稻田回归水模拟及其评价

以V ens im为工具,建立了稻田田间及中等尺度水量转化的系统动力学模型;通过漳河灌区团林试区实测资料检验,证实了模型的适用性及其精度。将模型用于田间及中等尺度回归水的模拟,探讨了回归水评价指标随田间及中等尺度的变化规律,对影响稻田回归水变化的因素进行了敏感性分析。结果表明:地表回归水量随田埂有效高度的增加线性减少;田埂回归水量随田块长度的增加线性增加,随田埂宽度的增加而明显减少;田埂回归水和田间回归水均随水力传导度的增加而增加;地下回归水随坡度的变陡而增大;地表回归水、田间回归水及田埂回归水均随旱作比例的增加而减少。田块狭长组合方式的回归水重复利用系数比宽窄组合方式大。回归水评价指标计算表明,灌溉降雨回归系数比灌溉回归系数能更好的反映田间出流及回归水的利用;中等尺度的灌溉回归系数和灌溉降雨回归系数分别是田间尺度的1倍左右;中等尺度上的重复利用系数不大,说明可以提供给下游使用的回归水量大;干旱年份的回归水重复利用系数比平水年的大。     

基于系统动力学的平原河网型灌区多尺度下灌溉用水量计算方法研究

以嘉兴市长水塘灌区为研究对象,建立基于系统动力学的灌区水循环过程模拟模型,并引入灌片灌溉水回归系数,应用于灌区灌溉回归水重复利用量模拟分析以及多尺度下灌溉用水量计算。结果表明：通过对模型的率定与验证,模拟得到典型泵站模拟水量与实测值基本吻合,相对差绝对值均在15%以内,模拟得到的灌区河网水位变化趋势与实测过程基本一致。模型能够较好的反映灌区水量转化过程,能够为灌区灌溉用水量统计工作提供支撑。     

基于HYDRUS对稻田不同阶段土壤水分的模拟与分析

在稻田淹水到排水干田的过程中,稻田的土壤水分由饱和态转为非饱和态,这一过程中稻田土壤水分运移规律的变化以及水量各平衡要素的转化对稻田水分管理以及减缓农业面源污染等方面具有实际意义.为探寻稻田不同阶段土壤水分状况下的差异性,基于重庆丘陵区紫色土常规轮作水稻土壤水分的连续监测数据,利用HYDRUS-1D模型对稻田淹水、排水落干和收获后3个不同干湿阶段(阶段Ⅰ,Ⅱ,Ⅲ)的土壤水力参数和土壤含水量开展验证模拟分析.研究表明:(1) 根据R²与RMSE的误差分析结果,HYDRUS可以实现对不同阶段稻田土壤水分变化的有效模拟.(2) 根据土壤水量平衡分析,阶段Ⅰ的稻田土壤水分以水分补充的形式为主;阶段Ⅱ和Ⅲ的土壤水分以水分损失为主,底层渗漏量分别占总水分损失量的52%和95%.(3)根据HYDRUS的模拟结果,降雨直接影响土壤上下边界流的变化;阶段Ⅱ的实际作物蒸腾量和实际地表蒸发量低于阶段Ⅰ的,阶段Ⅲ稻田土壤的地表实际蒸发量与日照时数的关系更密切.     

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。     

水稻旱涝胁迫条件下的Morgan模型研究

为了构建旱涝胁迫条件下水稻Morgan模型,以稻田水位作为水稻灌排调控指标,以测坑试验为基础,分析了旱涝交替胁迫对水稻干物质积累的影响,构建了以田间水位超过田间适宜水深上限的累积值和地下水位低于适宜埋深下限的累积值为自变量的修正系数,建立了水稻旱涝胁迫条件下的Morgan模型。结果表明,先涝后旱条件下受涝敏感指数中由大到小为:抽穗开花期分蘖期乳熟期拔节孕穗期;受旱敏感指数由大到小为:拔节孕穗期抽穗开花期分蘖期乳熟期,该结论与静态模型分析结果一致。     

