基于多源数据的内蒙古察汗淖尔流域作物生育期实际蒸散发分析

探究区域作物生育期实际蒸散发及其空间分布特征,为区域节水潜力评价提供依据.研究结合多源数据(种植结构、遥感数据和气象数据等)和遥感陆面蒸散反演方法,得到作物实际蒸散发(ET),并根据作物不同生长阶段的变化特点结合气象资料估算遥感数据缺失时期的ET.①基于遥感数据和SEBAL模型能够准确反演流域空间尺度的日蒸散发量,其生育初期和中期平均误差分别为11.49％和6.22％.5-7月,日蒸散发逐渐增大,且在7月达到峰值,8-10月日蒸散发逐渐降低,9-10月降低趋势较大;②不同作物之间,生育期ET差异明显,甜菜>土豆>玉米>小麦,分别为619.72 mm、558.67 mm、492.51 mm、456.58 mm.作物生育期ET变化范围分别在476.02～795.73 mm、405.41～684.84 mm、345.11～683.35 mm和313.34～604.62 mm之间;③同种作物因灌溉制度不同,其作物生育期ET在空间上表现出差异性.受流域南北降雨不均影响,4种主要作物生育期ET呈现明显的由南向北递减趋势.北部湖泊附近的小麦,因土壤含水量较高,其生育期ET高于周边其他区域.针对内蒙古察汗淖尔流域内作物生育期ET空间分布差异明显,部分区域地下水超采严重等特点,调整流域内种植结构及灌溉制度尤为重要.     

基于数据融合算法的灌区蒸散发空间降尺度研究

采用Landsat和MODIS数据,通过增强自适应融合算法(Enhanced spatial and temporal adaptive reflectance fusion model,ESTARFM)对蒸散发进行空间降尺度,构建田块尺度蒸散发数据集;利用2015年田间水量平衡方法计算的蒸散发数据对融合结果进行评价。在融合蒸散发基础上,结合解放闸灌域2000—2015年间种植结构信息,提取不同作物各自生育期和非生育期内年际蒸散发量,并分析了大型灌区节水改造以来,作物蒸散发占比的年际变化。研究结果表明:融合蒸散发与水量平衡蒸散发变化过程较吻合,小麦耗水峰值出现在6月中下旬—7月初,玉米和向日葵峰值出现在7月份。在相关性分析中,玉米、小麦和向日葵的决定系数R2分别达到了0.85、0.79和0.82;生育期内玉米(5—10月份)、小麦(4—7月份)和向日葵(6—10月份)的均方根误差均不高于0.70 mm/d;平均绝对误差均不高于0.75 mm/d;相对误差均不高于16%。在农田蒸散发总量验证中,融合蒸散发与水量平衡蒸散发相关性较好,两者决定系数达到了0.64。基于ESTARFM融合算法生成的高分辨率蒸散发(ET)结果可靠,具有较好的融合精度。融合结果与Landsat蒸散发的空间分布和差异性一致,7月23日、8月24日和9月1日相关系数分别达到0.85、0.81和0.77;差值均值分别为0.24 mm、0.19 mm和0.22 mm;标准偏差分别为0.81 mm、0.72 mm和0.61 mm。ESTARFM融合算法在农田蒸散发空间降尺度得到较好的应用,可有效区分不同作物蒸散发之间的差异。不同作物在生育期和非生育期内耗水量差别较大;生育期内套种(4—10月份)耗水量最大,达到637 mm,玉米(5—10月份)和向日葵(6—10月份)次之,分别为598 mm和502 mm,小麦(4—7月份)最低为412 mm;非生育期内,小麦(8—10月份)耗水量最大,年均达到214 mm,玉米(4月份)和向日葵(4—5月份)分别为42 mm和128 mm。不同作物多年平均耗水量(4—10月份)差异较小,其年际耗水总量主要随作物种植面积的变化而变化。     

下垫面特征变化对于旱区蒸散发的影响

下垫面土地利用类型及其变化对蒸散发(ET)的影响机制是一个重要课题,对旱区农业发展具有十分重要的意义。随着气候变化和人类活动范围扩张,中国旱区黄土高原的下垫面土地利用类型发生了巨大的改变,区域蒸发能力发生显著变化。结合卫星遥感数据和地面观测数据,基于Penman-Monteith-Leuning蒸散发反演模型,收集2010-2015年旱区内98个站点的土地利用类型数据,对区域ET值变化特征进行定量研究。分析不同下垫面土地利用类型的蒸发能力变化特征,重点观察水田、旱地、草地转变为城市的过程对蒸散发的影响。发现旱地城镇化过程显著增加了区域蒸散发能力,ET变化幅度为0.044 9 mm/a。草地城镇化削弱了区域蒸发能力,ET变化幅度为-0.024 8 mm/a。水田城镇化过程中,区域蒸发能力没有明显变化。     

