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Li H.-Y.,Hydrology Technical Group | Sivapalan M.,University of Illinois at Urbana - Champaign | Tian F.,State Key Laboratory of Hydroscience and Engineering
Water Resources Research | Year: 2014

Inspired by the Dunne diagram, the climatic and landscape controls on the partitioning of annual runoff into its various components (Hortonian and Dunne overland flow and subsurface stormflow) are assessed quantitatively, from a purely theoretical perspective. A simple distributed hydrologic model has been built sufficient to simulate the effects of different combinations of climate, soil, and topography on the runoff generation processes. The model is driven by a sequence of simple hypothetical precipitation events, for a large combination of climate and landscape properties, and hydrologic responses at the catchment scale are obtained through aggregation of grid-scale responses. It is found, first, that the water balance responses, including relative contributions of different runoff generation mechanisms, could be related to a small set of dimensionless similarity parameters. These capture the competition between the wetting, drying, storage, and drainage functions underlying the catchment responses, and in this way, provide a quantitative approximation of the conceptual Dunne diagram. Second, only a subset of all hypothetical catchment/climate combinations is found to be “behavioral,“ in terms of falling sufficiently close to the Budyko curve, describing mean annual runoff as a function of climate aridity. Furthermore, these behavioral combinations are mostly consistent with the qualitative picture presented in the Dunne diagram, indicating clearly the commonality between the Budyko curve and the Dunne diagram. These analyses also suggest clear interrelationships amongst the “behavioral“ climate, soil, and topography parameter combinations, implying these catchment properties may be constrained to be codependent in order to satisfy the Budyko curve. © 2014. American Geophysical Union. All Rights Reserved.

Zhou S.,State Key Laboratory of Hydroscience and Engineering | Wang G.,State Key Laboratory of Hydroscience and Engineering
Water Resources Research | Year: 2016

Evapotranspiration (ET) is dominated by transpiration (T) in the terrestrial water cycle. However, continuous measurement of transpiration is still difficult, and the effect of vegetation on ET partitioning is unclear. The concept of underlying water use efficiency (uWUE) was used to develop a new method for ET partitioning by assuming that the maximum, or the potential uWUE is related to T while the averaged or apparent uWUE is related to ET. T/ET was thus estimated as the ratio of the apparent over the potential uWUE using half-hourly flux data from 17 AmeriFlux sites. The estimated potential uWUE was shown to be essentially constant for 14 of the 17 sites, and was broadly consistent with the uWUE evaluated at the leaf scale. The annual T/ET was the highest for croplands, i.e., 0.69 for corn and 0.62 for soybean, followed by grasslands (0.60) and evergreen needle leaf forests (0.56), and was the lowest for deciduous broadleaf forests (0.52). The enhanced vegetation index (EVI) was shown to be significantly correlated with T/ET and could explain about 75% of the variation in T/ET among the 71 site-years. The coefficients of determination between EVI and T/ET were 0.84 and 0.82 for corn and soybean, respectively, and 0.77 for deciduous broadleaf forests and grasslands, but only 0.37 for evergreen needle leaf forests. This ET partitioning method is sound in principle and simple to apply in practice, and would enhance the value and role of global FLUXNET in estimating T/ET variations and monitoring ecosystem dynamics. © 2016. American Geophysical Union. All Rights Reserved.

Zhao S.,State Key Laboratory of Hydroscience and Engineering | Yang D.,State Key Laboratory of Hydroscience and Engineering
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2011

Neural network is one of the popular and effective models used for hydrological forecasting. One of the major problems of this method is the selection of input variables. This study focuses on this problem and uses the mutual information (MI) to select neural network input variables. Application to the daily discharge forecasting at the Yichang hydrological station before the Three Gorges project shows that MI is an effective technique for selecting the input variables and thus for improving the runoff forecasting accuracy. © Copyright.

Han D.,Tsinghua University | Han D.,State Key Laboratory of Hydroscience and Engineering | Fang H.,Tsinghua University | Fang H.,State Key Laboratory of Hydroscience and Engineering | Chen M.,China Agricultural University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2012

Zero flow often occurs in river channel network in dry season. This paper presents an amended zero flow method for simulation of the impact of zero flow on flow splitting, siltation and erosion. This method combines the advantages of virtual flow area method and zero flow method, and it can correct coefficient matrix according to the zero flow conditions. The new method was applied to the Jingjiang-Dongting Lake region downstream the Three Gorges project to study the flow diversion features of the three lake outlets under the condition of zero flow discharge. The calculations of water level and flow discharge agree well with the measurements. The method avoids excessive estimation of split flow discharge by virtual flow area method and the singular coefficient matrix of zero flow method.