河套灌区种植结构变化对农田系统水量平衡的影响

种植结构调整是灌区农业节水的重要措施。1990年以来,河套灌区种植结构发生了剧烈变化,小麦等粮食作物种植面积大幅减小,葵花等经济作物种植面积大幅增加,对灌区水循环系统带来显著影响。针对这一问题,系统解析了灌区种植结构变化对农田系统的影响机制,采用阿维里扬诺夫经验公式、修正的Penman公式(1948)、Penman-Monteith公式(1973)等分别计算了河套灌区1990—2013年潜水蒸发量、蒸散耗水量等各水量平衡要素的变化情况,并从多个时间尺度分析了种植结构的变化对灌区农田系统水量平衡要素的影响。结果表明,1种植结构变化对垂向水量平衡要素蒸发耗水量和潜水蒸发量影响最为显著,其通量值明显减小;其次是对灌溉水量和田间入渗量的影响;对水平向水量平衡要素地表排水量影响最小。2潜水蒸发量、蒸发耗水量、灌溉用水量和田间入渗量在丰、平、枯3种典型年均呈不同程度的减小趋势,而地表排水量在不同水平年变化差异较大。3月尺度上,5月灌溉水量和6月潜水蒸发量与经济作物种植比例增加显著相关。4农田系统总输入水量与总输出水量总体呈下降趋势,水循环通量减小,水循环强度减弱。1990—2005年水分蓄变量整体呈现负平衡的状态,2006—2013年土壤层水分蓄变量为正,但由于实际土壤层增厚、土壤含水率仍然呈下降趋势。     

三峡水库中长期来水水量平衡模型研究

研究三峡水库中长期来水水量平衡模型。在利用中长期降雨预报的基础上,通过对2参数水量平衡模型进行参数率定并采用实际过程进行检验,提出了适合三峡水库的水量平衡模拟模型。结果显示2参数水量平衡模型模拟的三峡水库中长期径流过程与实测径流过程吻合度较高,峰值对应关系也较好,取得较高模拟精度。     

水库汛限水位动态控制回蓄时机的确定方法研究

合理确定汛限水位动态控制回蓄时机可以减轻水库在回蓄过程中的开闸频率。提出了动态剩余水量的概念,构建了综合考虑当前流量、峰后延迟时间、洪峰流量及峰型指数等表征洪水退水规律的指标体系,建立了动态剩余水量多元线性回归模型,提出了基于动态剩余水量确定水库汛限水位动态控制回蓄时机的方法。以河口村水库为背景进行实例研究,结果表明:采用动态剩余水量多元线性回归模型的计算结果,可以较好地实现水库汛限水位动态控制的回蓄目标。     

不同空间尺度下灌区灌溉水利用效率研究——以察尔森灌区为例

根据察尔森灌区2013-2014年实测数据,应用实测法与水量平衡法计算了田间水利用效率,通过典型渠道测试法计算了渠道水利用效率,在此基础上计算了察尔森灌区不同空间尺度下灌溉水利用效率;同时应用首尾法测算了察尔森灌区的灌溉水利用效率。结果表明,察尔森灌区从田间到斗渠尺度以及支渠到干渠尺度灌溉水利用效率降低明显,下一步灌区节水改造的重点是斗渠及干渠的工程建设和运行管理;首尾法所得灌区尺度下的灌溉水利用效率略大于典型渠道测试法,原因在于首尾法考虑了部分回归水的利用。     

灌区耗水量变化对地下水均衡影响研究

从宝鸡峡灌区水资源形成及转化的角度出发界定了灌区耗水量的概念。通过对灌区水量平衡关系分析,建立了灌区地下水量平衡模型,通过模型计算与分析,结果表明渠系及田间入渗补给量、地下水开采量是主要的地下水平衡要素;宝鸡峡灌区1991~2003年渠系蒸发及浸润损失量和渠系渗漏补给量总体呈递减的趋势,当渠首引水量和渠系利用系数一定时,渠系蒸发及浸润损失量和渠系渗漏补给量呈反比关系。灌区田间灌溉耗水量与田间灌溉入渗补给量也呈递减趋势;灌区地下水耗水量和地下水开采量总体呈上升趋势。     

Evaluation of the flood mitigation effect of a Paddy Field Dam project

To mitigate flood damage due to a recent increase in the frequency and magnitude of heavy rainfall events, the Kamihayashi district in Niigata prefecture, Japan, has undertaken flood mitigation measures using paddy fields by installing runoff control devices in drainage boxes of paddy field plots. The purpose of this study is to evaluate the flood mitigation performance of the Paddy Field Dam project in terms of a decrease in discharge volume, drop in channel water level and reduction of inundation damage using combined hydrologic analyses and flood routing. The model constructed for runoff analysis is composed of three modules: a hilly/residential area module in which the overland flow is estimated using the kinematic wave method, a paddy field module in which runoff from paddy fields is calculated using water balance analysis, and a channel network module in which flood routing is performed using a one-dimensional unsteady flow model. The outputs of the first two modules are the input of the third module. The result of the simulation shows the main channel discharge decreased by 26% and the water level dropped by 0.17 m in the case of the largest observed rainfall event. The simulated effect was larger for larger rainfall events. In terms of flood water volume, the runoff control devices have the effect of reducing the flood damage due to the 50-year return period rainfall event to almost that due to the 10-year return period rainfall event.     

