ABSTRACT: To quantify the influences of soil heterogeneity on infiltration, a spatial averaging infiltration model for layered soil
(SAI model) is developed by coupling the spatial averaging approach proposed by Chen et al. and the Generalized Green-Ampt
model proposed by Jia et al. In the SAI model, the spatial heterogeneity along the horizontal direction is described by a
probability distribution function, while that along the vertical direction is represented by the layered soils. The SAI model
is tested on a typical soil using Monte Carlo simulations as the base model. The results show that the SAI model can directly
incorporate the influence of spatial heterogeneity on infiltration on the macro scale. It is also found that the homogeneous
assumption of soil hydraulic conductivity along the horizontal direction will overestimate the infiltration rate, while that
along the vertical direction will underestimate the infiltration rate significantly during rainstorm periods. The SAI model
is adopted in the spatial averaging hydrological model developed by the authors, and the results prove that it can be applied
in the macro-scale hydrological and land surface process modeling in a promising way.
Science in China Series E Technological Sciences 05/2012; 52(4):1050-1058. · 1.02 Impact Factor
ABSTRACT: Scale adaptable hydrological models have attracted more and more attentions in the hydrological modeling research community,
and the constitutive relationship at the macro-scale is one of the most important issues, upon which there are not enough
research activities yet. Taking the constitutive relationships of soil water movement—soil water retention curve (SWRC) as
an example, this study extends the definition of SWRC at the micro-scale to that at the macro-scale, and aided by Monte Carlo
method we demonstrate that soil property and the spatial distribution of soil moisture will affect the features of SWRC greatly.
Furthermore, we assume that the spatial distribution of soil moisture is the result of self-organization of climate, soil,
ground water and soil water movement under the specific boundary conditions, and we also carry out numerical experiments of
soil water movement at the vertical direction in order to explore the relationship between SWRC at the macro-scale and the
combinations of climate, soil, and groundwater. The results show that SWRCs at the macro-scale and micro-scale presents totally
different features, e.g., the essential hysteresis phenomenon which is exaggerated with increasing aridity index and rising
groundwater table. Soil property plays an important role in the shape of SWRC which will even lead to a rectangular shape
under drier conditions, and power function form of SWRC widely adopted in hydrological model might be revised for most situations
at the macro-scale.
Science in China Series E Technological Sciences 04/2012; 52(10):2990-2996. · 1.02 Impact Factor
ABSTRACT: Soil particle size distribution (PSD), one of the most important soil physical attributes, is of great importance to soil
water movement, soil erosion and soil solute migration. In this study, the soil PSD of 563 soil samples from the mulched drip
irrigated cotton fields in Xinjiang of China were measured by laser diffraction particle size analyzer. The soil PSD characteristics
and its relations with soil water and salt were studied by using the combined methods of textural triangle, fractal and multifractal
analysis. The results showed very low clay content (about 1.52%) while really high sand content of the studied soil, and a
complex shape of bimodal or unimodal of soil PSD. The results also showed that the two indices, i.e., standard deviation and
the peak value of soil particle relative volumes, were good indicators of soil PSD and thus had good relations with fractal
and multifractal characteristics. The correlative analysis further indicated that the mulched drip irrigation had a significant
impact on the distribution of the soil salt, while this impact withered for the deeper soil layer. The soil texture feature
was found to dominate soil water and salt distribution, especially the surface soil salt content and the deep soil water content.
Keywordssoil particle size distribution–soil water and salt–mulched drip irrigation–fractal analysis–multifractal analysis–textural triangle
Science China Technological Sciences 04/2012; 54(6):1568-1574. · 0.75 Impact Factor
ABSTRACT: The Tuoshigan–Kumalake River alluvial plain is an oasis located in the Tarim River Basin of Xinjiang, China. Large water consumption
reduces the discharge and jeopardizes the ecosystem of the lower reaches of the Tarim River. Therefore a recent regulation
is enacted to limit water use in the plain. The objective of this paper is to investigate the hydrological cycle inside an
intensively cultivated plain at upstream Tarim River. A conceptual water balance methodology was used for evaluating groundwater
movement among riverway, irrigation ditches, irrigation area and non-irrigation area, based on the recorded water diversion.
Results show that both irrigation area and non-irrigation area are supported by the water from river way in hyper-arid environment.
Irrigation area is supported by surface water through canal system and non-irrigation area is supported by groundwater from
canal loss and irrigation area. Nearly half of the water in the non-irrigation area comes from the irrigation area in the
form of groundwater. This indicates that water supply of natural plants relies on the water from agricultural ecosystem. Tight
water connection between irrigation area and non-irrigation area suggests that natural ecosystem needs to be considered in
agricultural management in arid environment.
