| The Liudaogou Basin is located at the northern Loess Plateau has been affected by the wind-water erosion for the long time,which has deteriorated the water resources in the region.The check dam plays an important role in measuring of soil-water conservation,improving the water resource efficiencies(storage and usage),and it has provided some usefulness to the soil hydrological cycle and plant growth.The paper took a check dam as the research area which located at the Liudaogou Basin,and selected the check dam area and slope as the research object.The calculations of reference crop evapotranspiration(ET0)and grassland evapotranspiration(ET)were achieved base on modified and original Penman-Monteith formulas,which were recommended by the United Nations Food and Agriculture Organization(FAO).The variation in water availability(ma)describes the temporal fluctuation in water evapotranspiration and availability for study area.The research developed one-dimensional numerical model for surface soil water content(0?10cm)from the finite difference method in combination with motion equation of unsaturated soil water.In order to evaluate the model simulation and validation,the standard error(RMSE),consistency coefficient(d)and Nash-Sutcliffe efficiency coefficient(NSE)were used.The results of this research can be describe as the following points:(1)From January 1,2006 to September 30,2007,the curves of ET0,ET,ma change with time and look similar between the check dam area and slope.The total amount of 2006 or within 9 months of 2007 the ET0,ET and ma showed the check dam area was slightly higher than slope.ET and ma has been more strongly affected by the change in rainfall and soil moisture for two points.The ma was 0.16 and 0.14 in 2006 at check dam area and over the slope,and 0.20 and 0.18 within 9 months of 2007,and it indicates that,the water availability of the check dam area was slightly higher than slope during the period of calculation every year.(2)The diurnal variation trend of 5 and 30 cm depths for the soil moisture were more obvious in non rainy season of the check dam area and slope,while the diurnal variation trend was week and fluctuation frequently during the rainy season in 2006.On other hand,the diurnal variation trend of soil water for two depths was existed over the slope were more obvious than the same depths at check dam area.(3)The simulation results of surface soil water was:The standard error(RMSE)in surface soil water were 0.015 and 0.017,consistency coefficient(d)were 0.974 and 0.953 and Nash-Sutcliffe efficiency coefficient(NSE)were 0.901 and 0.830 for the check dam area and slope respectively.The calculation model for two soil moisture simulation results was a satisfactory and it implies that,the developed model exhibited a high simulation accuracy,meanwhile the accuracy of check dam area was higher than slope.Moreover,the model showed a sensitive to the rainfall and high accuracy simulation during the non rainy season in specific year.These results might provide a reference method for the research on water availability and soil water motion at the check dam area at northern Loess Plateau and also could provide basic data for developing the agricultural and construction of soil-water conservation at Liudaogou Basin. |
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