Runoff nitrogen from a large sized paddy field during a crop period

Nutrient load management is an important environmental issue because nutrient loads from farmlands degrade surface waters as a result of anthropogenic eutrophication. Nitrogen load from a large sized paddy field during the crop period was examined from the results of field measurements carried out in 2004. The 1.5 ha paddy field was located east of Biwa Lake. Irrigation water volume and ponded water depth were continuously observed. Field measurements were carried out at least once a week to analyze total nitrogen (TN) concentration in the irrigation water and ponded water. Daily inflow and outflow of nitrogen was obtained by multiplication of the nitrogen concentration and transported water volume, consisting of irrigation, precipitation, evapotranspiration, percolation and surface discharge. Water outflow volume was calculated by a tank model that consisted of three small tanks connected to represent ponded water depth differences in the large paddy field. The calculated nitrogen load was 18.8 kg ha⁻¹, with 7.2 kg ha⁻¹ from surface drainage and 11.6 kg ha⁻¹ from percolation loss. The runoff nitrogen value of 18.8 kg ha⁻¹ was within the range of the reported values investigated in a medium-sized paddy field. The observed value was close to the value for a low percolation flux paddy field where less irrigation water has been applied. These results suggest that less irrigation water keep runoff nitrogen low. This also indicates that irrigation water management can reduce nitrogen load from large sized paddy fields.     

Estimation of irrigation return flow from paddy fields considering the soil moisture

The objective of this study was to estimate irrigation return flow in irrigated paddy fields considering the soil moisture. The proposed model was applied to examine its feasibility with regard to the growing period of rice. Simulation results showed a good agreement between the observed and simulated values: root mean square error (RMSE) of 6.05-7.27 mm day⁻¹, coefficient of determination (R²) of 0.72-0.73, and coefficient of efficiency (E) of 0.54-0.55. The estimated average annual irrigation return flow during the period from 1998 to 2001 was 306.2 mm, which was approximately 25.7% of the annual irrigation amounts. Of this annual irrigation return flow, 14.1% was attributable to quick and 11.6% to delayed return flow. These results indicate that considerable amounts of irrigation water in the paddy fields were returned to streams and canals by surface runoff and groundwater discharge. The modeling assessment method proposed in this study can be used to manage agriculture water and estimate irrigation return flow under different hydrological and water management conditions.     

土地利用方式对平原-丘陵-湿地交融区水资源的影响

近年来三江平原的平原-丘陵-湿地交融区土地利用方式变化显著,造成地下水水位下降、水资源紧缺等问题,然而揭示该区土地利用方式变化对水资源影响的报道较少,且难于精准描述地表、地下、湿地和绿水等水资源量时空变化。本文联合基于格子波尔兹曼法的分布式TOPMODEL和湿地水流运动模型构建平原-丘陵-湿地交融区水文模型,利用GIS和RS技术,结合地学信息图谱与空间自相关方法,分析了挠力河流域土地利用方式变化及其对水资源量影响。结果表明:根据耕地面积变化和动态度分布得1990—2013年间挠力河流域草地和林地面积变化不大,旱地面积轻微下降;挠力河流域中部与北部区域生产条件优越的未利用地和旱地转为水田;土地利用方式变化对水资源影响由强到弱的顺序为灌溉水田抽取地下水量、绿水储量、径流深、绿水流量、补给地下水量;水稻田不同生育期蒸发量不同,造成了挠力河流域5—6月期间绿水流量增加、绿水储量减少、径流深减少、补给地下水量增加和灌溉水田抽取地下水量增加等趋势,7—8月期间这一增加趋势逐渐减弱,8月后这一趋势结束;水田密集区域绿水流量大,绿水储量和径流深减少,而补给地下水量和灌溉水田抽取地下水量增加。     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

