Using shallow saline groundwater for irrigation and regulating for soil salt-water regime

Drought and fresh water shortage are the main limiting factorsfor sustainable development of agriculture in North China Plain.Using saline water for irrigation plays important role forovercoming the constraints and increasing crops yields. Theexploitation and utilization of shallow saline groundwaterenables to regulate the groundwater depth and to promote thetransform of precipitation into available water resources.Thispaper reviews the research and practice on the utilization ofshallow saline groundwater in the part east of South GreatCanal in Haihe River Plain. Findings are presented on the useof saline water, cycling and blending of saline and fresh waterfor irrigation, indexing of crops salt tolerances, regulating forsoil salt-water regime, saline-alkali land reclamation andgroundwater quality freshening. These approaches help therational regulation and utilization of the local water resourcesfor comprehensive control of drought, waterlogging and salinity.     

Farm salinity appraisal with water reuse

The need for a better understanding of the interaction between irrigation practices and the elevation and quality of the water table is of paramount importance for developing irrigation management strategies to ameliorate the regional problems of elevated saline water tables in the San Joaquin Valley, California. An area of approximately 3000 ha which includes portions of the Diener Ranch and the adjacent University of California, Westside Research and Extension Center, located south of Five Points in the Westlands Water District on the west side of the San Joaquin Valley was chosen for extensive field measurements. Field work consisted of four main activities namely, field instrumentation, collection of records of field activities, periodic data collection, and analyses of field data. Field measurements of water table carried out during 1994 indicated that the water table elevation was sensitive to the irrigation practices. There was a general increase in the area with a water table close to the surface during the irrigation season, and a return to water table elevations similar to the starting conditions at the end of the season. During the study period, the surface water quality deteriorated more in areas irrigated with reuse water and persisted through the end of the season. Depth averaged electrical conductivity for the study area over 6.5 m decreased between December 1993 and December 1994. Vertical hydraulic gradients in the saturated zone, were found to be an order of magnitude larger than horizontal gradients. The direction of vertical gradients changed, with downward gradients following pre-irrigations and upward gradients later in the season, when crop water requirements increased. Based on the results of the field study, it can be concluded that the irrigation management practices have a direct effect on local water table response as well as on water quality. Therefore, irrigation practices that promote less deep percolation losses may be helpful in controlling the water table rise.     

大型灌区节水改造后地下水动态的

以黄河河套灌区的节水灌溉工程改造为目标，通过一个试验区（沙壕渠灌域）的实际分析，在地下水动力学数值模拟基础上，用Galerkin法对节水工程实施后的地下水动态进行预测，通过更大范围（解放闸灌域）用人工神经网络BP模型的快速算法进行了检验比较认为：成果基本可靠，有一定代表性，可供河套灌区水环境评估与宏观水管理预测和决策参考。     

灌区土壤盐渍化发展模拟预测与对策研究

以秦王川灌区观测和调查资料为依据,采用目前广为实用的MODFLOW地下水模拟软件,对灌区地下水动态进行了预测和分析,并对地下水质的发展趋势作出评价。灌溉实施以来,秦王川灌区地下水位逐年上升。未来10年内盐沼区面积扩大约为28 km2,并且将继续增加,地下水埋深0~2 m的面积达31.4 km2,占灌区面积的比例约为6%。未来20年地下水埋深0~2 m的面积达47 km2,占灌区面积的比例为10%左右。根据地下水位的变化特征,对控制土壤盐渍化发展的因素和对策进行了分析,提出以明沟排水为主,加大灌区下游地下水排泄能力;以渠灌为主,适度发展井灌,大力推行田间节水灌溉技术等对策。     

井渠结合灌区水资源多目标优化配置模型与应用

将灌区的经济效益和生态环境效益结合在一起综合考虑，在灌区水资源配置时不仅只追求获得最大经济效益，同时尽量将地下水位控制在适宜范围内，以维持地下水资源的采补平衡，实现水资源的可持续利用。按此原则，建立了井渠结合灌区水资源多目标优化配置模型。实例计算表明：应用此模型指导井渠结合灌区的水资源配置可实现真正意义上的地表水和地下水联合运用，提高水资源利用效率。     

淮北平原涝渍兼治的组合排水工程形式

由于淮北平原砂姜黑土区的气候、地形、地貌、水文地质、土壤等多方面原因，致使旱、涝、渍频繁，且涝渍灾害往往是紧密相连，先涝后渍，涝渍相随．造成大面积减产．甚至绝收，旱、涝、渍灾害一直困扰着本区的农业发展。通过试验及调查，从治理涝渍效果、提高农业产量、投入产出等方面进行综合分析，提出了几种适宜于本区的组合排水形式。     

