Spatially varied soil erosion under different climates     

PIERRE Y. JULIEN  MARTA GONZALEZ DEL TANAGO 《水文科学杂志》2013,58(6):511-524

Abstract

The spatial variability of the factors of the universal soil loss equation is examined on the mediterranean basin of Conca de Tremp covering 43.1 km² in Spain. The evaluation of the rainfall erosivity R and the soil erodibility K is relatively straightforward and spatially-averaged values of these parameters can be applied to the entire basin. Conversely, the spatial variability of annual soil erosion losses on large basins depends primarily on the factors L, S and C describing topographic, vegetation and land use parameters. A grid size analysis of soil erosion losses from the Conca de Tremp basin under mediterranean climatic conditions in Spain shows excellent agreement with the earlier results on the Chaudière basin in Canada. It is concluded for both basins that unbiassed estimates of soil erosion losses are obtained for grid sizes less than about 0.125 km². The analysis of the Conca de Tremp basin validates the use of the grid size factor proposed by Julien & Frenette (1987). It is also found that the grid size factor primarily depends on the average slope gradient which decreases with increasing grid size or drainage area. On the other hand, the grid size factor does not depend on the spatial variability of the factors R, K, L and C.  相似文献   

From drought to flood: A water balance analysis of the Tuolumne River basin during extreme conditions (2015–2017)     

Andrew R. Hedrick  Danny Marks  Hans-Peter Marshall  James McNamara  Scott Havens  Ernesto Trujillo  Micah Sandusky  Mark Robertson  Micah Johnson  Kat J. Bormann  Thomas H. Painter 《水文研究》2020,34(11):2560-2574

The degree to which the hydrologic water balance in a snow-dominated headwater catchment is affected by annual climate variations is difficult to quantify, primarily due to uncertainties in measuring precipitation inputs and evapotranspiration (ET) losses. Over a recent three-year period, the snowpack in California's Sierra Nevada fluctuated from the lightest in recorded history (2015) to historically heaviest (2017), with a relatively average year in between (2016). This large dynamic range in climatic conditions presents a unique opportunity to investigate correlations between annual water availability and runoff in a snow-dominated catchment. Here, we estimate ET using a water balance approach where the water inputs to the system are spatially constrained using a combination of remote sensing, physically based modelling, and in-situ observations. For all 3 years of this study, the NASA Airborne Snow Observatory (ASO) combined periodic high-resolution snow depths from airborne Lidar with snow density estimates from an energy and mass balance model to produce spatial estimates of snow water equivalent over the Tuolumne headwater catchment at 50-m resolution. Using observed reservoir inflow at the basin outlet and the well-quantified snowmelt model results that benefit from periodic ASO snow depth updates, we estimate annual ET, runoff efficiency (RE), and the associated uncertainty across these three dissimilar water years. Throughout the study period, estimated annual ET magnitudes remained steady (222 mm in 2015, 151 mm in 2016, and 299 mm in 2017) relative to the large differences in basin input precipitation (547 mm in 2015, 1,060 mm in 2016, and 2,211 mm in 2017). These values compare well with independent satellite-derived ET estimates and previously published studies in this basin. Results reveal that ET in the Tuolumne does not scale linearly with the amount of available water to the basin, and that RE primarily depends on total annual snowfall proportion of precipitation.  相似文献   

Assessing climate change impacts on the ecohydrology of the Jinghe River basin in the Loess Plateau,China     

Hui Peng  Yangwen Jia  Yaqin Qiu  Cunwen Niu  Xiangyi Ding 《水文科学杂志》2013,58(3):651-670