一种简化蒸散发遥感反演模型及其在灌区的应用

提出简化的地表能量平衡模型(SSEB)将站点作物蒸散发量递推到整个灌区。首先由气象观测资料计算作物潜在蒸散发量,结合Landsat ETM+60 m热红外波段反演的地表温度差异把站点单日ET扩展到灌区,再融合ETM+和MODIS 1 km热红外时间系列数据,进一步提取全年灌区尺度蒸散发分布图。用湖北漳河灌区2000年的影像资料,将SSEB与SEBAL模型计算结果进行对比,结果表明,二者的决定系数R2达到了0.89。漳河灌区蒸散发主要来源于二、三干渠,年总蒸散发量中,作物蒸发蒸腾占67%,林地蒸散发占17%,水面加上裸地等其它用地的无效蒸散发占16%。     

吉兰泰及周边地区蒸散发的时空变化规律

【目的】探索吉兰泰及周边地区蒸散发的时空变化规律。【方法】以吉兰泰为对象,利用MODIS数据通过SEBAL模型估算了研究区2017年植被生长季5—10月的日蒸散发,并分析了蒸散发与环境因子的相关性。【结果】①生长季日平均蒸散量整体趋势呈单峰型分布趋势,日均蒸散量最大值在7月(3.98 mm),最小值在10月(1.11 mm);②在空间分布上,研究区东南部蒸散发最高,东北部蒸散发最低;不同土地利用类型中蒸散发值由大到小分别为林地、耕地、草地、戈壁、沙漠;各土地利用类型蒸散发量的时间动态表现一致,呈生长期>生长初期>生长后期;③归一化植被指数、高程与蒸散发正相关,风速以及地表温度与蒸散发负相关。【结论】SEBAL模型估算的蒸散发与P-M作物系数法的蒸散发进行对比,相对误差在允许范围之内,表明SEBAL模型对本研究区蒸散发的估算是可靠的。研究区靠近山地的蒸散发大于荒漠区的蒸散发。在植被生长季中生长初期的蒸散发受温度和风速影响最大,生长期和生长后期的蒸散发受地表温度和高程影响最大。     

考虑坡面地形的蒸散发遥感估算及空间分布研究

为了研究非均匀地表的蒸散特征,结合地面气象资料,考虑地形效应增加了坡地辐射计算方法,结合Landsat 8波段特征构建双层蒸散发遥感模型。以北京市西北方位的水源上游区为例,进行了蒸散发的估算、验证与分析。估算结果与地表通量站实测值对比发现,感热通量和潜热通量的平均误差分别为4.12%和8.36%,确定系数为0.82和0.98,相关关系较强;与坡地日蒸散发观测数据对比,平均相对误差为8.12%,均方根误差为0.35mm/d,具有较好的估算精度。结合土地利用探讨了水热通量、蒸散发的空间分布情况,同时分析了蒸散发与坡面地形之间的关系:坡度小于35°时,随坡度上升,日蒸散发有较为明显的增加趋势;当坡度大于35°时,受植被覆盖率影响,各季节代表日的日蒸散发呈现不同的变化趋势。各季节代表日蒸散发与坡向同样存在较为显著的相关关系,趋势线呈反抛物线。     

基于遥感蒸散发模型的净灌溉水量测算空间尺度研究

[目的]农业用水总量和灌溉水有效利用系数是最严格水资源管理考核总量红线和效率红线控制的重要指标.目前遥感蒸散发模型在珠江片区域蒸散发量估算和净灌溉水量评估的应用度不高,对其空间适用尺度缺乏研究.[方法]以广西区为例,通过试验观测-遥感解译等技术计算不同空间尺度遥感蒸散发量,并与相应尺度直接量测的净灌溉水量建立线性相关关...     