Zhou J.,State key Laboratory of Hydroscience and Engineering | Zhang M.,State key Laboratory of Hydroscience and Engineering | Lin B.,State key Laboratory of Hydroscience and Engineering | Lu P.,Water Environment Monitoring Center for the Upper Reach of Yangtze River
Water Resources Research | Year: 2015

Dams affect ecosystems, but their physical link to the variations in fluvial fluxes and downstream ecological consequences are inadequately understood. After estimating the current effects of the Three Gorges project and other reservoirs upstream on the Yangtze River on the fluvial phosphorus (P) in the middle and lower Yangtze River, we further investigated the long-term effects of dams on the fluvial regimes of P and P-enriched sediment (PES). Simultaneously measured P distributions with sediment size (PDSS) from the Three Gorges Reservoir (TGR) proved that the areal density of particulate P (PP) bound on graded sediment can be measured using the surface area concentration of the total sediment. A PDSS relationship is obtained and the selective transport and long-term sedimentation of P are simulated using a nonuniform suspended sediment model, which incorporates the PDSS formula. The computations revealed that a reservoir would significantly lower the downstream availability of P in the dry season and promote high pulses of P in summer when the reservoir is flushed as sedimentation accumulates. As a result, the P buffering and replenishing mechanism in the pristine ecosystem from upstream supplies and local re-suspension are permanently eliminated when a regulating reservoir is built upstream. This change is irreversible if reservoir regulation continues. Changes could potentially aggravate the existing P-limitation, decrease the water's ability to adjust nutrient/pollutant fluctuations, accumulate a greater surplus of carbon and nitrogen, and even exacerbate blooms in favorable conditions. © 2015. American Geophysical Union. All Rights Reserved.

Li H.-Z.,Central Research Institute of Building and Construction | Hu L.-M.,Tsinghua University | Hu L.-M.,State Key Laboratory of Hydroscience and Engineering | Xin H.-B.,Central Research Institute of Building and Construction
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

The groundwater pollution by organic contaminants is becoming more and more severe, making groundwater remediation be imperative. The researches on the remediation technology are of theoretical and practical importance. Based on the review of in-situ groundwater remediation technology for organic contaminants and micro-nano bubble MNBs technology, MNB technology is proposed for groundwater remediation. The scheme using MNB for in-situ groundwater remediation is introduced. The contaminants can be removed by biodegradation enhanced by MNB. The numerical simulation results of in-situ application show a great enhancement on dissolved oxygen and a significant influence zone for contaminant removal. The MNB technology is effective, energy-efficient and environment-friendly to clean up contaminants, which has great potential in groundwater remediation. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.

Feng D.-K.,State Key Laboratory of Hydroscience and Engineering | Feng D.-K.,Tsinghua University | Hou W.-J.,Ministry of Housing and Urban Rural Development of the Peoples Republic of China | Zhang J.-M.,State Key Laboratory of Hydroscience and Engineering | Zhang J.-M.,Tsinghua University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

A new apparatus is developed to investigate the stress-controlled behavior of the interface between structure and gravelly soil under constant normal stiffness condition. The test results indicate that: (1) the volumetric change is induced by cyclic shear and can be divided into reversible and irreversible parts. The reversible part is governed by tangential displacement amplitude, and the irreversible part is significantly affected by shear distance; (2) the anisotropy of interface volumetric change is obviously observed and has great concern with shear paths and control modes; (3) the tangential displacement accumulates and migrates gradually with shear cycles. The shear paths and control modes have influences on the relationship between shear stress, stress ratio, normal displacement versus tangential displacement; (4) the interface shear strength is gradually mobilized after the first few shear cycles under stress control, and its friction angle is independent of the control modes.

Niu X.,State Key Laboratory of Hydroscience and Engineering | Yu X.,Tsinghua University
Wave Motion | Year: 2011

An analytical solution of the mild-slope wave equation is derived to describe long wave propagating over the idealized dredge excavation pit. The pit is assumed to be axisymmetrical and composed of a flat bottom and a convex slope. The convex slope is expressed by a simple power function. The problem is solved in the polar coordination system by the separation of variables. By the obtained solution, the characteristics of the wave refraction and reflection over the dredge excavation pit are discussed. The results show that wave amplitude is attenuated within and in the lee side of the pit and amplified at the rear flank of the pit due to wave refraction. The effects of the incident wave length and the shape of the pit on wave refraction are also discussed. © 2010 Elsevier B.V.

