SWAP模型模拟暗管排水条件下土壤水盐运移

【目的】研究内蒙古河套灌区暗管排水条件下作物根系层水分通量和盐分通量变化,寻求适宜当地的农田排水暗管规格。【方法】基于2018年和2019年田间试验观测数据,对SWAP模型进行率定和验证,并利用该模型对不同暗管埋深(1.5、2.0 m)和间距(30、45 m)下的40 cm土壤剖面处水分通量和盐分通量进行数值模拟。【结果】①存在灌水和降雨时,40 cm土壤剖面的水分通量向下,在暗管间距为45 m,埋深为1.5 m时,就2019年整个生育期而言,暗管间距减小15 m,向下的水分通量累积量增加5.2%,暗管埋深增加0.5 m时,向下的水分通量累积量增加83.9%;没有灌水和降雨时,40 cm剖面处的土壤水分通量以向上为主,暗管埋深和间距的变化对向上的水分通量影响不大,向上的水分通量在0～0.14 cm/d之间变动。②土壤盐分通量变化趋势和水分通量一致,在暗管间距为45 m,埋深为1.5 m时,就2019年整个生育期而言,暗管间距减小15 m,向下盐分通量累积量增加5.1%,暗管埋深增加0.5 m时,向下盐分通量累积量增加82.6%,增幅与向下水分通量累积量基本一致,且暗管埋深的变化对向下的盐分通量影响较明显。【结论】合适的暗管布设埋深和间距有助于土壤根系层的排水脱盐,其中暗管埋深对排除土壤盐分的影响更为明显,综合考虑不同暗管布局的排水排盐效果以及对产量的影响,认为当地暗管埋深取2.0 m,暗管间距取45 m较为适宜。     

暗管排水控盐对盐渍化灌区土壤盐分淋洗有效性评价

【目的】解决盐渍化灌区土壤盐渍化较严重问题,明确暗管排水控盐对土壤盐分淋洗效果的影响。【方法】以灌区下游乌拉特灌域为研究区,通过野外实测和室内试验分析结合,采用经典统计学与地质统计原理,分析收获后、春灌前后暗管排水土壤盐分统计特征和空间异质性,及其土壤盐分和盐分离子脱盐效率和暗管排水对地下水埋深的影响。【结果】暗管排水0～20、20～40、40～100 cm土壤平均脱盐率分别为61.14%、52.78%、40.37%,随着土壤深度的增加,脱盐率减小。春灌后土壤盐分变异系数降低、空间自相关性增强,说明春灌后土壤盐分空间异质性均有所下降。土壤中除CO_3~(2-)表现为上升趋势外,其余各离子均表现为下降趋势,且HCO_3~-脱盐率最小,几乎不变,土壤各盐分离子脱盐率大小表现为:Cl~-K~++Na~+SO_4~(2-)Mg~(2+)Ca~(2+)HCO_3~-。暗管排水地下水埋深在灌后7 d开始下降,且下降速率较快,排水明沟深1.5 m,对地下水埋深的控制效果较好。【结论】利用暗管排水均能降低土壤含盐量,弱化土壤含盐量的空间异质性,土壤盐分由"高盐异质性"向"低盐均质性"转变,有效降低土壤盐分离子量,避免盐渍化过程中离子平衡失调,防止盐类向单一化方向发展。利用暗管排水技术降低河套灌区土壤盐分,控制地下水埋深,保证作物正常生长,防止土壤次生盐渍化具有重要意义;暗管排水技术可在河套灌区农业生产中推广应用。     

膜下滴灌暗管排水规律及土壤脱盐效果试验研究

为了探索膜下滴灌盐碱地在灌溉过程中暗管排水规律及土壤脱盐效率,设计了一种暗管排水模型试验装置系统来探究灌溉过程中暗管排水规律和排盐效果.试验通过控制灌水时间、灌水量、观测并记录暗管出水时间、排水流量、排水矿化度、土壤盐分剖面等指标,分析灌溉排水过程中暗管排水流速和排水矿化度特征以及各土层土壤脱盐效率.结果表明:经过3次灌水淋洗试验后,暗管排水流速最终趋于1.5~3.5 L/h稳定范围,排水矿化度稳定在20~40 g/L内;0~40 cm土层脱盐率高达85%,0~80 cm土层土壤脱盐率为80.5%,两暗管中间位置处脱盐率最小分别为57.96%,56.73%,69.29%,暗管上方脱盐率最大分别为71.73%,73.34%,84.26%,暗管排盐量占0~80 cm土层总盐分含量的28.9%,其余盐分被淋洗到了80 cm土层以下.     