石羊河流域典型畦灌玉米蒸散发量变化规律及归因分析

【目的】明确石羊河流域典型畦灌玉米蒸散发量变化规律及其驱动因素。【方法】基于涡度相关系统,在2015—2018年于中国农业大学石羊河试验站对西北典型畦灌玉米蒸散发量进行了连续观测。基于偏相关分析及结构方程模型分析了玉米蒸散发量与环境因子之间的关系。【结果】畦灌玉米生育期平均蒸散发量为524.3 mm,日平均蒸散发量为3.5 mm/d,生育期内日蒸散发量呈先上升后下降的单峰变化趋势,在7月达到峰值。净辐射量与蒸散发量之间的相关性最高,对蒸散发量影响程度较大的环境因子为净辐射量、温度、饱和水汽压差。结构方程结果表明,叶面积指数作为中间变量与蒸散发量之间存在正相关性。【结论】畦灌玉米生育期内日蒸散发量呈先上升后下降的变化趋势,净辐射量、温度、饱和水汽压差是对蒸散发量影响较大的环境因子。     

基于SEBAL模型和环境卫星的区域蒸散发量及灌溉水利用系数估算研究

【目的】探索基于遥感技术建立准确快捷评估区域蒸散发量和灌溉水利用系数的方法。【方法】以河套灌区义长灌域为研究区,基于SEBAL(Surface Energy Balance Algorithm for Land)模型和较高时空分辨率的环境卫星影像,建立了SEBAL遥感蒸散发估算模型,并与降水量、灌水量和地下水位数据结合,计算了研究区的灌溉水利用系数。【结果】SEBAL模型反演的作物蒸散发量的平均绝对误差在5%以内;2013—2017年研究区灌溉水利用系数在0.427～0.572之间,平均值0.492,高于河套灌区的平均水平。人民支渠区的灌溉水利用系数在0.447～0.688之间,均值为0.516。研究区地下水补给量均值为52.13 mm,约占灌水量的3%～7%,忽略地下水补给量会对灌溉水利用系数准确计算带来0.03～0.08的误差。【结论】基于SEBAL遥感蒸散发模型快速测算了灌溉水利用系数,计算结果具有较好的精度和可信度。模型尺度差异性较小,在不同空间尺度的适用性较好。     

基于MODIS数据的区域蒸散发估算研究

应用遥感方法计算区域蒸散发具有很多常规方法所没有的优势.在基于地表能量平衡原理的SEBAL模型基础上提出了将新一代对地观测数据MODIS应用于反演区域地表蒸散的计算方法,并对新疆焉耆盆地的日蒸散发与月蒸散发情况进行了计算模拟,获取了相关地面特征参数.通过与基于ETM数据的SEBAL模型计算结果进行对比分析,验证了MODIS数据计算结果的合理性,并利用研究区实测水面蒸发值与区域水均衡方法对MODIS计算结果进行进一步的验证,说明了利用MODIS数据反演区域蒸散发的方法是切实可行的.     

Estimation of evapotranspiration,transpiration ratio and water-use efficiency from a sparse canopy using a compartment model

Using the Shuttleworth and Wallace (S–W) model, evapotranspiration (ET); transpiration ratio (T/ET), which is the ratio of transpiration (T) to ET; and water-use efficiency (WUE) were estimated for a sparsely planted sorghum canopy that was well irrigated. That model is designed to estimate separately the evaporation from soil and transpiration from crops.The evapotranspiration estimates for both short- and long-term measurement periods coincided closely with the Bowen ratio energy balance (BREB) measurements. The transpiration ratios were affected by the canopy resistances and the soil surface resistances during the day. The regression curve between leaf area index (LAI) and transpiration ratio suggests that LAI, less than 1.6, determined the transpiration ratio in the absence of water stresses by soil water drought and extreme weather condition. The WUEs for transpiration (WUEt) and evapotranspiration (WUEet), which are the total dry matter (TDM) production for 1 kg T and ET, reached the peaks of 9.0 and 4.5 g kg⁻¹ H₂O, respectively, in the end of July when the total dry matter increasing rate was greatest. These two WUEs degraded to less than zero in the end of August when the plant biomass decreased due to drying and death. The WUEs are largely affected by the TDM seasonal increment rate.Thus, in a sparse crop, the crop growth properties (i.e. LAI and TDM increment) mainly determine the crop water uses (i.e. the transpiration ratio and water-use efficiency) in the absence of water stresses.     

Surface energy balance model of transpiration from variable canopy cover and evaporation from residue-covered or bare soil systems: model evaluation