Water Resources Management 04/2012; 21(10):1703-1715. · 2.05 Impact Factor
ABSTRACT: Land surface process is of great importance in global climate change, moisture and heat exchange in the interface of the earth
and atmosphere, human impacts on the environment and ecosystem, etc. Soil freeze/thaw plays an important role in cold land
surface processes. In this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied.
A sophisticated land surface model is developed, the particular aspect of which is its physical consideration of soil freeze/thaw
and vapor flux. The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone
to frozen fringe in freezing/thawing soil, but also demonstrates the change of moisture and temperature field induced by vapor
flux from high temperature zone to low temperature zone, which makes the model applicable for various circumstances. The modified
Picard numerical method is employed to help with the water balance and convergence of the numerical scheme. Finally, the model
is applied to analyze the diurnal energy and water cycle characteristics over the Tibetan Plateau using the Game/Tibet datasets
observed in May and July of 1998. Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism
between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary
apparently, in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii)
during thawing period, ground heat flux increases, and sensible heat flux decreases, but latent heat flux does not change
much; and (iv) during freezing period, soil temperature decreases, though ground heat flux increases.
Science in China Series D Earth Sciences 04/2012; 49(12):1311-1322. · 1.59 Impact Factor
ABSTRACT: The representative elementary watershed (REW) approach proposed by Reggiani et al. was the first attempt to develop scale
adaptable equations applicable directly at the macro scale. Tian et al. extended the initial definition of REW for simulating
the energy related processes, and re-organized the deriving procedure of balance equations so that additional sub-regions
and substances could be easily incorporated. The resultant ordinary differential equation set can simulate various hydrological
processes in a physically reasonable way. However, constitutive and geometric relationships have not been developed for Tian
et al.’s equation set, which are necessary for the thermodynamic watershed hydrological model to apply in hydrological modeling
practice. In this work, the constitutive equations for mass exchange terms and momentum exchange terms were developed as well
as geometric relationships. The closed ordinary differential equation set with nine equations was finally obtained.
Science in China Series E Technological Sciences 04/2012; 51(9):1353-1369. · 1.02 Impact Factor
ABSTRACT: Stream-gauge data indicate that the flow of the Yellow River has declined during the past several decades. Zero flow in sections of the river channel, i.e. the Yellow River drying-up phenomenon, has occurred since the 1970s. In this paper we present an analysis of changes in the spatial patterns of climatic and vegetation condition data in the Yellow River basin based on data from meteorological stations and satellites. The climatic data are from 1960 to 2000 and the vegetation condition data are from 1982 to 2000. The angular-distance-weighted interpolation method is used to get climatic data coverage from station observations. The spatial distribution of tendency is detected with Student's t-test. The spatial patterns of climatic and vegetation condition change was analysed together with the statistical data on human activities. The analysis indicates that the precipitation decreases and temperature increases in most parts of the Yellow River basin, the evaporative demand of the atmosphere decreases in the upper reaches and increases in the lower reaches, and human activities have improved the vegetation condition in the irrigation districts. The Loess Plateau, the Tibetan Plateau, and the irrigation districts are respectively suggested as precipitation, temperature, and human activity hot spots of the Yellow River drying-up phenomenon. Copyright © 2007 John Wiley & Sons, Ltd.
Hydrological Processes 01/2008; 22(3):451 - 458. · 2.49 Impact Factor
ABSTRACT: Groundwater recharge and discharge in the Akesu alluvial plain were estimated using a water balance method. The Akesu alluvial plain (4842 km2) is an oasis located in the hyperarid Tarim River basin of central Asia. The land along the Akesu River has a long history of agricultural development and the irrigation area is highly dependent on water withdrawals from the river. We present a water balance methodology to describe (a) surface water and groundwater interaction and (b) groundwater interaction between irrigated and non-irrigated areas. Groundwater is recharged from the irrigation system and discharged in the non-irrigated area. Uncultivated vegetation and wetlands are supplied from groundwater in the hyperarid environment. Results show that about 90% of groundwater recharge came from canal loss and field infiltration. The groundwater flow from irrigated to non-irrigated areas was about 70% of non-irrigated area recharge and acted as subsurface drainage for the irrigation area. This desalinated the irrigation area and supplied water to the non-irrigated area. Salt moved to the non-irrigation area following subsurface drainage. We conclude that the flooding of the Akesu River is a supplemental groundwater replenishment mechanism: the river desalinates the alluvial plain by recharging fresh water in summer and draining saline regeneration water in winter. Copyright © 2007 John Wiley & Sons, Ltd.
Hydrological Processes 05/2007; 21(10):1345 - 1353. · 2.49 Impact Factor