Abstract

Quantifying the impacts of climate change on the hydrology and ecosystem is important in the study of the Loess Plateau, China, which is well known for its high erosion rates and ecosystem sensitivity to global change. A distributed ecohydrological model was developed and applied in the Jinghe River basin of the Loess Plateau. This model couples the vegetation model, BIOME BioGeochemicalCycles (BIOME-BGC) and the distributed hydrological model, Water and Energy transfer Process in Large river basins (WEP-L). The WEP-L model provided hydro-meteorological data to BIOME-BGC, and the vegetation parameters of WEP-L were updated at a daily time step by BIOME-BGC. The model validation results show good agreement with field observation data and literature values of leaf area index (LAI), net primary productivity (NPP) and river discharge. Average climate projections of 23 global climate models (GCMs), based on three emissions scenarios, were used in simulations to assess future ecohydrological responses in the Jinghe River basin. The results show that global warming impacts would decrease annual discharge and flood season discharge, increase annual NPP and decrease annual net ecosystem productivity (NEP). Increasing evapotranspiration (ET) due to air temperature increase, as well as increases in precipitation and LAI, are the main reasons for the decreasing discharge. The increase in annual NPP is caused by a greater increase in gross primary productivity (GPP) than in plant respiration, whilst the decrease in NEP is caused by a larger increase in heterotrophic respiration than in NPP. Both the air temperature increase and the precipitation increase may affect the changes in NPP and NEP. These results present a serious challenge for water and land management in the basin, where mitigation/adaption measures for climate change are desired.

Editor Z.W. Kundzewicz; Associate editor D. Yang

Citation Peng, H., Jia, Y.W., Qiu, Y.Q., and Niu, C.W., 2013. Assessing climate change impacts on the ecohydrology of the Jinghe River basin in the Loess Plateau, China. Hydrological Sciences Journal, 58 (3), 651–670.  相似文献   

应用MODIS数据监测千岛湖流域植被覆盖动态(2001-2013年)     

汤旭光  李恒鹏  聂小飞  李鹏程 《湖泊科学》2015,27(3):511-518

流域植被覆盖状况对于水源地生态环境保护具有重要的指示作用.当前的水质目标管理不仅要着眼于湖库水质参数控制,更应该从整个流域的角度维系生态平衡.在此背景下,依托长时间序列MODIS遥感数据对千岛湖流域2001-2013年植被覆盖状况进行监测,采用最小二乘法趋势分析和Mann-Kendall显著性检验方法分析了千岛湖流域植被的空间分布特征、时间变化特征与长期变化趋势.研究表明该方法能够有效地监测流域植被覆盖的时空动态变化:1)从空间分布上来看,千岛湖流域植被覆盖状况整体较好,但同时也发现受人为干扰较大的地域如河、湖附近的城镇建设用地、农业用地以及园地,其NDVI值明显低于自然林地;2)从时间变化特征上看,2001-2013年千岛湖流域植被年际NDVI在0.69~0.73之间波动,且近年来有增长趋势,年内季节性NDVI动态分析表明高时间分辨率的MODIS数据能够用来区分常绿植被与落叶植被的物候特征,以分析不同植被类型对流域氮、磷流失的风险差异;3)从变化趋势上看,2001-2013年植被覆盖状况改善的区域远大于退化的区域,其中改善区域约占流域面积的55.90%,呈现出一定退化状态的区域约占29.60%(严重退化区域仅占3.97%),而相对稳定不变区域约占14.51%.经与气温与降水等气候因子进行相关性分析表明,植被NDVI与气温呈显著正相关,而降水则不敏感,说明气温是研究区植被生长的主导气候因子.同时发现,人类活动对局部植被变化影响较大.研究结果可为流域水资源与生态环境保护提供空间数据支撑.  相似文献   

Climate sensitivity of water use by riparian woodlands at landscape scales     

Marc Mayes  Kelly K. Caylor  Michael Bliss Singer  John C. Stella  Dar Roberts  Pamela Nagler 《水文研究》2020,34(25):4884-4903

Semi-arid riparian woodlands face threats from increasing extractive water demand and climate change in dryland landscapes worldwide. Improved landscape-scale understanding of riparian woodland water use (evapotranspiration, ET) and its sensitivity to climate variables is needed to strategically manage water resources, as well as to create successful ecosystem conservation and restoration plans for potential climate futures. In this work, we assess the spatial and temporal variability of Cottonwood (Populus fremontii)-Willow (Salix gooddingii) riparian gallery woodland ET and its relationships to vegetation structure and climate variables for 80 km of the San Pedro River corridor in southeastern Arizona, USA, between 2014 and 2019. We use a novel combination of publicly available remote sensing, climate and hydrological datasets: cloud-based Landsat thermal remote sensing data products for ET (Google Earth Engine EEFlux), Landsat multispectral imagery and field data-based calibrations to vegetation structure (leaf-area index, LAI), and open-source climate and hydrological data. We show that at landscape scales, daily ET rates (6–10 mm day⁻¹) and growing season ET totals (400–1,400 mm) matched rates of published field data, and modelled reach-scale average LAI (0.80–1.70) matched lower ranges of published field data. Over 6 years, the spatial variability of total growing season ET (CV = 0.18) exceeded that of temporal variability (CV = 0.10), indicating the importance of reach-scale vegetation and hydrological conditions for controlling ET dynamics. Responses of ET to climate differed between perennial and intermittent-flow stream reaches. At perennial-flow reaches, ET correlated significantly with temperature, whilst at intermittent-flow sites ET correlated significantly with rainfall and stream discharge. Amongst reaches studied in detail, we found positive but differing logarithmic relationships between LAI and ET. By documenting patterns of high spatial variability of ET at basin scales, these results underscore the importance of accurately accounting for differences in woodland vegetation structure and hydrological conditions for assessing water-use requirements. Results also suggest that the climate sensitivity of ET may be used as a remote indicator of subsurface water resources relative to vegetation demand, and an indicator for informing conservation management priorities.  相似文献   