A surface energy balance model (SEB) was extended by Lagos et al. Irrig Sci 28:51–64 (2009) to estimate evapotranspiration (ET) from variable canopy cover and evaporation from residue-covered or bare soil systems. The model estimates latent, sensible, and soil heat fluxes and provides a method to partition evapotranspiration into soil/residue evaporation and plant transpiration. The objective of this work was to perform a sensitivity analysis of model parameters and evaluate the performance of the proposed model to estimate ET during the growing and non-growing season of maize (Zea Mays L.) and soybeans (Glycine max) in eastern Nebraska. Results were compared with measured data from three eddy covariance systems under irrigated and rain-fed conditions. Sensitivity analysis of model parameters showed that simulated ET was most sensitive to changes in surface canopy resistance, soil surface resistance, and residue surface resistance. Comparison between hourly estimated ET and measurements made in soybean and maize fields provided support for the validity of the surface energy balance model. For growing season’s estimates, Nash–Sutcliffe coefficients ranged from 0.81 to 0.92 and the root mean square error (RMSE) varied from 33.0 to 48.3 W m^?2. After canopy closure (i.e., after leaf area index (LAI = 4) until harvest), Nash–Sutcliffe coefficients ranged from 0.86 to 0.95 and RMSE varied from 22.6 to 40.5 W m^?2. Performance prior to canopy closure was less accurate. Overall, the evaluation of the SEB model during this study was satisfactory.     

Combining an ecological model with remote sensing and GIS techniques to monitor soil water content of croplands with a monsoon climate

Soil water is an important factor affecting photosynthesis, transpiration, growth, and yield of crops. Accurate information on soil water content (SWC) is crucial for practical agricultural water management at various scales. In this study, remotely sensed parameters (leaf area index, land cover type, and albedo) and spatial data manipulated using the geographic information system (GIS) technique were assimilated into the boreal ecosystem productivity simulator (BEPS) model to monitor SWC dynamics of croplands in Jiangsu Province, China. The monsoon climate here is characterized by large interannual and seasonal variability of rainfall causing periods of high and low SWC. Model validation was conducted by comparing simulated SWC with measurements by a gravimetric method in the years 2005 and 2006 at nine agro-meteorological stations. The model-to-measurement R² values ranged from 0.40 to 0.82. Nash-Sutcliffe efficiency values were in the range from 0.10 to 0.80. Root mean square error (RMSE) values ranged from 0.028 to 0.056 m³ m⁻³. Simulated evapotranspiration (ET) was consistent with ET estimated from pan evaporation measurements. The BEPS model successfully tracked the dynamics and extent of the serious soil water deficit that occurred during September-November 2006. These results demonstrate the applicability of combining process-based models with remote sensing and GIS techniques in monitoring SWC of croplands and improving agricultural water management at regional scales in a monsoon climate.     

冬小麦、春玉米间作条件下作物需水规律

通过田间试验研究了冬小麦、春玉米间作条件下各生育期的作物需水规律.结果表明:与单作相比,第1个试验期内冬小麦全生育期内间作麦田土壤蒸发量增加34.63 mm,作物蒸腾量减小65.81 mm, 蒸发蒸腾量减小31.18 mm.第2个试验期内冬小麦生育期内间作麦田土壤蒸发量增加26.00 mm,作物蒸腾量减小64.81 mm, 蒸发蒸腾量减小40.81 mm.与单作春玉米相比,间作春玉米的土壤蒸发减少了40.94 mm,作物蒸腾增加了147.73 mm,ET值增加了106.79 mm.可为间作种植的水分管理提供参考.     

Remote sensing to estimate ET-fluxes and the performance of an irrigation district in southern Italy

Satellite remote sensed data on canopy biophysical properties, ground data and agro-meteorological information were combined to estimate evapotranspiration (ET) fluxes of orange orchards using a modified Penman–Monteith equation. The study was carried out during the irrigation season 2004 in an irrigation district, cover for about 95% with orange groves, of 1550 ha located in eastern Sicily (Italy). The spatial pattern in ET-fluxes have been analysed using IKONOS high-resolution satellite and hyper-spectral ground data acquired and processed for the study-area. The remote estimates of ET-fluxes varied between 1.3 and 5.7 mm/day, with a daily average value of about 4.2 mm, showing a good agreement with crop ET values determined as residual of soil water balance of selected ground control sites. Crop coefficient estimates ranged between 0.22 and 1.08 showing positive correlations with percentages of ground cover (C_g) increasing from 30 to 80% ground shading and with LAI values. By comparing ET estimates with water volumes supplied in each sub-district of the study-area, the performance indicator “IP” was evaluated, allowing to rank the conditions of un-fulfilment of crop water requirements by public and private water distribution systems. Generally, out of 29 sub-districts, 14 had “IP” values less than 50%, revealing a sub-optimal water supply for the study-area.     