暗管排水对鄂尔多斯地区重度盐碱地盐分迁移规律的影响

【目的】探究暗管排水对鄂尔多斯市达拉特旗重度盐碱地土壤盐分运移的影响机制。【方法】按照暗管间距18 m、吸水管埋深1.2～1.5 m、集水管埋深1.8～2.0 m的参数,铺设暗管进行田间小区试验,利用空间插值、线性回归、主成分分析等统计方法,对2019年5—10月暗管排水条件下1 m土层的土壤含盐量、地下水埋深、地下水矿化度、灌排水水质、盐分离子等数据及其相互关系进行分析。【结果】(1)试验区1 m土层的盐分空间分布属于中等变异(25%～75%),土壤盐分类型为表聚型。(2)铺设暗管使地下水埋深增加了50～60 cm,试验结束时土壤盐分较试验开始时土壤盐分平均降低10%左右。(3)暗管铺设条件下,土壤盐分的主导离子为K~++Na~+、SO_4~(2-)和Cl~-,地下水中主导离子为K~++Na~+、Cl~-和HCO_3~-。(4)暗管铺设下黄河水灌溉后,土壤中HCO_3~-量增加56%,而其他盐离子量降低,SO_4~(2-)、K~++Na~+、Cl~-降幅较大分别为36%、34%、31%;灌水淋洗后,排水、地下水中各离子量均增加,排水矿化度增加幅度是地下水矿化度增加幅度的3.43倍。【结论】重度盐碱地铺设暗管,能控制地下水埋深,并降低土壤含盐量,有效促进土壤中SO_4~(2-)、K~++Na~+、Cl~-的淋洗排出,但同时要注意黄河水灌溉中HCO_3~-可能引起的土壤碱化问题。     

滴灌条件下排水暗管间距对土壤盐分淋洗的影响

在滴灌淋洗条件下设计暗管排水试验,研究暗管不同埋设间距(15、20、25 m)对土壤剖面盐分分布及脱盐淋洗效果的影响。结果表明:滴灌淋洗期间,0~70 cm土层含盐量显著降低,与CK相比,试验地不同地段土壤平均含盐量减少10 g/kg以上。从暗管上方至相邻暗管中点位置处不同剖面土壤平均脱盐率逐渐减小,15、20、25 m间距小区在0~100 cm埋深土壤中点位置处最大脱盐率分别为84.01%、77.75%、73.98%,土壤整体脱盐率介于51.82%~60.43%之间。吸水管埋管间距越小,小区暗管排水阶段排水流量越大,排水矿化度、电导率也越大,但成本会略高。15 m间距相比20、25 m间距小区每公顷多投入的成本和平均脱盐率差值分别为8 430、12 570元和4.78%、8.61%;15 m间距暗管处理在水平距离暗管0、5、7.5 m处土壤脱盐率最大值分别为86.47%、85.15%、84.01%,且排水期间排水流量、矿化度、电导率最大,分别为2 m~3/h、189.15 g/L和35.9 mS/cm;土壤盐分淋洗效果优于20、25 m间距小区,淋洗相同盐分含量土壤所需灌水量也低于20、25 m间距;2次灌水后0~70 cm土层盐分整体已降至10 g/kg以下,作物生长条件大为改善,适宜作为指导新疆盐渍土改良滴管条件下暗管间距布设参数的依据。     

棉花花铃期以持续受渍为特征的排水控制指标试验研究

以地下水动态指标 SEWX 反映作物的受渍程度 ,利用田间小区试验研究了棉花花铃期持续受渍对产量与品质的影响。结果表明 :随着受渍程度加重 ,蕾铃脱落率上升 ,产量明显下降 ,此外 ,品质也受到一定影响。统计分析表明 :作物相对产量 RY与 SEW30 和 SEW50 之间有极显著的线性负相关关系 ,RY与 SEW50 之间的拟合优于 RY 与 SEW30 之间的拟合。考虑到持续受渍对作物产量的影响远比品质大 ,建议以产量作为作物排水指标选择的依据。如果以减产 1 0 %～ 1 5 %作为棉花排水控制指标选择的标准 ,则棉花花铃期的排渍控制指标 SEW30 应取 80～ 1 2 0 (cm· d)。     