基于压电薄膜的免耕播种机播种深度控制系统

为使免耕播种机在秸秆覆盖地作业时自动保证播种深度的一致性和稳定性,设计了一种主动作用式播种深度自动控制系统。采用聚偏二氟乙烯(Polyvinylidence fluoride,PVDF)压电薄膜传感器将免耕播种机限深轮的胎面形变量转换为电压信号,信号处理电路对传感器产生的信号放大滤波,提取信号峰值,系统根据峰值信号实时监测播种单体对地表的压力,控制信号形成电路在压力不足时发出控制信号,控制安装在播种机机架与播种单体四连杆间的空气弹簧产生推力,使播种单体能够产生对地表的压力,从而保证播种深度的一致性。试验结果表明,所设计的主动作用式播种深度自动控制系统能够精确控制开沟深度,仿形性能可靠,作业速度为5~8 km/h时,播深合格率达到90%,作业速度大于8 km/h时,播深合格率明显高于被动作用式播种深度控制装置。     

Simulation of drainage water quality with DRAINMOD

The design and management of drainage systems should consider impacts on drainage water quality and receiving streams, as well as on agricultural productivity. Two simulation models that are being developed to predict these impacts are briefly described. DRAINMOD-N uses hydrologic predictions by DRAINMOD, including daily soil water fluxes, in numerical solutions to the advective-dispersive-reactive (ADR) equation to describe movement and fate of NO₃-N in shallow water table soils. DRAINMOD- CREAMS links DRAINMOD hydrology with submodels in CREAMS to predict effects of drainage treatment and controlled drainage losses of sediment and agricultural chemicals via surface runoff. The models were applied to analyze effects of drainage intensity on a Portsmouth sandy loam in eastern North Carolina. Depending on surface depressional storage, agricultural production objectives could be satisfied with drain spacings of 40 m or less. Predicted effects of drainage design and management on NO₃-N losses were substantial. Increasing drain spacing from 20 m to 40 m reduced predicted NO₃-N losses by over 45% for both good and poor surface drainage. Controlled drainage further decreases NO₃-N losses. For example, predicted average annual NO₃-N losses for a 30 m spacing were reduced 50% by controlled drainage. Splitting the application of nitrogen fertilizer, so that 100 kg/ha is applied at planting and 50 kg/ha is applied 37 days later, reduced average predicted NO₃-N losses but by only 5 to 6%. This practice was more effective in years when heavy rainfall occurred directly after planting. In contrast to effects on NO₃-N losses, reducing drainage intensity by increasing drain spacing or use of controlled drainage increased predicted losses of sediment and phosphorus (P). These losses were small for relatively flat conditions (0.2% slope), but may be large for even moderate slopes. For example, predicted sediment losses for a 2% slope exceeded 8000 kg/ha for a poorly drained condition (drain spacing of 100 m), but were reduced to 2100 kg/ha for a 20 m spacing. Agricultural production and water quality goals are sometimes in conflict. Our results indicate that simulation modeling can be used to examine the benefits of alternative designs and management strategies, from both production and environmental points-of-view. The utility of this methodology places additional emphasis on the need for field experiments to test the validity of the models over a range of soil, site and climatological conditions.     

农田灌溉限量开采地下水的主要途径与方法

针对山西省运城地区因地下水超采而产生的地面下沉、地裂、农用机井报废等一系列环境问题，通过计算分析，提出了一个既能满足农业发展对水的需求，又能维持地下水资源环境平衡的地下水可开采量，并就实施限量开采地下水的途径、技术措施、管理机制、水价体系及政策保障等进行了综合分析与阐述。     

引黄灌区引水补源优化运行模型研究

应用非线性优化理论 ,并基于 Philip入渗方程和其它边界约束条件 ,建立了引水补源区优化运行数学模型。模型目标是确定在补源区自然物理条件、地下水流运动、入渗以及连续方程等约束下 ,使得入渗量最大的运行准则 ,应用非线性优化规划法对模型求解 ,得到了满意效果。以黄河下游陈垓引黄灌区 1 993年 3月对灌区下游补源区一个单周期引水补源过程为例 ,计算了一次引黄最大优化入渗补源量 ,本方法对开辟学术研究新思路 ,指导生产实践具有重要参考价值