基于蒸渗仪的冬小麦-夏玉米ET估算模型特征参数研究

为快速准确估算农田蒸散量,利用24个群集式蒸渗仪,在国家节水灌溉北京工程技术研究中心大兴节水灌溉试验站进行了两年的灌溉试验,获得冬小麦-夏玉米生育期的日内冠气温差和实际日蒸散量(ET_a)等数据,对不同水分处理下的S-I蒸散量估算模型进行率定及验证,并分析模型特征参数a、b的变化规律及两者的差异。结果表明:冬小麦的S-I模型特征参数a在日间随时间变化先增大、后减小,在严重水分胁迫处理时a为负值、且数值较小,其余灌溉处理时参数a由正值逐渐变化至负值;不同灌水处理b均为负值,充分灌溉处理时b在日间随时间变化逐渐增大,严重水分胁迫处理时b相对较大,日间变化趋势不稳定。水分胁迫对夏玉米模型参数的影响程度低于冬小麦,特征参数a均为正值,参数b均为负值,且随时间变化逐渐增大;水分胁迫处理时b变化范围明显小于其他两个处理,干旱处理特征参数日间变化较大。冬小麦与夏玉米不同处理之间模型参数a、b变化差异较大,但冠层温度和空气温度差T_c-T_a与日蒸散量和日净辐射量差ET_d-Rn_d间拟合精度都在13:00时最高,此时充分灌溉冬小麦和夏玉米的模型参数a、b分别为1.082、-1.127和1.588、-1.363。利用率定的S-I模型计算冬小麦和夏玉米主要生育期ET_d与实测ET_a之间的决定系数R~2均在0.7以上,均方根误差RMSE均小于0.89 mm/d,一致性系数d均在0.9以上。尤其是充分灌溉处理的数据间R~2和d均较高,RMSE小于其他处理,说明水分胁迫影响模型的估算精度,S-I模型能够更准确地估算水分胁迫较少农田的蒸散量。     

夏玉米生育期叶面蒸腾与棵间蒸发比例试验研究

利用大型称重式蒸渗仪测定夏玉米生育期的总腾发量,用小型蒸发器测定棵间蒸发量,用茎流计测定叶面蒸腾量。通过3种设备实测数据的对比分析,得到夏玉米生育期的总耗水量为436.3 mm,其中叶面蒸腾316.4 mm,棵间蒸发119.9 mm,棵间蒸发占总腾发量的比例达到27.5%。茎流计所测得的蒸腾量与大蒸渗仪和小蒸发器联合测得的蒸腾量相关性良好,从而验证了用茎流计法测定叶面蒸腾方法的可行性。根据茎流计实测数据分析了叶面蒸腾的日变化过程,发现夏玉米叶面蒸腾与净辐射密切相关,呈周期性变化。     

Using remote sensing to evaluate the spatial variability of evapotranspiration and crop coefficient in the lower Rio Grande Valley,New Mexico

Pecan is a major crop in the lower Rio Grande Valley (LRGV), New Mexico. Currently, about 11,000 ha of pecan orchards at various stages of growth are consuming about 40% of irrigation water in the area. Pecan evapotranspiration (ET) varies with age, canopy cover, soil type and method of water management. There is a need for better quantification of pecan ET for the purpose of water rights adjudication, watershed management and agronomical practices. This paper describes a process where remote sensing information from Landsat-5 and Landsat-7 were combined with ground level measurements to estimate pecan ET and field scale actual crop coefficient (K _c) for the LRGV. The results showed that annual pecan water use for 279 fields ranged from 498 to 1,259 mm with an average water use of 1,054 mm. For fields with NDVI > 0.6 (normalized difference vegetation index), which represented mature orchards (total of 232 fields), the annual water use ranged from 771 to 1,259 mm with an average water use of 1,077 mm. The results from remote sensing model compared reasonably well with ground level ET values determined by an eddy covariance system in a mature pecan orchard with an average error of 4% and the standard error of estimate (SEE) ranging from 0.91 to 1.06 mm/day. A small fraction (5%) of the pecan fields were within the range of maximum ET and K _c.     

Quantifying water stress on wheat using remote sensing in the Yaqui Valley, Sonora, Mexico

Remote sensing can allow a more efficient irrigation water management by applying the water when crops require it or when symptoms of water stress appear. In this study, the spatial and temporal distribution of the water deficit index (WDI) and crop evapotranspiration (ET) in wheat were determined through analysis of satellite-based remote sensing images in the Yaqui Valley, Sonora, México. We utilize an empirical model based on the canopy temperature–vegetation cover relationship methodology known as the Moran's trapezoid. We analyze and discuss the spatial and temporal distributions of WDI and ET at the regional and local scales. Results show a linear relationship (R² = 0.96) between the values of WDI and the number of days elapsed since the last irrigation. The water deficit index could be utilized to estimate the quantity of available water in wheat and to know the degree of stress presented by the crop. Advantages offered by this methodology include obtaining WDI and evapotranspiration values in zones with partial or null vegetation cover and for large irrigation schemes lacking the necessary data for traditional water management.