基于RZWQM2模型的农田排水暗管优化布置研究

【目的】研究河套灌区葵花种植区暗管排水条件下农田土壤水分变化状态,探求当地适宜的农田排水暗管布置和控制排水方案。【方法】基于2018—2020年田间试验数据,对RZWQM2模型进行率定和验证,并利用该模型对不同排水暗管布置方案(同一间距不同埋深和同一埋深不同间距)和控制排水方案(不同时期不同排水口深度)下的土壤水分运移和作物生长情况进行数值模拟。【结果】(1)模型率定和验证阶段,砂土层土壤含水率RMSE为0.049～0.065 cm3/cm3,其余土层土壤含水率RMSE为0.012～0.037 cm3/cm3,累计排水量和产量MRE分别在5.88%和3.40%以下,地下水位、1 m土层土壤储水量和叶面积指数R2分别在0.798、0.817和0.912以上;(2)以现有排水暗管埋深1.5 m、间距45 m为基础,模拟得到采用埋深1.4 m、间距45 m的布置方案其地下水位抬高5.2 cm、排水量减少40.0%、增产85.3 kg/hm2;(3)采用雨季1.5 m、非雨季1.2 m排水口深度的控制排水方案,地下水位抬高2.2 cm、排水量减少46.0%、增产66.4 kg/hm2。【结论】RZWQM2模型能较好模拟排水条件下葵花种植区农田土壤水分变化,研究区推荐采用1.4 m埋深、45 m间距的排水暗管布置方案,在现有布置下雨季1.5 m、非雨季1.2 m的控制排水方案较为合适。     

宁夏银北灌区暗管排水技术应用与工程效果监测

宁夏银北灌区引进机械施工的暗管排水工程施工技术,开展了大面积的暗管排水工程建设。在对暗管排水效果、工程质量监测的基础上,对暗排区土壤盐分动态、地下水动态、排水水质、工程的管理等进行跟踪监测,总结出暗管排水工程成功的经验、不足,为暗管排水工程的实施提供有益参考。     

膜下滴灌盐碱地排水工程控盐效果试验研究

针对新疆玛纳斯河流域下野地灌区土壤盐渍化问题,以试验区已有的支排和农沟为基础,增加暗管排水工程,形成暗管和明沟相结合的排水系统,并对试验区膜下滴灌与明沟及暗管排水工程相结合的农田灌排模式控盐效果进行试验研究.设置距明沟(暗管)8,16,24 m处为取样点,于2012—2014年不同季节在试验区对地下水位、土壤剖面(0~200 cm)盐分进行监测,对土壤总盐含量进行分析,结果表明:暗管及明沟均能有效降低地下水位,明沟和暗管可将地下水位分别控制在1.6~2.2,1.5~2.2 m;2014年相比2012年,0~200 cm土层深度,暗管取样点处(8,16,24 m)土壤总盐含量分别下降42.99%,36.84%,24.41%;根系层(0~80 cm)土壤总盐含量分别下降50.34%,40.70%,30.76%;明沟取样点处(8,16,24 m)0~200 cm深度土壤总盐含量分别下降46.85%,38.12%,30.80%;根系层(0~80 cm)土壤总盐含量分别下降54.88%,43.39%,33.21%.研究可为干旱、半干旱灌区有效治理盐碱地提供理论依据和技术参考.     