Spatial Quantification of Groundwater Abstraction in the Irrigated Indus Basin     

M.J.M. Cheema  W.W. Immerzeel  W.G.M. Bastiaanssen 《Ground water》2014,52(1):25-36

Groundwater abstraction and depletion were assessed at a 1‐km resolution in the irrigated areas of the Indus Basin using remotely sensed evapotranspiration (ET) and precipitation; a process‐based hydrological model and spatial information on canal water supplies. A calibrated Soil and Water Assessment Tool (SWAT) model was used to derive total annual irrigation applied in the irrigated areas of the basin during the year 2007. The SWAT model was parameterized by station corrected precipitation data (R) from the Tropical Rainfall Monitoring Mission, land use, soil type, and outlet locations. The model was calibrated using a new approach based on spatially distributed ET fields derived from different satellite sensors. The calibration results were satisfactory and strong improvements were obtained in the Nash‐Sutcliffe criterion (0.52 to 0.93), bias (?17.3% to ?0.4%), and the Pearson correlation coefficient (0.78 to 0.93). Satellite information on R and ET was then combined with model results of surface runoff, drainage, and percolation to derive groundwater abstraction and depletion at a nominal resolution of 1 km. It was estimated that in 2007, 68 km³ (262 mm) of groundwater was abstracted in the Indus Basin while 31 km³ (121 mm) was depleted. The mean error was 41 mm/year and 62 mm/year at 50% and 70% probability of exceedance, respectively. Pakistani and Indian Punjab and Haryana were the most vulnerable areas to groundwater depletion and strong measures are required to maintain aquifer sustainability.  相似文献   

Trends in land surface evapotranspiration across China with remotely sensed NDVI and climatological data for 1981–2010     

X. Mo  S. Liu  Z. Lin  S. Wang  S. Hu 《水文科学杂志》2013,58(12):2163-2177

Abstract

Using satellite observations of Normalized Difference Vegetation Index (NDVI) from NOAA-AVHRR and Terra-MODIS, together with climatic data in a physical evapotranspiration (ET) model, the spatio-temporal variability of ET is investigated in terrestrial China from 1981 to 2010. The model predictions of actual ET (ET_a) are validated with ET values from in situ eddy covariance flux measurements and from basin water balance calculations. The national averaged crop reference ET (ET_p) and ET_a values are 916 ± 21 and 415 ± 12 mm year^-1, respectively. The annual ET_a pattern is closely associated with vegetation conditions in the eastern part of China, whereas ET_a is low in the sparsely-vegetated areas and deserts in the northwestern region, corresponding to scarce rainfall events and amounts. The trends of ET_p and ET_a are remarkably different over the country, and the complementary relationship between ET_p and ET_a is revealed for the study period. Averaged over the whole country, ET_a showed an increasing trend from the 1980s to the mid-1990s, followed by a decreasing trend, consistent with the precipitation anomaly. Across the main vegetation types, annual ET_a amounts are found to correspond clearly with the bands of precipitation and ET_p.  相似文献   

Improving evapotranspiration estimation models through quantitative watershed parameter analysis and remote sensing applications     

Meimei Xue  Yixuan Pan  Yundi Zhang  Jianping Wu  Wenting Yan  Xiaodong Liu  Yuchan Chen  Guoyi Zhou  Xiuzhi Chen 《水文研究》2024,38(5):e15153

