基于回归水重复利用的灌溉用水效率指标及节水潜力评价方法研究

This proposal aims to establish two study sites, one for surface irrigation system for paddy-rice in Southern China and another for surface-groundwater conjunctive use system in Northern China, based on which water balance monitoring and agro-hydrological modeling will be setup. Water balance components monitoring systems at different scales will be conducted in the two irrigation systems. Distributed hydrological models are applied in combination with field crop simulation and soil water movement models. Water balance components and crop yields are then simulated under various scenarios combing land use changes, rainfall, and water-saving irrigation options (such as field water-saving irrigation techniques, canal maintenance and upgrade, ponds & small reservoirs development, and alternate water sources using ratio and prioritization). The return flows from irrigation supply and rainfall as well as their reuse efficiencies under different conditions will be calculated and analyzed. The crop yields will also be simulated under different water-saving scenarios to assess the water management impacts on production. The responses of reuse efficiency of return flows to irrigation water management and development practices together with the scale effects will be investigated. The calculation method for quantitative description of reuse efficiency of return flow will be established. The irrigation efficiency benchmark indices and water-saving irrigation potential assessment framework with consideration of return flow reuses will be proposed. Water-saving potential with three different methods (based on tradition Irrigation Efficiency (IE), ET reduction, and IE with return flow reuse proposed by this study) will be calculated and compared for typical irrigation systems to reveal the differences and their relations to return flow reuse efficiency. The findings of this study will provide much needed support for rational assessment of irrigation efficiency and water-saving potential, and guide to establish appropriate water-saving strategies and water resources development plan.

在典型灌区(南方水稻灌区和北方井渠结合灌区)开展不同尺度水平衡观测试验，建立灌区分布式水文模型和田间作物生长及水分运移模型。对不同节水情景（田间节水灌溉模式、渠道防渗标准、塘堰集雨面积、不同灌溉水源用水比）、不同土地利用和降雨下灌区水平衡过程及作物产量进行模拟，计算分析不同条件下灌溉及降雨回归水量及其重复利用率，以及不同节水情景对作物产量的影响，探明回归水重复利用率随不同影响因素的变化规律，揭示回归水重复利用的尺度效应。建立定量描述回归水重复利用率的计算方法，提出考虑回归水重复利用的灌溉用水效率评价指标及灌区节水潜力计算方法。针对典型灌区开展基于灌溉取水节水量、资源节水量及本项目提出的回归水节水量的节水潜力分析评价，探明三种节水潜力之间的差异及其与回归水重复利用的关系。研究成果为合理评价灌溉用水效率及真实节水潜力，指导灌区节水的主攻方向，制定节水灌溉发展及水资源高效利用策略提供科学依据。

在典型灌区开展不同尺度水平衡观测试验，基于试验数据和Hydrus-1D模型的模拟结果建立了田间尺度回归水量模拟模型，同时基于GIS平台开发了适用于水稻灌区中等尺度的回归水量分布式模拟模型，应用结果表明，田间尺度和中等尺度的回归水量模拟模型能够有效模拟回归水变化规律。对于南方灌区，针对水稻灌区水转化特点对SWAT模型进行了二次开发，使其能够有效应用于南方灌区的水循环过程模拟。结合ORYZA模型结果，在保证作物不减产的前提下，基于改进SWAT模型设置了不同节水情景进行水循环模拟；对于北方地表水与地下水联合应用灌区，改进SWAT与Modflow耦合模型能够有效模拟其水循环过程。基于模型模拟结果，提出了有效区分灌区降雨及灌溉回归水及计算其重复利用量的方法，揭示了灌区回归水重复利用随尺度的变化规律并分析了其原因，探明了不同节水情景下回归水重复利用的变化规律。提出了考虑回归水重复利用的灌溉用水效率及节水潜力计算方法，分析了灌溉取水节水潜力、回归水节水潜力以及资源节水潜力之间的关系及其原因。此外，基于改进SWAT模型提出了多水源灌区灌溉用水量的有效统计方法并模拟分析了灌区农业面源污染变化规律及其调控措施；分析了全国范围内参考作物蒸发蒸腾量（ET0）的时空差异性并对ET0预报模型进行了研究。

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