基于不同供水压力不同土壤添加物的暗管灌溉特性研究——以吉林西部苏打盐碱土为例

为改善吉林西部苏打盐碱土土壤特性,提高暗管系统在苏打盐碱地区的灌溉效果,在不同供水压力下进行暗管灌溉特性研究.依据土壤水动力学理论,以暗管系统为研究对象,基于室内暗管系统灌溉试验,根据前期试验结论选择3％稻壳与5％玉米秸秆作为添加物与土壤混掺,从不同供水压力下湿润锋水平向右、竖直向上、竖直向下运移距离,累计入渗量以及土壤水盐分布状况三方面研究暗管系统灌溉时土壤水盐运移特性.结果表明:供水压力越大,各方向上湿润锋运移距离越远,灌溉历时越短,累计入渗量越大,平均入渗速率越快.同一供水压力下各方向上湿润锋运移距离大小关系为:竖直向上>水平向右>竖直向下.玉米秸秆作用效果强于稻壳.湿润体内部竖直向上、水平向右两个方向的土壤剖面含水率均随着与暗管滤层顶端的距离增大而减小.土壤盐分随着水分向湿润锋附近运移,土壤表面以及水平向右方向上湿润锋附近含盐量皆大于0.45％.选择供水压力为100 cm,5％玉米秸秆与土壤混掺方案,可以为农作物提供足够的根系吸水量,加快水分到达农作物根系的速度,增加农作物产量,对治理土壤盐碱化和农业可持续发展具有一定意义.     

基于DRAINMOD模型的不同灌排模式稻田水氮运移模拟

【目的】研究不同灌排模式稻田水氮动态变化,为南方稻作区节水减排提供科学依据。【方法】基于实测的田间灌排水量及氮素变化数据,采用Morris方法检测DRAINMOD模型水氮运移相关参数的灵敏度,并利用DRAINMOD模型对传统灌排模式和控制灌排模式下稻田水氮动态进行模拟。【结果】20~40 cm土层侧向饱和导水率对稻田水分运移模拟结果影响最大,弥散系数、反硝化参数、硝化反应参数、有机质适宜分解温度对稻田氮素运移模拟结果影响较大;DRAINMOD模型能够较好地模拟不同灌排模式稻田水氮动态变化、灌排水量、氮素径流总负荷模拟值与实际值差别小于11%;与传统灌排模式相比,控制灌排模式排水量减少33.0%~72.6%,灌水量减少9.7%~37.1%,铵态氮径流负荷减少43.6%~45.0%,硝态氮径流负荷分别减少29.8%~53.1%。【结论】控制灌排模式稻田节水减排效果较好,利用DRAINMOD模型进行不同灌排模式稻田水氮动态模拟可行有效。     

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.     

不同棉田暗管布置方式对氮素流失影响的模拟分析

为了研究不同棉田暗管布置方式对暗管排水中硝态氮流失量的影响,结合2007—2009年在湖北荆州丫角排灌试验站的控制排水试验,采用DRAINMOD田间水文模型进行数值模拟。结果表明,暗管出口高程和暗管间距对暗管排水中的硝态氮流失量均有极显著的影响,是进行农田控制排水设计的关键因素。具体而言,暗管排水中硝态氮的流失量随着暗管出口高程的减小而减小,随着暗管间距的增大而减小。因此,在进行农田控制排水设计时,应根据当地的环境要求以及作物的具体生长要求,调整暗管的出口高程和暗管间距,做到作物高产和环境保护的统一。     

Predicting effects of drainage water management in Iowa's subsurface drained landscapes

Long-term hydrologic simulations are presented predicting the effects of drainage water management on subsurface drainage, surface runoff and crop production in Iowa's subsurface drained landscapes. The deterministic hydrologic model, DRAINMOD was used to simulate Webster (fine-loamy, mixed, superactive, mesic) soil in a Continuous Corn rotation (WEBS_CC) with different drain depths from 0.75 to 1.20 m and drain spacing from 10 to 50 m in a combination of free and controlled drainage over a weather record of 60 (1945-2004) years. Shallow drainage is defined as drains installed at a drain depth of 0.75 m, and controlled drainage with a drain depth of 1.20 m restricts flow at the drain outlet to maintain a water table at 0.60 m below surface level during the winter (November-March) and summer (June-August) months. These drainage design and management modifications were evaluated against conventional drainage system installed at a drain depth of 1.20 m with free drainage at the drain outlet. The simulation results indicate the potential of a tradeoff between subsurface drainage and surface runoff as a pathway to remove excess water from the system. While a reduction of subsurface drainage may occur through the use of shallow and controlled drainage, these practices may increase surface runoff in Iowa's subsurface drained landscapes. The simulations also indicate that shallow and controlled drainage might increase the excess water stress on crop production, and thereby result in slightly lower relative yields. Field experiments are needed to examine the pathways of water movement, total water balance, and crop production under shallow and controlled drainage in Iowa's subsurface drained landscapes.     