Numerous models had been developed to predict the annual evapotranspiration (ET) in vegetated lands across various spatial scales. Fu's (Scientia Atmospherica Sinica, 5, 23–31) and Zhang's (Water Resources Research, 37, 701–708) ET simulation models have emerged as highly effective and have been widely used. However, both formulas have the non-quantitative parameters (m in Fu's model and w in Zhang's model). Based on the collected 1789 samples from global long-term hydrological studies, this study discovered significant relations between m (or w) and vegetation coverage or greenness in collected catchments. Then, we used these relations to qualify the parameters in both Zhang's and Fu's models. Results show that the ET estimation accuracies of Fu's (or Zhang's) model are significantly improved by about 13.49 mm (or 6.74 mm) for grassland and cropland, 38.52 mm (or 29.84 mm) for forest and shrub land (coverage<40%), 19.74 mm (or 16.17 mm) for mixed land (coverage<40%), respectively. However, Zhang's model shows higher errors compared with Fu's model, especially in regions with high m (or w) values, such as those with dense vegetations or P/E₀ (annual precipitation to annual potential ET) smaller than 1.0. Additionally, this study also reveals that for regions with vegetation cover less than 40%, the annual ET is not only determined by vegetation types, but also relates to the sizes of vegetation-covered areas. Conversely, for regions with vegetation cover more than 40%, the annual ET is mainly determined by the vegetation density rather than vegetation types or vegetation coverage. Thus, linking m (or w) parameters with vegetation greenness allows leveraging remote sensing for forest management in data-scarce areas, safeguarding regional water resources. This study pioneers integrating vegetation-related indices with basin parameters, advocating for their crucial role in more effective hydrological modelling.  相似文献   

利用重力卫星GRACE监测亚马逊流域2002-2010年的陆地水变化   总被引：2，自引：0，他引：2       下载免费PDF全文

冯伟  Jean-Michel LEMOINE  钟敏  许厚泽 《地球物理学报》2012,55(3):814-821

本文利用GRACE (Gravity Recovery and Climate Experiment) 卫星重力资料研究了亚马逊流域2002-2010年的陆地水变化,并与水文模式和降雨资料进行了比较分析.在年际尺度上,GRACE结果表明:2002-2003年和2005年,亚马逊流域发生明显的干旱现象;2007年至2009年,陆地水呈逐年增加的趋势,并在2009年6月变化值达到最大,为772±181 km³;自2009年6月至2010年12月,陆地水总量又急剧减少了1139±262 km³,这相当于全球海平面上升3.2±0.7 mm所需的水量.水文模式得到的亚马逊流域陆地水在2010年也表现出明显的减少.降雨资料与GRACE观测资料有很好的一致性.在2005年和2010年的干旱期,亚马逊流域的降雨显著减少,说明降雨是亚马逊流域陆地水变化的重要因素.此外,本文采用的尺度因子的方法有效地降低了GRACE后处理误差的影响.  相似文献   

Spatial and temporal variation of precipitation in Sudan and their possible causes during 1948–2005     

Zengxin Zhang  Chong-Yu Xu  Majduline El-Haj El-Tahir  Jianrong Cao  V. P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(3):429-441

Temporal and spatial patterns of precipitation are essential to the understanding of soil moisture status which is vital for vegetation regeneration in the arid ecosystems. The purposes of this study are (1) to understand the temporal and spatial variations of precipitation in Sudan during 1948–2005 by using high quality global precipitation data known as Precipitation REConstruction (PREC), which has been constructed at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center, and (2) to discuss the relationship between precipitation variability and moisture flux based on the NCEP/NCAR reanalysis data in order to ascertain the potential causes of the spatial and temporal variations of precipitation in the region. Results showed that (1) annual and monthly precipitation in Sudan had great spatial variability, and mean annual precipitation varied from almost nil in the North to about 1500 mm in the extreme Southwest; (2) precipitation of the main rain season, i.e., July, August and September, and annual total precipitation in the central part of Sudan decreased significantly during 1948–2005; (3) abrupt change points were found in the annual, July, August and September in the late 1960s, when precipitation decreased more rapidly than in other periods; and (4) the decreasing precipitation was associated with the weakening African summer monsoon. The summer moisture flux over Sudan tended to be decreasing after the late 1960s which decreased the northward propagation of moisture flux in North Africa. This study provides a complementary view to the previous studies that attempted to explain the Sahel persistent drought and possible causes.  相似文献   

