基于遥感蒸散发的干旱区灌区水盐运移模型及其应用

Irrigation is essential for agricultural production in arid region. In irrigation district with mismatching irrigation and drainage projects, irrigation can cause serious problems as soil salinization. Hydrological processes in arid irrigation district are featured by water diversion and irrigation processes and evapotranspiration process, which is intrinsically different from hydrological processes in watershed characterized by runoff yield and concentration. To analyze the processes and patterns of water flow and salt transport in irrigation district of arid region, representative irrigation district will be selected as the study region. Remote sensing-based evapotranspiration model will be used to study the spatial and temporal patterns of evapotranspiration in the whole region and different landscapes, which will be further used to analyze the processes, patterns, and main influencing factors of water flow and consumption in different landscapes. Then, a model for water flow and consumption in arid irrigation district based on the remote sensed-evapotranspiration will be developed by considering water exchange between different landscapes, which will be used to analyze the processes, patterns, and main influencing factors of water exchange between different landscapes at different time scales. Moreover, a salt transport and balance model will be developed to analyze the processes and main influencing factors of salt exchange between different landscapes, and the effect of interior drainage and dry drainage. Based on the above results, a rational regulation mode of water and salt in the study irrigation district will be proposed, which will provide the base for high-efficient use of water and rational regulation of water and salt.

灌溉是干旱区农业生产的基础，对于灌溉与排水不配套的灌区，大量引水灌溉可能导致土壤盐渍化等问题。干旱区灌区水循环以输配水与灌水过程、蒸散发过程为主，与以产汇流过程为基础的流域水文过程有本质的区别。为深入分析干旱区灌区水盐运移过程与规律，拟以干旱区代表性灌区为研究区，利用遥感蒸散发模型计算分析干旱区灌区及其不同景观单元蒸散发的时空变化特性，分析典型景观单元的水分转化与消耗过程、规律及其主要影响因素；考虑不同景观单元之间的水分交换，建立基于遥感蒸散发的干旱区灌区水分转化与消耗模型，分析不同时间尺度下不同景观单元之间的水分转化关系、规律及其主要影响因素；进一步建立灌区盐分迁移与平衡模型，分析不同景观单元之间的盐分迁移过程及其影响因素，分析灌区内排水及旱排的效果。综合以上研究结果，提出研究区水盐合理调控模式，为灌区水分高效利用、水盐合理调控提供技术支撑。

灌溉是干旱区农业生产的基础，对于灌溉与排水不配套的灌区，大量引水灌溉可能导致地下水位较浅、进而导致土壤盐渍化等问题。干旱区灌区水循环以输配水与灌水过程、蒸散发过程为主，与以产汇流过程为基础的流域水文过程有本质的区别。以干旱区最大的灌区——河套灌区为代表，开展以下干旱区灌区遥感蒸散发模型、分布式水、盐模型及其应用的研究工作。将混合双源梯形遥感蒸散发模型（HTEM）与时间积分大气边界层模型（ABL）相耦合，建立了一个新的混合双源遥感蒸散发模型（HTEM-ABL）。该模型利用日内2个卫星过境时刻的陆面温度信息，可以不用地面温度观测资料作为输入，在地面气象站点稀疏、下垫面强异质性条件下有很好的适用性。根据遥感蒸散发模型计算结果，揭示干旱区典型灌区及其不同景观单元（不同类型农田、草地、荒地、水体等）蒸散发时空变化规律。基于遥感蒸散发计算结果，耦合灌区排水模型、长周期地下水波动模型、冻结期地下水位变化经验模型以及地下水横向交换（内排水）模型，建立了干旱区灌区分布式水文模型DAHMID（图2.2.1），实现了空间上分单元、时间上分时段、水平上分灌溉地和非灌溉地的多角度灌区农业水文过程模拟，揭示不同景观单元的水分转化与消耗规律及不同景观单元之间的水分转化关系。在此基础上，进一步发展了干旱区地下水浅埋灌区的盐分迁移与平衡模型，并将模型应用于河套灌区，分析了灌区灌溉引盐、沟道排盐、旱排（内排水对应的盐分转移量）、地下水补给和排泄的盐分以及灌区的水盐演变趋势，揭示盐分迁移与平衡规律及旱排作用，提出干旱区典型灌区水盐合理调控模式，可为灌区水分高效利用、水盐合理调控提供技术支撑。