基于非恒定渐变流-急变流方程的变流量畦灌数值模型

传统畦灌模型多是基于非恒定渐变流方程建立的,在模拟变流量畦灌水流运动时的精度难以保障。本文综合分析了变流量畦灌过程中田面水流的运动状况,将其按照边界条件的不同划分为恒定流量进水阶段、变流量进水阶段、畦首消退阶段、田面消退第1阶段、田面消退第2阶段等5个阶段,基于非恒定渐变流方程和非恒定急变流方程构建了适用于变流量畦灌系统的渐变流-急变流数值模型,通过2组恒定流量畦灌、4组变流量畦灌的田间试验以及2组文献资料中的畦灌试验数据对模型进行了验证。结果表明,渐变流-急变流畦灌模型模拟值与现场实测结果吻合较好,模拟推进时间决定系数R2均大于0.96、模拟消退时间R2大于0.90。与目前常用的WinSRFR模型相比,渐变流-急变流畦灌数值模型在模拟恒定流量畦灌方面具有相似的精度,且在模拟变流量畦灌方面精度更高。渐变流-急变流畦灌模型可以较精准地模拟变流量畦灌的水流运动状况,可为分析变流量畦灌系统、优化变流量畦灌方案提供支撑。     

Prediction of irrigation return flows through a hierarchical modeling approach

The quantity of water available for irrigation is getting scarce in many countries and it assumes great importance for assured crop production, especially in view of the erratic behavior of the monsoon. Thus, there is a pressing need to improve the water efficiency of irrigation systems. One-way of improving the efficiency of the irrigation system is reusing the return flow from the irrigation system. This task requires quantification of return flow, which still remains as a grey area in irrigation water management. The estimation of return flow from the irrigation system is usually obtained using thumb rules depending upon the site-specific conditions like command area conditions and soil properties. In this paper, a hierarchical modeling technique, namely, regression tree is developed for return flow estimation. Regression tree is built through binary recursive partitioning. The effective rainfall, inflow, consumptive water demand, and percolation loss are taken as predictor variables and return flow is treated as the target variable. The applicability of the hierarchical model is demonstrated through a case study of Periyar-Vaigai Irrigation System in Tamil Nadu, India. The model performance shows a good match between the simulated and the field measured return flow values. Results of statistical analysis indicated that the correlation coefficients are high for both single as well as double crop seasons.     

水稻灌区农业面源污染物迁移转化规律模拟研究

模拟水稻灌区中非自然水文过程及其驱动下的面源污染物迁移转化过程对了解水稻灌区面源污染形成机理以及污染控制具有重要的意义。将水稻灌区水文过程分为陆面水文过程和排水沟道水文过程,采用均衡法模拟陆面水文过程中稻田深层渗漏水量以及氨氮(NH4~+)、硝氮(NO_3~-)和磷酸根(PO_4~(3-))的渗漏通量,在此基础上,基于非稳定饱和渗流方程计算稻田深层渗漏过程所形成的侧向排水过程,作为排水沟道水文过程的输入项,基于动力波方程和一阶动力学方程描述了水稻灌区排水网络下的面源污染物运移和转化过程,提出了水稻灌区农业面源污染物迁移转化模型。根据前郭灌区2008—2009年的监测数据对模型渗流过程、主要面源污染物迁移转化过程参数进行率定,采用2010年的监测资料对模拟结果进行了验证。结果表明,基于所提出的方法模拟了稻田和排水沟道2个水文过程中NH4~+,NO_3~-和PO_4~(3-)的质量浓度峰值过程的差异,实现了水稻灌区陆面水文和排水沟水文过程的耦合。稻田水层中模拟NH4~+,NO_3~-和PO_4~(3-)的Nash-Sutcliffe系数分别为0.772、0.758和0.709,相对均方根误差(RMSE)分别为0.042、0.050和0.071,排水系统中模拟NH4~+、NO_3~-和PO_4~(3-)污染物的Nash-Sutcliffe系数分别为0.645、0.704和0.854,相对均方根误差(r RMSE)分别为0.072、0.060和0.031。所提出的方法可有效地模拟稻田渗流过程和排水过程中的面源污染物迁移转化过程。     

分蘖期稻田不同水层深度下暴雨后地表水TP的变化

暴雨前在稻田内设定不同水层深度（20、40、60、80mm）,次暴雨后考察地表水TP浓度的变化。结果表明,由于雨滴击溅破坏了稻田表层土壤结构,导致地表水中悬浮物和TP浓度增加;一定深度的水层能有效减少悬浮物浓度和TP浓度,水层越深效果越明显,雨后地表水悬浮物浓度和TP的浓度从高到低顺序为20mm〉40mm〉60mm〉8...