区域气候模式RegCM3对华北地区未来气候变化的数值模拟   总被引：5，自引：0，他引：5       下载免费PDF全文

张冬峰  石英 《地球物理学报》2012,55(9):2854-2866

采用高水平分辨率区域气候模式进行区域未来气候变化预估,对理解全球增暖对区域气候的潜在影响和科学评估区域气候变化有很好的参考价值.这里对国家气候中心使用25 km高水平分辨率区域气候模式RegCM3单向嵌套全球模式MIROC3.2_hires在观测温室气体(1951—2000)和IPCC A1B温室气体排放情景下(2001—2100)进行的共计150年长时间模拟结果,进行华北地区未来气温、降水和极端气候事件变化的分析.模式检验结果表明:模式对当代(1981—2000)气温以及和气温有关的极端气候事件(霜冻日数、生长季长度)的空间分布和数值模拟较好;对降水及和降水有关的极端气候事件(强降水日期、降水强度、五日最大降水量)能够模拟出它们各自的主要空间分布特征,但在模拟数值上存在偏大、偏强的误差.和全球模式驱动场相比,区域模式模拟的气温、降水和极端气候事件有明显的改进.2010—2100年华北地区随时间区域平均气温升高幅度逐渐增大,随之霜冻日数逐渐减少,生长季长度逐渐增多;同时随温室效应的不断加剧,未来降水呈增加的趋势,强降水日期和五日最大降水量逐渐增多、降水强度逐渐增大.从空间分布看,21世纪末期(2081—2100)气温、降水以及有关的极端气候事件变化比21世纪中期(2041—2060)更加明显.  相似文献   

Scaling and physiographic controls on streamflow behaviour on the Precambrian Shield, south-central Ontario     

J.M. Buttle  M.C. Eimers   《Journal of Hydrology》2009,374(3-4):360-372

Relationships explaining streamflow behaviour in terms of drainage basin physiography greatly assist efforts to extrapolate streamflow metrics from gauged to ungauged basins in the same landscape. The Dorset Environmental Science Centre (DESC) has monitored streamflow from 22 small basins (3.4–190.5 ha) on the Precambrian Shield in south-central Ontario, in some cases since 1976. The basins exhibit regional coherence in their interannual response to precipitation; however, there is often a poor correlation between streamflow metrics from basins separated by as little as 1 km. This study assesses whether inter-basin variations in such metrics can be explained in terms of basin scale and physiography. Several characteristics (annual maximum, minimum and average flow) exhibited simple scaling with basin area, while magnitude, range and timing of annual maximum daily runoff showed scaling behaviour consistent with the Representative Elementary Area (REA) concept. This REA behaviour is partly attributed to convergence of fractional coverage of the two dominant and hydrologically-contrasting land cover types in the DESC region with increasing basin size. Three Principal Components (PCs) explained 82.4% of the variation among basin physiographic properties, and several runoff metrics (magnitude and timing of annual minimum daily runoff, mean number of days per year with 0 streamflow) exhibited significant relationships with one or more PC. Significant relationships were obtained between basin quickflow (QF) production and the PCs on a seasonal and annual basis, almost all of which were superior to simple area-based relationships. Basin physiography influenced QF generation via its control on slope runoff, water storage and hydrologic connectivity; however, this role was minimized during Spring when QF production in response to large rain-on-snow events was relatively uniform across the DESC basins. The PC-based relationships and inter-seasonal changes in their form were consistent with previous research conducted at point, slope and basin scales in the DESC region, and perceptions of key hydrological processes in these small basins may not have been as readily obtained from scaling studies using streamflow from larger basins. This process understanding provides insights into scaling behaviour beyond those derived from simple scaling and REA analyses. The physiography of the study area is representative of large portions of the Precambrian Shield, such that basin streamflow behaviour could potentially be extended across much of south-central Ontario. This would assist predictions of streamflow conditions at ungauged locations, development and testing of hydrological models for this landscape, and interpretation of inter-basin and intra-annual differences in hydrochemical behaviour on the southern Precambrian Shield.  相似文献   

Evaluating actual evapotranspiration and impacts of groundwater storage change in the North China Plain   总被引：2，自引：0，他引：2       下载免费PDF全文

