内蒙古河套灌区农田水土环境安全因子限制下引黄水量阈值与环境预报研究

Hetao Irrigation Area is facing the severe situation that the water supply from Yellow River is reducing a lot, the long-term founded and balanced soil and water environment will be changed. It will be of great importance to the sustainable development for Hetao Irrigation Area to look for a soil and water environment prediction method that suit for regional characteristics and propose the threshold of the water supply from Yellow River under the restriction factors of soil and water environment. The research is under the background of Hetao Irrigation Area, through experiment and data summary, the limiting factor threshold under the farmland soil and water environment safety is put forward. With the strong support of 3S technology and well developed long-term observation data, combined with field experiment, the evolution of water and soil environment of the regional farmlands is assessed. Based on the flow and solute transferring model that calibrated and verified in unsaturated and saturated zones, the prediction coupling model and calculation method of unsaturated and saturated farmland soil and water environment in regional scale are developed. Predict the irrigation amount in different periods of crop growth and autumn irrigation with different hydrological year condition，which suit for the threshold of farmland soil and water environment. Propose the water supply threshold from Yellow River objectively. Forecast the medium and long-term trend of farmland soil and water environment of the area, under the threshold of water supply from Yellow River.The results could be used in formulating the ecological environmental and agricultural sustainable development in the area.

内蒙古河套灌区面临引黄水量大幅减少的严峻形势，长期形成并在一定程度上趋于稳定的区域农田水土环境必将发生改变，寻求适合地区特点的区域农田水土环境预测方法，较客观的提出农田水土环境限制因子下灌区引黄水量的阈值，将对灌区生态农业可持续发展具有重要的科学及现实意义。研究以内蒙古河套灌区为背景，通过试验与资料总结提出农田水土环境安全下限制因子阈值；在灌区完善的长系列历史监测资料及先进的3S技术支撑下，评估田间试验条件下区域农田水土环境的变迁；以率定检验后的区域非饱和带及饱和带水流溶质运移模型为基础，构建适合地区特点的区域尺度非饱和-饱和农田水土环境耦合预测模型及其算法；预测满足农田水土环境阈值下研究区不同水平年生育期、秋浇期灌水量，较客观的提出河套灌区引黄水量的阈值；预报在引黄水量阈值条件下区域农田水土环境的中、长期变化趋势。研究结果将为地区生态环境及农业可持续发展战略的制定提供科学依据。

研究以内蒙古河套灌区为背景，以永济灌域隆盛试验示范区为典型研究区，以耗水量大且对盐分呈中度敏感的玉米为代表作物，综合确定了农田水土环境限制因子（土壤水分、盐分、地下水埋深及矿化度）的阈值（满足玉米正常生长）；建立了分布式非饱和-饱和带水盐运移耦合模型，基于农田水土环境阈值分别对典型研究区生育期、秋浇期的灌水量阈值进行了模拟预测；初步得到河套灌区引黄水量阈值。本文取得的主要研究成果如下：.通过不同土壤质地凋萎系数试验与不同盐分土壤作物出苗率试验，结合适宜土壤含水率、作物耐盐阈值与地下水适宜埋深值等相关研究结果，综合确定出玉米种植期、苗期-拔节期、拔节-抽雄期、抽雄-灌浆期、秋浇后封冻前的各限制因子阈值，其中土壤含水率阈值为：10%~15%、15%~20%、18%~25%、18%~25%、20%~24%；土壤含盐量阈值：0.5 mS/cm、0.8 mS/cm、1.5 mS/cm、1.7 mS/cm、0.45 mS/cm；地下水埋深阈值为：1.8~2.2 m、1.6~2.0 m、1.6~1.8 m、1.6~2.0 m、1.8~2.0 m；地下水矿化度阈值为：3 g/l、1.7 g/l、1.8 g/l、2 g/l、3 g/l。.本项目利用地质统计学原理将典型研究区划分为土壤表层（0~20cm）盐分、质地相对均一的3个小区，在此基础上建立了分布式非饱和带土壤水盐运移SWAP模型，并对模型参数进行了率定和验证；以Visual MODFLOW为平台建立了典型研究区的地下水流及溶质运移模型；以非饱和带在地下水位处的水流通量和溶质通量以及地下水埋深作为耦合边界，构建了区域分布式非饱和带-饱和带耦合水盐运移模型及其算法，并对耦合模型进行了循环检验。.运用检验后的耦合模型预测满足农田水土环境限制因子阈值下典型研究区的灌水量阈值，典型研究区不同水文年生育期的灌水量阈值分别为：枯水年296 ~ 308 mm、平水年197 ~ 220 mm、丰水年118 ~ 130 mm；秋浇期的灌水量阈值平均为：178 ~194 mm。.以典型研究区灌水量与各灌域的灌水量建立了回归关系，在典型研究区灌水量阈值的基础上，反求各灌域灌水量阈值，通过直接计算法得到河套灌区引黄水量平均年阈值为38.1389 ~ 41.8257亿m³。