Land-use induced spatial heterogeneity of soil hydraulic properties on the Loess Plateau in China

Abstract On the Loess Plateau in China, soil erosion amounts to between 10 000 and 25 000 tons/km2/year. In 1998, the EROCHINA project was started, with the major objective of developing alternative land-use and soil and water conservation strategies for the Loess Plateau, using the LISEM soil erosion model. In order to provide the model with accurate input on soil hydraulic properties of the catchment, this study tried to quantify these properties for major land-use units and to examine the effects of the statistically identified in-field heterogeneity on model outcome. The study area (Danangou catchment) is located in the middle part of the Loess Plateau in the northern part of Shaanxi Province. The catchment is about 3.5 km2 in size. To determine the hydraulic properties of the soil, a sampling scheme was implemented to measure unsaturated conductivity and water retention characteristics. The saturated conductivity measurements were performed on land-use clusters, based on treatment and plant and soil differences. A 100×100 m sampling grid was set out on 12 fields, with 1×1 m grid squares. On each field, 10 sampling spots were randomly selected, using Simple Random Sampling. The sensitivity of the LISEM model to the measured heterogeneity of saturated conductivity was analysed by using the geometric mean and standard deviation (S.D.) of the Ks-optimized of the various land-use units to calculate discharge and soil loss during a single rain event. This proved that, using the standard deviation of the saturated conductivity, which was 30–50%, the calculated discharge and total sediment losses varied by a factor 2. Using the standard deviation had a minor effect on the calculated sediment concentration. As regards the on-site effects, the use of the geometric mean of Ks minus the S.D. resulted in an increase in the level of erosion, while the use of geometric mean of Ks plus the S.D. value resulted in a significant decrease in erosion level relative to that obtained using the geometric mean of Ks itself. Using randomly selected sampling spots and a calibration procedure as was done in the present study make detailed information on Ks available, which can be used to compare alternative land-use options for their effectiveness in reducing discharge and sediment losses.

[1]  A. D. Roo,et al.  LISEM: A SINGLE‐EVENT, PHYSICALLY BASED HYDROLOGICAL AND SOIL EROSION MODEL FOR DRAINAGE BASINS. II: SENSITIVITY ANALYSIS, VALIDATION AND APPLICATION , 1996 .

[2]  Jaap de Gruijter.  Spatial sampling schemes for remote sensing , 1999 .

[3]  J. Stricker,et al.  INFLUENCE OF SPATIALLY VARIABLE SOIL HYDRAULIC PROPERTIES AND RAINFALL INTENSITY ON THE WATER BUDGET , 1996 .

[4]  C. Ritsema,et al.  Effects of crust and cracks on simulated catchment discharge and soil loss , 1997 .

[5]  Diederik Jacques,et al.  Spatial variability of hydraulic properties in a multi-layered soil profile , 1996 .

[6]  Baoyuan Liu,et al.  Calibration of the LISEM model for a small Loess Plateau catchment , 2003 .

[7]  Timothy A. Quine,et al.  Soil erosion rates on sloping cultivated land on the Loess Plateau near Ansai, Shaanxi Province, China: An investigation using 137Cs and rill measurements , 1998 .

[8]  Coen J. Ritsema.  Introduction: soil erosion and participatory land use planning on the Loess Plateau in China , 2003 .

[9]  L. Nelson,et al.  Spatial and temporal variability of soil physical properties of norfolk loamy sand as affected by tillage , 1985 .

[10]  J. Bouma,et al.  VARIABILITY OF SATURATED HYDRAULIC CONDUCTIVITY IN A GLOSSAQUIC HAPLUDALF WITH MACROPORES , 1988 .

[11]  Nunzio Romano,et al.  Spatial variability of the hydraulic properties of a volcanic soil , 1995 .

[12]  Coen J. Ritsema,et al.  Soil erosion simulations of land use scenarios for a small Loess Plateau catchment , 2003 .

[13]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[14]  V. Singh,et al.  SENSITIVITY OF LINEAR AND NONLINEAR SURFACE RUNOFF MODELS TO INPUT ERRORS , 1976 .

[15]  M. Sharma,et al.  Spatial variability of infiltration in a watershed , 1980 .

[16]  Liding Chen,et al.  Soil conditions in a small catchment on the Loess Plateau in China , 2003 .

[17]  D. Russo,et al.  On the spatial variability of parameters of the unsaturated hydraulic conductivity , 1997 .

[18]  G. P. Wind,et al.  Capillary conductivity data estimated by a simple method , 1966 .

[19]  D. A. Woolhiser,et al.  Effects of Spatial Variability of Saturated Hydraulic Conductivity on Hortonian Overland Flow , 1996 .

[20]  Feike J. Leij,et al.  The RETC code for quantifying the hydraulic functions of unsaturated soils , 1992 .

[21]  C. Ritsema,et al.  ESTABLISHING TEMPORALLY AND SPATIALLY VARIABLE SOIL HYDRAULIC DATA FOR USE IN A RUNOFF SIMULATION IN A LOESS REGION OF THE NETHERLANDS , 1996 .

[22]  A. Stein,et al.  Spatial statistics for remote sensing , 2002 .

[23]  J. Feyen,et al.  Spatial analysis of saturated hydraulic conductivity in a soil with macropores , 1997 .

[24]  Kunqing Xie,et al.  Crop characteristics and their temporal change on the Loess Plateau of China , 2003 .

[25]  A. D. Roo,et al.  LISEM: a single-event physically based hydrological and soil erosion model for drainage basins; I: theory, input and output , 1996 .

[26]  Y. Mualem.  A New Model for Predicting the Hydraulic Conductivity , 1976 .

[27]  B. Mohanty,et al.  Spatial analysis of hydraulic conductivity measured using disc infiltrometers , 1994 .

[28]  A. De Roo,et al.  Infiltration experiments on loess soils and their implications for modelling surface runoff and soil erosion , 1992 .

[29]  G. Heuvelink,et al.  Estimating the effects of spatial variability of infiltration on the output of a distributed runoff and soil erosion model using Monte Carlo methods , 1992 .

[30]  R. Green,et al.  Temporal variability of soil hydraulic properties with wetting and drying subsequent to tillage , 1986 .