Guoliang Cao  Dongmei Han  Xianfang Song 《水文研究》2014,28(4):1797-1808

As a critical water discharge term in basin‐scale water balance, accurate estimation of evapotranspiration (ET) is therefore important for sustainable water resources management. The understanding of the relationship between ET and groundwater storage change can improve our knowledge on the hydrological cycle in such regions with intensive agricultural land usage. Since the 1960s, the North China Plain (NCP) has experienced groundwater depletion because of overexploitation of groundwater for agriculture and urban development. Using meteorological data from 23 stations, the complementary relationship areal evapotranspiration model is evaluated against estimates of ET derived from regional water balance in the NCP during the period 1993–2008. The discrepancies between calculated ET and that derived by basin water balance indicate seasonal and interannual variations in model parameters. The monthly actual ET variations during the period from 1960 to 2008 are investigated by the calibrated model and then are used to derive groundwater storage change. The estimated actual ET is positively correlated with precipitation, and the general higher ET than precipitation indicates the contributions of groundwater irrigation to the total water supply. The long term decreasing trend in the actual ET can be explained by declining in precipitation, sunshine duration and wind speed. Over the past ~50 years, the calculated average annual water storage change, represented by the difference between actual ET and precipitation, was approximately 36 mm, or 4.8 km³; and the cumulative groundwater storage depletion was approximately 1700 mm, or 220 km³ in the NCP. The significantly groundwater storage depletion conversely affects the seasonal and interannual variations of ET. Irrigation especially during spring cause a marked increase in seasonal ET, whereas the rapid increasing of agricultural coverage over the NCP reduces the annual ET and is the primary control factor of the strong linear relationship between actual and potential ET. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Scaling effects on modeled surface energy-balance components using the NOAH-OSU land surface model   总被引：3，自引：0，他引：3  

V. Sridhar  Ronald L. Elliott  Fei Chen 《Journal of Hydrology》2003,280(1-4):105-123

As surface exchange processes are highly non-linear and heterogeneous in space and time, it is important to know the appropriate scale for the reasonable prediction of these exchange processes. For example, the explicit representation of surface variability has been vital in predicting mesoscale weather events such as late-afternoon thunderstorms initiated by latent heat exchanges in mid-latitude regions of the continental United States. This study was undertaken to examine the effects of different spatial scales of input data on modeled fluxes, so as to better understand the resolution needed for accurate modeling. A statistical procedure was followed to select two cells from the Southern Great Plains 1997 hydrology experiment region, each 20 km×20 km, representing the most homogeneous and the most heterogeneous surface conditions (based on soil and vegetation) within the study region. The NOAH-OSU (Oregon State University) Land Surface Model (LSM) was employed to estimate surface energy fluxes. Three scales of study (200 m, 2 and 20 km) were considered in order to investigate the impacts of the aggregation of input data, especially soil and vegetation inputs, on the model output. Model results of net radiation and latent, sensible and ground heat fluxes were compared for the three scales. For the heterogeneous area, the model output at the 20-km resolution showed some differences when compared with the 200-m and 2-km resolutions. This was more pronounced in latent heat (12% decrease), sensible heat (22% increase), and ground heat flux (44% increase) estimation than in net radiation. The scaling effects were much less for the relatively homogeneous land area with 5% increase in sensible heat and 4% decrease in ground heat flux estimation. All of the model outputs for the 2- and 20-km resolutions were in close agreement. The results suggested that, for this study region, soils and vegetation input resolution of about 2 km should be chosen for realistic modeling of surface exchange processes. This resolution was sufficient to capture the effects of sub-grid scale heterogeneity, while avoiding the data and computational difficulties associated with higher spatial resolutions.  相似文献   

Simulated impacts of irrigation on evapotranspiration in a strongly exploited region: a case study of the Haihe River basin,China          下载免费PDF全文

Huimin Lei  Dawen Yang  Hanbo Yang  Zaijian Yuan  Huafang Lv 《水文研究》2015,29(12):2704-2719