应用DRAINMOD对测坑控制排水条件下地下水位的模拟分析

为研究控制排水措施对农田地下水位的影响,在湖北省荆州市四湖工程管理局丫角排灌试验站进行了测坑控制排水试验,并利用DRAINMOD模型对不同试验方案下地下水位进行数值模拟。模拟结果表明：在棉花生育期内,地下水位模拟结果和实测结果的一致性较好,该模型可有效地模拟预测水测坑控制排水条件下地下水位特性;控制排水措施能有效调控地下水位．     

Evaluation and application of DRAINMOD in an Australian sugarcane field

DRAINMOD is a water management model developed to simulate the performance of drainage and water table control systems for shallow water table soils, and it has been widely used in the United States over the last 20 years. This model has been evaluated and applied for predicting water table fluctuations in a sugarcane field for acid drainage management in north-eastern New South Wales, Australia. The reliability of the model has been evaluated using 2-year experimental field data from water level recorders installed in a sugarcane field. Good agreement was found between the observed and simulated values with a standard error of about 0.07 m. However, the model is not readily applicable to daily water management in Australian soils since it requires extensive soil and climate data, which are normally not available for most Australian sugarcane areas. In this application, refinements have been attempted in evapotranspiration estimation and in soil input data preparation so that the model requires only easily obtainable input data but still retains acceptable accuracy. With these improvements, the model can be used as a practical tool for investigating drainage management options for different site conditions. This will assist decision-makers in providing appropriate subsurface drainage management policies, such as acid drainage management, in Australian estuarine sugarcane areas.     

淮北砂姜黑土区暗管排水氮素流失模拟研究

农田氮素流失是水环境氮素污染的主要来源,农田排水是造成农田土壤养分流失的主要途径。利用DRAINMOD排水管理模型通过对试验区排水量的模拟,确定了氮素流失量,氮肥淋失量与农田排水条件的关系,暗管排水强度增大,会增加氮肥淋失量,提出了进行合理水位管理,减少氮素流失的方法。     

油菜花果期以持续受渍为特征的排水控制指标试验研究

为了探索易涝易渍地区作物排水管理 ,以地下水动态指标 SEW3 0 反映作物的受渍程度 ,利用测坑和小区试验研究了油菜花果期持续受渍对产量和含油量的影响。研究表明 ,持续受渍对产量的影响远比含油量大 ,因此 ,宜以产量作为油菜排水控制指标的选择依据。统计分析表明 ,持续受渍程度 SEW3 0 与作物相对产量 Ry 之间有极显著的线性负相关关系。以 SEW3 0 作为评价作物持续受渍的指标 ,以作物减产 10 %～ 15 %作为选择排水指标的尺度 ,油菜花果持续受渍下的排水控制指标宜取 80～ 12 0 cm· d。     

Evaluation of DRAINMOD for predicting water table heights in irrigated fields at the Jordan Valley

A detailed field experiment was carried out in the Jordan Valley, south of Lake Kinneret, Israel for evaluation of the water management model DRAINMOD. This field was chosen to represent the local agro-climate conditions of that zone. Banana crop was grown and was irrigated daily with about 3200 mm/year and 0.5 leaching fraction. Subsurface drainage system with 2.5 m drain depth and 160 m drain spacing existed in the field. The water table depth was measured with about 100 piezometers, in which most of them were observed weekly, and four were continuosly recording piezometers. Five identical drainage plots were selected, out of 10 existing, as replicates for the evaluation of DRAINMOD. Deviations in a range of 0.3–1.7 m between observed water table depth and that simulated by DRAINMOD were found in four out of the five replicates. A reasonable agreement was found only in one drainage plot out of the five tested. These findings contradict the world wide convention that DRAINMOD simulation is in a good agreement with observed field data. An additional study was therefore conducted to explore the reasons for these large deviations. Three reasons were suggested: (i) a strong side effect by the Jordan River, which flows some 350 m west to the test field; a very steep 4.6% gradient was found toward the Jordan River; (ii) presence of sandy permeable layers below the depth of the drains which magnifies the boundary condition effect of the Jordan River; (iii) a very significant component of deep and lateral seepage (more than 50% of the yearly irrigation plus rainfall). A combination of these three reasons was suggested as an explanation to the apparent large disagreement. It was therefore recommended not to use DRAINMOD or similar vertical flow models for simulation of water table depths in irrigated fields with subsurface drain pipe systems in the Jordan Valley.