Chen H.,State Key Laboratory of Hydroscience and Engineering | Chen H.,Tsinghua University | Yang D.,State Key Laboratory of Hydroscience and Engineering | Yang D.,Tsinghua University | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Quantitative estimation of evapotranspiration (ET) plays a significant role in the mechanism study of water cycling and agriculture management. Remotely sensed satellites provide spatial continuous surface parameters, which make estimation of regional surface ET possible. However, surface parameters retrieved by remote sensing data is discontinuous temporally, which can only provide 1-2 instantaneous values at satellite over-passing time. Thus, time scale extrapolation process is of crucial necessity for daily ET estimation. Recently, many ET time scale extrapolation methods have been proposed, such as sine function method, constant evaporative fraction (EF) method, and crop coefficient method. It has been proved that different models have different applicability and accuracy over variant climate conditions and underlying surfaces. Many studies assemble these extrapolation methods into remote sensing models to estimate regional daily ET in China, however, little researches focus on the accuracy assessment of these methods. The purpose of this study is to compare and assess the accuracy of four commonly used ET extrapolation methods over variant climate conditions and vegetation types. The study was conducted at Gaoying flux site located in North China Plain and Tongyu flux long-term land surface processes observational station located in North-east China Plain to represent semi-humid and semi-arid climate respectively. The predominant crops of Gaoying site are winter wheat and summer maize planted in rotation. Tongyu long-term land surface processes observational station has two flux sites located on the sorghum and degraded grassland, respectively. Each site of Tongyu station as well as Gaoying site has an EC system to record half-hour latent heat flux and sensible heat flux. Four commonly used ET extrapolation methods selected from literatures were tested in this study. The selection was carried out considering their applicability to the Remote sensing data used. The first method is the constant evaporative fraction (EF) method, which assumes the evaporative fraction, defined as the ratio between latent heat flux and available energy is stable during daytime under fair weather. The second method is a variance to constant EF method (so called variant EF method), with a change that soil heat flux is neglected. One assumption implied in variant EF method is the average daily soil heat tends to be zero and could be excluded in estimating daily ET. The third method is sine function method, that proposed by the assumption that the ratio of instantaneous latent heat flux to daily ET to the diurnal trend of solar irradiance with a sine curve. The fourth method is the crop coefficient method, which implies the ratio of actual ET to reference ET (i.e. crop coefficient) stays stable during the day. Four wheat seasons and four maize seasons from 2005 to 2008 at Gaoying flux site, two seasons of sorghum, grass land and bare soil at Tongyu flux site are used in this study. By accumulating the half-hour LE measurements, daily ET is calculated and used as validation data. Results show that all the four methods have the similar patterns, but the variant EF method has the best accuracy and performs well over the typical croplands in north China. The assumption implying in the extrapolation methods that a certain parameter (such as EF, crop coefficient, etc.) remains stable during daytime does not work in the study areas. Therefore, estimation derived from morning satellite underestimates the daily evapotranspiration, but overvalues from afternoon satellite. The diurnal pattern of evaporative fraction will come next to get a better understand of extrapolation from instantaneous value to daily evapotranspiration, and a new extrapolation approach will be proposed.

PubMed | Nanjing Medical University, Qingdao Institute of Animal Science and Veterinary Medicine, Qingdao Agricultural University and State key Laboratory of Hydroscience and Engineering
Type: | Journal: BMC genetics | Year: 2015

Sheep are valuable resources for the animal fibre industry. Therefore, identifying genes which regulate wool growth would offer strategies for improving the quality of fine wool. In this study, we employed Agilent sheep gene expression microarray and proteomic technology to compare the gene expression patterns of the body side (hair-rich) and groin (hairless) skins of Aohan fine wool sheep (a Chinese indigenous breed).Comparing the body side to the groin skins (S/G) of Aohan fine wool sheep, the microarray study revealed that 1494 probes were differentially expressed, including 602 more highly expressed and 892 less highly expressed probes. The microarray results were verified by means of quantitative PCR. Cluster analysis could distinguish the body side skin and the groin skin. Based on the Database for Annotation, Visualization and Integrated Discovery (DAVID), 38 of the differentially expressed genes were classified into four categories, namely regulation of receptor binding, multicellular organismal process, protein binding and macromolecular complex. Proteomic study revealed that 187 protein spots showed significant (p < 0.05) differences in their respective expression levels. Among them, 46 protein entries were further identified by MALDI-TOF/MS analyses.Microarray analysis revealed thousands of differentially expressed genes, many of which were possibly associated with wool growth. Several potential gene families might participate in hair growth regulation. Proteomic analysis also indentified hundreds of differentially expressed proteins.

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