Irrigation is the major water supply for crop production in water‐limited regions. However, this important water component is usually neglected or simplified in hydrological modelling primarily because information concerning irrigation is notably difficult to collect. To assess real effects of irrigation on the simulation of evapotranspiration (ET) in water‐limited region, the Community Land Model version 4 was established over a typical semi‐humid agricultural basin in the northern China – the Haihe River basin. In the irrigated cropland, incorporating an irrigation scheme can enhance the simulated ET and improve the simulation of spatial variability of soil moisture content. We found that different configurations in the irrigation scheme do not cause significant differences in the simulated annual ET. However, simulated ET with simulated irrigation differs clearly from that with observed irrigation in mean annual magnitude, long‐term trend and spatial distribution. Once the irrigation scheme is well‐calibrated against observations, it reasonably reproduces the interannual variability of annual irrigation, when irrigation water management is relatively stable. More importantly, parameter calibration should be consistent with the configuration of the source of irrigation water. However, an irrigation scheme with a constant parameter value cannot capture the trend in the annual irrigation amount caused by abrupt changes in agricultural water management. Compared with different remotely sensed ET products, the enhancement in the simulated ET by irrigation is smaller than the differences among these products, and the trend in simulated ET with the observed irrigation cannot be captured correctly by the remotely sensed ET. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Remote sensing and ground‐based measurements of evapotranspiration in an extreme cold Patagonian desert          下载免费PDF全文

P. M. Cristiano  D. A. Pereyra  S. J. Bucci  N. Madanes  F. G. Scholz  G. Goldstein 《水文研究》2016,30(24):4449-4461

Accurate estimates of seasonal evapotranspiration (ET) at different temporal and spatial scales are essential for understanding the biological and environmental determinants of ecosystem water balance in arid regions and the patterns of water utilization by the vegetation. For this purpose, remote sensing ET estimates of a Patagonian desert in Southern Argentina were verified with field measurements of soil evaporation and plant transpiration using an open top chamber. Root distribution and seasonal variation in soil volumetric water content were also analysed. There was a high correlation between remote sensing and field measurements of ecosystem water fluxes. A substantial amount of the annual ET occurred in spring and early summer (73.4 mm) using winter rain stored in the soil profile and resulting in water content depletion of the upper soil layers. A smaller amount of annual ET was derived from few rainfall events occurring during the mid or late summer (41.4 mm). According to remote sensing, the 92.9% of the mean annual precipitation returns to the atmosphere by transpiration or evaporation from the bare soil and by canopy interception. Only 7.1% infiltrates to soil layers deeper than 200 cm contributing to the water table recharge. Fourier time series analysis, cross‐correlation methods and multiple linear regression models were used to analyse 11 years of remote sensing data to assess determinants of water fluxes. A linear model predicts well the variables that drive complex ecosystem processes such as ET. Leaf area index and air temperature were not linearly correlated to ET because of the multiple interaction among variables resulting in time lags with ET variations and thus these two variables were not included in the linear model. Soil water content, the fraction of photosynthetic active radiation and precipitation explained 86% of the ET monthly variations. The high volumetric water content and the small seasonal variations at 200‐cm depth were probably the result of little water uptake from deeper soil horizons by roots with low hydraulic conductivity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Impact of flooded rice paddy on remotely sensed evapotranspiration in the Krishna River basin,India     

Pardhasaradhi Teluguntla  Dongryeol Ryu  Biju George  Jeffrey P. Walker 《水文研究》2020,34(10):2190-2199

Evapotranspiration (ET) is one of the major water exchange processes between the earth's surface and the atmosphere. ET is a combined process of evaporation from open water bodies, bare soil and plant surfaces, and transpiration from vegetation. Remote sensing-based ET models have been developed to estimate spatially distributed ET over large regions, however, many of them reportedly underestimate ET over semi-arid regions (Jamshidi et al., Journal of Hydrometeorology, 2019, 20, 947–964). In this work, we show that underestimation of ET can occur due to the open water evaporation from flooded rice paddies ignored in the existing ET models. To address the gap in ET estimation, we have developed a novel approach that accounts for the missing ET component over flooded rice paddies. Our method improved ET estimates by a modified Penman-Monteith algorithm that considered the fraction of open water evaporation from flooded rice paddies. Daily ET was calculated using ground based meteorological data and the MODIS satellite data over the Krishna River Basin. Seasonal and annual ET values over the Krishna Basin were compared with two different ET algorithms. ET estimates from these two models were also compared for different crop combinations. Results were validated with flux tower-based measurements from other studies. We have identified a 17 mm/year difference in average annual ET over the Krishna River Basin with this new ET algorithm. This is very critical in basin scale water balance analysis and water productivity studies.  相似文献