分布式水文模型、分布式农业生长模型以及优化算法等各种方法工具，开展了基于土壤水空间分布规律的区域农业干旱识别与评价及其灌溉制度优化的研究，取得如下结果：.（1）解析了区域冬小麦关键生长期土壤含水量“横纵广度-深度”三维空间特征及其演变规律。结果表明区域土壤含水率呈现东高西低分布，垂直方向上呈现逐层增加的特点。不同深度土壤水分布规律解析得出，冬小麦关键生长期0-60cm土层为重要的土壤水供给层。无论哪个乡镇，冬小麦种在4月28日-5月4日期间均表现对土壤水极大的需求。.（2）构建了区域MODCYCLE模型，并与SM-AWC农业干旱指标体系耦合。模拟分析了设计情景下的区域农业旱情时空演变规律，表明中部的刘营镇和讲武镇最容易发生干旱，且干旱程度重于其他冬小麦种植区，在3种干旱情景下均出现特大干旱；其次，东部的张西堡镇和西庄镇乡也极易发生干旱，其干旱发展速度较快，极易从轻旱转为重旱或发生特大干旱；上述乡镇在抗旱减灾中需重点关注。代表性子流域SM-AWC演变规律分析表明，进入4月中旬后开始出现干旱状况，并持续发展到5月上旬，之后在5月中旬左右干旱得到缓解。进一步分析表明，土壤底墒条件、灌溉制度以及降水都是影响区域干旱重要因素。.（3）构建了区域APEX模型，根据水资源刚性约束条件确定了灌溉总量，且考虑当地灌溉习惯，设计了24种的灌溉情景开展永年区单位产量模拟，筛选的冬小麦关键生长期最优灌溉制度为：起身-拔节、拔节-抽穗、抽穗-开花进行三次正常节点灌水，灌溉总量240mm时产生的增产效果最明显，较现行灌溉制度的增产率达5.28%。.（4）迄今为止，本课题已发表论文13篇，其中SCI/EI收录7篇，核心期刊6篇，其他文章1篇；专著已申请书号；已完成专利授权3项，其中，实用新型授权1项，南非国际专利及荷兰国际专利各1项；培养研究生8名，其中硕士获取学位7名、博士在读1名；参加国内学术会议20人次，国际学术会议3人次，作报告1次。